Impact analysis of threat directions to hydrodynamic Ram vulnerability of aircraft fuel tank

Hydrodynamic Ram (HRAM) is one of the mostserious damage modes to military aircraft, and researching tanks'dynamic response is helpful for identifying high risk region and critical threat directions. In simulating the HRAM of fragments impacting metal fuel tanks the PAM-Crash is employed, in solving the fluid-structure interaction the smoothing particle hydrodynamics (SPH) method is used, and then critical threat directions under typical flight modes were confirmed. Results indicate: impacting directions can influence damage degree; flight and fuel conditions have effect on critical threat directions, vulnerable area and kill probability; when an aircraft is in level, threats from upside are more critical; when it maneuvering to vertical climb/dive or horizontal hover, both sides of wings are critical directions and the most critical conditions will occur.