Monte-Carlo Simulation-Based Air-to-Ground Missile Clearance Analysis using Downwash Database of Helicopter

The safety criteria of a helicopter-launched missile is defined in MIL-STD-1289D as rotor disk clearance; 5-degree half angle cone between rotor blade and the outermost surface of the missile. Unlike an unguided rocket, missile's performance is not affected by the initial variation due the helicopter downwash. The safety condition, however, can be quite different according to the missile's initial dynamics. CFD(Computational Fluid Dynamics) is a conventional approach to analyze this kind of safety problem, but it may take several days or even months to solve a single case. For this safety problem, Monte-Carlo simulation method should be applied to consider various error conditions, which means CFD-based analysis is not applicable. In this paper we acquired CFD-based downwash database and applied the data on the missile's aerodynamic database. This method can check the safety conditions of 1,000 cases in a few hours and was validated by the launch test results.