|Bell Model 54 / XH-15
By February 1946, action was begun by the USAAF to procure a new type of liaison and observation aircraft. The specification called for a two-seat, single main rotor type of about 1360kg gross weight and to be powered by a supercharged engine of approximately 260hp. G & A Aircraft Co (Firestone) of Willow Grove, Pennsylvania, won first place and was awarded a contract for three examples of its 100hp Continental A100 powered XR-14-GA (s/n 46-527/529) which were never built. Bell, with its Model 54 proposal, won only second place in this design competition. But at that time, some AAF personnel advocated a contract with Bell and in May 1946 action was initiated for the building and development of three examples of the Model 54 under the designation XR-15-BE (to be redesignated XH-15-BE in 1948). The formal contract was signed a few weeks later. The XR-15 was to be developed both for the Air Force and Army Ground Forces. It was to have all equipment, instrumentation, and performance required by the Ground Forces.
The Model 54 was an all-metal four-seat helicopter using the same basic rotor system employed in other Bell models, featuring a two-blade rotor with stabilising bar. Power was provided by one 275hp Continental XO-47-5 engine located at the bottom of the rear cabin. Accommodation was provided for a crew of two seated side-by-side in a largely glazed cabin. It had a semi-monocoque fuselage reinforced with stiffeners and fitted with a horizontal stabiliser, and a tricycle (later quadricycle) non-retractable undercarriage. The two-bladed anti-torque rotor was fitted on the starboard side. Three aircraft were built (s/n 46-530/532) and tested but no production contracts followed. Development of the Model 54 came to a halt at the end of 1950. No XH-15 has survived.
A.J.Pelletier "Bell Aircraft since 1935", 1992
Late in 1946 the Army Air Forces ordered three Bell Model 54 light helicopters for evaluation in the observation, liaison, and light utility roles. The aircraft were initially designated XR-15, but this had been changed to XH-15 by the time the first example made its maiden flight in March 1948.
The XH-15 was of conventional pod-and-boom layout, and its metal tube framework was covered with aluminium skin. The craft was characterized by a wheeled tricycle landing gear and an early version of the rounded plexiglass 'bubble' cockpit enclosure that eventually became de rigueur for seemingly all light civil and military helicopters. The XH-15 was powered by a turbosupercharged 285hp engine, and used the stabilizer bar-equipped two-bladed rotor developed by Bell for the earlier Model 30 helicopter of 1943.
Though funded by the Army Ground Forces (AGF) the XH-15 was evaluated almost exclusively by the Air Force, the latter service having taken control of several AGF aviation projects following the 1947 creation of the USAF. Though an essentially capable machine the XH-15 was not adopted for service use, and all three examples acquired were used by the Army as high altitude research vehicles until stricken from the inventory in the early 1950s.
S.Harding "U.S.Army Aircraft since 1947", 1990