In 1971 the USAF began to put together the specification of a new transport as a possible replacement for its fleet of Lockheed C-130 Hercules aircraft. In early 1972 requests for proposals were sent out to nine US manufacturers, and those of the Boeing Company and McDonnell Douglas Corporation were selected for competitive evaluation under the respective designations YC-14 and YC-15.
The Boeing Model 953 design for STOL performance was based on the use of a supercritical wing, developed by NASA from the wind-tunnel research of Dr Richard Whitcomb, which provides highly efficient performance from the wing at high subsonic speeds. To this wing Boeing added an advanced wing upper-surface blowing concept, mounting the twin engines above the wing so that their efflux was exhausted over the wing. With the wing's leading-edge and Coanda-type trailing-edge flaps extended, the high-speed airflow from the engines tended to cling to the upper surface of the wing/flap system, and was thus directed downwards to provide powered lift.
Designed to carry 27,000 pounds of cargo in and out of short, unimproved airfields, the Boeing YC-14 is powered by two shoulder-mounted GE CF6-50 engines
The Boeing YC-14 prototype (72-1873) for competitive evaluation against the McDonnell Douglas YC-15 was flown for the first time on 9 August 1976. Maximum payload was 150 troops or 36,742kg of freight in conventional operations, while for STOL operations from an airfield of less than 572m the payload was still a useful 12,247kg.
At the completion of testing, in the late summer of 1977, the YC-14 prototype was returned to Boeing for continuing development, if the company so wished, but no further government funding for development or procurement was forthcoming.
Boeing’s YC-14 program was aborted after 600 hours of flight testing with two prototypes.
Engines: 2 x GE CF 6-50D, 226.9kN
Take-off weight: 97977 kg / 216003 lb
Empty weight: 54000 kg / 119050 lb
Wingspan: 39.3 m / 128 ft 11 in
Length: 40.1 m / 131 ft 7 in
Height: 14.7 m / 48 ft 3 in
Wing area: 163.7 sq.m / 1762.05 sq ft
Cruise speed: 750 km/h / 466 mph
Range w/max.fuel: 740 km / 460 miles