CH-53E M3M Ramp Mounted Weapon System

The U.S. Marine Corps (USMC) CH-53E Super Stallion has always had a .50-caliber crew-served machine gun mounted on each side of the aircraft to provide suppressive, defensive fire. However, these door guns only provide partial protection in the forward hemisphere, leaving the rear hemisphere of the aircraft completely unprotected. This defensive shortcoming is especially dangerous during long-range missions where the CH-53E may go unescorted by shorter-range attack helicopters. Air Test and Evaluation Squadron Two One (HX-21) was tasked to evaluate a Ramp Mounted Weapon System (RMWS), which would provide a rear hemisphere, defensive fire capability. The RMWS tested was an M3M .50-caliber machine gun and mount assembly developed by Fabrique National (FN) Herstal. Ground testing was conducted to evaluate compatibility and functionality of the system. Flight testing was conducted to evaluate compatibility, functionality, and effectiveness of the RMWS. Safe separation of ammunition links and casings was evaluated through a flight envelope expansion in airspeed, pitch, pitch rate, roll, roll rate, and rate of descent. Flight tests also involved structural data gathering and an in-depth ramp-to-deck clearance evaluation to optimize pilot technique during takeoff and landing with the system employed. The primary deficiencies discovered during testing were not a function of the gun system itself but a result of the aircraft and crew station when employing the gun system.