Unmanned Aerial Systems (UASs) are increasingly starting to dominate the lower airspace. This increases the chance that a UAS will hit the means of transport of people e.g. aircraft, helicopters. For air traffic, the European Union Aviation Safety Agency (EASA) and the Federal Aviation Administration (FAA) are in the process of determining the threat of a UAS impact on aircraft. This will result in new rules that may impose new, or additional, requirements on the ‘wetted zones’ of aircraft and the like. Current research suggests that aircraft wetted-areas (e.g. wing leading edge) that are certified for so called ‘bird-impact’ may not sustain a ‘UAS-impact’, such an UAS-impact may even damage the primary load carrying structure. But what would happen if multiple UASs are flying close to one other? To the authors’ knowledge, the damage caused by multiple UAS impacts on a wetted surface zone has not yet been established.

A finite element modelling approach is chosen for the UAS; specifically, a Lagrangian approach is applied using material nonlinearity and damage. A comparison is made between the damage caused by a bird impactor and a UAS impactor model. To establish the resulting damage of multiple UAS impacts on a wing leading edge, a multiple-UAS impact scenario is executed. The results show that a wing leading edge capable of sustaining a bird impact may not be capable of sustaining a UAS impact, which supports previous findings. Furthermore, for all simulated cases the front spar was not penetrated by components that managed to enter the leading edge. However, for the heavier drone some deformation of the front spar was observed. The multiple UAS impact scenario causes additional damage to the leading edge with respect to the single UAS impact, with greater deformation of the front spar being observed.