Final Report Summary - HAIC (High Altitude Ice Crystals)
Executive Summary:
Commercial aircraft have been experiencing in-service events while flying in the vicinity of deep convective clouds since at least the early 1990s. Heated probes and engines are the areas of aircraft most prone to mixed phase and glaciated icing threat.
In anticipation of regulations evolution linked to this phenomenon, the HAIC project has been put in place to provide European Aeronautical industry with necessary Acceptable Means of Compliance and detection/awareness technologies in order to continuously enhance flight safety. HAIC also developed international cooperation and collaboration thanks to the involvement of key international organisations and companies as partners of the project or through the advisory board.
Microphysics probes were developed and improved beyond the state of the art, in order to allow in-flight measurements and to support wind tunnel calibrations. The selection of the most advanced instrumentation was performed for the three flight test campaigns and for calibration and commissioning tests of four wind tunnel faciilities. Both, the wind tunnel instruments and the instrumentation integrated in research aircraft were inter-compared in a wind tunnel and the repeatability of wind tunnel conditions were assessed. Beside the development of ice particle probes, the effects of aerosol on convection, the height of glaciation and particle size distributiuons was evaluated using airborne data in polluted continental (and clean maritime) convection above Brazil.
Three flight tests campaigns were conducted in three different regions of the world, with two types of convection (continental and oceanic). These campaigns were the successful result of cooperation between multiple entities (airframers, engine manufacturers, equipment & system suppliers, research institutes and academics, meteorological services and SME’s able to provide specific knowledge, service, or support in specific areas) and even of international collaboration between the HAIC, EASA-HighIWC, ICC and HIWC projects for two of these campaigns. They allowed supporting the assessment of mixed phase and glaciated icing conditions regulations by providing 99th percentile total water content statistics and other relevant clouds characteristics. They also allowed exposing the detection and awareness technologies in real conditions and thus improving their maturity. Flight test data were also used to support the development of numerical simulation tools.
From detection and awareness perspective, two space borne nowcasting technologies (KNMI High IWC Mask and RDT) were improved to enable identification of areas prone to high IWC. Those technologies were validated through comparison with measurements from HAIC and AIRBUS flight campaigns, from AIRBUS in-service events and from a long series of Low Earth Orbiting A-train IWC profiles. RDT technology is now close to TRL6 level, and KNMI High IWC mask reached TRL6 level. An on-board radar technology was developed for awareness of high IWC areas. This technology benefited from the flight tests for validation and reached TRL6 level. Several detector technologies were also developed and step by step down selected. Icing wind tunnel tests and flight tests allowed to mature their design and to validate their performances. Different TRL levels were reached depending on the technologies (up to TRL5 for PDP detector) and further progress will be achieved beyond HAIC project.
Four wind tunnel test facilities were improved or modified to be capable of ice crystals conditions simulation. Calibration of these wind tunnel test means has been performed, and their performances have been cross compared. These facilities have also been used to support the validation of detectors performances, to intercompare W/T and F/T instrumentation and to provide experimental cases for the numerical simulation tools. TRL5 maturity was reached for the four facilities.
Numerical models and tools were also developed to enable numerical simulation of the phenomenom. Numerous experiments were conducted in different facilities, allowing improvement and then validation of the trajectory, impingement and accretion models. Industrial 2D and 3D numerical tools were developed with implementation of those models and delivered to industrial partners. Those latter ran first validation tests to check integration in industrial environment. Anyway, some more work is needed beyond HAIC project to reach the expected TRL6 maturity level.
As a main conclusion, even if some topics will still be explored or consolidated after HAIC project, a huge gap was filled thanks to the project regarding the understanding of the Ice Crystal Icing phenomena, the means to experimentally or numerically simulate the conditions and the means to detect the conditions in order for the aircraft to either avoid them or to adapt its protections.
In addition, the HAIC project allowed setting up and consolidating a strong international community of experts on the icing topics, which will be very valuable in the future.
Project Context and Objectives:
Commercial aircraft have been experiencing in-service events while flying in the vicinity of deep convective clouds since at least the early 1990s. Heated probes and engines are the areas of aircraft most prone to mixed phase and glaciated icing threat.
In anticipation of regulation changes according to mixed phase and glaciated icing conditions, the HAIC project will provide the necessary Acceptable Means of Compliance (numerical and test capabilities) and appropriate ice particle detection/awareness technologies to the European Aeronautical industry for use on-board commercial aircraft in order to enhance safety when an aircraft is flying in such weather conditions. HAIC will also develop international cooperation and collaboration thanks to the involvement of key international organisations and companies as partners of the project or through the advisory board.
The main objectives of the HAIC project are to allow the European aeronautical industry to face challenges related to the evolution of regulation regarding mixed phase and glaciated icing conditions by characterising high ice water content environments and developing the Acceptable Means of Compliance (test facilities and numerical tools) to improve aircraft operation in such weather conditions by developing appropriate detection and awareness technologies to be fitted on aircraft and being able to alert the flight crew, thus continuously enhancing international flight safety.
This can be broken down into the following scientific, technical and dissemination objectives:
• Characterise, optimise, enhance and select the most sophisticated cloud microphysics probes to measure mixed phase and glaciated icing conditions during flight tests and to calibrate icing wind tunnels
o To measure mixed phase and glaciated icing conditions (TWC, LWC, IWC, etc.) with an accuracy better than 10%
• Measure and characterise the microphysical properties of core or near-core regions of deep convective clouds, including cloud liquid and ice water contents, particle size distributions and particle shapes and provide 99th percentile total water content statistics as a function of distance scale to assess Appendix D and P diagrams representativeness vs real atmosphere
o To sample monsoon oceanic convection, oceanic tropical storms and more vigorous continental convection as safety permits
o To get statistics of the 99th percentile of Total Water Content averaged over a distance of 20 statute miles of a convective storm centre, with an accuracy of ± 20%
o To state on Appendix D and P diagrams representativeness vs. real atmosphere
• Upgrade European icing wind tunnels to allow reproduction of mixed phase and glaciated icing conditions to allow the European Aeronautical industry to perform equipment qualification and generate a detailed experimental database to validate numerical tools
o Achieve a TRL6 on the considered technologies
o Simulate the considered flight and mixed phase and glaciated icing conditions (Mach number ~0.85 Altitude up to ~40kft, Static temperature down to -70°C, IMMD in the range 20-500µm, IWC up to 20g.m-3 mixed phase capability) with an accuracy at least equivalent to the current covered icing envelope ie 15%
o Generate a detailed experimental database to validate numerical tools
• Understand and model involved physical phenomena and develop numerical tools to simulate the impact of mixed phase and glaciated icing conditions on aircraft components (mainly engines and probes) for supporting both design and certification phases and perform an integrated cross-validation between in-flight measurements, wind-tunnel measurements and model predictions
o Achieve a TRL6 on the considered technologies
o Provide models and tools able to simulate the considered icing envelope and associated impact on aircraft components with an accuracy at least equivalent to test facilities i.e. 15%
o Perform an integrated cross-validation between in-flight measurements, wind-tunnel measurements and model predictions
• Develop and validate mixed phase and glaciated icing conditions awareness and detection technologies to alert the crew of flight in these particular icing conditions or to adapt the flight path well in advance in order to avoid such weather conditions
o Achieve a TRL6 on the considered technologies
• Assess the proposed mixed phase and glaciated icing environment as defined in Appendix D and P in light of the analysis of the research flight tests performed as part of the HAIC project and provide recommendations to the regulatory bodies (EASA and FAA)
• Develop international cooperation and collaboration thanks to the involvement of key international organisations and companies as partners of the project or through the HAIC Advisory Board.
The HAIC project is broken down into six technical sub-projects and one sub-project devoted to consortium management and dissemination and exploitation activities:
• SP1 Instrumentation improves and selects the most appropriate instrumentation to characterise mixed phase and glaciated icing conditions to be encountered during the two HAIC flight tests campaigns (SP2) and to support the calibration of test facilities (SP5).
• SP2 High IWC Flight tests Campaigns organises, manages and conducts three flight test campaigns in 2014, 2015 and in 2016. In the two first flight test campaigns, it brings, in collaboration with HIWC US study, the French Falcon 20 equipped with active remote sensing (airborne cloud radar) and in situ microphysics probes. Based on these measurements and previous results from Airbus field campaigns in 2010 and 2012, the SP2 characterises the microphysical properties of the high IWC regions and distributes these inputs to other SPs. In the third flight test campaign, SP2 brings for the first time a Flying Test Platform (large payload and long endurance Airbus flight test A/C) to the industrial and scientific community for validation and demonstration of the maturity of the technologies (up to TRL6) developed within HAIC project.
• SP3 Space-borne Observation & Nowcasting of High IWC Regions develops space-borne remote detection and nowcasting techniques to support the second flight test campaign and ultimately provide near real-time weather data through ATM as being studied as part of SESAR.
• SP4 High IWC Detection & Awareness Technology develops on-board detection and awareness systems (probes or radar) complying with the industrial requirements of performance, operability, reliability, weight and cost, and able to discriminate the different icing conditions encountered.
• SP5 High IWC Test Capability Enhancement improves test facilities for the simulation of mixed phase and glaciated icing conditions in order to be able to support methods & tools development and validation and to perform qualification of equipment in European facilities.
• SP6 High IWC Tools & Simulation Development develops, validates and verifies models and tools able to simulate the impact of mixed phase and glaciated icing conditions on A/C components (mainly engines and probes) in order to support both A/C design and certification phases. Lastly, SP6 performs integrated cross-validation between in-flight measurements (SP2), wind-tunnel measurements (SP5) and model predictions, in order to demonstrate the capability of AMCs to reproduce the response of equipment and systems in mixed phase and glaciated icing conditions.
• SP7 Consortium Management, Technical Management and Integration is in charge of the project monitoring, administration, dissemination and reporting and ensures the technical consistency and convergence towards HAIC high level objectives. It is the “Architect and Integrator” and defines and manages the TRL process and roadmap. It manages the activities of standardisation related related to technologies specification or icing wind tunnel calibration built as part of other SPs. Finally, it coordinates the communication to the Advisory Board and external participants and, as such, is in charge of providing a set of recommendations to regulatory bodies (EASA/FAA) based on the outcomes of the SP2 regarding the assessment of the proposed mixed phase and glaciated icing environment as defined in Appendix D and P.
The HAIC project is a 4.5-year level 2 project of the 7th Framework Programme of the European Union coordinated by Airbus Operations SAS and kicked off in August 2012. It comprises 34 partners representing the European stakeholders of the aeronautical industry from eleven European countries and 5 partners from Australia, Canada and the United States. Its total budget is 23 million EUR.
Project Results:
1.3. DESCRIPTION OF THE MAIN S&T RESULTS/FOREGROUNDS
1.3.1. Instrumentation
The three HAIC F/T measurement campaigns address for the first time with a comprehensive set of measurements the engineering and scientific issues related to the in-service events in convective clouds, and a variety of fundamental scientific issues related to the microphysical properties and structure of deep convective cloud systems over land and over the warm tropical ocean.
Airworthy probes have been developed to provide size distributions and total water content in clouds (either during flight tests or tunnel tests). Few of them are able to perform measurements in mixed phase and glaciated icing conditions. Nevertheless, measurements of high IWC are technically very challenging and, before HAIC project, measurements were subject to unacceptable level of uncertainty and to very strong limitations (particles size, water concentrations, airspeed...). Instruments had to be improved and developed to provide sufficient accuracy for the characterisation of this environment.
Therefore, SP1 was designed to support the preparatory work for the SP2, SP4, and SP5 programs within HAIC. Its focus was primarily on the characterisation and improvement of microphysical and bulk cloud probes to measure in high ice water content regions in the atmosphere in convective cloud systems. Also, instrumentation was developed and characterised to enhance the capacities of current wind tunnels and extent the measurement range to high ice water content in glaciated and mixed phase conditions.
Beyond the state of the art, SP1 within HAIC helps to review, identify and optimise the performances of emerging technologies to allow the most appropriate instrument configuration to be chosen for F/T and W/T measurements.
1.3.1.1. Improvement and characterisation of microphysical and bulk cloud instruments for flight test F/T campaigns
The principal measurement challenges in icing conditions are related to the capability to measure small ice particle properties (<100 µm), avoid shattering (modified probe tips) and/or remove (filtering) shattered/splashed particles, discriminate the phase of particles (solid / liquid), and enhance IWC measurements of high IWC on aircraft by a better characterisation of collection efficiencies of probes. Finally, the selected probes for HAIC first F/T campaigns will also include highly sophisticated cloud radars capable of small ice particles measurement.
Significant work has been performed in SP1 related to characterisation of bulk TWC probes, characterisation/improvement of new maturing imaging and sizing probes, work on combination probes, and improvements of a the set of field mill sensors in order to support payload decision for the HAIC F/T campaigns. Therefore newest cloud probes have been optimised to measure bulk ice and individual small ice particles in convective cloud systems, while avoiding splashing and shattering.
1.3.1.1.1. Characterisation of bulk TWC probes (Robust hot-wire, IKP, field mill sensor)
Robust and Nevzorov hot-wire probes to detect the total water content have been characterised within SP1. From a comparison to IKP data, a temperature and TWC dependent characterisation of the sampling efficiency has been achieved. Further, SEA developed a new ROBUST probe sensor design, potentially increasing the efficiency by a factor of 2 as compared to classical ROBUST probe. This design was tested during the 2016 A340 campaign. The Nevzorov probe has been excluded from possible bulk probe candidates due to saturation at TWC beyond 1-1.5 g/m3.
The AMPERA field mill sensor to measure the voltage potential of HAIC aircraft in order to retrieve the TWC has been integrated on the Falcon and the A340 for the HAIC campaigns. An inversion method to retrieve IWC from field mill data has been derived.
1.3.1.1.2. Improvement and characterisation of new maturing probes (CAS-DPOL, CPSPD, HSI)
The CAS-DPOL (Cloud Aerosol Spectrometer with Depolarisation) cloud probe has been employed during the ACRIDICON projects for a phase discrimination of cloud particles based on the polarisation ratio. Laboratory measurements under defined conditions were used to calibrate the probes response to liquid/ice particles with known sizes. Shattering of larger cloud particles on the inlet of the instrument has been corrected based on particle interarrival time information.
As a new topic within HAIC, the aerosol effect on convective clouds is determined from measurements in continental convection under polluted and less polluted conditions in Brazil.
The CPSPD (Cloud Particle Spectrometer with Polarisation Detection) is the newly developed open path version of the CAS-DPOL and shows identical capacities of distinguishing cloud droplets and small crystals. The geometry of the probe is optimised to avoid shattering as much as possible.
The HSI (High Speed Imager) uses a multi beam approach to eliminate shadows from out-of-focus particles to improve measurement accuracy. It has been further developed within the HAIC project and successfully deployed on the NRC Convair 580 during the 2015 Cayenne campaign within the HAIC/HIWC collaboration.
1.3.1.1.3. Optimisation of instrumentation and design of combination probes (CDP-2/Robust, FCDP/2D-S)
The Cloud Droplet Probe -2 CDP-2 / Robust combination probe has been developed within HAIC for the Falcon 20. In order to reduce the number of canisters on the A340, the Fast Cloud Droplet Probe FCDP has been integrated onto the canister of the 2-dimensional stereo probe 2D-S to operate as combination probe for the detection of particles between 2 µm and 1.2 mm. Two of those probes were improved within HAIC. The 2D-S, FSSP and CDP tips were sharpened within the HAIC project to avoid shattering of particles.
1.3.1.1.4. Suggestion of instrumentations for F/T campaigns
High condensed water content is often found in deep convective clouds present in the warm tropical regions around the globe. These high ice water content regions are in principle not visible from current on-board weather radar of commercial aircraft and cannot be detected by current on-board icing detectors (detectors for classical icing due to the presence of supercooled water). The Engine Harmonisation Working Group (EHWG) has recommended a technology plan in order to develop means of compliance to provide guidance to manufacturers, and also to update or validate proposed certification rules for compliance in mixed phase and glaciated icing conditions. This technology plan includes an important task: Instrumentation development and evaluation for high ice water content and flight test research to characterise high ice water content environments.
Within SP1 instrumentation, a set of most sophisticated cloud microphysics probes has been selected for Falcon and A340 flight tests to enhance the capacities and accuracies of F/T in measuring high ice water contents, to allow for phase separation in mixed phase and glaciated icing conditions and to provide new IWC information by comparing in-situ IWCs with radar derived cloud properties. Also technologies developed within SP4 should be included. Figure 4 shows the cloud probes and size range, currently available for cloud observations from aircraft.
The requirements for the selection of the most adequate microphysical payload were to perform quantitative measurements of small ice particle properties (<100μm, if possible), minimise possible small ice crystals contamination on spectrometer data due to ice particle shattering, discriminate cloud particle phase, and enhance the maximum value of measurable total water content. Overall, very good progress has been achieved in the definition, selection, preparation and certification of the HAIC A/C instrumental payload for the 3 consecutive F/T campaigns: Falcon 20 out of Darwin (2014) and Cayenne (2015), and A340 (2016).
The selection of the payload for the HAIC international A340 F/T campaign 2016 allows in particular to measure ice particle concentration and sizes up to 1.2 mm and down to 2 μm with the 2D-S/FCDP combination probe, measure large TWCs with the Robust probe, continue collecting cloud data in deep convective clouds to complete the icing envelope for aircraft safety and validate the maturity of awareness and detection technologies developed in the frame of HAIC SP4.
1.3.1.2. Improvement and characterisation of microphysical and bulk cloud instruments for wind tunnel W/T test campaigns
It is the scope of HAIC to enhance the capacities for European wind tunnels to icing and mixed phase conditions. To this end, wind tunnel facilities have to be further developed to allow for the injection of ice and mixed phase particles at temperatures down to -40 °C and velocities up to 100 m/s. In order to allow for the commissioning of these novel achievements, wind tunnel instruments have to be further developed and characterised, which are able to measure the provided IWC and TWC as well as the particle size distribution in the selected wind tunnel facilities, exhibiting limited sizes of experimental sections. Therefore instruments have been developed and characterised within SP1, which can determine microphysical and bulk cloud properties in the experimental section of W/T facilities. The instruments’ measurement ranges have been adjusted to the conditions provided by the wind tunnels and the mechanical set-up has been optimised for instrument integration in the “small” experimental section of the wind tunnels. Developments and SP1 results are given below.
1.3.1.2.1. Development of the Isokinetic Probe (CU-IKP)
An isokinetic probe (CU-IKP) has been developed by the University of Cranfield to measure LWC, IWC and CWC in the different European wind tunnels. Air and cloud particles are pumped into the forward facing inlet of the IKP at a speed matching the wind tunnel air speed (isokinetic). Thus the particles are not enriched or depleted with respect to the wind tunnel particle concentration. Water vapor in the gas phase is detected with a backward facing inlet. Sublimated/evaporated total and gas-phase water are measured with a LICOR LI-7000 differential infrared gas analyser.
During HAIC, the pumping system and the water vapour detection of the instrument have been optimised. Laboratory and tunnel calibrations show that the CU-IKP measures CWC with an uncertainty < 20 % for 0.5 < LWC < 3 g/m³ and < 30 % for IWC < 12 g/m³ at selected pumping speeds < 50 m/s and at temperatures of 5° to -20°.
1.3.1.2.2. Development and characterisation of the High Speed Imager HSI
In order to derive microphysical particle information from single particles in wind tunnels, the high speed imager (HSI) has been developed by CIRA/Artium in SP1. It measures the size, habit, sphericity and various microphysical properties of particles in the size range of nominally ~20 to <1200 µm. The high speed imaging with 3 diode lasers focussed at the same focal point help to better define the system’s depth of field (DOF) and hence allows the rejection of out of focus particles for accurate particle sizing. A CMOS camera collects the images at high frequency (300 images per sec). The instrument has been further developed as canister probe for larger wind tunnels (TU-BS) and as modular version with open path optics for small wind tunnels (DGA, Esterline, GKN). The HSI has also been integrated in the NRC Convair aircraft during the Cayenne campaign 2015.
1.3.1.2.3. Phase Doppler Interferometer PDI
As an independent measurement technique, the Phase Doppler Interferometer PDI has been developed by CIRA/Artium as single and modular versions for the measurement of microphysical particle properties of liquid clouds in the size range < 100 µm. The Phase Doppler measures scattered light from small droplets passing through the probe volume in the intersection of two coherent laser beams. The interference of two scattered waves on the detectors creates a fringe pattern in which the droplet velocity information is contained due to the Doppler effect. The PDI is used for the wind tunnel particle velocity measurements and for size distribution measurements of small liquid droplets and has extensively been characterised theoretically within SP1.
1.3.1.2.4. Selection of microphysical and bulk cloud instruments for wind tunnel calibrations
Prerequisites given by the measurement range and mechanical considerations led to the selection of the following instruments for wind tunnel commissioning measurements.
Regarding the detection of bulk properties, Robust probes may encounter an under-sampling of the ice water content in glaciated or mixed phase conditions due to splashing of ice particles on the probes head. Thus, the CU-IKP has been selected to detect the IWC, LWC and CWC during the wind tunnel commissioning measurements. A second instrument is required for the detection of microphysical properties of single particles or the particle size distribution (PSD). The high speed imager HSI uses an advanced technique with several laser beams to accurately derive the depths of field and thus allows for an accurate counting of particles and a sizing in the expected size range provided by the wind tunnels. In addition, the HSI has been developed in modular and canister version for the use also in small wind tunnel test sections. Thus, the HSI has been selected for the determination of the concentration and the PSD for W/T commissioning. Finally the Phase Doppler Interferometer PDI has been chosen for particle velocity measurements.
1.3.1.2.5. Intercomparison of wind tunnel and flight test instruments
Generally, different instrumentations are used in W/T and F/T campaigns, thus limiting the comparability of atmospheric and laboratory measurements. To overcome this issue, an instrument intercomparison campaign has been planned and conducted with the objective to directly intercompare the instruments used on aircraft and in the wind tunnel.
The campaign took place in September 2016 in the Braunschweig wind tunnel, which has a large test section and thus allows for the integration of aircraft and wind tunnel instruments. Table 7 shows the F/T and W/T instrumentation selected for intercomparison. The objectives of the intercomparison campaign are threefold: the direct comparison of 2D-S and HSI derived PSD and IWCs, the intercomparison of the 2 2D-S probes, the comparison of data evaluation methods derived from aircraft flight tests. Figure 20 shows the canister HSI and the 2D-S integrated in the Braunschweig wind tunnel and the laser beams of the modular HSI and PDI focussed on the same sampling area.
The evaluation method applied to the 2D-S data of the Lamp-2D-S and the DLR 2D-S was similar to the one used during the HAIC campaigns. IWC was derived using the Brown and Francis, 1995, M-D relationship applied to the area equivalent diameter (Deq). In summary, the results show a good agreement between the two 2D-S instruments using similar data analysis methods (D15.2). MMDs were derived from four instruments. In general, the standard deviations from the HSIs are higher than for the 2D-S due to a lower sampling statistics. On average, MMDs between 70 ± 12 µm (i09) and 85 ± 8 µm (i06) have been inferred by the four instruments. Out of the 25 mean IWC values retrieved, 21 values agree with the prescribed TUBS IWC within 20%. On average, the IWC from the four instruments agree within 15 % (i01), 8% (i02), 6% (i03), 4% (i05), 33% (i06), 2% (i09) and 11% (i10) with the TUBS IWC, despite the sometimes large variabilities of condition encountered within one experiment (e.g. i01). Larger uncertainties and instabilities were observed for temperatures above the freezing temperature due to melting of ice crystals near the wall of the wind tunnel. Also higher IWC (> 10 g m-3) inferred by the instruments showed a larger deviation from the prescribed IWC. Further tests are required to evaluate the HSI performance at higher MMD and lower particle concentrations.
