Initially procured in 1956, the Sikorsky (model S-56) CH-37A/CH-37B, with a crew of three, was a large medium lift transport helicopter. Clam shell doors in the nose provided access to a cargo compartment that could accommodate two jeeps or a 105mm howitzer. The Mojave could carry 26 troops or 24 litters in the MedEvac role. The CH-37 had a single five-bladed main rotor and a metal four-bladed tail rotor. The CH-37 was powered by two Pratt & Whitney R-2800-54 2100 hp piston engines and had a speed of 131 mph (114 knots). It was used for aircraft recovery in Vietnam.