One of the objectives of GRC5 was to implement a tool for the minimisation of noise impact on the ground, capable of being executed on-board “on-the-fly”, providing flight directives to the FMS of the helicopter. To this end reliable and fast noise predictions were made, based on actual flight conditions. The envisaged semi-empirical model to be used for this purpose required information to be derived from experimental data.

The main objective of ANCORA was to determine the transfer function between the noise measured on-board the helicopter, close to the noise sources, and the noise received on the ground by a grid of microphones, during a flight test campaign. ANCORA investigated the application of surface microphones on the helicopter fuselage and will subsequently use this knowledge for the flight test campaign. ANCORA delivered a robust and reliable mobile noise measurement system, easily scalable and optimised for minimum deployment time and cost.

During the test campaign a large number of steady-state conditions and manoeuvres were flown over a grid consisting of 31 microphones. ANCORA developed an advanced method for the determination of the transfer functions between on-board and ground microphones. All results from the flight tests and data analysis (raw data, 1/3 octave spectra, transfer functions) were made available through a data repository.