1.3.2. High IWC Flight tests Campaigns
SP2 was dedicated to the organisation, management, conduction and post-processing of the three flight test campaigns of the project that were conducted in 2014, 2015 and in 2016. Then, based on these measurements and previous results from Airbus field campaigns in 2010 and 2012 and HYMEX in 2011, SP2 helped to characterise the microphysical properties of High IWC regions and supported the rulemaking activities at international level.
In the first two flight tests campaigns, it brought, in collaboration with HIWC US study, the French Falcon 20 equipped with active remote sensing and in situ microphysics probes. In the third flight tests campaign, SP2 brought for the first time a Flying Test Platform (large payload and long endurance aircraft) to the industrial and scientific community for validation and demonstration of the maturity of the new technologies (up to Technology Readiness Level 6) developed within HAIC project.
1.3.2.1. Darwin 2014 and Cayenne 2015 Flight Tests Campaigns
Two campaigns have been conducted in the frame of HAIC/HIWC international collaboration. These campaigns took place in Darwin (Australia) from January 15, 2014 to March 7, 2014 and Cayenne (French Guyana) from May 9, 2015 to May 29, 2015.
1.3.2.1.1. Preparation of international field campaigns
The selected A/C for these campaigns is the SAFIRE Falcon20 fitted with state-of-the art instruments, as selected by SP1, to measure cloud microphysics and RASTA multi-beam Doppler radar active remote sensing:
In addition to Aircraft instrumentation to measure in-situ conditions, other tools were developed to support the campaign, like PLANET. PLANET is a tool for scientific flight guidance that was adapted for field campaigns. PLANET was additionally upgraded for Cayenne campaign to allow the operations with three aircraft and to include real time SP3 satellite based retrieval products.
An observation network was also available to monitor and record all meteorological conditions. This included ground weathers radars and satellite data.
1.3.2.1.2. HAIC/HIWC Darwin 2014 Flight Tests Campaign
The first campaign took place in Darwin, Australia from January 15, 2014 to March 7, 2014. It was planned to operate primarily over ocean areas within 300 nm of Darwin in Australian airspace extending to over the Gulf of Carpentaria whenever possible.
Campaign started as planned on the 16th of January 2014: all team members, equipment and the Falcon 20 arrived in Darwin on time. Significant monsoon conditions were present from the start through mi-February 2014. 23 research flights were conducted during Darwin campaign, corresponding to 72 flight hours. A large amount of data was collected, and the first part of the campaign was successful, with no A/C or instrumentation failure.
Following aircraft unexpected failures (not linked to high IWC) it has been decided to stop campaign on 07/03/2014. Due to early termination and risk to not reach rulemaking objective because of lack of data for statistical approach, HAIC and HIWC teams worked out the preparation of a new campaign to collect missing data and achieve the objectives.
1.3.2.1.3. HAIC/HIWC Cayenne 2015 Flight Test Campaign
The second HAIC/HIWC flight campaign took place from May 9th, 2015 to May 29th, 2015 out of Cayenne, French Guyana. During this campaign, two other A/C had joint the research effort:
• NRC Convair 580 aircraft equipped with active remote sensing (airborne Doppler cloud radar) and in situ microphysics probes to sample -10°C Flight Level and vicinity of clouds.
• Honeywell B757 aircraft equipped with enhanced weather radar to evaluate radar ice crystals’ awareness function developed as part of SP4
Aircraft operated primarily within 300 nm of Cayenne in FIR Paramaribo and Piarco. Some issues were experienced with Brazilian ATC for operation within FIR Atlantico and Amazonica.
The flight campaign had been successful for all three aircraft. 19 days of flights were performed representing 60F/H for the Falcon 20, 50F/H for the CV-580 and around 40F/H for the B757.Among the 19 days of flights performed,
• 5 flights were performed with 1 aircraft alone
• 8 flights were performed coordinating 2 aircraft
• 6 flights were performed with all 3 flight tests aircraft at the same time.
This campaign was intense and fruitful and it allowed collecting a large set of data to support regulatory objectives, science and the development of new ice crystals awareness system (aircraft on-board weather radar).
1.3.2.2. Darwin – Saint Denis 2016 Flight Tests Campaign
The purpose of the third flight test campaign was:
• To collect cloud data in deep convective clouds with cloud microphysics probes selected by SP1, and thus complement HAIC/HIWC database,
• To validate maturity of mixed phase and glaciated icing conditions awareness and detection technologies developed in the frame of HAIC SP4.
HAIC third Flight test campaign was performed with Airbus flight tests aircraft A340 MSN 1 at Toulouse (validation tests), Darwin (Australia) and Saint Denis (La Reunion). Oceanic conditions were not found in Darwin mainly due to El Niño phenomena occurrence in 2016. This is the reason for change of campaign location from Darwin to St-Denis (La Reunion).
The A340 MSN1 has shown its capacity as a flight test platform for environmental campaign: long range and large payload, good reliability, good agility demonstrated by the quick and efficient relocation from Darwin, Australia to Saint-Denis, La Reunion.
A total of 80 icing encounters have been flown over the 6 flights in high IWC environments. A good coverage of CS-25 Appendix P conditions has been achieved. Microphysical probes showed a satisfactory behaviour and only a few failures were observed, mainly for measurement of larger particles.
Icing Detection and Awareness technologies were evaluated in the ice crystals environment and results had been transmitted to SP4. Satellite retrievals products were also evaluated during the campaign and results were transmitted to SP3. First feedbacks from flight crew are positive and technologies look promising.
1.3.2.3. Atmosphere characterisation and assessment of CS25-Appendix P
A major objective of the HAIC project was to collect atmospheric data allowing for a full characterisation of the dynamical and microphysical properties of high ice water content regions, so that the conditions of formation and maintenance of these regions can be fundamentally understood, and so that current regulations regarding this potential threat to civil aviation can be assessed.
1.3.2.3.1. Atmosphere characterisation
In order to develop a better understanding of physical processes involved in the formation and maintenance of high ice water content conditions, the Falcon 20 aircraft, used during the two HAIC first campaigns, was equipped with state-of-the-art in-situ microphysical probes and a multi-beam airborne Doppler cloud radar.
1.3.2.3.1.1. In-situ measurements
At flight level HAIC project has produced quality-controlled particle size distributions, a detailed knowledge about the statistical relationship between ice crystal size and other properties such as crystal mass, projected area, and fall speed, and derived some crucial bulk microphysical properties such as ice water content, visible extinction, median mass diameter (and other diameter definitions), and number concentration.
The analysis and post-processing of the measurements made during the campaigns allowed to relate high IWC regions with high concentrations of small ice crystals, which is the main hypothesis explaining why these HIWC regions are not detected by the commercial pilot X-band radars, but it also allowed to derive key characteristics of high IWC regions to support rulemaking process.
The algorithms developed to perform analysis of the different in-situ probes were validated at international level thanks to huge collaboration and regular meetings, giving legitimacy to the final dataset released by HAIC project.
1.3.2.3.1.2. Remote sensing
Moving away from the flight-level, it was demonstrated that airborne cloud radar microphysical retrievals, trained using collocated data at flight level can, provide an accurate description of the full vertical profile of microphysical and dynamical properties of high ice water content regions (instantaneously and statistically), which paves the way for detailed studies of the dominant microphysical processes acting along the vertical atmospheric columns in these conditions.
A cloud radar retrieval technique has been developed as part of HAIC to characterise the dynamical and microphysical properties of high ice water content regions. The technique is validated using in-situ measurements of the three wind components and the Isokinetik Probe Total Water Content measurements. Horizontal wind components can be obtained with very little bias, and a standard deviation of the error of 2 ms-1 or better. Vertical air motions, which are an essential piece of the puzzle to understand processes responsible for the formation and maintenance of high ice water content regions, can also be obtained with less than 0.3 m s-1 bias, and a standard deviation of the error that varies with vertical motion itself, but generally remains below 50%, especially for convective drafts (large values). Retrieved water contents are characterized by standard deviations of the error generally less than 30%. This technique allows for the full vertical distribution of the internal dynamics and microphysics of high ice water content regions to be characterised.
1.3.2.3.2. Assessment of CS-25 Appendix P
The datasets collected during international field campaigns (in complement of existing preliminary measurements from Airbus flight tests campaign and HYMEX Megha Tropiques project) are used to assess the CS-25 appendix P: altitude-temperature envelope, TWC values and PSD. This assessment has been made all along the project, and a synthesis is available in project deliverables D71.7.
1.3.2.3.2.1. Altitude – Temperature Envelope
Based on in-service events analysis and review, an extension of proposed envelopes regarding mixed phase and glaciated icing conditions was proposed.
1.3.2.3.2.2. TWC Values
The data gathered during Airbus flight tests, Megha-Tropiques flight tests and HAIC/HIWC Flight Tests Campaigns show that the maximum TWC values encountered are lower than values provided by appendix D curves, and maximum values encountered are close to 75% of these maximum values.
In addition to TWC values to consider, the associated distance scale is to be assessed. Pending on the type of technology, the analysis of reported in-service events highlighted that different sizes of clouds should be considered (one for engines / one for air data probes). Additional post-processing is still required to finally state on these maximum values to consider, regarding IKP reference values analysis. Statistical analysis is on-going at international level to define the 99th percentile for these maximum TWC values. This work is conducted out in the frame of international collaboration and will be handled by an ARAC group. Launch of activities of this group is under process within FAA.
1.3.2.3.2.3. PSD Values
Preliminary analysis of measurements shows a need for revision of CS25 Appendix P with regards to Particle Sizes Distributions as measured MMDs are not in accordance with initial regulation values.
At cold levels, high IWC areas are primarily composed of small ice crystals (200-400 μm), which yield small MMDs around 300μm. As temperature increases, the concentrations of small ice crystals decrease while the concentrations of larger ice crystals (>300μm) increase, resulting in a MMD rise to roughly 500 μm. When the temperature reaches -20°C and then -10°C, there is almost no more decrease in the concentrations of the small sizes but a noticeable increase in the concentrations of particle larger than 1mm.
1.3.3. Space-borne Observation & Nowcasting of High IWC Regions
The detection of High IWC with different space-based techniques has been investigated during the HAIC project. This has been successfully performed through a multiple observational based approach methodology using as reference In-Service events, past Airbus and HAIC field campaigns, and the space-borne DARDAR (raDAR/liDAR) product. This approach aimed at developing, training and evaluating the different SP3 satellite-based products to successfully support the successive HAIC campaigns.
As mentioned above, several satellite-based products have been developed and tools used to detect High IWC and convection like KNMI High IWC mask, the DARDAR product, or RDT (Rapid Development Thunderstorm). These different products and tools should be seen as a first step, first, to replace High IWC in its cloud -environment and development, second, to understand the processes that lead to high IWC and potentially to an In-Service event.
In more detail a High IWC mask (IWC > 1 g/m3) was developed based on cloud properties derived from geostationary MSG SEVIRI measurements during daytime and trained with DARDAR active remote sensing IWC observations. Airborne observations were compared to MSG data for HAIC-2015 (Cayenne) and to HIMAWARI/MSG data for HAIC-2016 (Darwin/La Réunion). Thus several GEO satellites were used to support the HAIC campaigns worldwide. RDT was operated during the three HAIC campaigns. This required the adaptation of the High IWC mask algorithm to HIMAWARI measurements and to the development of several RDT chains with different settings according to the available GEO imagers over the domain of the field campaigns.
RDT is a software developed by Météo-France in the framework of NWCSAF (Satellite Application Facility on support to Nowcasting and Very Short-Range Forecasting). RDT detects, tracks and characterises convective systems. In the framework of the HAIC project, the RDT has been operated by Météo-France during all HAIC field campaigns on an operational basis through dedicated processing chains. The RDT was operated for various satellites and geographical domains: MTSAT for the first HAIC campaign (Darwin, 2014), MSG for the second one (Cayenne, 2015) and Himawari-8 and Meteosat 7 for the last campaign (Darwin/La Réunion, 2016). The first objective of RDT was to detect the convective areas to guide the research planes. Second RDT was used by weather forecasters for ground meteorological support. RDT outputs were also adapted to be up-linked to the research planes thanks to the PLANET system developed by the SME Atmosphere. This innovative development offered to the pilots and aircrew the possibility to assess the actual cloud environment surrounding the research planes. Interestingly the expansion of RDT to new geographical domains and new satellites has clearly made easier and faster the new global coverage version of RDT developed by Météo-France (since 2016).
The real-time SP3 products were delivered to the aircrew and the HOC (HAIC Operation Centre) during the HAIC campaigns. The capability to provide relevant and reliable information to potentially any aircraft and ATM was demonstrated, currently more for a strategic planning (due to the delay of the satellite data delivery to the Users) than for a tactical use. Space-based remote sensing of High IWC definitively appears to be one of the appropriate detection/awareness techniques to enhance flight safety, apart from in-situ and close-range sensitive weather radar detection on-board the aircraft. The different HAIC satellite products were qualified as useful during the campaigns to guide the research aircraft and identify potential targets in the vicinity of the research aircraft. This was confirmed during the two TRL6 reviews with an official feedback from the Users (i.e. the aircrew and HOC members). The High IWC masks were and are still publicly provided in near-real time via msgcpp.knmi.nl and adaguc.knmi.nl while RDT is continuously operated at Météo-France.
The MSG-CPP high IWC mask was extensively validated against independent DARDAR observations. Important sensitivities in the performance of the mask were identified (altitude of the High IWC, solar and viewing zenith angles). The performance of the MSG-CPP high IWC mask was also found to be sensitive to environmental conditions (small scale High IWC variability, size of the High IWC environments). Taking these sensitivities and environmental conditions into account, the probability of detection (POD) is around 90% or better for IWC above 1 g/m3.
Qualitative and quantitative studies of RDT performances against High IWC have provided reasonably good results, especially in terms of probability of detection. RDT reached TRL5. Based on the good performances of RDT assessed during the HAIC project, the last NWCSAF release of RDT (v2016) now includes an attribute describing high IWC risk for any identified convective cell.
The evaluation of the MSG-CPP high IWC mask against 2015 Cayenne campaign data – in situ, remotely sensed by the airborne RASTA radar and on board radar (WXR) – was performed. The evaluation based on RASTA IWC profiles confirmed the findings of the evaluation with DARDAR in terms of the POD of High IWC occurrence.
The HAIC Satellite and Nowcasting team also investigated the cloud systems that lead to In- Service events. A list of In-Service events was provided by Airbus. Four types of cloud system were identified: large tropical convective systems, moving convective lines, young convective clouds (that did not exist few hours before the In-Service event) and high altitude thick clouds apparently not connected to convective clouds during more than 24 hours prior the occurrence of the In-Service event. Amongst the In-Service events provided by Airbus, only nine of them were located within MSG-SEVIRI domain during daytime and High IWC was detected by KNMI High IWC mask algorithm at the location of all these In-Service events.
It should be noted that, although high IWC (IWC > 1 g/m3) is an important condition for the occurrence of In-Service icing events, it is not the only one. Without additional information provided by the aviation industry in the future, a detection of In-Service icing conditions beyond the current detection of High IWC environments as developed in the frame of the HAIC project cannot be achieved.
The HAIC Satellite & Nowcasting team has also explored the spatial and seasonal distributions of High IWC regions worldwide based on DARDAR IWC retrievals (Figure 15). This climatology confirms that High IWC above 8 km height and larger than 1 g/m3 is mainly detected over the tropical band and follows the seasonal regional cloud distribution. The climatology also pinpoints higher High IWC occurrence (< 3%) at typical cruising altitude over continent during the day and over ocean during the night. This provides a first step for a better assessment of the High IWC risk on a regional and seasonal aspect. The High IWC climatology was extended to KNMI High IWC mask during daytime revealing clear spatial patterns, which could be useful in the future for aviation strategic planning purposes,.
Finally the High IWC mask was adapted to LEO (Low Earth Orbit) MODIS (Moderate-Resolution Imaging Spectroradiometer) cloud properties showing overall consistency between the geostationary and polar orbit based masks. The MODIS High IWC mask can be used to generate a high-spatial resolution climatology over the world but also as product to contribute to the verification of the successful implementation of KNMI High IWC mask on other GEO missions. One additional interesting feature that the MODIS High IWC mask algorithm can provide is a better spatial description of High IWC clouds at higher latitude which are much less well described from geostationary.
1.3.4. High IWC Detection & Awareness Technology
1.3.4.1. Ice Crystal Long Range Awareness
One goal of the HAIC project was to provide the appropriate ice crystals awareness technologies for use on-board of commercial aircraft to enhance safety when an aircraft is flying in such weather conditions. Before the project, no dedicated technology based on X-Band Weather Radar was defined.
Two Weather Radar suppliers have been involved in the project: Rockwell-Collins and Honeywell.
Until the key TRL3, both suppliers performed activities as the state of the art of available technologies applicable to glaciated icing conditions detection and analyses of the data collected during previous Airbus flight test campaigns (Chile with Honeywell and Darwin/Cayenne with Rockwell-Collins). Taking as a basis the High level specification for mixed phase and glaciated icing conditions awareness technology as defined in WP42 (D42.3 deliverable), they also presented the basis of their algorithms to meet the main requirements: crew awereness of two level of IWC 80Nm before encounter with a probability of correct annunciation greater than 80%.
For the TRL3, a selection of potential technologies have been presented at TRL reviews:
• Rockwell-Collins presented a solution based on the software upgrade of the current X-Band MultiscanTM, but also double frequency and double polarization radars.
• Honeywell presented only a solution upgrading the current IntuVueTM RDR-4000 X-Band WXR to infer IWC from radar measurements
During the strategic TRL3 review with the Supplier Down selection (March 2014), Honeywell solution has been selected for prototype evaluation during the 2016 F/T campaign. The radar technologies other than X-Band Weather Radar were disregarded, as development of such technologies even if more performing (particle shape/size discrimination) would not have fit within the project timeframe and bring constraints for retrofit (impact on A/C installation, potentially the need of a new Radome...).
For prototype definition, further activities were done as IWC algorithm and HMI definitions:
• As not already existing in standards, a specific HMI for Ice Crystals display has been evaluated and defined after workshops performed Airbus pilots, radar specialists and human factors engineers from December 2014 to September Given the data already displayed (FMS, TCAS targets...) the following HMI was identified compatible with Airbus and already existing Weather Radar display and proposed as reference:
o For High concentration area (>3g/m3): red flakes
o For Low concentration area (between 1 and 3 g/m3): blue flakes
• From TRL3 to TRL5 (October 2015), Honeywell has developed the prototype to be flown during the 2016 Flight Test campaign based on the 3D-Buffer RDR-4000. This software update includes the implementation of a machine-learning algorithm using reflectivity data and other parameters already measured to discriminate area from moderate to high IWC. Data collected during all the flight test campaigns have been used either to train the algorithm or assess the preliminary performances. The HMI as presented in Error! Reference source not found. has also been implemented in the prototype.
The software has been delivered in November after the TRL5 review and tested in Airbus lab until late December. The agreed software has been installed in December 2015 on A340 MSN1 for the campaign in January 2016.
The operational feedback from Airbus pilots during the campaign was positive; depiction of high IWC areas (>3g/m3) was quite accurate up to 80 nm and the HMI was judged stable and comprehensive. However some areas of moderate IWC (<1g/m3) were judged overestimated.
After the campaign, the algorithm has been updated to take into account the feedback (e.g. reduction of undue moderate IWC areas determination). Performance methodology has also been refined to take into account the constraints of comparing Radar data (long range data) with in-situ measurements. Global performances assessed on the available data show good results. Nevertheless, more data of high IWC or at longer ranges (above 40Nm) would be necessary to have the whole envelope coverage with sufficient representativeness.
In parallel, from January 2015 until February 2017, Ice Crystals Awareness function based on Weather Radar has been discussed in international committees (EUROCAE WG95-SG and RTCA SC230). A feasibility report has been written and has been submitted for publication. The main conclusions are that using the reflectivity only does not allow to reach the operational requirements. However by taking into account additional parameters the Ice Crystals long range awareness function is possible. Further activities will be pursued on this function in the frame of the committees. Redaction of a MASPS (Minimum Aviation System Performance Standards) is envisaged to support early system development and prototyping by manufacturers and/or installers who may wish to develop such a system. The MASPS document would also define simulation models and appropriate test and validation strategies.
At the end of the HAIC project, the Honeywell Ice Crystal Weather Radar has reached the TRL6 maturity. However, the topic needs to be now further discussed in international committees to define the appropriate operational envelope, the necessity of the moderate threshold as specified in the D42.3 specification and the proper means for verification/validation before launching a product.
1.3.4.2. Ice crystal detectors
Another goal of the HAIC project was to provide the appropriate ice crystals detection technologies for use on-board of commercial aircraft to enhance safety when an aircraft is flying in such weather conditions. Before the project, no dedicated technology exists for commercial aircraft. Six detection technologies have been involved in the project. Aircraft manufacturers involved in HAIC defined the specification in WP42 for such detectors. Through the 4.5 years of the project, the detection technologies started at TRL2 level and one reached TRL5 level. A downselection was organized at TRL2 and TRL3 steps.
For TRL4 step, wind ice tunnel tests were performed with remaining technologies using SP5 capability improvements and SP1 instruments for comparison. DLR and Zodiac/CNRS-CORIA/VKI/IRSN developed specific prototypes from previous academic setup. These ice wind tunnel tests demonstrated the robustness of some probes, but also the weakness that needed to be solved. For ODIPP technology from DLR, IWT/T results show that the measured IWC of single phase test cases are in good agreement with the reference data. However, de-icing/de-fogging system performance issue was highlighted with high risk on F/T data quality. The robustness of AIIS from Zodiac hardware design in harsh icing conditions has been demonstrated, unfortunately, software algorithm needs to be reworked to prevent image saturation during post-treatment and ensure minimum of performance demonstration. ICD from SEA demonstrated its capability of Ice Crystals Conditions detection and results for discrimination and characterization capabilities in mixed phase and glaciated conditions are promising. Successful TRL4 reviews for NRC and SEA in 2015. Because of algorithm saturation, AIIS did not validate its TRL4 level even if hardware behaves well. For DLR, both hardware and software limitations could not allow a conclusive TRL4 review. New schedule was planned in 2016 for Zodiac and DLR to proceed development.
