Improved performance in next generation helicopters
Major challenges in the development of new helicopters can sometimes occur in the initial test flight or during the subsequent testing campaign. Depending on the severity of the problem, minor or even major redesigns may be necessary to ensure a configuration that is safe, economic, fast and quiet. This can result in expensive delays, especially when occurring late in the development process. The EU-funded CA3TCH project established an advanced simulation technology to predict the aerodynamic and aeroacoustic behaviour of fundamentally new rotorcraft configurations, such as the Rapid and Cost Effective Rotorcraft (RACER) developed by Airbus Helicopters. “The aim was to reproduce the full configuration as realistically as possible on the computer, as far aeromechanics and aeroacoustics are concerned,” states Manuel Kessler, CA3TCH coordinator and head of working group Helicopters and Aeroacoustics at the Institute of Aerodynamics and Gas Dynamics, University of Stuttgart. RACER specifically combines high speed and vertical take-off and landing (VTOL), allowing it to operate in remote areas and significantly extend the speed and range of emergency and rescue services. “The configuration features wings and propellers for propulsion support instead of a conventional tail rotor and is expected to reach cruise speeds of more than 400 km/h,” notes Kessler.
Faster and more versatile
RACER can achieve higher speeds than classic helicopter configurations while retaining the VTOL capability, in contrast to a conventional aeroplane. “This enables such a rotorcraft to be used for extended missions, where high speed is as important as the flexibility of VTOL without specific infrastructure, such as rescue operations in remote areas. However, certain challenges need to be addressed, like efficiency of power consumption and minimising noise,” explains Kessler. In response to these challenges, researchers further developed the high-fidelity simulation technology required to support the aerodynamic design and development of RACER. The aim was to extend from preliminary estimates to detailed design and analysis at different flight states, until the point of the rotorcraft’s first flight. The developed ‘digital flight test’ approach enables the careful examination of the rotorcraft’s performance long before the first hardware exists. “We are involved in the aerodynamic and aeroacoustic simulation of the overall system,” points out Kessler. “Our initial focus was on flight mechanical stability and aerodynamic interference of the rotor and wing. Different flight conditions were considered, including cross and reverse flights due to RACER’s wide range of expected applications. Further analyses then focused on the most efficient operation at high speeds and acoustic evaluation.”
Safer and more cost efficient
The high-fidelity computational fluid dynamics simulation of the complete configuration with all components, taking into account the fluid structure coupling at the elastic rotor blades, flight mechanically trimmed in stationary flight, provided accurate and reliable data on the expected behaviour of RACER. “This helped to identify critical points at an early stage and thus considerably reduce risk before the maiden flight, ultimately resulting in shorter development times and, of course, reduced costs,” Kessler concludes.
Keywords
CA3TCH, helicopter, simulation, Racer, rotorcraft, aeroacoustic, aerodynamic
