Bird strike mitigation in civil tiltrotor: A shielded leading edge approach

Bird strike is one of the most common events that could affect the flight safety, necessitating its consideration from the early design phases to guarantee the required safety level. Statistically, the most exposed parts are the leading edges of the wings and tailplanes, as well as the windshields and engine nacelles. The use of numerical techniques to estimate the damage status generated by a possible impact with birds is now commonplace and even certification authorities accept such approach. The present work aims to present an innovative structural architecture for the wing leading edge of a civil tilt rotorcraft (NGCTR-TD) effective in preventing catastrophic failures due to possible bird impact without significantly increasing the structural mass of the components. The novelty consists in a metallic thin shield placed between the leading edge skin and the front spar, to increase the protection level of the electrical and hydraulic line placed just in such zone. The effectiveness of the proposed solution was demonstrated numerically through finite element models using the classic Smoothed Particle Hydrodynamics (SPH) approach. Several impact conditions were investigated to evaluate the influence of the impact location in span direction, the impact angle with respect to the horizonal plane, and the sideslip angle. First, a comparison between a full Finite Element (FE) model and a reduced FE model is presented. The reduced model was developed by selectively omitting non-critical structural components while preserving key elements that govern the global structural response under bird strike conditions. It offered substantial computational savings and demonstrated robust capability in replicating the full model behaviour, with minimal differences in absorbed internal energy and maximum displacement. Also, the results confirm that the shield effectively prevents simultaneous failure of hydraulic and electrical lines. The impact angle and station significantly influence the damage severity, with oblique impacts causing more critical damage. Ductile damage predominantly affects the leading edge skin, while the spar remains largely undamaged when the skin thickness exceeds a specific value (2.4 mm).