Three technologies were tested on flight: PDP from NRC, ICD from SEA and AIIS from Zodiac. Unfortunately, AIIS has an ITAR component and was not able to fly in Australia. All three demonstrated their robustness during flights in various conditions: altitude between 30 and 41185 feet, temperature between -54°C and +33 °C, Mach between 0 and 0.85 and Total Water Content between 0 and 4.9 g/m3. 70 encounters of Glaciated and Mixed-Phase conditions for 30 flight hours. Once more, some weaknesses were observed on prototypes and imply design modifications. Coating erosion appeared on PDP due to ice crystals, not seen in tunnel or other flight testing. Modified material was identified as a solution. Several signal losses on ICD were identified as manufacturing default on heated elements and a new inspection process was settled. Solutions are identified to overcome this manufacturing issue. Algorithms already used for IWT/T were refined and last measurement analysis gave good correlations between the TWC results from aircraft instrumentation and the detectors measurementsError! Reference source not found.. All technologies demonstrated their capability to detect ice crystals conditions considering TWC detection threshold and associated response time. More evidences are expected in order to validate liquid, mixed and glaciated phase discrimination and characterization capabilities, however, more liquid and mixed phase reliable data concerning water phase are needed for that purpose (work in progress at CNRS based on 2D-S / FCDP data).
Despite great work performed by Zodiac in 2016 with its new prototype for flight test, AIIS TRL4 review was almost conclusive, mainly due to a lack of evidences concerning the performance assessment, many points being still open. Improvements of ODIPP, mainly focused in algorithm development, were not sufficient for TRL4 step. Within HAIC framework, TRL5 review for NRC PDP was conclusive despite lack of data for liquid and mixed phases. TRL5 for SEA was postponed due do unavailability before HAIC end.
A prototype is available for all four remaining technologies at the end of HAIC. HAIC highlighted the challenge of data post-treatment for optical technologies where all three ones (DANIELA from THALES/NLR, ODIPP from DLR and AIIS from Zodiac/CNRS-CORIA/VKI/IRSN) underestimated the difficulty to identify, measure and discriminate the particles in real time by an automatic algorithm. However, optical technologies seem today to be the only ones able to measure particle size. Further studies will say if this is relevant information for aircraft manufacturers and flight safety. Non optical technologies were in advance at the beginning of the project and potentially at higher TRL and have kept their advance but now need to focus on industrialisation. To reach TRL6, the main challenge now is to go through industrialisation, especially for academic technology developers, which implies finding an industrial partner.
1.3.4.3. Synthesis
Some issues appeared on the way of the project so the initial challenging goal to reach TRL6 was not achieved. Nevertheless, a huge amount of work was performed by WP43 and WP44 partners to come as close as possible of this level in the frame of HAIC. For ice crystals at least, these result give good confidence on the technologies. Now that all technologies reached a good level of performance assessment, it is time for them to go through a new and important step: environment robustness and industrialization processes, which is another challenge. Here is an overview of the maturity level of the various radar and detection technologies:
Technology Maturity at end of HAIC project Comment
Rockwell TRL3 Stopped at TRL3: radar technologies other than X-Band Weather Radar were not compatible of the timeframe of HAIC
Honeywell TRL6 Radar algorithm based on weather radar hardware demonstrated its performance in flight and reached TRL6 with data gathered through Airbus and HAIC flight test campaigns. A HMI solution was developed and tested. More data are required to determine if moderate threshold is necessary and to evaluate high threshold performance at long range (>40Nm).
DANIELA TRL2 Not part of the technology down selection during strategic TRL3
ODIPP TRL3 The ODIPP could not fly on the 2016 flight tests due to de-icing/de-fogging system issue. This led to no significant progress since the NOT CONLUSIVE TRL4 reviews.
AIIS TRL3+ The AIIS was installed on 2016 flight tests and showed good performances.
Actually, the maturity is very close to TRL4, but some icing wind tunnel tests are missing for the performance coverage.
This technology is supported post HAIC project through the CLEANSKY2 ICASSIO project.
ICD TRL4 The ICD was installed on 2016 flight tests. Preliminary report show good performances results.
TRL5 for SEA was postponed due do unavailability before HAIC end.
An industrial partner shall be found to continue the development of this detector beyond HAIC.
PDP TRL5 An industrial partner shall be found to continue the development of this detector beyond HAIC. NRC is looking for it.
1.3.5. High IWC Test Capability Enhancement
1.3.5.1. Definition of specifications and requirements for IWT
From the available data, the existing regulation and the needs of the manufacturers, basic specifications and requirements for the icing wind tunnels have been defined. Some requirements have been considered as essential. This set of requirements was the basis used to design the ice generators developed within the project.
It has been highlighted that, if IWC and MMD are fundamentals parameters, PSD, ice crystal density and particle shape are also important. Comparing the ice particles produced by current ice crystal generators and the natural ice crystals, the gap was mainly on these latter parameters.
1.3.5.2. Development of ice crystal and mixed phase capabilities in four facilities
Among the four facilities involved, two, GKN and ESTERLINE, were already able to generate ice crystals and mixed phase conditions at sea level, one, DGA, able to generate small ice crystals in altitude and the last one, TUBS, was not operational.
The strategy was to improve the current ice generators at GKN and ESTERLINE and to develop new ice crystal generators at TUBS and DGA (see Table 5).
GKN has redesigned its ice crystal generator to be able to produce smaller MVD for higher IWC.
ESTERLINE has extended the temperature operating envelope down to -60 °C for all velocity conditions by upgrading the cooling system of its facility. The ice crystal has been modified to increase of IWC capability.
DGA developed a new ice crystal generator to increase of MMD of the ice crystals and IWC capability.
TUBS, which is a new facility, developed an innovative ice crystals generator able to ice crystals with shapes close to natural ones.
1.3.5.3. Calibration
1.3.5.3.1. Methodology
The objective was to define of a common HAIC calibration methodology. This methodology has been shared with other worldwide facility owners and international working group (SAE). It could be as a basis to update the SAE ARP 5905.
The acceptance criteria are derived from the SAE ARP 5905. Some parameters and thresholds have been modified to take into account the specificities of the glaciated icing conditions.
1.3.5.3.2. Instrumentation
Two new probes have been selected as reference instrumentation for the calibration: the isokinetic probe from Cranfield University for TWC measurements and the High Speed Imaging probe for the particle size distribution and MMD measurements. Tests performed at GKN and DGA has been used to assess the performance of the probes.
1.3.5.4. Calibration tests
After the upgrading phase, all the facilities have been calibrated with the reference instrumentation.
1.3.5.5. Tests
A set of tests have been performed to assess the ice detectors developed within SP4, to intercompare F/T and W/T instrumentation for SP1 and to initiate a database for the validation of the code from SP6.
1.3.5.5.1. Assessment of ice crystal detectors
The detectors developed within SP4 have been tested at GKN and ESTERLINE. The results have been useful to assess the detectors and select those that could be used for flight test campaigns.
1.3.5.5.2. Instrumentation intercomparison
The HAIC intercomparison tests have been performed within a two-week test campaign at the TU Braunschweig Icing Wind Tunnel in August/September 2016. Three canister probes (CNRS-2DS, DLR-2DS and Artium HSI) have been mounted subsequently inside the test section and exposed to various ice cloud conditions. The test matrix and schedule had been agreed in advance by all involved HAIC partners (CIRA,CNRS-LAMP,DLR). Beside the canister probes, two modular probes (PDI and HSI) have been mounted externally on a mobile framework. Both probes allow to better cross-compare the canister probe measurements. Adaptor windows have been designed and manufactured by TUBS staff to precisely align the measurement volumes of all probes. Two TUBS engineers have supported the guest scientists by wind tunnel operation and general assistance.
1.3.5.5.2.1. PSD instrumentation
As discussed above, three canister and two modular probes have been mounted inside the wind tunnel test section to perform PSD measurements. Measurements have been taken at 16 different ice cloud conditions (supercooled droplets, mixed phase and glaciated clouds) for each probe. Prior to the tests, airflow measurements have been made by means of a CIRA Prandtl-probe. The tests have shown that the air speed inside the test volume is not influenced by blockage effects of the canister probes. Laser beams of modular HSI and PDI cross in front of the HSI probe volume. All three measurement volumes are aligned very precisely adjacent to each other.
1.3.5.5.2.2. TWC instrumentation
TWC instrumentation inter-comparison tests have been carried out at DGA. The selected airborne TWC probe tested was the Robust probe. The measurements were compared with the Cranfield IKP results done during the calibration. Data agreed within a maximum discrepancy of about 20 %.
1.3.5.5.3. Numerical code validation
1.3.5.5.3.1. 2D tests
Within the scope of HAIC WP5.5 experimental tests on ice crystal icing have been performed at the TU Braunschweig Icing Wind tunnel. The tests have been performed at various mixed phase cloud conditions at wet bulb temperatures up to the freezing point. As test articles a cylinder and a NACA0012 airfoil model have been designed and manufactured. Both test models are equipped with internal temperature sensors and heat foils.
The temperature sensors allow to monitor the local surface temperatures during the icing process. Heat introduction to the substrate can be simulated by switching on the internal heat foils. While tests with internal heat supply have been part of the experiments, the main focus had been set on ice accretion growth of not heated test bodies. This report explains the experimental procedure and sums up the results of the validation tests.
The tests results give new insight in the physics of ice crystal icing at mixed phase conditions. Further, the results are used to validate the ONERA icing code IGLOO2D and will also be included into an international benchmark of icing test cases.
1.3.5.5.3.2. 3D tests
Tests on a pitot probe have been performed at DGA to collect data in order to build a database for code validation. The probe was equipped with thermocouples and de-icing could be adjusted to get several thermal conditions. Pictures have been collected by ONERA to see the impact and the possible shattering of the ice crystals to the tip of the probe.
1.3.6. High IWC Tools & Simulation Development
1.3.6.1. Experimental investigation of ice crystal icing physics
A summary of the main experiments performed throughout the HAIC project in SP6 “High IWC Tools & Simulation Development” is given, outlining their variety, the physical insight gained through these experiments, the data which is now available for further model development and validation, and the remaining gaps left to close in future work. These experiments were designed specifically to allow refinements to be made to three key models in predicting ice crystal icing:
• Trajectory models,
• Impact models,
• Accretion models.
Trajectory Experiments
These experiments were performed largely by TUD and were concerned primarily with the question of how the non-sphericity of ice crystals might affect their ability to follow flow accelerations. Furthermore, it was not clear at the beginning, whether rotation of the particle would be significant in defining particle trajectory.
Two experiments were performed; one designed to measure drag coefficients of irregular particles and one used as validation data for accompanying simulations. Prior to the design of experiments, data was collected from partners within the HAIC consortium on expected size and density ranges of high altitude ice crystals, and, while this data was only preliminary at the start of the project, the values were subsequently proven to be reasonable.
The first experiment, capable of measuring the drag coefficient consisted of model particles falling or rising in a fluid column. By adjusting the density difference between particle and fluid, the realized particle velocity could be adjusted to attain Reynolds numbers expected under flight conditions. These all lie below 1000 and typically much lower. Numerical Euler-Lagrange simulations of spherical particles impinging onto various bodies (ONERA), for which drag coefficients are well known, confirmed this. The velocity of the particles was measured from high-speed video sequences from the segments in which the velocity was constant. Knowing the densities; hence the acting buoyancy forces, the drag force could be computed.
A large variety of non-spherical particles were examined and the measured drag coefficients were compared with numerous empirical correlations available in the literature, exhibiting varying degrees of complexity in describing particle shape. The correlation proposed by Ganser (1993) was the most appropriate for the available data set. For more complex particles, for example, capped cylinders, the correlation could be improved by considering the dimensions of the volume enclosing the particle, rather than the exact particle shape, in computing the shape parameters required in the correlation. One of the experiment consisted of a vertical wind tunnel, a target bluff body and an upstream particle injection. The particle trajectory in the vicinity of the target body was captured using high-speed video. The purpose of this experiment was to provide validation data for numerical simulations of particle trajectory. The trajectory, together with particle specifications, was documented in the form of tabulated coordinates in time. A further experiment was performed by AGI to investigate the melting of ice crystals under forced convection, since this occurs when ice crystals are ingested into warm parts of turbines. Existing correlations for Nusselt numbers are not applicable to highly non-spherical particles. In this experiment, ice crystals were held in an acoustic levitator and a warm airflow was directed over the particle. The melting process could be observed visually, from which heat transfer data could be deduced
Impact Experiments
Several experiments were performed with ice crystals, some concentrating on single crystal impact (AGI) others on accretion phenomena (AGI, TSAGI). The purpose of these experiments was manifold, ranging from first observation of physical phenomena to detailed data collection for model formulation. The influence of liquid film on the impact surface was also investigated. At AGI the experiments were performed in the icing and contamination research wind tunnel (iCORE).
First observations confirmed that accretion was negligible when ice crystals impacted onto cold surfaces. However, under mixed glaciated conditions or with warm surfaces, accretion immediately began, supporting the hypothesis that a liquid water content is essential to initiate accretion. This can come either from partial melting from the ice crystal before impact, or melting of fragments on a warm surface. This result emphasized the need for fragmentation models of impacting ice crystals.
Experiments were therefore performed to support fragmentation model formulation. Fragmentation was classified as no fragmentation, minor fragmentation, major fragmentation and catastrophic fragmentation.
A further series of experiments were performed in the iCORE facility at AGI in which ice crystal impact onto a thin water film was observed. The aim is to quantify the probability of sticking, bouncing and fragmentation. Typical results from this study in which the occurrences of no fragmentation and fragmentation for different intervals of film thickness (H/D0) are given. The tendency is clear: the thicker the water film, the more viscous and capillary forcers slow down the ice particle before impact onto the target and the higher the probability of no fragmentation. Modelling this complex phenomenon is clearly an important future task to properly predict onset of accretion.
Accretion Experiments
Experimental investigations on run-back ice formation on a heated wing airfoil model were conducted in TSAGI’s small icing wind tunnel, under ice crystal icing conditions, in the cases of presence and absence of artificially created liquid film on the model surface. The objective of the work was to investigate run-back ice growth rate for different operating conditions (in terms of air velocity, air temperature, leading edge wall temperature, ice crystal size, etc.) in order to improve our physical knowledge of ice crystal accretion on a heated surface and to get data for model calibration and validation. During the tests, the ice formation process was visually observed and video recorded. Operating conditions as well as the formed run-back ice mass were registered.The most interesting outcome of these experiments was the indirect measurement of the sticking efficiency. Without liquid water on the model surface, the sticking efficiency was found to be very low (never greater than 2%) whatever the operating conditions. But when a thin liquid film was present on the leading edge of the model (with a thickness of a few tens of microns), the sticking efficiency was found to be much higher, sometimes rising up to 30% (for the lowest air flow velocity).
1.3.6.2. Models and tools development and integration into industrial environment
1.3.6.2.1. Development of ice crystal icing models
As far as particle trajectory phenomena are concerned, the main difficulty was to take into account the influence of ice crystal non-spherical shapes on their interactions with the carrying air-flow (drag force, heat and mass exchange). The solution that was chosen consists of using global geometrical descriptors (equivalent volume diameter, sphericity, cross-wise sphericity, etc...) in the modified expression of the drag coefficient, Nusselt number and Sherwood number.
For impact and accretion phenomena, the microphysical mechanisms are very complex and, until the HAIC project, there were very few attempts in the literature to address their modeling. In SP6, two complementary approaches were followed:
• TUD and TSAGI focused on some specific aspects of the whole problem (impact regime thresholds, heat and mass transfers inside the accreted porous ice layer, run-back liquid film) and developed theoretically based models by combining analytical methods, DNS tools and experimental results.
• CIRA and ONERA chose to develop a comprehensive set of models (for sticking efficiency, secondary particle properties, accretion, erosion, etc ...) by employing a phenomenological approach based on empiricism and simplifying assumptions.
TUD and AGI experimental results (section 1.3.6.1 Experimental investigation of ice crystal icing physics) have been extensively used for model calibration (determination the model empirical parameters) and for model elementary validation (ice particle drag coefficient, melting time, etc.) .
1.3.6.2.2. Implementation in numerical tools and integration in industrial environment.
In HAIC SP6, all the models were mainly implemented and tested in 2D research tools, excepted for ice crystal trajectory models which were also implemented in the ONERA (Lagrangian and Eulerian), CIRA (Eulerian) and UTWENTE (Eulerian) 3D trajectory solvers. Important developments have been performed in all the tools to enable the implementation of the new ice crystal models.
• Starting from existing bricks, a new dedicated 2D ice crystal icing tool has been developed by TUD in the framework of D. Kintea’s PhD thesis.
• Deep modifications have been introduced in CIRA, UTWENTE and ONERA Eulerian trajectory solvers to take into account phase change phenomena and secondary particle re-emission (multi-bins methods)
• Iterative algorithms have been implemented in all 2D accretion solvers in order to take into account the coupling between accretion, impact and erosion phenomena.
ONERA 2D tool was successfully implemented in the industrial environments of SNECMA, AIRBUS and DASSAV. TAI implemented HAIC models into its in-house 2D icing tool. THAV improved its in-house probe-dedicated tool by using some outcomes of HAIC SP6 and ONERA support. PAI worked with CIRA to integrate CIRA’s icing tool in their environment.
ONERA 3D Lagrangian trajectory solver (SPARTE) being already used by SAFRAN before HAIC project, the integration of the updated version of SPARTE in SAFRAN environment did not encounter any difficulty. To date, the integration of ONERA 3D tool in AIRBUS environment is still in progress. Due to some technical difficulties, its installation on AIRBUS platform failed. As far as DASSAV is concerned, they preferred to focus on the integration and validation of ONERA2D tool in their environment.
1.3.6.3. Numerical tool validation
Validation was mostly limited to 2D tools. Model predictions were compared to experimental results issued from HAIC experiments (TSAGI heated wall accretion experiment, TUBS SP5 mixed phase ice accretion experiments) and from the literature (NRC and NASA-NRC accretion experiments mainly).
Even if there are still some discrepencies between the numerical results and the experimental ones, the agreement is generally good showing that the HAIC models are at least able to reproduce the main tendencies which are observed in the experiments. However a large part of empiriscm being involved in the elaboration of some models (sticking efficiency, erosion rate), their validity range is still an open question.
As far as 3D tools are concerned, real validation test cases have not been performed yet. In HAIC, 3D simulations have been carried out using ONERA 3D tool (CEDRE code) to simulate ice crystal trajectories in a turbofan engine and in the vicinity of an aircraft nose. However, these simulations were only aimed to prove the feasibility of such computations since result analysis was only qualitative.
1.3.6.4. Main achievements and way forward
Thanks to the work performed from the beginning in the HAIC SP6, a significant progress has been made beyond the state of the art:
• Several experiments have been carried out to improve our understanding and theoretical knowledge of the elementary physical processes which are involved in ice crystal icing phenomena: investigation of individual ice crystal impact onto a wall, individual ice crystal melting experiments, heated wall accretion experiments, observation and recording of non-spherical particle trajectories around an obstacle.
• A first comprehensive set of models has been developed, implemented in several European icing tools (mainly 2D) and partially validated against experimental results.
• Numerous validations and code cross-checking have been performed, showing the high potentiality of the new models and the feasibility of complex 3D simulations for representative configurations (engines, probe installation factors).
However, despite these major breakthroughs, some of the microphysical phenomena are not yet sufficiently understood (e.g. the most relevant physical dimensionless parameters are not identified) and data is still missing to cover the entire operating range (e.g. size, speed, temperature, melting ratio). New parametric experimental studies are still necessary to:
• better characterize ice crystal impact phenomena in terms of sticking efficiency and secondary particle properties,
• better identify relevant influencing parameters for ice erosion and quantify ice erosion rate,
• better understand and quantify the influence of wall heat transfers on ice accretion process
As far as impact and accretion models are concerned, HAIC models are not fully satisfactory. Most of them involve considerable empiricism and their calibration and validation so far was based on a limited dataset. In future work, attempts will have to be made to reduce model empiricism by employing relevant dimensionless physical numbers and improving our physical understanding of the underlying physical phenomena.
1.3.7. Coordination and Standardisation activities
Within the HAIC project, a huge effort was performed on the coordination activities. Technical activites had to be aligned among the 39 partners of the project, in order to reach common goals. This was particularly performed through formal project management with regular alignment meetings, but also through formal TRL process applied on the developed technologies.
One of the best examples of coordination is the management of the three HAIC flight test campaigns. These campaigns were the successful result of cooperation between multiple entities (airframers, engine manufacturers, equipment & system suppliers, research institutes and academics, meteorological services and SME’s able to provide specific knowledge, service, or support in specific areas) and even of international collaboration between the HAIC, EASA-HighIWC, ICC and HIWC projects for two of them. The 2015 Cayenne campaign even involved the coordination of three aircraft flying at the same time in the same area: the SAFIRE Falcon20, the NRC Convair 580 and the Honeywell B757 aircraft. This allowed comparison of in-situ measurements with remote measurements and also screening of different altitudes of the same cloud in the same period of time.
The handling of the flight test data and their analysis were also coordinated at international level between HAIC and HIWC projects through regular meetings, phone calls and HAIC-HIWC Science Team Meetings.
One objective of the HAIC project was to assess the proposed mixed phase and glaciated icing environment as defined in Appendix D of FAR 14 part 33 and P of CS-25 in light of the analysis of the available flight datasets (flights performed before and as part of the HAIC project), and provide appropriate recommendations to regulatory bodies.
At the end of HAIC project, a status of the Appendix D and P assessment was performed. Based on in-service events analysis and review, an extension of proposed envelopes regarding mixed phase and glaciated icing conditions was proposed. It also seems that different sizes of clouds should be considered depending on the type of technology (one for engines / one for air data probes). Considering the flight test measurements, Appendices D and P also seem to overestimate the real maximum TWC values, and it seems needed to revise the PSDs.
Additional post-processing is still required to finally state on the final recommendations. Statistical analysis is on-going at international level. At European level, this work is supported by the already running EASA HighIWC SC03 project. At US level, an FAA report will be issued mid of 2017, an AIAA group will cover the MoC and an ARAC Group will be created to amend Appendix D. International collaboration will be maintained on these topics, in order to keep a good harmonisation level of international regulations, which is key for aeronautical industrial actors.
Potential Impact:
1.4. POTENTIAL IMPACT AND THE MAIN DISSEMINATION ACTIVITIES AND EXPLOITATION OF RESULTS
1.4.1. Contribution of SP1 activities to the main expected impacts from HAIC
1.4.1.1. Contributions from measurements in continental convection to the main expected impacts from HAIC
We have investigated the dependence of the height of the level of freezing (occurrence of mixed phase clouds) in growing convective cumulus and the surrounding pollution conditions and their effects on the vertical evolution of cloud droplet size, aspherical fraction, as well as LWC. For this purpose we have used in-situ data of size distributions measured with scattering cloud probes mounted on HALO (High Altitude and Long Range Research Aircraft) during the ACRIDICON-CHUVA campaign, which took place over the Amazon during September 2014.
The level of freezing is here named the altitude region where LWC decreases and the aspherical fraction of small particles increases with altitude due to collision coalescence and freezing of droplets.
The results show that the level of freezing increases with increasing aerosol loadings. Also the formation of ice particles takes place at higher altitudes in clouds in polluted conditions, because the resulting smaller cloud droplets freeze at colder temperatures compared to the larger drops in the unpolluted cases. The altitude range where mixed phase clouds exist are higher over continental polluted conditions.
1.4.1.1.1. Impact
Our findings suggest implications of aerosol concentrations on the altitude and microphysical properties of glaciated clouds which may affect the IWC above polluted continental versus clean marine conditions as mainly probed during the HAIC project. Smaller, numerous ice crystals as observed in this continental convection may lead to a lower detection rate by commercial aircraft radars and therefore to a higher risk of flying into glaciated clouds impacting aircraft turbine operations.
