Experimental investigation of dynamic characteristic during civil aircraft ditching

A series of scaled model aircraft ditching tests are performed by launch facility system in Hydraulics Laboratory. According to the measured pitch angle, acceleration and pressure history, research on the impact characteristic of ditching is conducted. To solve the problem of cavitation effect which may occur in full scale aircraft, the action mechanism and effect of cavitation are studied, and an innovative experimental simulation measure is taken. It is shown that the cavitation bar directly and effectively separates aircraft bottom from water surface and therefore reduces negative pressure, thus enhancing the authenticity of the test results. The dynamic responses including stability and overload after impacting water at different initial pitch angles are analyzed to find the optimum one, which turns out to be heavily dependent on the bottom curvature of fuselage, and rebound phenomenon occurs when pitch angle exceeds a certain value because of the huge positive pressure acting at the spray root on rear fuselage. In addition, the influences of descent rate and horizontal velocity are analyzed. The results show that the descent rate mainly affects the overall load, which is of higher level of importance, while the horizontal velocity mainly affects the load of local structure.