New Technologies for Green Rotorcraft

The paper presents main results obtained in the DLR rotorcraft program within the last years such as computational tools (e.g. CFD development and validation for aerodynamics and aeroacoustic), noise studies, environmental studies such as all weather issues, new technologies for active rotor control and active blades, flight mechanics and handling quality studies, recent developments for tiltrotor applications, crash analysis and modelling and helicopter flight tests including studies for noise abatement procedures. The DLR rotorcraft research program is closely connected to the Onera rotorcraft program and is part of international networks of cooperation with many partner organizations. DLR and Onera have been designing rotorcraft airfoils for many years. Almost all Eurocopter helicopters use these airfoils. One important asset to improve the aerodynamic efficiency (i.e. reduce the fuel consumption and the exhaust) of rotorcraft or rotorcraft components is the access to accurate prediction tools. Therefore a large effort was spent during the last two decades to develop so called Computational Fluid Dynamics (CFD) methods which are able to compute the flow around a complete rotorcraft. In order to validate such methods the GOAHEAD (Generation of Advanced Helicopter Experimental Aerodynamic Database for CFD code Valication) project was carried out. One of the main factors restricting the use of rotorcaft in civil and partly in military missions, is the noise emission of these vehicles. Therefore ongoing research concerns itself with the development and validation of methods for the prediction of external and internal noise and specific solutions for noise reduction. This includes the main and tail rotor/Fenestron noise, as well as the engine noise. The successful application of helicopters in Emergency Medical Services (EMS), in rescue operations (Save and Rescue: SAR) and in specific military missions is limited by bad weather conditions, especially degraded visual environments and icing conditions. Helicopters are frequently operated in close proximity to the ground at short distances from obstacles (trees, power poles, etc.). The workload of the pilot and the accident risk in such difficult missions is considerably higher than that of a typical fixed wing aircraft. Therefore research is for flight control, man-machine-interface, sensor development, information display, pilot assistance and navigation systems. At the same time new operational procedures and redundancy concepts under safety- and certification aspects are developed. The results achieved with the flight test aircraft Flying Helicopter Simulator (FHS) of DLR are of specific importance. A complete test environment for the FHS has been developed (system identification, real time simulation, ground simulator, model following control system (MFCS), integration of an active sidestick including the required software in the aircraft and the ground simulator)