At the end of 2009, under the supervision of Mr. Václav Chvála, Eng., Chief Inspector for ULL equipment of the Amateur Aviation Association of the Czech Republic, we successfully carried out tests of the strength of the plane’s structure under various loads. The tests included the strength tests of the fuselage, wings, ailerons, flaps, empennage, landing gear, engine mount, and control system according to the Czech UL-2 and German LTF UL regulations. The strength of the wing was tested until its break, which occurred at the ultimate load of 5.3 g x 1.5 and the maximum take-off weight of 472.5 kg. The strength tests of the empennage were carried out with various prescribed loading combinations. The test of the landing gear also included a drop test.

The strength tests of the plane were successful and have proved that Viper SD4 meets all prescribed conditions for the structural strength in accordance with the mentioned regulations.