1.4.1.1.2. Recommendation and the way forward
Regarding these new findings the impact of pollution on the microphysical properties of glaciated clouds needs further investigation. Dedicated flight campaigns sampling in convective systems over polluted and clean inflow regions are needed to enhance our understanding of the environmental conditions, e.g. aerosol loading and updraft velocities, forming regions of high IWC. A relationship between cloud base droplet concentration and anvil IWC at different temperatures are important information for aircraft operators and can be used to better prognose regions with enhanced IWC in order to enhance aircraft safety. This could be implemented in models for safety regulations.
1.4.1.1.3. Impact on aviation industries and authorities
Enhanced aerosol concentration near tropical Mega-Cities and in polluted regions may enhance droplet concentration, the altitude of mixed phase cloud occurrence and alter IWC in convective systems near e.g. airports or routes with high traffic loads. This may particularly affect low-level flying aircraft and aircraft during take-off and landing. Information on the type of convective inflow may therefore be important indicators for pilots to reduce encounters of polluted convective clouds.
1.4.1.1.4. Impact and recommendation for wind tunnel facilities
General significant progress has been made in enhancing the capacities of European wind tunnels to produce defined icing conditions. While a first and large step has been made within HAIC, further action is needed to extend the experiment range to larger particles and mixed phase conditions and augment the stability of ice delivery to the experimental test sections in European wind tunnels beyond HAIC. This will help aviation industry to test specific parts and to enhance knowledge on aircraft icing in high ice water content regions beyond HAIC.
1.4.2. Contribution of SP2 activities to the main expected impacts from HAIC
Flight tests are a key aspect of HAIC project and thanks to the successful three flight tests campaigns that were conducted in the frame of its activities, SP2 has largely contributed to expected impacts from HAIC, as described hereafter.
1.4.2.1. Characterisation of high ice water content environments
In 2004 the Engine Harmonisation Working Group (EHWG), an international committee composed of airframe manufacturers, engine manufacturers, regulating authorities, and other government agencies was assembled to study the effect of a proposed extension of icing envelopes for supercooled large drops on engine icing certification. In the process of their investigations, approximately 100 engine events thought to be related to mixed phase or ice crystals conditions were investigated.
Many of these events were in the vicinity of deep convection. The EHWG concluded that the engine power loss events were caused by a previously unrecognised form of icing inside the engine that did not require the presence of atmospheric supercooled liquid water, and was largely due to ingestion of high mass concentration of ice particles. The EHWG identified flight test research of high IWC environments as a first-order priority, and specifically, to collect accurate information on the threat of high IWC in and around deep convective clouds, as well as information on the characteristic size of the particles in these clouds.
Darwin and Cayenne Flight Tests Campaigns, organised and conducted in the frame of HAIC SP2 project have allowed the establishment of an unprecedented database with regards to ice crystals (glaciated) icing conditions. This unique and complete dataset paves the way towards update of CS25 Appendix P regulation and is used as a reference at international level for the characterisation of high ice water content environments.
1.4.2.2. Development of acceptable Means of Compliance (test facilities and numerical tools)
The development of acceptable means of compliance is key for the future of aeronautical industries as they are required to demonstrate compliance with new requirements of new regulations.
The SP2 flight tests subproject of HAIC supported the development of acceptable means of compliance (test facilities and numerical tools) through its very good flight tests results. Indeed, the characterisation of ice crystals icing conditions allowed to derive the requirements for ice generation technologies developed as part of SP5 and to be fitted in test facilities. The flight conditions during encounters were also recorded to specify the operational envelope for these test facilities.
1.4.2.3. Improvement of aircraft operation in mixed phase and glaciated icing conditions
The third flight tests campaign conducted as part of HAIC SP2 activities allowed to test new ice detection and awareness technologies that should be fitted on aircraft in the future.
These new technologies will improve aircraft operation in mixed phase and glaciated icing conditions: new ice detection technologies will allow to alert the crew about the presence of these particular icing conditions and will allow the activation of dedicated protection devices when needed, when the future awareness system, based on current on-board weather radar technology, will allow to alert the crew, in advance of the presence of ice crystals icing conditions, so that they can adapt their flight path in advance.
Combination of these two technologies will improve aircraft operation, and the flight tests campaigns allowed to demonstrate the performance of the proposed and developed concepts.
1.4.2.4. Enhancement of understanding of near icing or icing conditions at high altitude
Conducting flight tests in high IWC environment have enhanced the understanding of near icing or icing conditions at high altitude, with regards to the understanding of the environment and of the structure of mesoscale convective systems in which these particular conditions exists.
The different measurements have enhanced the knowledge on the shape and sizes of particles present at these high levels of atmosphere, as well as the existing concentrations of water. These two pieces of information (size and concentration) are keys for modelling and reproduction of the ice accretion phenomenon on Aircraft systems.
1.4.2.5. Enhancement of measurement capacities
Instrumentation developed as part of SP1 has also been successfully flight tested during the three flight tests campaigns conducted as part of SP2. These flight tests supported the development and enhancement of these probes by identifying areas for improvements and giving feedback on behaviours of the probes in high ice water content area.
These measurement capacities can be used either on flight tests aircraft to measure atmosphere or in icing wind tunnels to perform calibration of the tunnel and measure the tested conditions.
1.4.2.6. Enhancement of modelling capacities
During the last campaign of the HAIC project, conducted in 2016 out of Darwin (Australia) and Saint Denis (La Reunion – France), two identical sensors were installed at different locations on the Aircraft skin to provide validation data for ice particles trajectory models developed in the framework of SP6. These results contribute to enhance the modelling capacities of the ice accretion phenomenon.
Moreover, the measurements made during the two first flight tests campaigns are shared at international level and are supporting the development of cloud resolving models, and thus helping contribute to enhance the cloud modelling. This activity on cloud modelling is mainly conducted by NASA partners beyond HAIC project.
1.4.2.7. Reduction of the risk of incidents when an aircraft is flying in such weather conditions
The experience and understanding of ice crystals icing conditions is helping in reducing the risk of incidents when an aircraft is flying in such weather conditions, as it will support the elaboration of adequate pilot’s training and advertising of these conditions in airlines’ community.
In this aim, videos of the environment were performed and are provided to Aircraft manufacturers members of HAIC project to support the elaboration of pilots’ trainings.
1.4.2.8. Development of cooperation with international working groups and with North America
Darwin and Cayenne field campaigns are the result of an international collaboration in between HAIC and HIWC projects and involves necessary expertise in a wide range of skills (airframers, engine manufacturers, equipment & systems suppliers, research institutes and academics, meteorology services and SME’s able to provide specific knowledge, service, or support in specific areas) and the main stakeholders in the field, whether they are based in Europe, North America or Australia.
All this cooperation was coordinated by SP2 of HAIC and cooperation between all regulatory and research agencies have been increased. Regular meetings have been organised to keep international partners posted of the latest progress made and share knowledge and latest findings.
1.4.3. Contribution of SP3 activities to the main expected impacts from HAIC
New capability for remote sensing detection of High IWC from space have been developed and validated to support strategic operations. Indeed a near-real time high IWC mask was developed based on daytime geostationary satellite data. This new satellite product definitively appears to be valuable to increase the awareness of high IWC environments, thus enhancing aviation safety. Its implementation for a display in the cockpit is rather straightforward. There is a current limitation for tactical operations due to the timeline between the satellite observations and the users, which is outside the responsibility of the HAIC project as it depends of the space agencies, on the way the space-based instruments operate and the applied data transferred strategy as well. Combined with RDT capability in tracking and characterising the temporal and spatial evolution of the convective cells over a large domain, this product should provide a first global operational view of High IWC worldwide. We remind that the new version of RDT will have the algorithm of the High IWC mask implemented and will be used to characterise the properties of the convective cells all along their lives.
The products developed within SP3 provide new input data for a better understanding on the meteorology and physical processes and/or validation of the hypothesis on High IWC formation. Indeed the satellite products allow discriminating in the cloud regions with different properties. During the HAIC project, the activities performed within SP3 mainly focussed on the detection of the High IWC. Now that the SP3 team has developed and validated some detection tools, those tools should be used to explore the temporal and spatial evolution of the parent clouds to assess some first order properties on the dynamics and the cloud microphysics. Comparison with numerical cloud simulations should also help investigating the physical processes of High IWC formation. A model-to-satellite approach would be applied to validate the cloud simulations by comparing simulated satellite signals of the modelled cloud profiles (through radiative transfer calculations) to concurrent satellite observations.
Climatology of high IWC was for the first time generated based on DARDAR data and based on the High IWC mask revealing the existence of High IWC at flight altitude and clear spatial patterns as well, which could be useful in the future for aviation strategic planning purposes. This climatology will be improved in the years to come thanks to the new or upcoming geostationary satellites that operate similar sensors as SEVIRI on MSG, but also thanks to LEO missions like the EarthCARE mission with its lidar and radar instrument package.
The SP3 team has been presenting its main results in front of the HAIC consortium and has been collaborating with different European Academics and Industries operating in different fields (satellite, weather, telecommunication, aeronautic). During the last 3 years, the SP3 team has collaborated with North American groups (NCAR, NASA, ECCC) of the HIWC project and exchanged scientific ideas, discussed on fair verification methodology and started discussing on way to promote HAIC-HIWC current results through a white paper and an overview paper summarizing the main discussions on Satellite and Nowcasting hold during successive HAIC-HIWC Science Meetings.
1.4.4. Contribution of SP4 activities to the main expected impacts from HAIC
Before the launch of HAIC, no ice crystal detector neither radar was available for commercial flights. Some European suppliers and academic teams had ideas of concepts on detection and awareness technologies. Some American academic teams started similar activities few years before and had more mature concepts of products. HAIC SP4 contributed in accelerating those products development, bringing together technology suppliers and airframers. Within the projet, aircraft manufacturers defined a common specification for ice and icing condition detection and awareness functions. In parallel, several contributors of SP4 as part of EUROCAE WG 95 updated the ED103 MOPS for detection technologies or write the feasibility report for Ice Crystals long range awareness function. This gave all suppliers a clear framework and targets, validated at international level.
HAIC enables detection technologies proceeding after TRL3 to be tested in the icing wind tunnels upgraded in SP5. These tests showed the performances of the prototypes that enable to identify some issues that implied modifications. In parallel, radar technologies used past flight campaign data to assess the algorithm development. Pilots were involved in defining a proposal for HMI that was assessed stable and comprehensive. The third flight test campaign conducted as part of HAIC SP2 activities gave the opportunity to flight test all detection and awareness technologies mature enough, and to compare results with research instrumentation. New prototypes were built for this purpose. All this worked and the campaign results gave good confidence that the technologies are promising and could be fitted on aircraft in the future. Now, detection technologies need to go through industrialisation process what will take some years of work. Radar software solution was judged mature but would require further activities (e.g. thresholds validation, performance assessment methodology) before implementing it on an Airbus aircraft or retrofiting it on in-service aircraft.
These new technologies will improve aircraft operation in mixed phase and glaciated icing conditions:
• new ice detection technologies will allow to alert the crew about the presence of these particular icing conditions and allow the activation of dedicated protection devices when needed,
• future awareness system, based on current on-board weather radar technology, will allow to alert the crew of the presence of ice crystals icing conditions in front of the aircraft, and so to adapt their flight path in advance.
1.4.5. Contribution of SP5 activities to the main expected impacts from HAIC
In SP5, four icing facilities have been enhanced to be able to produce glaciated and mixed phase icing conditions on wide range of speed, temperature and altitude in compliance with the requirements of the regulation and the specifications of the aircraft, engine and air data probe manufacturers. The objective was to develop these facilities in order to have experimental acceptable means of compliance that could be used for the certification of equipment like air data probes or detectors and useful tools for the validation of the numerical code, the understanding of the icing phenomena and the assessment of the technologies.
Icing facilities contributed to the development and the selection of the detection technologies developed in SP4 providing experimental data to assess their maturity before implementing them on aircraft for flight tests. They also participated to the inter-comparison of the wind tunnel and flight instrumentations from SP1 to check their consistency. Finally, icing facilities were used to build an experimental database in order to validate the numerical code developed in SP5.
One major objective of SP5 was to define a common methodology for the calibration of the facilities involved in the HAIC project. The methodology proposed includes the calibration process, the parameters to be measured and their acceptance criteria, the possible instrumentation recommended for calibration and a cross-comparison test procedure to check the consistency of the simulated test conditions of a facility after some modification or from one facility to another. This methodology has been shared with other facilities from North America to initiate discussions with the SAE icing committee AC-9C about the updating of the recommendation ARP5905.
1.4.6. Contribution of SP6 activities to the main expected impacts from HAIC
1.4.6.1. Enhancement of modelling capacities
The work performed in HAIC/SP6 allowed to strongly enhance the modelling capababilities related to ice crystal icing. Based on original dedicated laboratory experiments and as well on some published experimental results (mainly from CNRC and NASA), a first comprehensive set of models has been developed for crystal trajectories (dynamics, heat exchange with the air and phase change), crystal impact phenomena (impact regime thresholds, secondary particle characteristics), and ice accretion phenomena (sticking efficiency, freezing fraction, erosion rate, heat transfers, etc). Even if some of these models involve a large part of empiricism and if their calibration and validation were so far based on a limited dataset, these models represent a major progress beyond the state of the art compared to what was existing at the beginning of HAIC project.
1.4.6.2. Development of numerical tools as acceptable Means of Compliance
The overall objective of HAIC/SP6 was to provide the European industry with validated numerical tools which could be used as cost effective means to reduce the need for testing during the development phase and certification phase of new aircraft products (mainly probes and engines).
Thanks to the work performed in HAIC/SP6 a first generation of Ice Crystal Icing (ICI) simulation tools has been developed and integrated in several industrial environements. As far as 2D tools are concerned, the ONERA 2D icing suite (IGLOO2D) has been successfully integrated and tested in AIRBUS, SAFRAN and DASSAV’s environment. Piaggio Aero worked with CIRA in order to assess CIRA’s 2D icing tool. TAI chose to directly implement HAIC models in their own in-house icing tool. Even if these 2D tools have a limited use for industrial purposes (especially for engine and probe design and certification), they represent an essential milestone on the route to the development of validated 3D tools.
As far as 3D tools are concerned their development and validation were much more limited than for the 2D case. To date, ICI models have only been fully implemented and tested in ONERA 3D Lagrangian trajectory solver and in THALES in-house tool (2.5D dedicated tool for probe icing simulation). Validations have been performed (especially by SAFRAN and THALES) showing a correct qualtitative behavior of the codes and proving the feasibility of complex representative numerical simulations. However 3D tools still need to be further developed and validated before they could be used as acceptable means of compliance (AMC).
To sum up, even if the original overall objective was not reached, HAIC/SP6 has paved the way to make numerical tools usable by industry as an acceptable means of compliance for certification.
1.4.6.3. Development of cooperation with international working groups and with North America
A successful international cooperation has been initiated in HAIC/SP6 with NASA and CNRC. This cooperation was made possible thanks to the active participation of HAIC/SP6 researchers to the main international conferences dedicated to in-flight icing (AIAA conferences in 2014 and 2016 and SAE conference in 2015) for which the attendance of North-America researchers and engineers is always very important. There were also intense exchanges between NASA, CNRC and European reserachers during the “models & tools” sessions of the two HAIC public forums.
Thanks to the work performed in HAIC and the numerous publications and international communications, several European researchers are now considered as ICI experts by the international community and the collaboration with North-America should continue after HAIC project.
In parallel of the collaboration with NASA icing branch and CNRC, another international cooperation has been put in place through the involvement of HAIC/SP6 researchers (from TUD, AGI, UTWENTE and ONERA) in the Engine Icing Working Group (EIWG). Several HAIC researchers were invited to make a presentation of their main results and to participate to a round table during workshops and to participate to international teleconferences. EIWG is still active and several European researchers involved in HAIC/SP6 are now members of this working group.
1.4.6.4. Strengthening of the European aeronautic industry competitiveness
By accelerating certification and dramatically reducing costs, numerical simulation is a strong contributor to the industrial competitiveness, as well as to the reputation of manufacturers as it also helps mastering the development agenda.
By providing a first 2D ICI numerical capability in industrial environment and as well, but to a lesser extent, a first 3D capability, HAIC enabled to strengthen the European aeronautic industry competitiveness and to reduce its dependency on large ground testing facility (like the NASA PSL facility) which does not exist in Europe.
1.4.7. Main dissemination activities
HAIC communicated with the aeronautical community as a whole using means such as conference presentations (including 6th AIAA Atmospheric and Space Environments Conference, SAE 2015 International Conference on Icing of Aircraft, Engines, and Structures, and HAIC Forums), articles, press releases, newsletters, and the public website (www.haic.eu).
Many scientific papers were published during the course of the project (208 publications in conference proceedings and 49 publications in peer-reviewed journals). Leaflets and posters were displayed on various occasions and the project had a stand during the AeroDays in October 2015. The project also continuously liaised with international experts in particular through the HAIC Advisory Board (including FAA and EASA representatives), the HIWC project (High Ice Water Content), the EIWG (Engine Ice Working Group), the ICC (Ice Crystals Consortium) and the EUROCAE Working Group 95 (Ice Detection System and Weather Radar).
Various dissemination materials are also available through the public website as are the public deliverables in particular the synthesis of HAIC recommendations regarding standardisation topics & validation/amendment of Appendices D&P.
1.4.8. Exploitation of HAIC results
1.4.8.1. Exploitation of Instrumentation results
• New activities will be launched to increase the TRL and further exploit the AMPERA system
• The CU-IKP will be made available to other organisations for calibrations
• Cloud probe instrument inter-comparisons are proceeded within the EU funded projects DACCIWA and EUFAR and the German DFG Priority programm SPP1294 HALO. Acquired cloud data are accessible for collaborations on international level.
• A series of current and future science publications is planned.
• Improving the measurements capabilities in CIRA icing wind tunnel for extended cloud conditions (SLD)
1.4.8.2. Exploitation of High IWC Flight tests Campaigns results
• Aviation rulemaking:
o Issue recommendations for new regulations (FAA report planned for April 2017)
o Include IWCs deduced from Radar measurements to increase the number of data points for the statistics
• Radar calibrations and intercomparison thanks to the simultaneous flights of the F20 and the CONVAIR during the Cayenne F/T campaign + 1 flight collocated with Cloudsat path
• Intercomparison of measurements devices (ROBUST hot wire probe versus IKP-2, Airbus Nephelometer versus 2DS...)
1.4.8.3. Exploitation of SP3 Space-borne Observation & Nowcasting of High IWC Regions results
• Complete the operational implementation of SP3 High IWC detection schemes on new GEO missions (HIMAWARI, GOES-R) for a service with global coverage
• Pursue of the exploitation of HAIC database to develop new High IWC detection schemes (e.g. night-times detection algorithms), to produce state-of-the-art High IWC climatology, and to validate RDT prototypes identified during TRL6
• Update of operational SP3 products according to demonstrated improvement or new generation of SP3 product
• Investigate and understand High IWC occurrence through concurrent numerical cloud simulations, and airborne and space-based HAIC observations/products
• Scientific exploitation of the High IWC climatology from both LEO and GEO products
• KNMI partner in proposal ESA feasibility study with Dutch tech-innovation company S&T for testing real-time dynamic route planning tool for aviation (http://www.meandair.com)
• Exploratory talks between KNMI and Dutch airliner KLM for new data provision & services, including High IWC
• CNRS partner of a EU H2020 "FET-Open research and innovation actions" proposal submitted in January 2017 dealing with laboratory experiments and cloud simulations for which HAIC airborne measurements are also relevant (simulation and representation in atmosphere models of ice-ice interaction)
• High IWC mask and RDT will be used in French ANR EXAEDRE (Exploiting new Atmospheric Electricity Data for Research and the Enviromnent) field campaign with French Falcon in its HAIC SP2 configuration (September 2018 in Corsica, France)
• Promote HAIC SP3 results through formal and informal seminars
• Pursue the collaboration between CNRS, KNMI, Méto-France and Airbus on satellite-based High IWC detection and nowcasting
1.4.8.4. Exploitation of SP4 High IWC Detection & Awareness Technology results
Awareness system development (Radar)
• Use campaign results to further develop algorithms for the High Altitude Ice Crystals awareness technology based on Weather Radar
• Pursue radar development and exploit capability established within Europe
• Pursue radar development and exploit capability established within Europe (HONEYWELL)
Detection system development
• Further optimise sensor hardware and processing algorithms (ZA-INT)
• Continue to advance the existing ICD system for research aircraft, aircraft certification, and wind tunnel testing (SEA)
• Develop a single package ICD for commercialisation (SEA)
• Partner with an already approved aircraft supplier for development support and commercial production (SEA)
• Further advancement of detection algorithms for both bulk (large sample volume) and particle tracking (small sample volume) technologies (NRC)
• Comparison with PDP data from Cayenne flight campaign (different atmospheric conditions and installation) (NRC)
• Transition technology to an approved aircraft supplier (NRC)
1.4.8.5. Exploitation of SP5 High IWC Test Capability Enhancement results
Exploitation of the HAIC results in SP5 is mainly being done through:
• Communication and promotion of the tunnel upgrades to customers and aerospace contacts
• Usage of the upgraded facility for industrial tests.
1.4.8.6. Exploitation of SP6 High IWC Tools & Simulation Development results
• Pursue the research on icing through the submission of at least 5 collaborative research proposals.
• Support by ONERA and CIRA to European aerospace industries (Airbus, Dassault, SAFRAN, Thales, Piaggio, ...) for aircraft, engine and probe design/development and certification.
• Support to CIRA IWT’s customers thanks to integration of numerical and experimental capabilities.
• Writing of new publications based on the last HAIC SP6 results for submission to international scientific results (3 papers at least currently in preparation).
1.4.8.7. Exploitation by HAIC industrials partners
• Enhancement of instrumentation during future aircraft certification flight tests in supercooled droplets icing conditions or development flight tests in ice crystals icing conditions, based on HAIC results and lessons learnt.
• Launch of development of new detection and awareness technologies relying on HAIC results. This will conduct to improvement of in-service aircraft (retrofit and/or forward fit).
• Use of new IWT capabilities for probes, engines or detectors development or qualification tests in collaboration with suppliers.
• Use of new / enhanced analytical tools in the development of new products
• Enhancement of tools with the last models of HAIC.
• Continuous improvement of tools by taking into account
• Participation in additional research project to pursue the work of HAIC and the finalisation of acceptable Means of Compliance
• Validation of HAIC tools vs. internal experiments and datasets.
• Potential Creation of a dedicated icing department at TAI.
List of Websites:
More information about the project can be found on the project website: www.haic.eu
Main HAIC contacts are:
Florent Huet
HAIC Project Coordinator
AIRBUS Operations SAS
316, route de Bayonne, 31060 Toulouse Cedex 09, France
Tel. +33(5) 61 18 82 81
Florent.Huet@airbus.com
Alice Calmels Grandin
HAIC Technical Director
AIRBUS Operations SAS
316, route de Bayonne, 31060 Toulouse Cedex 09, France
Tel. +33(5) 61 93 66 91
Alice.Grandin@airbus.com
Commercial aircraft have been experiencing in-service events while flying in the vicinity of deep convective clouds since at least the early 1990s. Heated probes and engines are the areas of aircraft most prone to mixed phase and glaciated icing threat.
