The Royal Netherlands Air Force (RNLAF) purchased the M3M 0.50 caliber gun to be installed on their CH-47 Chinook helicopters next to cabin window, cabin door and on the ramp. The integration of such systems on board the helicopter must comply with airworthiness requirements in order to be certified by the Netherlands Military Aviation Authority. One of the requirements is the clearance between bullet trajectories and any part of the rotorcraft, which must be at least six inches. NLR is contracted to support the customer with the execution of the airworthiness qualification process and showing compliance to several airworthiness requirements, such as firing clearance. NLR has developed a method combining high fidelity simulations and flight tests with video recordings, to predict and verify the clearance between the worst-case bullet trajectories and rotor blade tip positions for a given envelope. The method was successfully applied to evaluate rotor clearance for the M3M gun installation in the CH-47.
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