To obtain the permit to flight, new equipments installed on a helicopter need to be evaluated even against vibratory behaviour.
Engineers of Vicoter (www.vicoter.it) were called from the DOA Boggi Aeronautics (www.boggiaeronautics.eu) to perform the experimental tests needed to demonstrate the compliance of an external mounted TC-300 Trakka Camera on a Bell 427.
During a vey busy day, at first the GVTs (Ground Vibration Tests) of the device were accomplished. A MIMO impact testing techinque, using seven triaxal accelerometers and three excitation locations, was made to obtain reliable and unbiased information about the modes with the camera really mounted on its support. A preliminary identification permitted to obtain the resonance fequencies and, comparing with the harmonics of the main and tail rotors, to exclude the possibility of coupling.
In the second part of the day, in flight measurements were performed. Using a boarded acquisition system, accelerations found in the various phases of the flight were recorded to be post-processes once in office. In this way it was possible to investigate the presence of vibratory phenomena not directly related to the mechanichs but induced by othe factors, e.g. aerodynamics.
Vicoter warmly thanks the friends Stefano Boggi and Tommaso Fiorini and all the staff of Elicompany (www.elicompany.it).