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 turbofan engines forward and above the wing so that their efflux was exhausted over the wing (this location also gave the airplane a quieter noise footprint.). With the wing’s leading-edge flaps 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 downward to provide powered lift. It was the most efficient powered-lift system ever developed.
The YC-14’s basic mission was to carry large, bulky payloads into and out of short, rough dirt fields that were less than 2,000 feet (610m) long, even if an engine failed. It had a large fuselage to accommodate most tanks, trucks and armored personnel carriers used by the U.S. Army.
The first Boeing YC-14 (#72-1873) took to the skies on 9 August 1976 and soon proved to have admirable performance. Two aircraft were built, the second being tail number 72-1874.
At the completion of testing in the late summer of 1977, the YC-14 prototypes were returned to Boeing for continuing development if the company so wished. Due to budget restrictions, no further government funding for development or procurement was made.
|Primary Role||STOL transport (prototype)|
|Operator||United States Air Force|
|Wingspan||129 feet (39.32m)|
|Length||131 feet, 8 inches (40.15m)|
|Height at Tail||48 feet, 4 inches (14.71m)|
|Engines||Two General Electric CF6-50D turbofans|
|Thrust||51,000 pounds (227kN) per engine|
|Cruise Speed||449 mph (723km/h)|
|Max Speed||504 mph (811km/h)|
|Range||3,190 miles (5,134km)|
|Climb Rate||6,350 feet (1,935m) per minute|
|Service Ceiling||45,000 feet (13,716m)|
|Operating Weight||117,500 pounds (53,297kg)|
|Max Payload (STOL)||27,000 pounds (12,247kg) with airfield length less than 1,875 feet (571.5m)|
|Max Payload||81,000 pounds (36,741kg) or 150 troops|
|Max Takeoff Weight (STOL)||170,000 pounds (77,111kg)|
|Max Takeoff Weight||251,000 pounds (113,852kg)|
|Takeoff/Landing Distances||Less than 2,000 feet (610m)|
|Date Deployed||August 1976|