The YC-14 was Boeing’s entry in the USAF Advanced Medium STOL Transport program. It had to haul 27,000 pounds over 1,000 miles from a 2,000-foot runway. To meet these extreme specs, Boeing used NASA research on powered lift and upper-surface blowing (USB) for cutting-edge STOL performance.
Instead of mounting engines under the wings, Boeing placed them on top. Exhaust blew over the wing’s upper surfaces and trailing-edge flaps, generating extra lift through the Coandă Effect. This allowed the YC-14 to take off and land in remarkably short distances for such a large aircraft.
Wind tunnel tests showed lift problems at low speeds. Boeing added retractable vortex generators behind the engines to maintain flap effectiveness and redesigned the tail for stability. These tweaks made the YC-14 precise, controllable, and an impressive STOL performer.
The YC-14 first flew on August 9, 1976. It could fly as slowly as 59 knots or as fast as 520 knots at 38,000 feet. Despite its size, pilots reported surprisingly nimble handling, proving Boeing’s engineering solutions worked in real-world flight.
With two General Electric CF6-50D turbofans producing 51,000 pounds of thrust each, the YC-14 could lift a 55-ton M-60 Patton tank. The combination of USB and a supercritical wing shape made it a short-field powerhouse, unmatched in its class at the time.
The YC-14 never entered production due to shifting USAF priorities. Its competitor, the YC-15, also didn’t. However, lessons from these prototypes informed the Boeing C-17 Globemaster III, showing how cutting-edge STOL research shaped future airlifters.
One YC-14 is stored at the AMARG boneyard at Davis-Monthan AFB, the other is on display at the Pima Air and Space Museum. Its innovative USB engines and short-field capabilities left a lasting legacy on STOL aircraft design.