Vibration verification test on a helicopter external mirror

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With well-established methodology, Vicoter performed the vibratory tests of a new setup for a rear view mirror to be installed on an AW109 helicopter produced by Leonardo Helicopters. The activity, commissioned by Boggi Aeronautics (www.boggiaeronautics.eu), was held at the helipad of the detachment of the firefighters of Malpensa airport, Fermo (VA), Italy. Focus of the tests was the acquisition of data for EASA certification.

The job was split in two phases: initially, an on-groud modal analysis was carried out. Seven triaxial accelerometers were installed on the mirror support and an impact MIMO technique used to measure the structural FRFs. Using these data, the experimental modes of the structure were identified and compared with the main tones excited by the aircraft (main rotor, 4x main rotor, tail rotor, …). Moreover, obtained modes were used to correlate a finite element model (frequency and shapes), accounting the real stiffness of the attachment points.

The second step consisted in the acquisition of accelerations in several flight conditions. Five triaxial accelerometers were acquired by a portable acquisition system which was boarded in the cabin and managed by the flight engineer. Purpose of this part of test campaign was to measure the vibratory levels reached during the flight and to verify the not coincidence of natural frequencies with excited ones, even in operative conditions.

The test was successfully completed.