Wright Cyclone P-1, Radial 9 Engine

Type: Reciprocating, 9 cylinders, radial, air cooled

Power rating: 303 kW (406 hp) at 1,650 rpm

Displacement: 27.1 L (1,654 cu in.)

Bore and Stroke: 152 mm (6.0 in.) x 165 mm (6.5 in.)

Weight (dry): 368 kg (812 lb)

About the middle of 1923, the U.S. Navy signed a contract with Wright Aeronautical for three large air-cooled engine designs, which were to be built successively. The first of these, based on a design proposed earlier to the U.S. Army by Charles Lawrance, was known as the P-1, and was the direct forerunner of the highly successful Wright Cyclone series of engines. In order to reduce aerodynamic drag, its design was limited to a frontal area no greater than that of the Navy's Lawrance J engine, despite the fact that the P-1 had twice the displacement.

The P-1 was tested extensively in 1924 in a Douglas DT-2 aircraft, and flown successfully in the Navy Douglas DT-6 and Boeing aircraft. However, magnesium alloy castings, being used for the first time, failed in endurance tests. The P-1 was then discontinued in favor of the larger P-2, which added Heron-type cylinders and a supercharger.