To investigate the transient processes by the mechanical foam destruction, a horizontal lamella is loaded with a falling drop. It is shown, that the drop can pass the lamella without destruction. The motion of the lamella is calculated numerically on the base of the describing differential equations, by considering the interia, surface tension and the Gibbs/Marangoni elasticity. The reduction of lamella thickness does not increase inevitably the rupture probability. A change between stable and unstable regions is found. The calculations show that high rupture probability occur when the minimum density of coverage has small values.