Flutter certification analysis of the Alpi Aviation P300 aircraft

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Vicoter completed the GVT (Ground Vibration Test) and flutter calculations of the Pioneer P300 produced by Alpi Aviation (www.alpiaviation.com). The activity, carried out in order to obtain the DULV certification of the aircraft, was carried out in two successive phases:

  1. Experimental measurement of aircraft modes in free-free condition.
  2. Extraction of mass matrices, stiffness and damping from the experimental results and numerical coupling between the dynamic and the aerodynamics structural behaviours, in order to obtain the aircraft V-g diagram and the minimum flutter speed.

The first phase of the work took place at the customer’s site in San Quirino, Pordenone.

The plane was suspended through a system of springs designed and manufactured by Vicoter. The springs had the purpose to decouple the rigid behavior of the aircraft from its modes.

The tests were carried out in two different mass configurations; in both configurations, 51 accelerometers appropriately distributed on all the surfaces were used. Tests were performed in MIMO mode (Multi Input Multi Output) by exciting the structure simultaneously with two electromagnetic shakers.

Moreover, dedicated impact tests were carried out to measure the modes of the control surfaces, both in stick-free and in stick-fixed configuration.

The test methodology adopted complies with the certification requirements of the LTF-UL standard and can also be used to meet the standards set by the CS_VLA, CS_VLR, CS-23, FAR-23.

The second phase of the work was dedicated to the coupling between the aerodynamics and the dynamic behaviour of the aircraft. The effect of the aerodynamic was numerically introduced by means of a DLM-type panel method (Doublet-Lattice Method) on the structure, which was represented with the matrices of mass, stiffness and damping directly extracted from the modes measured in the GVT tests. Several simulations were carried out using the NeoCASS aeroelastic software (www.neocass.org) in order to take into account: different mass configurations, different heights, the stick-free and the stick-fixed configuration. The results allowed to define the flutter-free flight envelope of the aircraft.

Vicoter thanks Alpi Aviation for the courtesy shown during the tests at its headquarters.