In anticipation of regulations evolution linked to this phenomenon, the HAIC project has been put in place to provide European Aeronautical industry with necessary Acceptable Means of Compliance and detection/awareness technologies in order to continuously enhance flight safety. HAIC also developed international cooperation and collaboration thanks to the involvement of key international organisations and companies as partners of the project or through the advisory board.
Microphysics probes were developed and improved beyond the state of the art, in order to allow in-flight measurements and to support wind tunnel calibrations. The selection of the most advanced instrumentation was performed for the three flight test campaigns and for calibration and commissioning tests of four wind tunnel faciilities. Both, the wind tunnel instruments and the instrumentation integrated in research aircraft were inter-compared in a wind tunnel and the repeatability of wind tunnel conditions were assessed. Beside the development of ice particle probes, the effects of aerosol on convection, the height of glaciation and particle size distributiuons was evaluated using airborne data in polluted continental (and clean maritime) convection above Brazil.
Three flight tests campaigns were conducted in three different regions of the world, with two types of convection (continental and oceanic). These campaigns were the successful result of cooperation between multiple entities (airframers, engine manufacturers, equipment & system suppliers, research institutes and academics, meteorological services and SME’s able to provide specific knowledge, service, or support in specific areas) and even of international collaboration between the HAIC, EASA-HighIWC, ICC and HIWC projects for two of these campaigns. They allowed supporting the assessment of mixed phase and glaciated icing conditions regulations by providing 99th percentile total water content statistics and other relevant clouds characteristics. They also allowed exposing the detection and awareness technologies in real conditions and thus improving their maturity. Flight test data were also used to support the development of numerical simulation tools.
From detection and awareness perspective, two space borne nowcasting technologies (KNMI High IWC Mask and RDT) were improved to enable identification of areas prone to high IWC. Those technologies were validated through comparison with measurements from HAIC and AIRBUS flight campaigns, from AIRBUS in-service events and from a long series of Low Earth Orbiting A-train IWC profiles. RDT technology is now close to TRL6 level, and KNMI High IWC mask reached TRL6 level. An on-board radar technology was developed for awareness of high IWC areas. This technology benefited from the flight tests for validation and reached TRL6 level. Several detector technologies were also developed and step by step down selected. Icing wind tunnel tests and flight tests allowed to mature their design and to validate their performances. Different TRL levels were reached depending on the technologies (up to TRL5 for PDP detector) and further progress will be achieved beyond HAIC project.
Four wind tunnel test facilities were improved or modified to be capable of ice crystals conditions simulation. Calibration of these wind tunnel test means has been performed, and their performances have been cross compared. These facilities have also been used to support the validation of detectors performances, to intercompare W/T and F/T instrumentation and to provide experimental cases for the numerical simulation tools. TRL5 maturity was reached for the four facilities.
Numerical models and tools were also developed to enable numerical simulation of the phenomenom. Numerous experiments were conducted in different facilities, allowing improvement and then validation of the trajectory, impingement and accretion models. Industrial 2D and 3D numerical tools were developed with implementation of those models and delivered to industrial partners. Those latter ran first validation tests to check integration in industrial environment. Anyway, some more work is needed beyond HAIC project to reach the expected TRL6 maturity level.
As a main conclusion, even if some topics will still be explored or consolidated after HAIC project, a huge gap was filled thanks to the project regarding the understanding of the Ice Crystal Icing phenomena, the means to experimentally or numerically simulate the conditions and the means to detect the conditions in order for the aircraft to either avoid them or to adapt its protections.
In addition, the HAIC project allowed setting up and consolidating a strong international community of experts on the icing topics, which will be very valuable in the future.
Project Context and Objectives:
Commercial aircraft have been experiencing in-service events while flying in the vicinity of deep convective clouds since at least the early 1990s. Heated probes and engines are the areas of aircraft most prone to mixed phase and glaciated icing threat.
In anticipation of regulation changes according to mixed phase and glaciated icing conditions, the HAIC project will provide the necessary Acceptable Means of Compliance (numerical and test capabilities) and appropriate ice particle detection/awareness technologies to the European Aeronautical industry for use on-board commercial aircraft in order to enhance safety when an aircraft is flying in such weather conditions. HAIC will also develop international cooperation and collaboration thanks to the involvement of key international organisations and companies as partners of the project or through the advisory board.
The main objectives of the HAIC project are to allow the European aeronautical industry to face challenges related to the evolution of regulation regarding mixed phase and glaciated icing conditions by characterising high ice water content environments and developing the Acceptable Means of Compliance (test facilities and numerical tools) to improve aircraft operation in such weather conditions by developing appropriate detection and awareness technologies to be fitted on aircraft and being able to alert the flight crew, thus continuously enhancing international flight safety.
This can be broken down into the following scientific, technical and dissemination objectives:
• Characterise, optimise, enhance and select the most sophisticated cloud microphysics probes to measure mixed phase and glaciated icing conditions during flight tests and to calibrate icing wind tunnels
o To measure mixed phase and glaciated icing conditions (TWC, LWC, IWC, etc.) with an accuracy better than 10%
• Measure and characterise the microphysical properties of core or near-core regions of deep convective clouds, including cloud liquid and ice water contents, particle size distributions and particle shapes and provide 99th percentile total water content statistics as a function of distance scale to assess Appendix D and P diagrams representativeness vs real atmosphere
o To sample monsoon oceanic convection, oceanic tropical storms and more vigorous continental convection as safety permits
o To get statistics of the 99th percentile of Total Water Content averaged over a distance of 20 statute miles of a convective storm centre, with an accuracy of ± 20%
o To state on Appendix D and P diagrams representativeness vs. real atmosphere
• Upgrade European icing wind tunnels to allow reproduction of mixed phase and glaciated icing conditions to allow the European Aeronautical industry to perform equipment qualification and generate a detailed experimental database to validate numerical tools
o Achieve a TRL6 on the considered technologies
o Simulate the considered flight and mixed phase and glaciated icing conditions (Mach number ~0.85 Altitude up to ~40kft, Static temperature down to -70°C, IMMD in the range 20-500µm, IWC up to 20g.m-3 mixed phase capability) with an accuracy at least equivalent to the current covered icing envelope ie 15%
o Generate a detailed experimental database to validate numerical tools
• Understand and model involved physical phenomena and develop numerical tools to simulate the impact of mixed phase and glaciated icing conditions on aircraft components (mainly engines and probes) for supporting both design and certification phases and perform an integrated cross-validation between in-flight measurements, wind-tunnel measurements and model predictions
o Achieve a TRL6 on the considered technologies
o Provide models and tools able to simulate the considered icing envelope and associated impact on aircraft components with an accuracy at least equivalent to test facilities i.e. 15%
o Perform an integrated cross-validation between in-flight measurements, wind-tunnel measurements and model predictions
• Develop and validate mixed phase and glaciated icing conditions awareness and detection technologies to alert the crew of flight in these particular icing conditions or to adapt the flight path well in advance in order to avoid such weather conditions
o Achieve a TRL6 on the considered technologies
• Assess the proposed mixed phase and glaciated icing environment as defined in Appendix D and P in light of the analysis of the research flight tests performed as part of the HAIC project and provide recommendations to the regulatory bodies (EASA and FAA)
• Develop international cooperation and collaboration thanks to the involvement of key international organisations and companies as partners of the project or through the HAIC Advisory Board.
The HAIC project is broken down into six technical sub-projects and one sub-project devoted to consortium management and dissemination and exploitation activities:
• SP1 Instrumentation improves and selects the most appropriate instrumentation to characterise mixed phase and glaciated icing conditions to be encountered during the two HAIC flight tests campaigns (SP2) and to support the calibration of test facilities (SP5).
• SP2 High IWC Flight tests Campaigns organises, manages and conducts three flight test campaigns in 2014, 2015 and in 2016. In the two first flight test campaigns, it brings, in collaboration with HIWC US study, the French Falcon 20 equipped with active remote sensing (airborne cloud radar) and in situ microphysics probes. Based on these measurements and previous results from Airbus field campaigns in 2010 and 2012, the SP2 characterises the microphysical properties of the high IWC regions and distributes these inputs to other SPs. In the third flight test campaign, SP2 brings for the first time a Flying Test Platform (large payload and long endurance Airbus flight test A/C) to the industrial and scientific community for validation and demonstration of the maturity of the technologies (up to TRL6) developed within HAIC project.
• SP3 Space-borne Observation & Nowcasting of High IWC Regions develops space-borne remote detection and nowcasting techniques to support the second flight test campaign and ultimately provide near real-time weather data through ATM as being studied as part of SESAR.
• SP4 High IWC Detection & Awareness Technology develops on-board detection and awareness systems (probes or radar) complying with the industrial requirements of performance, operability, reliability, weight and cost, and able to discriminate the different icing conditions encountered.
• SP5 High IWC Test Capability Enhancement improves test facilities for the simulation of mixed phase and glaciated icing conditions in order to be able to support methods & tools development and validation and to perform qualification of equipment in European facilities.
• SP6 High IWC Tools & Simulation Development develops, validates and verifies models and tools able to simulate the impact of mixed phase and glaciated icing conditions on A/C components (mainly engines and probes) in order to support both A/C design and certification phases. Lastly, SP6 performs integrated cross-validation between in-flight measurements (SP2), wind-tunnel measurements (SP5) and model predictions, in order to demonstrate the capability of AMCs to reproduce the response of equipment and systems in mixed phase and glaciated icing conditions.
• SP7 Consortium Management, Technical Management and Integration is in charge of the project monitoring, administration, dissemination and reporting and ensures the technical consistency and convergence towards HAIC high level objectives. It is the “Architect and Integrator” and defines and manages the TRL process and roadmap. It manages the activities of standardisation related related to technologies specification or icing wind tunnel calibration built as part of other SPs. Finally, it coordinates the communication to the Advisory Board and external participants and, as such, is in charge of providing a set of recommendations to regulatory bodies (EASA/FAA) based on the outcomes of the SP2 regarding the assessment of the proposed mixed phase and glaciated icing environment as defined in Appendix D and P.
The HAIC project is a 4.5-year level 2 project of the 7th Framework Programme of the European Union coordinated by Airbus Operations SAS and kicked off in August 2012. It comprises 34 partners representing the European stakeholders of the aeronautical industry from eleven European countries and 5 partners from Australia, Canada and the United States. Its total budget is 23 million EUR.
Project Results:
1.3. DESCRIPTION OF THE MAIN S&T RESULTS/FOREGROUNDS
1.3.1. Instrumentation
The three HAIC F/T measurement campaigns address for the first time with a comprehensive set of measurements the engineering and scientific issues related to the in-service events in convective clouds, and a variety of fundamental scientific issues related to the microphysical properties and structure of deep convective cloud systems over land and over the warm tropical ocean.
Airworthy probes have been developed to provide size distributions and total water content in clouds (either during flight tests or tunnel tests). Few of them are able to perform measurements in mixed phase and glaciated icing conditions. Nevertheless, measurements of high IWC are technically very challenging and, before HAIC project, measurements were subject to unacceptable level of uncertainty and to very strong limitations (particles size, water concentrations, airspeed...). Instruments had to be improved and developed to provide sufficient accuracy for the characterisation of this environment.
Therefore, SP1 was designed to support the preparatory work for the SP2, SP4, and SP5 programs within HAIC. Its focus was primarily on the characterisation and improvement of microphysical and bulk cloud probes to measure in high ice water content regions in the atmosphere in convective cloud systems. Also, instrumentation was developed and characterised to enhance the capacities of current wind tunnels and extent the measurement range to high ice water content in glaciated and mixed phase conditions.
Beyond the state of the art, SP1 within HAIC helps to review, identify and optimise the performances of emerging technologies to allow the most appropriate instrument configuration to be chosen for F/T and W/T measurements.
1.3.1.1. Improvement and characterisation of microphysical and bulk cloud instruments for flight test F/T campaigns
The principal measurement challenges in icing conditions are related to the capability to measure small ice particle properties (<100 µm), avoid shattering (modified probe tips) and/or remove (filtering) shattered/splashed particles, discriminate the phase of particles (solid / liquid), and enhance IWC measurements of high IWC on aircraft by a better characterisation of collection efficiencies of probes. Finally, the selected probes for HAIC first F/T campaigns will also include highly sophisticated cloud radars capable of small ice particles measurement.
Significant work has been performed in SP1 related to characterisation of bulk TWC probes, characterisation/improvement of new maturing imaging and sizing probes, work on combination probes, and improvements of a the set of field mill sensors in order to support payload decision for the HAIC F/T campaigns. Therefore newest cloud probes have been optimised to measure bulk ice and individual small ice particles in convective cloud systems, while avoiding splashing and shattering.
1.3.1.1.1. Characterisation of bulk TWC probes (Robust hot-wire, IKP, field mill sensor)
Robust and Nevzorov hot-wire probes to detect the total water content have been characterised within SP1. From a comparison to IKP data, a temperature and TWC dependent characterisation of the sampling efficiency has been achieved. Further, SEA developed a new ROBUST probe sensor design, potentially increasing the efficiency by a factor of 2 as compared to classical ROBUST probe. This design was tested during the 2016 A340 campaign. The Nevzorov probe has been excluded from possible bulk probe candidates due to saturation at TWC beyond 1-1.5 g/m3.
The AMPERA field mill sensor to measure the voltage potential of HAIC aircraft in order to retrieve the TWC has been integrated on the Falcon and the A340 for the HAIC campaigns. An inversion method to retrieve IWC from field mill data has been derived.
1.3.1.1.2. Improvement and characterisation of new maturing probes (CAS-DPOL, CPSPD, HSI)
The CAS-DPOL (Cloud Aerosol Spectrometer with Depolarisation) cloud probe has been employed during the ACRIDICON projects for a phase discrimination of cloud particles based on the polarisation ratio. Laboratory measurements under defined conditions were used to calibrate the probes response to liquid/ice particles with known sizes. Shattering of larger cloud particles on the inlet of the instrument has been corrected based on particle interarrival time information.
As a new topic within HAIC, the aerosol effect on convective clouds is determined from measurements in continental convection under polluted and less polluted conditions in Brazil.
The CPSPD (Cloud Particle Spectrometer with Polarisation Detection) is the newly developed open path version of the CAS-DPOL and shows identical capacities of distinguishing cloud droplets and small crystals. The geometry of the probe is optimised to avoid shattering as much as possible.
The HSI (High Speed Imager) uses a multi beam approach to eliminate shadows from out-of-focus particles to improve measurement accuracy. It has been further developed within the HAIC project and successfully deployed on the NRC Convair 580 during the 2015 Cayenne campaign within the HAIC/HIWC collaboration.
1.3.1.1.3. Optimisation of instrumentation and design of combination probes (CDP-2/Robust, FCDP/2D-S)
The Cloud Droplet Probe -2 CDP-2 / Robust combination probe has been developed within HAIC for the Falcon 20. In order to reduce the number of canisters on the A340, the Fast Cloud Droplet Probe FCDP has been integrated onto the canister of the 2-dimensional stereo probe 2D-S to operate as combination probe for the detection of particles between 2 µm and 1.2 mm. Two of those probes were improved within HAIC. The 2D-S, FSSP and CDP tips were sharpened within the HAIC project to avoid shattering of particles.
1.3.1.1.4. Suggestion of instrumentations for F/T campaigns
High condensed water content is often found in deep convective clouds present in the warm tropical regions around the globe. These high ice water content regions are in principle not visible from current on-board weather radar of commercial aircraft and cannot be detected by current on-board icing detectors (detectors for classical icing due to the presence of supercooled water). The Engine Harmonisation Working Group (EHWG) has recommended a technology plan in order to develop means of compliance to provide guidance to manufacturers, and also to update or validate proposed certification rules for compliance in mixed phase and glaciated icing conditions. This technology plan includes an important task: Instrumentation development and evaluation for high ice water content and flight test research to characterise high ice water content environments.
Within SP1 instrumentation, a set of most sophisticated cloud microphysics probes has been selected for Falcon and A340 flight tests to enhance the capacities and accuracies of F/T in measuring high ice water contents, to allow for phase separation in mixed phase and glaciated icing conditions and to provide new IWC information by comparing in-situ IWCs with radar derived cloud properties. Also technologies developed within SP4 should be included. Figure 4 shows the cloud probes and size range, currently available for cloud observations from aircraft.
The requirements for the selection of the most adequate microphysical payload were to perform quantitative measurements of small ice particle properties (<100μm, if possible), minimise possible small ice crystals contamination on spectrometer data due to ice particle shattering, discriminate cloud particle phase, and enhance the maximum value of measurable total water content. Overall, very good progress has been achieved in the definition, selection, preparation and certification of the HAIC A/C instrumental payload for the 3 consecutive F/T campaigns: Falcon 20 out of Darwin (2014) and Cayenne (2015), and A340 (2016).
The selection of the payload for the HAIC international A340 F/T campaign 2016 allows in particular to measure ice particle concentration and sizes up to 1.2 mm and down to 2 μm with the 2D-S/FCDP combination probe, measure large TWCs with the Robust probe, continue collecting cloud data in deep convective clouds to complete the icing envelope for aircraft safety and validate the maturity of awareness and detection technologies developed in the frame of HAIC SP4.
1.3.1.2. Improvement and characterisation of microphysical and bulk cloud instruments for wind tunnel W/T test campaigns
It is the scope of HAIC to enhance the capacities for European wind tunnels to icing and mixed phase conditions. To this end, wind tunnel facilities have to be further developed to allow for the injection of ice and mixed phase particles at temperatures down to -40 °C and velocities up to 100 m/s. In order to allow for the commissioning of these novel achievements, wind tunnel instruments have to be further developed and characterised, which are able to measure the provided IWC and TWC as well as the particle size distribution in the selected wind tunnel facilities, exhibiting limited sizes of experimental sections. Therefore instruments have been developed and characterised within SP1, which can determine microphysical and bulk cloud properties in the experimental section of W/T facilities. The instruments’ measurement ranges have been adjusted to the conditions provided by the wind tunnels and the mechanical set-up has been optimised for instrument integration in the “small” experimental section of the wind tunnels. Developments and SP1 results are given below.
1.3.1.2.1. Development of the Isokinetic Probe (CU-IKP)
An isokinetic probe (CU-IKP) has been developed by the University of Cranfield to measure LWC, IWC and CWC in the different European wind tunnels. Air and cloud particles are pumped into the forward facing inlet of the IKP at a speed matching the wind tunnel air speed (isokinetic). Thus the particles are not enriched or depleted with respect to the wind tunnel particle concentration. Water vapor in the gas phase is detected with a backward facing inlet. Sublimated/evaporated total and gas-phase water are measured with a LICOR LI-7000 differential infrared gas analyser.
During HAIC, the pumping system and the water vapour detection of the instrument have been optimised. Laboratory and tunnel calibrations show that the CU-IKP measures CWC with an uncertainty < 20 % for 0.5 < LWC < 3 g/m³ and < 30 % for IWC < 12 g/m³ at selected pumping speeds < 50 m/s and at temperatures of 5° to -20°.
1.3.1.2.2. Development and characterisation of the High Speed Imager HSI
In order to derive microphysical particle information from single particles in wind tunnels, the high speed imager (HSI) has been developed by CIRA/Artium in SP1. It measures the size, habit, sphericity and various microphysical properties of particles in the size range of nominally ~20 to <1200 µm. The high speed imaging with 3 diode lasers focussed at the same focal point help to better define the system’s depth of field (DOF) and hence allows the rejection of out of focus particles for accurate particle sizing. A CMOS camera collects the images at high frequency (300 images per sec). The instrument has been further developed as canister probe for larger wind tunnels (TU-BS) and as modular version with open path optics for small wind tunnels (DGA, Esterline, GKN). The HSI has also been integrated in the NRC Convair aircraft during the Cayenne campaign 2015.
1.3.1.2.3. Phase Doppler Interferometer PDI
As an independent measurement technique, the Phase Doppler Interferometer PDI has been developed by CIRA/Artium as single and modular versions for the measurement of microphysical particle properties of liquid clouds in the size range < 100 µm. The Phase Doppler measures scattered light from small droplets passing through the probe volume in the intersection of two coherent laser beams. The interference of two scattered waves on the detectors creates a fringe pattern in which the droplet velocity information is contained due to the Doppler effect. The PDI is used for the wind tunnel particle velocity measurements and for size distribution measurements of small liquid droplets and has extensively been characterised theoretically within SP1.
1.3.1.2.4. Selection of microphysical and bulk cloud instruments for wind tunnel calibrations
Prerequisites given by the measurement range and mechanical considerations led to the selection of the following instruments for wind tunnel commissioning measurements.
Regarding the detection of bulk properties, Robust probes may encounter an under-sampling of the ice water content in glaciated or mixed phase conditions due to splashing of ice particles on the probes head. Thus, the CU-IKP has been selected to detect the IWC, LWC and CWC during the wind tunnel commissioning measurements. A second instrument is required for the detection of microphysical properties of single particles or the particle size distribution (PSD). The high speed imager HSI uses an advanced technique with several laser beams to accurately derive the depths of field and thus allows for an accurate counting of particles and a sizing in the expected size range provided by the wind tunnels. In addition, the HSI has been developed in modular and canister version for the use also in small wind tunnel test sections. Thus, the HSI has been selected for the determination of the concentration and the PSD for W/T commissioning. Finally the Phase Doppler Interferometer PDI has been chosen for particle velocity measurements.
1.3.1.2.5. Intercomparison of wind tunnel and flight test instruments
Generally, different instrumentations are used in W/T and F/T campaigns, thus limiting the comparability of atmospheric and laboratory measurements. To overcome this issue, an instrument intercomparison campaign has been planned and conducted with the objective to directly intercompare the instruments used on aircraft and in the wind tunnel.
The campaign took place in September 2016 in the Braunschweig wind tunnel, which has a large test section and thus allows for the integration of aircraft and wind tunnel instruments. Table 7 shows the F/T and W/T instrumentation selected for intercomparison. The objectives of the intercomparison campaign are threefold: the direct comparison of 2D-S and HSI derived PSD and IWCs, the intercomparison of the 2 2D-S probes, the comparison of data evaluation methods derived from aircraft flight tests. Figure 20 shows the canister HSI and the 2D-S integrated in the Braunschweig wind tunnel and the laser beams of the modular HSI and PDI focussed on the same sampling area.
The evaluation method applied to the 2D-S data of the Lamp-2D-S and the DLR 2D-S was similar to the one used during the HAIC campaigns. IWC was derived using the Brown and Francis, 1995, M-D relationship applied to the area equivalent diameter (Deq). In summary, the results show a good agreement between the two 2D-S instruments using similar data analysis methods (D15.2). MMDs were derived from four instruments. In general, the standard deviations from the HSIs are higher than for the 2D-S due to a lower sampling statistics. On average, MMDs between 70 ± 12 µm (i09) and 85 ± 8 µm (i06) have been inferred by the four instruments. Out of the 25 mean IWC values retrieved, 21 values agree with the prescribed TUBS IWC within 20%. On average, the IWC from the four instruments agree within 15 % (i01), 8% (i02), 6% (i03), 4% (i05), 33% (i06), 2% (i09) and 11% (i10) with the TUBS IWC, despite the sometimes large variabilities of condition encountered within one experiment (e.g. i01). Larger uncertainties and instabilities were observed for temperatures above the freezing temperature due to melting of ice crystals near the wall of the wind tunnel. Also higher IWC (> 10 g m-3) inferred by the instruments showed a larger deviation from the prescribed IWC. Further tests are required to evaluate the HSI performance at higher MMD and lower particle concentrations.
