Live optical digitisation of flight instruments for flight guidance in helicopter noise measurements

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Timmermans, B.
Tuinstra, M.
Uiterlinden, R.M.
Oosten, N. van
Ionescu, S.E.
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In the second half of 2016 and the first quarter of 2017, NLR in conjunction with Anotec successfully executed a flight test campaign to collect helicopter noise and performance data. This data will form the basis for the development and validation of a numerical model for noise emission in helicopters, to complement the existing set of aircraft noise models. Based on an analysis of the European helicopter fleet, a total of eight different helicopter types have been tested during this campaign. The flight test programme consisted mainly of take-offs, overflights and approaches, based on the noise certification flight procedures described in ICAO Annex 16 Volume I. In order to capture the helicopter parameters, a carry-on measurement system was developed. This system is non-intrusive and has no parts that need to be fixed to the exterior of the aircraft. The data recorded by the carry-on system is used in the post-flight analyses, but is also fed to a guidance computer in real-time. In addition to a GNSS receiver and an IMU to measure the helicopter position and orientation, the on-board system uses a video camera and imaging software to acquire data from indicators on the instrument panel. The digitised parameters were found to correspond well with the GNSS data of similar parameters. The digitisation process is insensitive to vibrations and the system can be operated under a wide range of lighting conditions for long periods of time without requiring adjustments. The carry-on measurement system can be flexibly adapted for use in a different aircraft.