Rockwell International's XFV-12A was a supersonic fighter/attack "Thrust Augmenter Wing" concept. The design used a modified
30,000 lb thrust Pratt & Whitney F401 engine. For vertical lift, a diverter valve in the engine exhaust system blocked the nozzle and directed
the gases through ducts to ejector nozzles in the wings and canards for vertical lift. An auxiliary engine inlet for use in vertical flight was
located immediately behind the cockpit. The prototype aircraft used parts from the A-4 and F-4; the fuselage was 44 ft long with a 28.5 ft
wingspan and a 12 ft canard span. Operational vertical take-off weight was expected to be 19,500 lb, with a maximum speed of over Mach 2
anticipated by Rockwell. Engine rig testing began in 1974, aircraft ground testing in July 1977. Only one of two contracted aircraft were
completed. Differences from the lab models to the full scale system caused the actual augmentation to be only 19% for the wing
and 6% for the canard. The thrust available for vertical flight was insufficient to permit powered-lift flights. The aircraft never made it into
the air - not even for a test flight under conventional power. Lift improvement testing and plans to modify the ejector/augmentor system
were discontinued in 1981 due to cost overruns and waning Navy V/STOL interest.