1.3.2. High IWC Flight tests Campaigns
SP2 was dedicated to the organisation, management, conduction and post-processing of the three flight test campaigns of the project that were conducted in 2014, 2015 and in 2016. Then, based on these measurements and previous results from Airbus field campaigns in 2010 and 2012 and HYMEX in 2011, SP2 helped to characterise the microphysical properties of High IWC regions and supported the rulemaking activities at international level.
In the first two flight tests campaigns, it brought, in collaboration with HIWC US study, the French Falcon 20 equipped with active remote sensing and in situ microphysics probes. In the third flight tests campaign, SP2 brought for the first time a Flying Test Platform (large payload and long endurance aircraft) to the industrial and scientific community for validation and demonstration of the maturity of the new technologies (up to Technology Readiness Level 6) developed within HAIC project.
1.3.2.1. Darwin 2014 and Cayenne 2015 Flight Tests Campaigns
Two campaigns have been conducted in the frame of HAIC/HIWC international collaboration. These campaigns took place in Darwin (Australia) from January 15, 2014 to March 7, 2014 and Cayenne (French Guyana) from May 9, 2015 to May 29, 2015.
1.3.2.1.1. Preparation of international field campaigns
The selected A/C for these campaigns is the SAFIRE Falcon20 fitted with state-of-the art instruments, as selected by SP1, to measure cloud microphysics and RASTA multi-beam Doppler radar active remote sensing:
In addition to Aircraft instrumentation to measure in-situ conditions, other tools were developed to support the campaign, like PLANET. PLANET is a tool for scientific flight guidance that was adapted for field campaigns. PLANET was additionally upgraded for Cayenne campaign to allow the operations with three aircraft and to include real time SP3 satellite based retrieval products.
An observation network was also available to monitor and record all meteorological conditions. This included ground weathers radars and satellite data.
1.3.2.1.2. HAIC/HIWC Darwin 2014 Flight Tests Campaign
The first campaign took place in Darwin, Australia from January 15, 2014 to March 7, 2014. It was planned to operate primarily over ocean areas within 300 nm of Darwin in Australian airspace extending to over the Gulf of Carpentaria whenever possible.
Campaign started as planned on the 16th of January 2014: all team members, equipment and the Falcon 20 arrived in Darwin on time. Significant monsoon conditions were present from the start through mi-February 2014. 23 research flights were conducted during Darwin campaign, corresponding to 72 flight hours. A large amount of data was collected, and the first part of the campaign was successful, with no A/C or instrumentation failure.
Following aircraft unexpected failures (not linked to high IWC) it has been decided to stop campaign on 07/03/2014. Due to early termination and risk to not reach rulemaking objective because of lack of data for statistical approach, HAIC and HIWC teams worked out the preparation of a new campaign to collect missing data and achieve the objectives.
1.3.2.1.3. HAIC/HIWC Cayenne 2015 Flight Test Campaign
The second HAIC/HIWC flight campaign took place from May 9th, 2015 to May 29th, 2015 out of Cayenne, French Guyana. During this campaign, two other A/C had joint the research effort:
• NRC Convair 580 aircraft equipped with active remote sensing (airborne Doppler cloud radar) and in situ microphysics probes to sample -10°C Flight Level and vicinity of clouds.
• Honeywell B757 aircraft equipped with enhanced weather radar to evaluate radar ice crystals’ awareness function developed as part of SP4
Aircraft operated primarily within 300 nm of Cayenne in FIR Paramaribo and Piarco. Some issues were experienced with Brazilian ATC for operation within FIR Atlantico and Amazonica.
The flight campaign had been successful for all three aircraft. 19 days of flights were performed representing 60F/H for the Falcon 20, 50F/H for the CV-580 and around 40F/H for the B757.Among the 19 days of flights performed,
• 5 flights were performed with 1 aircraft alone
• 8 flights were performed coordinating 2 aircraft
• 6 flights were performed with all 3 flight tests aircraft at the same time.
This campaign was intense and fruitful and it allowed collecting a large set of data to support regulatory objectives, science and the development of new ice crystals awareness system (aircraft on-board weather radar).
1.3.2.2. Darwin – Saint Denis 2016 Flight Tests Campaign
The purpose of the third flight test campaign was:
• To collect cloud data in deep convective clouds with cloud microphysics probes selected by SP1, and thus complement HAIC/HIWC database,
• To validate maturity of mixed phase and glaciated icing conditions awareness and detection technologies developed in the frame of HAIC SP4.
HAIC third Flight test campaign was performed with Airbus flight tests aircraft A340 MSN 1 at Toulouse (validation tests), Darwin (Australia) and Saint Denis (La Reunion). Oceanic conditions were not found in Darwin mainly due to El Niño phenomena occurrence in 2016. This is the reason for change of campaign location from Darwin to St-Denis (La Reunion).
The A340 MSN1 has shown its capacity as a flight test platform for environmental campaign: long range and large payload, good reliability, good agility demonstrated by the quick and efficient relocation from Darwin, Australia to Saint-Denis, La Reunion.
A total of 80 icing encounters have been flown over the 6 flights in high IWC environments. A good coverage of CS-25 Appendix P conditions has been achieved. Microphysical probes showed a satisfactory behaviour and only a few failures were observed, mainly for measurement of larger particles.
Icing Detection and Awareness technologies were evaluated in the ice crystals environment and results had been transmitted to SP4. Satellite retrievals products were also evaluated during the campaign and results were transmitted to SP3. First feedbacks from flight crew are positive and technologies look promising.
1.3.2.3. Atmosphere characterisation and assessment of CS25-Appendix P
A major objective of the HAIC project was to collect atmospheric data allowing for a full characterisation of the dynamical and microphysical properties of high ice water content regions, so that the conditions of formation and maintenance of these regions can be fundamentally understood, and so that current regulations regarding this potential threat to civil aviation can be assessed.
1.3.2.3.1. Atmosphere characterisation
In order to develop a better understanding of physical processes involved in the formation and maintenance of high ice water content conditions, the Falcon 20 aircraft, used during the two HAIC first campaigns, was equipped with state-of-the-art in-situ microphysical probes and a multi-beam airborne Doppler cloud radar.
1.3.2.3.1.1. In-situ measurements
At flight level HAIC project has produced quality-controlled particle size distributions, a detailed knowledge about the statistical relationship between ice crystal size and other properties such as crystal mass, projected area, and fall speed, and derived some crucial bulk microphysical properties such as ice water content, visible extinction, median mass diameter (and other diameter definitions), and number concentration.
The analysis and post-processing of the measurements made during the campaigns allowed to relate high IWC regions with high concentrations of small ice crystals, which is the main hypothesis explaining why these HIWC regions are not detected by the commercial pilot X-band radars, but it also allowed to derive key characteristics of high IWC regions to support rulemaking process.
The algorithms developed to perform analysis of the different in-situ probes were validated at international level thanks to huge collaboration and regular meetings, giving legitimacy to the final dataset released by HAIC project.
1.3.2.3.1.2. Remote sensing
Moving away from the flight-level, it was demonstrated that airborne cloud radar microphysical retrievals, trained using collocated data at flight level can, provide an accurate description of the full vertical profile of microphysical and dynamical properties of high ice water content regions (instantaneously and statistically), which paves the way for detailed studies of the dominant microphysical processes acting along the vertical atmospheric columns in these conditions.
A cloud radar retrieval technique has been developed as part of HAIC to characterise the dynamical and microphysical properties of high ice water content regions. The technique is validated using in-situ measurements of the three wind components and the Isokinetik Probe Total Water Content measurements. Horizontal wind components can be obtained with very little bias, and a standard deviation of the error of 2 ms-1 or better. Vertical air motions, which are an essential piece of the puzzle to understand processes responsible for the formation and maintenance of high ice water content regions, can also be obtained with less than 0.3 m s-1 bias, and a standard deviation of the error that varies with vertical motion itself, but generally remains below 50%, especially for convective drafts (large values). Retrieved water contents are characterized by standard deviations of the error generally less than 30%. This technique allows for the full vertical distribution of the internal dynamics and microphysics of high ice water content regions to be characterised.
1.3.2.3.2. Assessment of CS-25 Appendix P
The datasets collected during international field campaigns (in complement of existing preliminary measurements from Airbus flight tests campaign and HYMEX Megha Tropiques project) are used to assess the CS-25 appendix P: altitude-temperature envelope, TWC values and PSD. This assessment has been made all along the project, and a synthesis is available in project deliverables D71.7.
1.3.2.3.2.1. Altitude – Temperature Envelope
Based on in-service events analysis and review, an extension of proposed envelopes regarding mixed phase and glaciated icing conditions was proposed.
1.3.2.3.2.2. TWC Values
The data gathered during Airbus flight tests, Megha-Tropiques flight tests and HAIC/HIWC Flight Tests Campaigns show that the maximum TWC values encountered are lower than values provided by appendix D curves, and maximum values encountered are close to 75% of these maximum values.
In addition to TWC values to consider, the associated distance scale is to be assessed. Pending on the type of technology, the analysis of reported in-service events highlighted that different sizes of clouds should be considered (one for engines / one for air data probes). Additional post-processing is still required to finally state on these maximum values to consider, regarding IKP reference values analysis. Statistical analysis is on-going at international level to define the 99th percentile for these maximum TWC values. This work is conducted out in the frame of international collaboration and will be handled by an ARAC group. Launch of activities of this group is under process within FAA.
1.3.2.3.2.3. PSD Values
Preliminary analysis of measurements shows a need for revision of CS25 Appendix P with regards to Particle Sizes Distributions as measured MMDs are not in accordance with initial regulation values.
At cold levels, high IWC areas are primarily composed of small ice crystals (200-400 μm), which yield small MMDs around 300μm. As temperature increases, the concentrations of small ice crystals decrease while the concentrations of larger ice crystals (>300μm) increase, resulting in a MMD rise to roughly 500 μm. When the temperature reaches -20°C and then -10°C, there is almost no more decrease in the concentrations of the small sizes but a noticeable increase in the concentrations of particle larger than 1mm.
1.3.3. Space-borne Observation & Nowcasting of High IWC Regions
The detection of High IWC with different space-based techniques has been investigated during the HAIC project. This has been successfully performed through a multiple observational based approach methodology using as reference In-Service events, past Airbus and HAIC field campaigns, and the space-borne DARDAR (raDAR/liDAR) product. This approach aimed at developing, training and evaluating the different SP3 satellite-based products to successfully support the successive HAIC campaigns.
As mentioned above, several satellite-based products have been developed and tools used to detect High IWC and convection like KNMI High IWC mask, the DARDAR product, or RDT (Rapid Development Thunderstorm). These different products and tools should be seen as a first step, first, to replace High IWC in its cloud -environment and development, second, to understand the processes that lead to high IWC and potentially to an In-Service event.
In more detail a High IWC mask (IWC > 1 g/m3) was developed based on cloud properties derived from geostationary MSG SEVIRI measurements during daytime and trained with DARDAR active remote sensing IWC observations. Airborne observations were compared to MSG data for HAIC-2015 (Cayenne) and to HIMAWARI/MSG data for HAIC-2016 (Darwin/La Réunion). Thus several GEO satellites were used to support the HAIC campaigns worldwide. RDT was operated during the three HAIC campaigns. This required the adaptation of the High IWC mask algorithm to HIMAWARI measurements and to the development of several RDT chains with different settings according to the available GEO imagers over the domain of the field campaigns.
RDT is a software developed by Météo-France in the framework of NWCSAF (Satellite Application Facility on support to Nowcasting and Very Short-Range Forecasting). RDT detects, tracks and characterises convective systems. In the framework of the HAIC project, the RDT has been operated by Météo-France during all HAIC field campaigns on an operational basis through dedicated processing chains. The RDT was operated for various satellites and geographical domains: MTSAT for the first HAIC campaign (Darwin, 2014), MSG for the second one (Cayenne, 2015) and Himawari-8 and Meteosat 7 for the last campaign (Darwin/La Réunion, 2016). The first objective of RDT was to detect the convective areas to guide the research planes. Second RDT was used by weather forecasters for ground meteorological support. RDT outputs were also adapted to be up-linked to the research planes thanks to the PLANET system developed by the SME Atmosphere. This innovative development offered to the pilots and aircrew the possibility to assess the actual cloud environment surrounding the research planes. Interestingly the expansion of RDT to new geographical domains and new satellites has clearly made easier and faster the new global coverage version of RDT developed by Météo-France (since 2016).
The real-time SP3 products were delivered to the aircrew and the HOC (HAIC Operation Centre) during the HAIC campaigns. The capability to provide relevant and reliable information to potentially any aircraft and ATM was demonstrated, currently more for a strategic planning (due to the delay of the satellite data delivery to the Users) than for a tactical use. Space-based remote sensing of High IWC definitively appears to be one of the appropriate detection/awareness techniques to enhance flight safety, apart from in-situ and close-range sensitive weather radar detection on-board the aircraft. The different HAIC satellite products were qualified as useful during the campaigns to guide the research aircraft and identify potential targets in the vicinity of the research aircraft. This was confirmed during the two TRL6 reviews with an official feedback from the Users (i.e. the aircrew and HOC members). The High IWC masks were and are still publicly provided in near-real time via msgcpp.knmi.nl and adaguc.knmi.nl while RDT is continuously operated at Météo-France.
The MSG-CPP high IWC mask was extensively validated against independent DARDAR observations. Important sensitivities in the performance of the mask were identified (altitude of the High IWC, solar and viewing zenith angles). The performance of the MSG-CPP high IWC mask was also found to be sensitive to environmental conditions (small scale High IWC variability, size of the High IWC environments). Taking these sensitivities and environmental conditions into account, the probability of detection (POD) is around 90% or better for IWC above 1 g/m3.
Qualitative and quantitative studies of RDT performances against High IWC have provided reasonably good results, especially in terms of probability of detection. RDT reached TRL5. Based on the good performances of RDT assessed during the HAIC project, the last NWCSAF release of RDT (v2016) now includes an attribute describing high IWC risk for any identified convective cell.
The evaluation of the MSG-CPP high IWC mask against 2015 Cayenne campaign data – in situ, remotely sensed by the airborne RASTA radar and on board radar (WXR) – was performed. The evaluation based on RASTA IWC profiles confirmed the findings of the evaluation with DARDAR in terms of the POD of High IWC occurrence.
The HAIC Satellite and Nowcasting team also investigated the cloud systems that lead to In- Service events. A list of In-Service events was provided by Airbus. Four types of cloud system were identified: large tropical convective systems, moving convective lines, young convective clouds (that did not exist few hours before the In-Service event) and high altitude thick clouds apparently not connected to convective clouds during more than 24 hours prior the occurrence of the In-Service event. Amongst the In-Service events provided by Airbus, only nine of them were located within MSG-SEVIRI domain during daytime and High IWC was detected by KNMI High IWC mask algorithm at the location of all these In-Service events.
It should be noted that, although high IWC (IWC > 1 g/m3) is an important condition for the occurrence of In-Service icing events, it is not the only one. Without additional information provided by the aviation industry in the future, a detection of In-Service icing conditions beyond the current detection of High IWC environments as developed in the frame of the HAIC project cannot be achieved.
The HAIC Satellite & Nowcasting team has also explored the spatial and seasonal distributions of High IWC regions worldwide based on DARDAR IWC retrievals (Figure 15). This climatology confirms that High IWC above 8 km height and larger than 1 g/m3 is mainly detected over the tropical band and follows the seasonal regional cloud distribution. The climatology also pinpoints higher High IWC occurrence (< 3%) at typical cruising altitude over continent during the day and over ocean during the night. This provides a first step for a better assessment of the High IWC risk on a regional and seasonal aspect. The High IWC climatology was extended to KNMI High IWC mask during daytime revealing clear spatial patterns, which could be useful in the future for aviation strategic planning purposes,.
Finally the High IWC mask was adapted to LEO (Low Earth Orbit) MODIS (Moderate-Resolution Imaging Spectroradiometer) cloud properties showing overall consistency between the geostationary and polar orbit based masks. The MODIS High IWC mask can be used to generate a high-spatial resolution climatology over the world but also as product to contribute to the verification of the successful implementation of KNMI High IWC mask on other GEO missions. One additional interesting feature that the MODIS High IWC mask algorithm can provide is a better spatial description of High IWC clouds at higher latitude which are much less well described from geostationary.
1.3.4. High IWC Detection & Awareness Technology
1.3.4.1. Ice Crystal Long Range Awareness
One goal of the HAIC project was to provide the appropriate ice crystals awareness technologies for use on-board of commercial aircraft to enhance safety when an aircraft is flying in such weather conditions. Before the project, no dedicated technology based on X-Band Weather Radar was defined.
Two Weather Radar suppliers have been involved in the project: Rockwell-Collins and Honeywell.
Until the key TRL3, both suppliers performed activities as the state of the art of available technologies applicable to glaciated icing conditions detection and analyses of the data collected during previous Airbus flight test campaigns (Chile with Honeywell and Darwin/Cayenne with Rockwell-Collins). Taking as a basis the High level specification for mixed phase and glaciated icing conditions awareness technology as defined in WP42 (D42.3 deliverable), they also presented the basis of their algorithms to meet the main requirements: crew awereness of two level of IWC 80Nm before encounter with a probability of correct annunciation greater than 80%.
For the TRL3, a selection of potential technologies have been presented at TRL reviews:
• Rockwell-Collins presented a solution based on the software upgrade of the current X-Band MultiscanTM, but also double frequency and double polarization radars.
• Honeywell presented only a solution upgrading the current IntuVueTM RDR-4000 X-Band WXR to infer IWC from radar measurements
During the strategic TRL3 review with the Supplier Down selection (March 2014), Honeywell solution has been selected for prototype evaluation during the 2016 F/T campaign. The radar technologies other than X-Band Weather Radar were disregarded, as development of such technologies even if more performing (particle shape/size discrimination) would not have fit within the project timeframe and bring constraints for retrofit (impact on A/C installation, potentially the need of a new Radome...).
For prototype definition, further activities were done as IWC algorithm and HMI definitions:
• As not already existing in standards, a specific HMI for Ice Crystals display has been evaluated and defined after workshops performed Airbus pilots, radar specialists and human factors engineers from December 2014 to September Given the data already displayed (FMS, TCAS targets...) the following HMI was identified compatible with Airbus and already existing Weather Radar display and proposed as reference:
o For High concentration area (>3g/m3): red flakes
o For Low concentration area (between 1 and 3 g/m3): blue flakes
• From TRL3 to TRL5 (October 2015), Honeywell has developed the prototype to be flown during the 2016 Flight Test campaign based on the 3D-Buffer RDR-4000. This software update includes the implementation of a machine-learning algorithm using reflectivity data and other parameters already measured to discriminate area from moderate to high IWC. Data collected during all the flight test campaigns have been used either to train the algorithm or assess the preliminary performances. The HMI as presented in Error! Reference source not found. has also been implemented in the prototype.
The software has been delivered in November after the TRL5 review and tested in Airbus lab until late December. The agreed software has been installed in December 2015 on A340 MSN1 for the campaign in January 2016.
The operational feedback from Airbus pilots during the campaign was positive; depiction of high IWC areas (>3g/m3) was quite accurate up to 80 nm and the HMI was judged stable and comprehensive. However some areas of moderate IWC (<1g/m3) were judged overestimated.
After the campaign, the algorithm has been updated to take into account the feedback (e.g. reduction of undue moderate IWC areas determination). Performance methodology has also been refined to take into account the constraints of comparing Radar data (long range data) with in-situ measurements. Global performances assessed on the available data show good results. Nevertheless, more data of high IWC or at longer ranges (above 40Nm) would be necessary to have the whole envelope coverage with sufficient representativeness.
In parallel, from January 2015 until February 2017, Ice Crystals Awareness function based on Weather Radar has been discussed in international committees (EUROCAE WG95-SG and RTCA SC230). A feasibility report has been written and has been submitted for publication. The main conclusions are that using the reflectivity only does not allow to reach the operational requirements. However by taking into account additional parameters the Ice Crystals long range awareness function is possible. Further activities will be pursued on this function in the frame of the committees. Redaction of a MASPS (Minimum Aviation System Performance Standards) is envisaged to support early system development and prototyping by manufacturers and/or installers who may wish to develop such a system. The MASPS document would also define simulation models and appropriate test and validation strategies.
At the end of the HAIC project, the Honeywell Ice Crystal Weather Radar has reached the TRL6 maturity. However, the topic needs to be now further discussed in international committees to define the appropriate operational envelope, the necessity of the moderate threshold as specified in the D42.3 specification and the proper means for verification/validation before launching a product.
1.3.4.2. Ice crystal detectors
Another goal of the HAIC project was to provide the appropriate ice crystals detection technologies for use on-board of commercial aircraft to enhance safety when an aircraft is flying in such weather conditions. Before the project, no dedicated technology exists for commercial aircraft. Six detection technologies have been involved in the project. Aircraft manufacturers involved in HAIC defined the specification in WP42 for such detectors. Through the 4.5 years of the project, the detection technologies started at TRL2 level and one reached TRL5 level. A downselection was organized at TRL2 and TRL3 steps.
For TRL4 step, wind ice tunnel tests were performed with remaining technologies using SP5 capability improvements and SP1 instruments for comparison. DLR and Zodiac/CNRS-CORIA/VKI/IRSN developed specific prototypes from previous academic setup. These ice wind tunnel tests demonstrated the robustness of some probes, but also the weakness that needed to be solved. For ODIPP technology from DLR, IWT/T results show that the measured IWC of single phase test cases are in good agreement with the reference data. However, de-icing/de-fogging system performance issue was highlighted with high risk on F/T data quality. The robustness of AIIS from Zodiac hardware design in harsh icing conditions has been demonstrated, unfortunately, software algorithm needs to be reworked to prevent image saturation during post-treatment and ensure minimum of performance demonstration. ICD from SEA demonstrated its capability of Ice Crystals Conditions detection and results for discrimination and characterization capabilities in mixed phase and glaciated conditions are promising. Successful TRL4 reviews for NRC and SEA in 2015. Because of algorithm saturation, AIIS did not validate its TRL4 level even if hardware behaves well. For DLR, both hardware and software limitations could not allow a conclusive TRL4 review. New schedule was planned in 2016 for Zodiac and DLR to proceed development.
