The YC-14 was Boeing's entry into the USAF's Advanced Medium STOL Transport (AMST) competition, to replace the C-130 Hercules as the USAF's standard STOL tactical transport. The AMST project introduced a number of innovative features, such as under-surface blowing, which used double-slotted flaps to direct part of the jet exhaust downwards, while the rest of the exhaust passed through and downward over the flaps, introducing the Coanda effect.
The unique ___location of the General Electric F103 engines, seen only on a few other aircraft, such as the Antonov An-72 'Coaler' (which flew later), increased lift by passing the exhaust directly over the wing. This also made the aircraft quieter.
The YC-14, as well as McDonnell-Douglas' entry into the competition, the YC-15, met or exceeded the specifications of the contest. However, the project was cancelled before either product could be chosen.
Two YC-14s were built and tested. One is stored at the Aerospace Maintenance and Regeneration Center at Davis-Monthan Air Force Base; the other is on display at the nearby Pima Air & Space Museum.