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Manoeuvring Noise Evaluation Using Validated Rotor State Estimation Systems

Final Report Summary - MANOEUVRES (Manoeuvring Noise Evaluation Using Validated Rotor State Estimation Systems)

Executive Summary:
This report presents a description of MANOEUVRES context and the main objectives. In particular, it provides a description of the main S & T results/foregrounds, the potential impact (including the socio-economic impact and the wider societal implications of the project so far) and the main dissemination activities and the exploitation of results.

Project Context and Objectives:
Radiated noise is among the main factors that limit public acceptance of rotorcraft vehicles, hindering a wider diffusion of these unique machines that still exhibit a considerable growth potential in terms of performance, cost effectiveness and social usefulness at large. The problem is particularly felt when operating in proximity to the ground, as in approach and departure procedures, in densely populated areas.
Several European research projects have already dealt with identification of optimal rotorcraft trajectories, minimising the noise emitted nearby populate area. At the moment, all these developed noise optimization tools use static acoustic maps that neglect the influence of unsteady flight conditions. MANOEUVRES investigates these limitations and seeks improvement performing real-time noise estimation based on in-flight rotor flapping measurement. Furthermore, while actual blade flapping sensor systems are experimental applications, the MANOEUVRES system is intended for application on production helicopters (designed from the beginning tacking into account constraints and requirements of a possible future certification under CS 27/29), so design and development consider all relevant requirements, in particular regarding safety, operating and environmental conditions, human-machine interface and software implementation.

The MANOEUVRES project aims to study and develop enabling technologies towards an innovative approach to noise abatement in rotorcraft manoeuvres by way of an enhanced pilot noise awareness. This is based on the real-time presentation of the emitted noise level, through a new cockpit instrument: the Pilot Acoustic Indicator (PAI). By monitoring the PAI, the pilot will be able to appropriately adjust flight controls, to avoid highly disturbing flight conditions, such as those when strong main rotor BVI (Blade-Vortex Interaction) occurs. Emitted noise is estimated through a suited acoustic database fed by information retrievable on-board (advance ratio, thrust coefficient) plus an innovative in-flight measurement of the main rotor tip-path-plane angle of attack. This measurement represents the core technology of the project and is performed through a novel contactless sensor system able to estimate the blade flapping angles.

Project Results:
The project involved the design, develop and testing of a novel sensor system intended to return run-time information on vehicle noise in non-steady conditions.
The MANOEUVRES system includes:
- an innovative on-board apparatus devoted to the measurement of main rotor flap angles;
- the necessary signal conditioning system;
- an estimation algorithm for main rotor angle of attack (AOA);
- an acoustic prediction algorithm;
- a graphical display (Pilot Acoustic Indicator) of the noise signal to the pilot.
Furthermore, the MANOEUVRES project provides an in-depth study of the non-steady effects of manoeuvring flight on noise prediction and innovative, reliable flight control laws capable to reduce pilot workload in manoeuvring flight
a) Timeline & main milestones
The project duration was 32 months.
Three technical work packages (WP1, WP2, WP4) were running since the beginning of the project. WP3 focusing on the flapping measurement system development is starting at Month 16. Support activities (WP5) were ongoing for the whole period.
The PAI solution has been chosen and implemented, and has been tested in the second year of the project.
Unsteady noise predictions and correlation with flight test data have been performed in the second period of the project. The MANOEUVRES sensor system has been integrated and tested on a ground test vehicle (AW139) in the last 6 months of the project for final validation and functional/performance assessment.
b) Environmental benefits
The MANOEUVRES system will significantly contribute to the reduction of rotorcraft environmental impact in term of noise emissions, including during non-stationary manoeuvring flight conditions, enhancing public acceptance of rotary wing operations in populated/environmentally sensitive areas.
c) Maturity of works performed
A full-scale integrated prototype of the rotor state measurement system has been installed on a ground test vehicle (AW139) and validated, demonstrating a level of maturity up to TRL6. The pilot acoustic indicator has been assessed through a test campaign on an industrial R&D flight simulator.
The PAI solution has been chosen, implemented and tested in the second year of the project.
Unsteady noise predictions and correlation with flight test data have been performed in the second year of the project. The MANOEUVRES sensor system has been integrated and tested on a ground test vehicle (AW139) in the last 6 months of the project for final validation and functional/performance assessment.

Potential Impact:
MANOEUVRES addressed a very sensitive topic in rotorcraft operations, that is external noise generated during manoeuvring flight in terminal areas, which is commonly recognized as a limiting factor for this kind of air transportation and aerial work. A very promising methodology calls for evaluating the emitted noise in flight, based on the knowledge of characteristic parameters of the state of the rotor(s), and finding a way to appropriately convey this information to the pilot, in order to allow adequate actions on his part. MANOEUVRES therefore stands out as the first co-ordinated and product-oriented approach to this methodology, aimed to the development, prototypal implementation and preliminary testing of novel equipment to be fitted on production helicopters, covering the whole spectrum of habilitating technologies: acoustic prediction models, rotor state measurement systems, and pilot in-flight monitoring systems. Investigation of novel concepts in rotorcraft control, monitoring and identification based on the availability of new rotor state measures is also foreseen. However, the main impact of the project is to be found in the availability of a full-scale integrated prototype of the system composed by rotor state measurement systems and the subsystems necessary for the integration within the actual helicopter avionics, and the pilot acoustic indicator.

The academic and industrial partners have been strongly committed to communicate and disseminate the scientific and technical results developed in the MANOEUVRES project. Hence, dissemination has been based on a combined effort in the online communication (partners’ web site, project web site), publications (scientific journals, lectures, magazines and journals of aerospace sector), aerospace exhibitions, fora, conference and events.

The Consortium has identified three main mechanisms for the exploitation of the project results:
- Influencing practices and products: careful exploitation of the project results allow project stakeholders to assess the applicability of the project results to their cases and will ultimately allow the consortium to influence products, commercial practice and scientific research.
- Strategic and brand influence: a partner can exploit knowledge gained during the project to influence strategic direction within the company and to make better business decisions.
- Patent: the possibility to apply for a patent has been investigated by the Consortium in accordance with the Topic Manager. The request for patent registration has already been submitted.

List of Websites:
www.manoeuvres.eu