Three technologies were tested on flight: PDP from NRC, ICD from SEA and AIIS from Zodiac. Unfortunately, AIIS has an ITAR component and was not able to fly in Australia. All three demonstrated their robustness during flights in various conditions: altitude between 30 and 41185 feet, temperature between -54°C and +33 °C, Mach between 0 and 0.85 and Total Water Content between 0 and 4.9 g/m3. 70 encounters of Glaciated and Mixed-Phase conditions for 30 flight hours. Once more, some weaknesses were observed on prototypes and imply design modifications. Coating erosion appeared on PDP due to ice crystals, not seen in tunnel or other flight testing. Modified material was identified as a solution. Several signal losses on ICD were identified as manufacturing default on heated elements and a new inspection process was settled. Solutions are identified to overcome this manufacturing issue. Algorithms already used for IWT/T were refined and last measurement analysis gave good correlations between the TWC results from aircraft instrumentation and the detectors measurementsError! Reference source not found.. All technologies demonstrated their capability to detect ice crystals conditions considering TWC detection threshold and associated response time. More evidences are expected in order to validate liquid, mixed and glaciated phase discrimination and characterization capabilities, however, more liquid and mixed phase reliable data concerning water phase are needed for that purpose (work in progress at CNRS based on 2D-S / FCDP data).
Despite great work performed by Zodiac in 2016 with its new prototype for flight test, AIIS TRL4 review was almost conclusive, mainly due to a lack of evidences concerning the performance assessment, many points being still open. Improvements of ODIPP, mainly focused in algorithm development, were not sufficient for TRL4 step. Within HAIC framework, TRL5 review for NRC PDP was conclusive despite lack of data for liquid and mixed phases. TRL5 for SEA was postponed due do unavailability before HAIC end.
A prototype is available for all four remaining technologies at the end of HAIC. HAIC highlighted the challenge of data post-treatment for optical technologies where all three ones (DANIELA from THALES/NLR, ODIPP from DLR and AIIS from Zodiac/CNRS-CORIA/VKI/IRSN) underestimated the difficulty to identify, measure and discriminate the particles in real time by an automatic algorithm. However, optical technologies seem today to be the only ones able to measure particle size. Further studies will say if this is relevant information for aircraft manufacturers and flight safety. Non optical technologies were in advance at the beginning of the project and potentially at higher TRL and have kept their advance but now need to focus on industrialisation. To reach TRL6, the main challenge now is to go through industrialisation, especially for academic technology developers, which implies finding an industrial partner.
1.3.4.3. Synthesis
Some issues appeared on the way of the project so the initial challenging goal to reach TRL6 was not achieved. Nevertheless, a huge amount of work was performed by WP43 and WP44 partners to come as close as possible of this level in the frame of HAIC. For ice crystals at least, these result give good confidence on the technologies. Now that all technologies reached a good level of performance assessment, it is time for them to go through a new and important step: environment robustness and industrialization processes, which is another challenge. Here is an overview of the maturity level of the various radar and detection technologies:
Technology Maturity at end of HAIC project Comment
Rockwell TRL3 Stopped at TRL3: radar technologies other than X-Band Weather Radar were not compatible of the timeframe of HAIC
Honeywell TRL6 Radar algorithm based on weather radar hardware demonstrated its performance in flight and reached TRL6 with data gathered through Airbus and HAIC flight test campaigns. A HMI solution was developed and tested. More data are required to determine if moderate threshold is necessary and to evaluate high threshold performance at long range (>40Nm).
DANIELA TRL2 Not part of the technology down selection during strategic TRL3
ODIPP TRL3 The ODIPP could not fly on the 2016 flight tests due to de-icing/de-fogging system issue. This led to no significant progress since the NOT CONLUSIVE TRL4 reviews.
AIIS TRL3+ The AIIS was installed on 2016 flight tests and showed good performances.
Actually, the maturity is very close to TRL4, but some icing wind tunnel tests are missing for the performance coverage.
This technology is supported post HAIC project through the CLEANSKY2 ICASSIO project.
ICD TRL4 The ICD was installed on 2016 flight tests. Preliminary report show good performances results.
TRL5 for SEA was postponed due do unavailability before HAIC end.
An industrial partner shall be found to continue the development of this detector beyond HAIC.
PDP TRL5 An industrial partner shall be found to continue the development of this detector beyond HAIC. NRC is looking for it.
1.3.5. High IWC Test Capability Enhancement
1.3.5.1. Definition of specifications and requirements for IWT
From the available data, the existing regulation and the needs of the manufacturers, basic specifications and requirements for the icing wind tunnels have been defined. Some requirements have been considered as essential. This set of requirements was the basis used to design the ice generators developed within the project.
It has been highlighted that, if IWC and MMD are fundamentals parameters, PSD, ice crystal density and particle shape are also important. Comparing the ice particles produced by current ice crystal generators and the natural ice crystals, the gap was mainly on these latter parameters.
1.3.5.2. Development of ice crystal and mixed phase capabilities in four facilities
Among the four facilities involved, two, GKN and ESTERLINE, were already able to generate ice crystals and mixed phase conditions at sea level, one, DGA, able to generate small ice crystals in altitude and the last one, TUBS, was not operational.
The strategy was to improve the current ice generators at GKN and ESTERLINE and to develop new ice crystal generators at TUBS and DGA (see Table 5).
GKN has redesigned its ice crystal generator to be able to produce smaller MVD for higher IWC.
ESTERLINE has extended the temperature operating envelope down to -60 °C for all velocity conditions by upgrading the cooling system of its facility. The ice crystal has been modified to increase of IWC capability.
DGA developed a new ice crystal generator to increase of MMD of the ice crystals and IWC capability.
TUBS, which is a new facility, developed an innovative ice crystals generator able to ice crystals with shapes close to natural ones.
1.3.5.3. Calibration
1.3.5.3.1. Methodology
The objective was to define of a common HAIC calibration methodology. This methodology has been shared with other worldwide facility owners and international working group (SAE). It could be as a basis to update the SAE ARP 5905.
The acceptance criteria are derived from the SAE ARP 5905. Some parameters and thresholds have been modified to take into account the specificities of the glaciated icing conditions.
1.3.5.3.2. Instrumentation
Two new probes have been selected as reference instrumentation for the calibration: the isokinetic probe from Cranfield University for TWC measurements and the High Speed Imaging probe for the particle size distribution and MMD measurements. Tests performed at GKN and DGA has been used to assess the performance of the probes.
1.3.5.4. Calibration tests
After the upgrading phase, all the facilities have been calibrated with the reference instrumentation.
1.3.5.5. Tests
A set of tests have been performed to assess the ice detectors developed within SP4, to intercompare F/T and W/T instrumentation for SP1 and to initiate a database for the validation of the code from SP6.
1.3.5.5.1. Assessment of ice crystal detectors
The detectors developed within SP4 have been tested at GKN and ESTERLINE. The results have been useful to assess the detectors and select those that could be used for flight test campaigns.
1.3.5.5.2. Instrumentation intercomparison
The HAIC intercomparison tests have been performed within a two-week test campaign at the TU Braunschweig Icing Wind Tunnel in August/September 2016. Three canister probes (CNRS-2DS, DLR-2DS and Artium HSI) have been mounted subsequently inside the test section and exposed to various ice cloud conditions. The test matrix and schedule had been agreed in advance by all involved HAIC partners (CIRA,CNRS-LAMP,DLR). Beside the canister probes, two modular probes (PDI and HSI) have been mounted externally on a mobile framework. Both probes allow to better cross-compare the canister probe measurements. Adaptor windows have been designed and manufactured by TUBS staff to precisely align the measurement volumes of all probes. Two TUBS engineers have supported the guest scientists by wind tunnel operation and general assistance.
1.3.5.5.2.1. PSD instrumentation
As discussed above, three canister and two modular probes have been mounted inside the wind tunnel test section to perform PSD measurements. Measurements have been taken at 16 different ice cloud conditions (supercooled droplets, mixed phase and glaciated clouds) for each probe. Prior to the tests, airflow measurements have been made by means of a CIRA Prandtl-probe. The tests have shown that the air speed inside the test volume is not influenced by blockage effects of the canister probes. Laser beams of modular HSI and PDI cross in front of the HSI probe volume. All three measurement volumes are aligned very precisely adjacent to each other.
1.3.5.5.2.2. TWC instrumentation
TWC instrumentation inter-comparison tests have been carried out at DGA. The selected airborne TWC probe tested was the Robust probe. The measurements were compared with the Cranfield IKP results done during the calibration. Data agreed within a maximum discrepancy of about 20 %.
1.3.5.5.3. Numerical code validation
1.3.5.5.3.1. 2D tests
Within the scope of HAIC WP5.5 experimental tests on ice crystal icing have been performed at the TU Braunschweig Icing Wind tunnel. The tests have been performed at various mixed phase cloud conditions at wet bulb temperatures up to the freezing point. As test articles a cylinder and a NACA0012 airfoil model have been designed and manufactured. Both test models are equipped with internal temperature sensors and heat foils.
The temperature sensors allow to monitor the local surface temperatures during the icing process. Heat introduction to the substrate can be simulated by switching on the internal heat foils. While tests with internal heat supply have been part of the experiments, the main focus had been set on ice accretion growth of not heated test bodies. This report explains the experimental procedure and sums up the results of the validation tests.
The tests results give new insight in the physics of ice crystal icing at mixed phase conditions. Further, the results are used to validate the ONERA icing code IGLOO2D and will also be included into an international benchmark of icing test cases.
1.3.5.5.3.2. 3D tests
Tests on a pitot probe have been performed at DGA to collect data in order to build a database for code validation. The probe was equipped with thermocouples and de-icing could be adjusted to get several thermal conditions. Pictures have been collected by ONERA to see the impact and the possible shattering of the ice crystals to the tip of the probe.
1.3.6. High IWC Tools & Simulation Development
1.3.6.1. Experimental investigation of ice crystal icing physics
A summary of the main experiments performed throughout the HAIC project in SP6 “High IWC Tools & Simulation Development” is given, outlining their variety, the physical insight gained through these experiments, the data which is now available for further model development and validation, and the remaining gaps left to close in future work. These experiments were designed specifically to allow refinements to be made to three key models in predicting ice crystal icing:
• Trajectory models,
• Impact models,
• Accretion models.
Trajectory Experiments
These experiments were performed largely by TUD and were concerned primarily with the question of how the non-sphericity of ice crystals might affect their ability to follow flow accelerations. Furthermore, it was not clear at the beginning, whether rotation of the particle would be significant in defining particle trajectory.
Two experiments were performed; one designed to measure drag coefficients of irregular particles and one used as validation data for accompanying simulations. Prior to the design of experiments, data was collected from partners within the HAIC consortium on expected size and density ranges of high altitude ice crystals, and, while this data was only preliminary at the start of the project, the values were subsequently proven to be reasonable.
The first experiment, capable of measuring the drag coefficient consisted of model particles falling or rising in a fluid column. By adjusting the density difference between particle and fluid, the realized particle velocity could be adjusted to attain Reynolds numbers expected under flight conditions. These all lie below 1000 and typically much lower. Numerical Euler-Lagrange simulations of spherical particles impinging onto various bodies (ONERA), for which drag coefficients are well known, confirmed this. The velocity of the particles was measured from high-speed video sequences from the segments in which the velocity was constant. Knowing the densities; hence the acting buoyancy forces, the drag force could be computed.
A large variety of non-spherical particles were examined and the measured drag coefficients were compared with numerous empirical correlations available in the literature, exhibiting varying degrees of complexity in describing particle shape. The correlation proposed by Ganser (1993) was the most appropriate for the available data set. For more complex particles, for example, capped cylinders, the correlation could be improved by considering the dimensions of the volume enclosing the particle, rather than the exact particle shape, in computing the shape parameters required in the correlation. One of the experiment consisted of a vertical wind tunnel, a target bluff body and an upstream particle injection. The particle trajectory in the vicinity of the target body was captured using high-speed video. The purpose of this experiment was to provide validation data for numerical simulations of particle trajectory. The trajectory, together with particle specifications, was documented in the form of tabulated coordinates in time. A further experiment was performed by AGI to investigate the melting of ice crystals under forced convection, since this occurs when ice crystals are ingested into warm parts of turbines. Existing correlations for Nusselt numbers are not applicable to highly non-spherical particles. In this experiment, ice crystals were held in an acoustic levitator and a warm airflow was directed over the particle. The melting process could be observed visually, from which heat transfer data could be deduced
Impact Experiments
Several experiments were performed with ice crystals, some concentrating on single crystal impact (AGI) others on accretion phenomena (AGI, TSAGI). The purpose of these experiments was manifold, ranging from first observation of physical phenomena to detailed data collection for model formulation. The influence of liquid film on the impact surface was also investigated. At AGI the experiments were performed in the icing and contamination research wind tunnel (iCORE).
First observations confirmed that accretion was negligible when ice crystals impacted onto cold surfaces. However, under mixed glaciated conditions or with warm surfaces, accretion immediately began, supporting the hypothesis that a liquid water content is essential to initiate accretion. This can come either from partial melting from the ice crystal before impact, or melting of fragments on a warm surface. This result emphasized the need for fragmentation models of impacting ice crystals.
Experiments were therefore performed to support fragmentation model formulation. Fragmentation was classified as no fragmentation, minor fragmentation, major fragmentation and catastrophic fragmentation.
A further series of experiments were performed in the iCORE facility at AGI in which ice crystal impact onto a thin water film was observed. The aim is to quantify the probability of sticking, bouncing and fragmentation. Typical results from this study in which the occurrences of no fragmentation and fragmentation for different intervals of film thickness (H/D0) are given. The tendency is clear: the thicker the water film, the more viscous and capillary forcers slow down the ice particle before impact onto the target and the higher the probability of no fragmentation. Modelling this complex phenomenon is clearly an important future task to properly predict onset of accretion.
Accretion Experiments
Experimental investigations on run-back ice formation on a heated wing airfoil model were conducted in TSAGI’s small icing wind tunnel, under ice crystal icing conditions, in the cases of presence and absence of artificially created liquid film on the model surface. The objective of the work was to investigate run-back ice growth rate for different operating conditions (in terms of air velocity, air temperature, leading edge wall temperature, ice crystal size, etc.) in order to improve our physical knowledge of ice crystal accretion on a heated surface and to get data for model calibration and validation. During the tests, the ice formation process was visually observed and video recorded. Operating conditions as well as the formed run-back ice mass were registered.The most interesting outcome of these experiments was the indirect measurement of the sticking efficiency. Without liquid water on the model surface, the sticking efficiency was found to be very low (never greater than 2%) whatever the operating conditions. But when a thin liquid film was present on the leading edge of the model (with a thickness of a few tens of microns), the sticking efficiency was found to be much higher, sometimes rising up to 30% (for the lowest air flow velocity).
1.3.6.2. Models and tools development and integration into industrial environment
1.3.6.2.1. Development of ice crystal icing models
As far as particle trajectory phenomena are concerned, the main difficulty was to take into account the influence of ice crystal non-spherical shapes on their interactions with the carrying air-flow (drag force, heat and mass exchange). The solution that was chosen consists of using global geometrical descriptors (equivalent volume diameter, sphericity, cross-wise sphericity, etc...) in the modified expression of the drag coefficient, Nusselt number and Sherwood number.
For impact and accretion phenomena, the microphysical mechanisms are very complex and, until the HAIC project, there were very few attempts in the literature to address their modeling. In SP6, two complementary approaches were followed:
• TUD and TSAGI focused on some specific aspects of the whole problem (impact regime thresholds, heat and mass transfers inside the accreted porous ice layer, run-back liquid film) and developed theoretically based models by combining analytical methods, DNS tools and experimental results.
• CIRA and ONERA chose to develop a comprehensive set of models (for sticking efficiency, secondary particle properties, accretion, erosion, etc ...) by employing a phenomenological approach based on empiricism and simplifying assumptions.
TUD and AGI experimental results (section 1.3.6.1 Experimental investigation of ice crystal icing physics) have been extensively used for model calibration (determination the model empirical parameters) and for model elementary validation (ice particle drag coefficient, melting time, etc.) .
1.3.6.2.2. Implementation in numerical tools and integration in industrial environment.
In HAIC SP6, all the models were mainly implemented and tested in 2D research tools, excepted for ice crystal trajectory models which were also implemented in the ONERA (Lagrangian and Eulerian), CIRA (Eulerian) and UTWENTE (Eulerian) 3D trajectory solvers. Important developments have been performed in all the tools to enable the implementation of the new ice crystal models.
• Starting from existing bricks, a new dedicated 2D ice crystal icing tool has been developed by TUD in the framework of D. Kintea’s PhD thesis.
• Deep modifications have been introduced in CIRA, UTWENTE and ONERA Eulerian trajectory solvers to take into account phase change phenomena and secondary particle re-emission (multi-bins methods)
• Iterative algorithms have been implemented in all 2D accretion solvers in order to take into account the coupling between accretion, impact and erosion phenomena.
ONERA 2D tool was successfully implemented in the industrial environments of SNECMA, AIRBUS and DASSAV. TAI implemented HAIC models into its in-house 2D icing tool. THAV improved its in-house probe-dedicated tool by using some outcomes of HAIC SP6 and ONERA support. PAI worked with CIRA to integrate CIRA’s icing tool in their environment.
ONERA 3D Lagrangian trajectory solver (SPARTE) being already used by SAFRAN before HAIC project, the integration of the updated version of SPARTE in SAFRAN environment did not encounter any difficulty. To date, the integration of ONERA 3D tool in AIRBUS environment is still in progress. Due to some technical difficulties, its installation on AIRBUS platform failed. As far as DASSAV is concerned, they preferred to focus on the integration and validation of ONERA2D tool in their environment.
1.3.6.3. Numerical tool validation
Validation was mostly limited to 2D tools. Model predictions were compared to experimental results issued from HAIC experiments (TSAGI heated wall accretion experiment, TUBS SP5 mixed phase ice accretion experiments) and from the literature (NRC and NASA-NRC accretion experiments mainly).
Even if there are still some discrepencies between the numerical results and the experimental ones, the agreement is generally good showing that the HAIC models are at least able to reproduce the main tendencies which are observed in the experiments. However a large part of empiriscm being involved in the elaboration of some models (sticking efficiency, erosion rate), their validity range is still an open question.
As far as 3D tools are concerned, real validation test cases have not been performed yet. In HAIC, 3D simulations have been carried out using ONERA 3D tool (CEDRE code) to simulate ice crystal trajectories in a turbofan engine and in the vicinity of an aircraft nose. However, these simulations were only aimed to prove the feasibility of such computations since result analysis was only qualitative.
1.3.6.4. Main achievements and way forward
Thanks to the work performed from the beginning in the HAIC SP6, a significant progress has been made beyond the state of the art:
• Several experiments have been carried out to improve our understanding and theoretical knowledge of the elementary physical processes which are involved in ice crystal icing phenomena: investigation of individual ice crystal impact onto a wall, individual ice crystal melting experiments, heated wall accretion experiments, observation and recording of non-spherical particle trajectories around an obstacle.
• A first comprehensive set of models has been developed, implemented in several European icing tools (mainly 2D) and partially validated against experimental results.
• Numerous validations and code cross-checking have been performed, showing the high potentiality of the new models and the feasibility of complex 3D simulations for representative configurations (engines, probe installation factors).
However, despite these major breakthroughs, some of the microphysical phenomena are not yet sufficiently understood (e.g. the most relevant physical dimensionless parameters are not identified) and data is still missing to cover the entire operating range (e.g. size, speed, temperature, melting ratio). New parametric experimental studies are still necessary to:
• better characterize ice crystal impact phenomena in terms of sticking efficiency and secondary particle properties,
• better identify relevant influencing parameters for ice erosion and quantify ice erosion rate,
• better understand and quantify the influence of wall heat transfers on ice accretion process
As far as impact and accretion models are concerned, HAIC models are not fully satisfactory. Most of them involve considerable empiricism and their calibration and validation so far was based on a limited dataset. In future work, attempts will have to be made to reduce model empiricism by employing relevant dimensionless physical numbers and improving our physical understanding of the underlying physical phenomena.
1.3.7. Coordination and Standardisation activities
Within the HAIC project, a huge effort was performed on the coordination activities. Technical activites had to be aligned among the 39 partners of the project, in order to reach common goals. This was particularly performed through formal project management with regular alignment meetings, but also through formal TRL process applied on the developed technologies.
One of the best examples of coordination is the management of the three HAIC flight test campaigns. These campaigns were the successful result of cooperation between multiple entities (airframers, engine manufacturers, equipment & system suppliers, research institutes and academics, meteorological services and SME’s able to provide specific knowledge, service, or support in specific areas) and even of international collaboration between the HAIC, EASA-HighIWC, ICC and HIWC projects for two of them. The 2015 Cayenne campaign even involved the coordination of three aircraft flying at the same time in the same area: the SAFIRE Falcon20, the NRC Convair 580 and the Honeywell B757 aircraft. This allowed comparison of in-situ measurements with remote measurements and also screening of different altitudes of the same cloud in the same period of time.
The handling of the flight test data and their analysis were also coordinated at international level between HAIC and HIWC projects through regular meetings, phone calls and HAIC-HIWC Science Team Meetings.
One objective of the HAIC project was to assess the proposed mixed phase and glaciated icing environment as defined in Appendix D of FAR 14 part 33 and P of CS-25 in light of the analysis of the available flight datasets (flights performed before and as part of the HAIC project), and provide appropriate recommendations to regulatory bodies.
At the end of HAIC project, a status of the Appendix D and P assessment was performed. Based on in-service events analysis and review, an extension of proposed envelopes regarding mixed phase and glaciated icing conditions was proposed. It also seems that different sizes of clouds should be considered depending on the type of technology (one for engines / one for air data probes). Considering the flight test measurements, Appendices D and P also seem to overestimate the real maximum TWC values, and it seems needed to revise the PSDs.
Additional post-processing is still required to finally state on the final recommendations. Statistical analysis is on-going at international level. At European level, this work is supported by the already running EASA HighIWC SC03 project. At US level, an FAA report will be issued mid of 2017, an AIAA group will cover the MoC and an ARAC Group will be created to amend Appendix D. International collaboration will be maintained on these topics, in order to keep a good harmonisation level of international regulations, which is key for aeronautical industrial actors.
Potential Impact:
1.4. POTENTIAL IMPACT AND THE MAIN DISSEMINATION ACTIVITIES AND EXPLOITATION OF RESULTS
1.4.1. Contribution of SP1 activities to the main expected impacts from HAIC
1.4.1.1. Contributions from measurements in continental convection to the main expected impacts from HAIC
We have investigated the dependence of the height of the level of freezing (occurrence of mixed phase clouds) in growing convective cumulus and the surrounding pollution conditions and their effects on the vertical evolution of cloud droplet size, aspherical fraction, as well as LWC. For this purpose we have used in-situ data of size distributions measured with scattering cloud probes mounted on HALO (High Altitude and Long Range Research Aircraft) during the ACRIDICON-CHUVA campaign, which took place over the Amazon during September 2014.
The level of freezing is here named the altitude region where LWC decreases and the aspherical fraction of small particles increases with altitude due to collision coalescence and freezing of droplets.
The results show that the level of freezing increases with increasing aerosol loadings. Also the formation of ice particles takes place at higher altitudes in clouds in polluted conditions, because the resulting smaller cloud droplets freeze at colder temperatures compared to the larger drops in the unpolluted cases. The altitude range where mixed phase clouds exist are higher over continental polluted conditions.
1.4.1.1.1. Impact
Our findings suggest implications of aerosol concentrations on the altitude and microphysical properties of glaciated clouds which may affect the IWC above polluted continental versus clean marine conditions as mainly probed during the HAIC project. Smaller, numerous ice crystals as observed in this continental convection may lead to a lower detection rate by commercial aircraft radars and therefore to a higher risk of flying into glaciated clouds impacting aircraft turbine operations.
