10-Ton-Payload USAF V/STOL Studied
Paris—Boeing Co. and North American Aviation are expected to receive Air Force approval soon for detailed design studies of powerplant configurations for a proposed C-6A 10-ton-payload V-STOL transport. If approved the aircraft would be a direct follow-on to the 4-ton-payload Ling-Temco-Vought XC-142 tilt-wing aircraft now under evaluation. Powerplants to be studied include vectored- thrust, direct-lift and fans.
Current C—6A studies being conducted by Boeing and North American under separate contracts of $330.000 each are designed primarily to determine penalties that must be paid in over-all performance, range and operating costs to gain capability of vertical flight as compared with aircraft designed solely for short takeoffs and landings.
Both firms are scheduled to present their findings this week to Air Force officials at the Pentagon.
The configuration of an early North American C-6A-type design was shown at the Paris Air Show here. It now has been superseded by later designs, including study of a compound vehicle using helicopter techniques for vertical lift and those of a conventional aircraft for range and endurance.
Air Force mission requirements laid down for both companies include a stipulation that the aircraft must have ferry range of at least 2,600 mi. The high-wing model shown by North American here was to have been powered by two high-bypass-ratio. vectored-thrust powerplants, housed in pods on either side of fuselage. Power would have been augmented by direct-lift engines located in root sections of the two pods. A tilt-wing design such as that employed on the XC-l42 is not being considered for the C-6A because of additional strains that would be involved in lifting relatively heavy loads and carrying them over long distances.
Primarily, the aircraft probably would be employed to carry cargo over medium ranges in support of combat troops in the field, although there are some proponents
in the Air Force who would employ it as vehicle to make deliveries from the continental U. S. or other major supply area directly to a battle zone. Current studies by the two contractors also include investigation of safety factors, the minimum time required for the aircraft to remain in an approach stage where it would be particularly susceptible to enemy ground fire and use considerable fuel and new techniques that might be required for identifying landing zones so that pilots could recognize them in various kinds of terrain.
An official of one of the two companies says initial assessments indicate there are no significant penalties for vertical as opposed to short-takeoff flight in an aircraft such as the C-6A if pilots can be trained to make minimum approach and hover. “If he needs 2,000 ft. to make an approach, then there's no need to have a vertical capability' he added. “Then vou might just as well stick with STOL"