Innovative measurement system to curb helicopter noise
External noise generated by a helicopter creates negative public opinion despite its high performance, cost effectiveness and usefulness. Over the last decade, many EU efforts have been devoted to reducing noise near densely populated areas by identifying optimal rotorcraft trajectories. However, all the developed noise optimisation tools use static acoustic maps that neglect the impact of unsteady flight. The EU-funded MANOEUVRES (Manoeuvring noise evaluation using validated rotor state estimation systems) project sought to overcome this limitation by performing noise computations through an innovative in-flight measurement system that computes the rotor flapping angles. The approach to abating noise in rotorcraft manoeuvres was based on the pilot acoustic indicator (PAI), a new cockpit instrument. The PAI solution was successfully implemented and tested. Project partners designed and developed a novel sensor system intended to return run-time information on rotorcraft vehicle noise in unsteady conditions. The system includes an innovative on-board apparatus to measure main rotor flap angles, a signal conditioning system, an estimation algorithm for main rotor angle of attack, an acoustic prediction algorithm and a graphical display of the noise signal to the pilot. The sensor system was integrated and successfully tested on a ground test vehicle. The MANOEUVRES team performed unsteady noise predictions and investigated their correlation with flight test data. It also assessed the PAI through a flight simulator test. MANOEUVRES outcomes will significantly contribute to reducing rotorcraft environmental impact in terms of noise emissions, even during non-stationary manoeuvring flight conditions.
Keywords
Helicopter noise, noise computation, rotorcraft, MANOEUVRES, pilot acoustic indicator
