4 - Flutter Tests (Aerodynamic Resonance) Before its first flight, the CAP10C underwent ground vibration tests over the weekend of 17-18 February 2001. The purpose of these tests was to show that there is no risk of flutter (aerodynamic resonance) up to 1.2 VD, the speed calculated in a dive, making it possible to calculate VNE, with which pilots are more familiar. VNE being equal to 0.9VD and the VNE of the CAP10 being 340 km/h, VD is therefore 378 km/h and 1.2VD is 453 km/h. That is however, not a reason to exceed VNE! Only the test pilot is authorized to do so and must even check in flight for the absence of vibrations up to VD. Apex Aircraft trusts its ground vibration tests and analysis results from Professor NIEDBAL. The illustrations show a CAP10 equipped with many sensors, in fact miniature acceleration gauges, which are connected to recording units. The airframe is isolated from the ground by placing air mattresses under the wheels, and various parts of the aircraft are excited by a vibration system. The measurement part requires two and a half days of work, but the first elements of the analysis were not published until two or three weeks later.

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