Analyzing Helicopter Evasive Maneuver Effectiveness Against Rocket-Propelled Grenades

Abstract

It has long been acknowledged that military helicopters are vulnerable to groundlaunched threats, in particular the RPG-7 rocket-propelled grenade. Current helicopter threat mitigation strategies rely on a combination of operational tactics and selectivelyplaced armour plating which offer little protection. However in recent years a number of active protection systems (APS) designed to protect land-based vehicles from rocket and missile fire have been developed. These systems all use a sensor suite to detect, track and predict the threat trajectory, which is then employed in the computation of a defensive kill mechanism intercept trajectory. In this paper it is proposed that although a complete APS in its current form is unsuitable for helicopters, the APS track and threat trajectory prediction sub-system could be used in the computation of an optimal evasive manoeuvre. It is further proposed that this manoeuvre can be found by solving a specific pursuit-evasion differential game. To evaluate the game, nonlinear dynamic and spatial models for a helicopter, RPG-7 round and gunner & evasion strategies were developed and integrated into a bespoke simulation engine. Analysis of the results from representative vignettes demonstrates that the simulation yields the value of the engagement pursuit-evasion game. It is also shown that in the majority of cases survivability can be significantly improved by performing an appropriate evasive manoeuvre. Consequently this simulation may be used as an important tool for designing and evaluating evasive tactics and manoeuvres leading to improved rotorcraft survivability.