Investigation into the aerodynamic effects of simulated battle damage to a wing

A key stage in the design-cycle of a military aircraft is the assessment of its vulnerability to hostile threat mechanisms. Such mechanisms inflict battle-damage to the aircraft structure and systems. This experimental investigation considered the aerodynamic consequences of simulated battle-damage to a two-dimensional wing. Key assumptions and techniques were identified leading to the modelling of both gunfire and missile fragmentation damage. Wind tunnel balance measurements were undertaken, together with surface pressure measurements and flow-visualisation methods. Force and moment results indicated extensive changes in coefficient values, whilst both smoke and surface visualisation paint successfully indicated the flow mechanisms present. Using these techniques the influences of damage and experimental variables were investigated, including damage type, size, location and Reynolds Number. Studies were also made into cases of multiple gunfire holes and the influence of internal wing construction. Results indicated that damage at quarter and half-chord locations gave greater coefficient changes than those seen for either leading or trailing edge damage. This was primarily due to reductions in the upper surface pressure peak due to through-flow. Such reductions were seen to extend in both a chordwise and spanwise direction. The flow mechanism identified indicated both similarities and differences to those of flat-plate jets in crossflows. Analysis of both gunfire and missile damage data lead to the development of a set of empirical relationships, which related damage location and size to coefficient changes.