1.4.1.1.2. Recommendation and the way forward
Regarding these new findings the impact of pollution on the microphysical properties of glaciated clouds needs further investigation. Dedicated flight campaigns sampling in convective systems over polluted and clean inflow regions are needed to enhance our understanding of the environmental conditions, e.g. aerosol loading and updraft velocities, forming regions of high IWC. A relationship between cloud base droplet concentration and anvil IWC at different temperatures are important information for aircraft operators and can be used to better prognose regions with enhanced IWC in order to enhance aircraft safety. This could be implemented in models for safety regulations.
1.4.1.1.3. Impact on aviation industries and authorities
Enhanced aerosol concentration near tropical Mega-Cities and in polluted regions may enhance droplet concentration, the altitude of mixed phase cloud occurrence and alter IWC in convective systems near e.g. airports or routes with high traffic loads. This may particularly affect low-level flying aircraft and aircraft during take-off and landing. Information on the type of convective inflow may therefore be important indicators for pilots to reduce encounters of polluted convective clouds.
1.4.1.1.4. Impact and recommendation for wind tunnel facilities
General significant progress has been made in enhancing the capacities of European wind tunnels to produce defined icing conditions. While a first and large step has been made within HAIC, further action is needed to extend the experiment range to larger particles and mixed phase conditions and augment the stability of ice delivery to the experimental test sections in European wind tunnels beyond HAIC. This will help aviation industry to test specific parts and to enhance knowledge on aircraft icing in high ice water content regions beyond HAIC.
1.4.2. Contribution of SP2 activities to the main expected impacts from HAIC
Flight tests are a key aspect of HAIC project and thanks to the successful three flight tests campaigns that were conducted in the frame of its activities, SP2 has largely contributed to expected impacts from HAIC, as described hereafter.
1.4.2.1. Characterisation of high ice water content environments
In 2004 the Engine Harmonisation Working Group (EHWG), an international committee composed of airframe manufacturers, engine manufacturers, regulating authorities, and other government agencies was assembled to study the effect of a proposed extension of icing envelopes for supercooled large drops on engine icing certification. In the process of their investigations, approximately 100 engine events thought to be related to mixed phase or ice crystals conditions were investigated.
Many of these events were in the vicinity of deep convection. The EHWG concluded that the engine power loss events were caused by a previously unrecognised form of icing inside the engine that did not require the presence of atmospheric supercooled liquid water, and was largely due to ingestion of high mass concentration of ice particles. The EHWG identified flight test research of high IWC environments as a first-order priority, and specifically, to collect accurate information on the threat of high IWC in and around deep convective clouds, as well as information on the characteristic size of the particles in these clouds.
Darwin and Cayenne Flight Tests Campaigns, organised and conducted in the frame of HAIC SP2 project have allowed the establishment of an unprecedented database with regards to ice crystals (glaciated) icing conditions. This unique and complete dataset paves the way towards update of CS25 Appendix P regulation and is used as a reference at international level for the characterisation of high ice water content environments.
1.4.2.2. Development of acceptable Means of Compliance (test facilities and numerical tools)
The development of acceptable means of compliance is key for the future of aeronautical industries as they are required to demonstrate compliance with new requirements of new regulations.
The SP2 flight tests subproject of HAIC supported the development of acceptable means of compliance (test facilities and numerical tools) through its very good flight tests results. Indeed, the characterisation of ice crystals icing conditions allowed to derive the requirements for ice generation technologies developed as part of SP5 and to be fitted in test facilities. The flight conditions during encounters were also recorded to specify the operational envelope for these test facilities.
1.4.2.3. Improvement of aircraft operation in mixed phase and glaciated icing conditions
The third flight tests campaign conducted as part of HAIC SP2 activities allowed to test new ice detection and awareness technologies that should be fitted on aircraft in the future.
These new technologies will improve aircraft operation in mixed phase and glaciated icing conditions: new ice detection technologies will allow to alert the crew about the presence of these particular icing conditions and will allow the activation of dedicated protection devices when needed, when the future awareness system, based on current on-board weather radar technology, will allow to alert the crew, in advance of the presence of ice crystals icing conditions, so that they can adapt their flight path in advance.
Combination of these two technologies will improve aircraft operation, and the flight tests campaigns allowed to demonstrate the performance of the proposed and developed concepts.
1.4.2.4. Enhancement of understanding of near icing or icing conditions at high altitude
Conducting flight tests in high IWC environment have enhanced the understanding of near icing or icing conditions at high altitude, with regards to the understanding of the environment and of the structure of mesoscale convective systems in which these particular conditions exists.
The different measurements have enhanced the knowledge on the shape and sizes of particles present at these high levels of atmosphere, as well as the existing concentrations of water. These two pieces of information (size and concentration) are keys for modelling and reproduction of the ice accretion phenomenon on Aircraft systems.
1.4.2.5. Enhancement of measurement capacities
Instrumentation developed as part of SP1 has also been successfully flight tested during the three flight tests campaigns conducted as part of SP2. These flight tests supported the development and enhancement of these probes by identifying areas for improvements and giving feedback on behaviours of the probes in high ice water content area.
These measurement capacities can be used either on flight tests aircraft to measure atmosphere or in icing wind tunnels to perform calibration of the tunnel and measure the tested conditions.
1.4.2.6. Enhancement of modelling capacities
During the last campaign of the HAIC project, conducted in 2016 out of Darwin (Australia) and Saint Denis (La Reunion – France), two identical sensors were installed at different locations on the Aircraft skin to provide validation data for ice particles trajectory models developed in the framework of SP6. These results contribute to enhance the modelling capacities of the ice accretion phenomenon.
Moreover, the measurements made during the two first flight tests campaigns are shared at international level and are supporting the development of cloud resolving models, and thus helping contribute to enhance the cloud modelling. This activity on cloud modelling is mainly conducted by NASA partners beyond HAIC project.
1.4.2.7. Reduction of the risk of incidents when an aircraft is flying in such weather conditions
The experience and understanding of ice crystals icing conditions is helping in reducing the risk of incidents when an aircraft is flying in such weather conditions, as it will support the elaboration of adequate pilot’s training and advertising of these conditions in airlines’ community.
In this aim, videos of the environment were performed and are provided to Aircraft manufacturers members of HAIC project to support the elaboration of pilots’ trainings.
1.4.2.8. Development of cooperation with international working groups and with North America
Darwin and Cayenne field campaigns are the result of an international collaboration in between HAIC and HIWC projects and involves necessary expertise in a wide range of skills (airframers, engine manufacturers, equipment & systems suppliers, research institutes and academics, meteorology services and SME’s able to provide specific knowledge, service, or support in specific areas) and the main stakeholders in the field, whether they are based in Europe, North America or Australia.
All this cooperation was coordinated by SP2 of HAIC and cooperation between all regulatory and research agencies have been increased. Regular meetings have been organised to keep international partners posted of the latest progress made and share knowledge and latest findings.
1.4.3. Contribution of SP3 activities to the main expected impacts from HAIC
New capability for remote sensing detection of High IWC from space have been developed and validated to support strategic operations. Indeed a near-real time high IWC mask was developed based on daytime geostationary satellite data. This new satellite product definitively appears to be valuable to increase the awareness of high IWC environments, thus enhancing aviation safety. Its implementation for a display in the cockpit is rather straightforward. There is a current limitation for tactical operations due to the timeline between the satellite observations and the users, which is outside the responsibility of the HAIC project as it depends of the space agencies, on the way the space-based instruments operate and the applied data transferred strategy as well. Combined with RDT capability in tracking and characterising the temporal and spatial evolution of the convective cells over a large domain, this product should provide a first global operational view of High IWC worldwide. We remind that the new version of RDT will have the algorithm of the High IWC mask implemented and will be used to characterise the properties of the convective cells all along their lives.
The products developed within SP3 provide new input data for a better understanding on the meteorology and physical processes and/or validation of the hypothesis on High IWC formation. Indeed the satellite products allow discriminating in the cloud regions with different properties. During the HAIC project, the activities performed within SP3 mainly focussed on the detection of the High IWC. Now that the SP3 team has developed and validated some detection tools, those tools should be used to explore the temporal and spatial evolution of the parent clouds to assess some first order properties on the dynamics and the cloud microphysics. Comparison with numerical cloud simulations should also help investigating the physical processes of High IWC formation. A model-to-satellite approach would be applied to validate the cloud simulations by comparing simulated satellite signals of the modelled cloud profiles (through radiative transfer calculations) to concurrent satellite observations.
Climatology of high IWC was for the first time generated based on DARDAR data and based on the High IWC mask revealing the existence of High IWC at flight altitude and clear spatial patterns as well, which could be useful in the future for aviation strategic planning purposes. This climatology will be improved in the years to come thanks to the new or upcoming geostationary satellites that operate similar sensors as SEVIRI on MSG, but also thanks to LEO missions like the EarthCARE mission with its lidar and radar instrument package.
The SP3 team has been presenting its main results in front of the HAIC consortium and has been collaborating with different European Academics and Industries operating in different fields (satellite, weather, telecommunication, aeronautic). During the last 3 years, the SP3 team has collaborated with North American groups (NCAR, NASA, ECCC) of the HIWC project and exchanged scientific ideas, discussed on fair verification methodology and started discussing on way to promote HAIC-HIWC current results through a white paper and an overview paper summarizing the main discussions on Satellite and Nowcasting hold during successive HAIC-HIWC Science Meetings.
1.4.4. Contribution of SP4 activities to the main expected impacts from HAIC
Before the launch of HAIC, no ice crystal detector neither radar was available for commercial flights. Some European suppliers and academic teams had ideas of concepts on detection and awareness technologies. Some American academic teams started similar activities few years before and had more mature concepts of products. HAIC SP4 contributed in accelerating those products development, bringing together technology suppliers and airframers. Within the projet, aircraft manufacturers defined a common specification for ice and icing condition detection and awareness functions. In parallel, several contributors of SP4 as part of EUROCAE WG 95 updated the ED103 MOPS for detection technologies or write the feasibility report for Ice Crystals long range awareness function. This gave all suppliers a clear framework and targets, validated at international level.
HAIC enables detection technologies proceeding after TRL3 to be tested in the icing wind tunnels upgraded in SP5. These tests showed the performances of the prototypes that enable to identify some issues that implied modifications. In parallel, radar technologies used past flight campaign data to assess the algorithm development. Pilots were involved in defining a proposal for HMI that was assessed stable and comprehensive. The third flight test campaign conducted as part of HAIC SP2 activities gave the opportunity to flight test all detection and awareness technologies mature enough, and to compare results with research instrumentation. New prototypes were built for this purpose. All this worked and the campaign results gave good confidence that the technologies are promising and could be fitted on aircraft in the future. Now, detection technologies need to go through industrialisation process what will take some years of work. Radar software solution was judged mature but would require further activities (e.g. thresholds validation, performance assessment methodology) before implementing it on an Airbus aircraft or retrofiting it on in-service aircraft.
These new technologies will improve aircraft operation in mixed phase and glaciated icing conditions:
• new ice detection technologies will allow to alert the crew about the presence of these particular icing conditions and allow the activation of dedicated protection devices when needed,
• future awareness system, based on current on-board weather radar technology, will allow to alert the crew of the presence of ice crystals icing conditions in front of the aircraft, and so to adapt their flight path in advance.
1.4.5. Contribution of SP5 activities to the main expected impacts from HAIC
In SP5, four icing facilities have been enhanced to be able to produce glaciated and mixed phase icing conditions on wide range of speed, temperature and altitude in compliance with the requirements of the regulation and the specifications of the aircraft, engine and air data probe manufacturers. The objective was to develop these facilities in order to have experimental acceptable means of compliance that could be used for the certification of equipment like air data probes or detectors and useful tools for the validation of the numerical code, the understanding of the icing phenomena and the assessment of the technologies.
Icing facilities contributed to the development and the selection of the detection technologies developed in SP4 providing experimental data to assess their maturity before implementing them on aircraft for flight tests. They also participated to the inter-comparison of the wind tunnel and flight instrumentations from SP1 to check their consistency. Finally, icing facilities were used to build an experimental database in order to validate the numerical code developed in SP5.
One major objective of SP5 was to define a common methodology for the calibration of the facilities involved in the HAIC project. The methodology proposed includes the calibration process, the parameters to be measured and their acceptance criteria, the possible instrumentation recommended for calibration and a cross-comparison test procedure to check the consistency of the simulated test conditions of a facility after some modification or from one facility to another. This methodology has been shared with other facilities from North America to initiate discussions with the SAE icing committee AC-9C about the updating of the recommendation ARP5905.
1.4.6. Contribution of SP6 activities to the main expected impacts from HAIC
1.4.6.1. Enhancement of modelling capacities
The work performed in HAIC/SP6 allowed to strongly enhance the modelling capababilities related to ice crystal icing. Based on original dedicated laboratory experiments and as well on some published experimental results (mainly from CNRC and NASA), a first comprehensive set of models has been developed for crystal trajectories (dynamics, heat exchange with the air and phase change), crystal impact phenomena (impact regime thresholds, secondary particle characteristics), and ice accretion phenomena (sticking efficiency, freezing fraction, erosion rate, heat transfers, etc). Even if some of these models involve a large part of empiricism and if their calibration and validation were so far based on a limited dataset, these models represent a major progress beyond the state of the art compared to what was existing at the beginning of HAIC project.
1.4.6.2. Development of numerical tools as acceptable Means of Compliance
The overall objective of HAIC/SP6 was to provide the European industry with validated numerical tools which could be used as cost effective means to reduce the need for testing during the development phase and certification phase of new aircraft products (mainly probes and engines).
Thanks to the work performed in HAIC/SP6 a first generation of Ice Crystal Icing (ICI) simulation tools has been developed and integrated in several industrial environements. As far as 2D tools are concerned, the ONERA 2D icing suite (IGLOO2D) has been successfully integrated and tested in AIRBUS, SAFRAN and DASSAV’s environment. Piaggio Aero worked with CIRA in order to assess CIRA’s 2D icing tool. TAI chose to directly implement HAIC models in their own in-house icing tool. Even if these 2D tools have a limited use for industrial purposes (especially for engine and probe design and certification), they represent an essential milestone on the route to the development of validated 3D tools.
As far as 3D tools are concerned their development and validation were much more limited than for the 2D case. To date, ICI models have only been fully implemented and tested in ONERA 3D Lagrangian trajectory solver and in THALES in-house tool (2.5D dedicated tool for probe icing simulation). Validations have been performed (especially by SAFRAN and THALES) showing a correct qualtitative behavior of the codes and proving the feasibility of complex representative numerical simulations. However 3D tools still need to be further developed and validated before they could be used as acceptable means of compliance (AMC).
To sum up, even if the original overall objective was not reached, HAIC/SP6 has paved the way to make numerical tools usable by industry as an acceptable means of compliance for certification.
1.4.6.3. Development of cooperation with international working groups and with North America
A successful international cooperation has been initiated in HAIC/SP6 with NASA and CNRC. This cooperation was made possible thanks to the active participation of HAIC/SP6 researchers to the main international conferences dedicated to in-flight icing (AIAA conferences in 2014 and 2016 and SAE conference in 2015) for which the attendance of North-America researchers and engineers is always very important. There were also intense exchanges between NASA, CNRC and European reserachers during the “models & tools” sessions of the two HAIC public forums.
Thanks to the work performed in HAIC and the numerous publications and international communications, several European researchers are now considered as ICI experts by the international community and the collaboration with North-America should continue after HAIC project.
In parallel of the collaboration with NASA icing branch and CNRC, another international cooperation has been put in place through the involvement of HAIC/SP6 researchers (from TUD, AGI, UTWENTE and ONERA) in the Engine Icing Working Group (EIWG). Several HAIC researchers were invited to make a presentation of their main results and to participate to a round table during workshops and to participate to international teleconferences. EIWG is still active and several European researchers involved in HAIC/SP6 are now members of this working group.
1.4.6.4. Strengthening of the European aeronautic industry competitiveness
By accelerating certification and dramatically reducing costs, numerical simulation is a strong contributor to the industrial competitiveness, as well as to the reputation of manufacturers as it also helps mastering the development agenda.
By providing a first 2D ICI numerical capability in industrial environment and as well, but to a lesser extent, a first 3D capability, HAIC enabled to strengthen the European aeronautic industry competitiveness and to reduce its dependency on large ground testing facility (like the NASA PSL facility) which does not exist in Europe.
1.4.7. Main dissemination activities
HAIC communicated with the aeronautical community as a whole using means such as conference presentations (including 6th AIAA Atmospheric and Space Environments Conference, SAE 2015 International Conference on Icing of Aircraft, Engines, and Structures, and HAIC Forums), articles, press releases, newsletters, and the public website (www.haic.eu).
Many scientific papers were published during the course of the project (208 publications in conference proceedings and 49 publications in peer-reviewed journals). Leaflets and posters were displayed on various occasions and the project had a stand during the AeroDays in October 2015. The project also continuously liaised with international experts in particular through the HAIC Advisory Board (including FAA and EASA representatives), the HIWC project (High Ice Water Content), the EIWG (Engine Ice Working Group), the ICC (Ice Crystals Consortium) and the EUROCAE Working Group 95 (Ice Detection System and Weather Radar).
Various dissemination materials are also available through the public website as are the public deliverables in particular the synthesis of HAIC recommendations regarding standardisation topics & validation/amendment of Appendices D&P.
1.4.8. Exploitation of HAIC results
1.4.8.1. Exploitation of Instrumentation results
• New activities will be launched to increase the TRL and further exploit the AMPERA system
• The CU-IKP will be made available to other organisations for calibrations
• Cloud probe instrument inter-comparisons are proceeded within the EU funded projects DACCIWA and EUFAR and the German DFG Priority programm SPP1294 HALO. Acquired cloud data are accessible for collaborations on international level.
• A series of current and future science publications is planned.
• Improving the measurements capabilities in CIRA icing wind tunnel for extended cloud conditions (SLD)
1.4.8.2. Exploitation of High IWC Flight tests Campaigns results
• Aviation rulemaking:
o Issue recommendations for new regulations (FAA report planned for April 2017)
o Include IWCs deduced from Radar measurements to increase the number of data points for the statistics
• Radar calibrations and intercomparison thanks to the simultaneous flights of the F20 and the CONVAIR during the Cayenne F/T campaign + 1 flight collocated with Cloudsat path
• Intercomparison of measurements devices (ROBUST hot wire probe versus IKP-2, Airbus Nephelometer versus 2DS...)
1.4.8.3. Exploitation of SP3 Space-borne Observation & Nowcasting of High IWC Regions results
• Complete the operational implementation of SP3 High IWC detection schemes on new GEO missions (HIMAWARI, GOES-R) for a service with global coverage
• Pursue of the exploitation of HAIC database to develop new High IWC detection schemes (e.g. night-times detection algorithms), to produce state-of-the-art High IWC climatology, and to validate RDT prototypes identified during TRL6
• Update of operational SP3 products according to demonstrated improvement or new generation of SP3 product
• Investigate and understand High IWC occurrence through concurrent numerical cloud simulations, and airborne and space-based HAIC observations/products
• Scientific exploitation of the High IWC climatology from both LEO and GEO products
• KNMI partner in proposal ESA feasibility study with Dutch tech-innovation company S&T for testing real-time dynamic route planning tool for aviation (http://www.meandair.com)
• Exploratory talks between KNMI and Dutch airliner KLM for new data provision & services, including High IWC
• CNRS partner of a EU H2020 "FET-Open research and innovation actions" proposal submitted in January 2017 dealing with laboratory experiments and cloud simulations for which HAIC airborne measurements are also relevant (simulation and representation in atmosphere models of ice-ice interaction)
• High IWC mask and RDT will be used in French ANR EXAEDRE (Exploiting new Atmospheric Electricity Data for Research and the Enviromnent) field campaign with French Falcon in its HAIC SP2 configuration (September 2018 in Corsica, France)
• Promote HAIC SP3 results through formal and informal seminars
• Pursue the collaboration between CNRS, KNMI, Méto-France and Airbus on satellite-based High IWC detection and nowcasting
1.4.8.4. Exploitation of SP4 High IWC Detection & Awareness Technology results
Awareness system development (Radar)
• Use campaign results to further develop algorithms for the High Altitude Ice Crystals awareness technology based on Weather Radar
• Pursue radar development and exploit capability established within Europe
• Pursue radar development and exploit capability established within Europe (HONEYWELL)
Detection system development
• Further optimise sensor hardware and processing algorithms (ZA-INT)
• Continue to advance the existing ICD system for research aircraft, aircraft certification, and wind tunnel testing (SEA)
• Develop a single package ICD for commercialisation (SEA)
• Partner with an already approved aircraft supplier for development support and commercial production (SEA)
• Further advancement of detection algorithms for both bulk (large sample volume) and particle tracking (small sample volume) technologies (NRC)
• Comparison with PDP data from Cayenne flight campaign (different atmospheric conditions and installation) (NRC)
• Transition technology to an approved aircraft supplier (NRC)
1.4.8.5. Exploitation of SP5 High IWC Test Capability Enhancement results
Exploitation of the HAIC results in SP5 is mainly being done through:
• Communication and promotion of the tunnel upgrades to customers and aerospace contacts
• Usage of the upgraded facility for industrial tests.
1.4.8.6. Exploitation of SP6 High IWC Tools & Simulation Development results
• Pursue the research on icing through the submission of at least 5 collaborative research proposals.
• Support by ONERA and CIRA to European aerospace industries (Airbus, Dassault, SAFRAN, Thales, Piaggio, ...) for aircraft, engine and probe design/development and certification.
• Support to CIRA IWT’s customers thanks to integration of numerical and experimental capabilities.
• Writing of new publications based on the last HAIC SP6 results for submission to international scientific results (3 papers at least currently in preparation).
1.4.8.7. Exploitation by HAIC industrials partners
• Enhancement of instrumentation during future aircraft certification flight tests in supercooled droplets icing conditions or development flight tests in ice crystals icing conditions, based on HAIC results and lessons learnt.
• Launch of development of new detection and awareness technologies relying on HAIC results. This will conduct to improvement of in-service aircraft (retrofit and/or forward fit).
• Use of new IWT capabilities for probes, engines or detectors development or qualification tests in collaboration with suppliers.
• Use of new / enhanced analytical tools in the development of new products
• Enhancement of tools with the last models of HAIC.
• Continuous improvement of tools by taking into account
• Participation in additional research project to pursue the work of HAIC and the finalisation of acceptable Means of Compliance
• Validation of HAIC tools vs. internal experiments and datasets.
• Potential Creation of a dedicated icing department at TAI.
List of Websites:
More information about the project can be found on the project website: www.haic.eu
Main HAIC contacts are:
Florent Huet
HAIC Project Coordinator
AIRBUS Operations SAS
316, route de Bayonne, 31060 Toulouse Cedex 09, France
Tel. +33(5) 61 18 82 81
Florent.Huet@airbus.com
Alice Calmels Grandin
HAIC Technical Director
AIRBUS Operations SAS
316, route de Bayonne, 31060 Toulouse Cedex 09, France
Tel. +33(5) 61 93 66 91
Alice.Grandin@airbus.com