Toward noise abatement flight procedure design: DLR rotorcraft noise ground footprints model

Abstract

As a first step towards noise abatement flight procedure design, this paper presents techniques for rotorcraft noise ground footprint prediction developed at DLR, using either purely numerical computations or measured sound fields. When based on purely numerical computations or first-principles, a combination of 3D free wake unsteady panel method and a Ffowcs Williams-Hawkings (FW-H) method is used to provide noise source characteristics on a hemisphere. The noise ground footprints for a BO105 helicopter at 6° descent flight is simulated and compared with flight test data. The noise sources considered are only from a main rotor and tail rotor. When based on measured sound fields from the flight test, a depropagation procedure is used to define the noise source characteristics on the hemisphere. The verification of the depropagation procedure using purely numerical computations is introduced. Two hypothetic noise abatement procedures are simulated based on the RONAP test data.