Manoeuvring Noise Evaluation Using Validated Rotor State Estimation Systems

The MANOEUVRES project aimed at the demonstration of the feasibility of an innovative approach to noise abatement in rotorcraft terminal manoeuvres based on in-flight measurement of the rotor state. In particular, a novel sensor system for rotor tip-path-plane angle of attack was designed, developed, and tested, together with the necessary signal conditioning, in order to assess its capabilities in view of application on production helicopters.

This sensor was integrated on-board an actual helicopter for on-ground demonstrations and validation. Based on the availability of this new sensor, an algorithm was developed that, together with other vehicle data (such as airspeed), enabled the run-time estimation of the emitted noise. This algorithm exploited an acoustic data prediction process resulting from a dedicated study, which includes the analysis of the dependency of acoustic emissions on actual (unsteady) flight conditions as based on steady, quasi-steady and full-unsteady approaches, as well as the examination of the sensitivity of the emitted noise with respect to perturbations of a given trajectory.

The results from the acoustic prediction processes were considered correlated with experimental data provided by the GRC5 consortium. A human-machine interface was designed according to aeronautical standards to provide useful information to the pilot in terms of emitted noise, allowing for flying low noise procedures with improved awareness and effectiveness. Preliminary testing was carried out to assess compliance of this noise indicator with piloting requirements. The team involved Politecnico di Milano technical university; University of Roma Tre; Vicoter, a SME specializing in mechanical design, analysis, and testing; and Logic, a SME specializing in the design, implementation and testing of certified software and hardware for aeronautics, including rotorcraft systems.