Naval Aircraft Factory XV-715-2, Inverted V-12 Engine

Type: Reciprocating, 12 cylinders, V-type, air cooled

Power rating: 410 kW (550 hp) at 3,700 rpm

Displacement: 11.7 L (715 cu in)

Bore and Stroke: 102 mm (4.0 in.) x 121 mm (4.75 in.)

Weight: 349.3 kg (770 lb)

In 1934 the U.S. government required that at least 10 percent of military aircraft and aircraft engines be built in government factories, as a means of gauging the cost of similar articles produced by private sources. The Navy responded by authorizing the Naval Aircraft Factory (NAF) at the Philadelphia Naval Shipyard to build aircraft and engines.

After considering several engine models, the NAF first began to manufacture Wright Whirlwind radial engines for its N3N trainer. In August 1935, the factory received an order for two 12-cylinder, inverted, air-cooled XV-715 engines, one of which is displayed here. In June 1936, the Navy contracted with Fairchild to build a similar engine. That one, the Ranger V-770, with parts common to the 6-390 engine, was produced in quantity and used on cruiser- and battleship-based scout observation aircraft, such as the World War II era Curtiss SO3C Seamew.