The Boeing XP-4 was a prototype American

biplane A biplane is a fixed-wing aircraft with two main wings stacked one above the other. The first powered, controlled aeroplane to fly, the Wright Flyer, used a biplane wing arrangement, as did many aircraft in the early years of aviation. While ...

fighter of the 1920s. It was grounded permanently after just 4.5 hours of flight testing.

Development and design

In 1926, the

United States Army The United States Army (USA) is the land warfare, land military branch, service branch of the United States Armed Forces. It is one of the eight Uniformed services of the United States, U.S. uniformed services, and is designated as the Army o ...

was very interested in the

turbo-supercharger In an internal combustion engine, a turbocharger (often called a turbo) is a forced induction device that is powered by the flow of exhaust gases. It uses this energy to compress the intake gas, forcing more air into the engine in order to pro ...

as a way of improving engine performance, and requested that one be added to the last of the PW-9s, and the engine upgraded to a 510 hp

Packard 1A-1500 The Packard 1A-1500 was an American 12-cylinder liquid-cooled 60-degree Vee piston aircraft engine designed in 1924.Gunston 1989, p.109. Test flown in the second prototype Douglas XO-2 it proved to be unreliable. Only 29 engines w ...

. This machine was designated XP-4. In addition, the basic PW-9 armament of one .50 and one .30 cal.

machine gun A machine gun is a fully automatic, rifled autoloading firearm designed for sustained direct fire with rifle cartridges. Other automatic firearms such as automatic shotguns and automatic rifles (including assault rifles and battle rifl ...

s in the nose was supplemented by two added .30 cal. guns mounted under the lower wing, far enough out to be outside the propeller arc (thus not needing synchronization).Jones 1975, pp. 20–22. All these modifications added weight, so the lower wing span was extended by 9.5 feet. The airplane was delivered to

Wright Field Wilbur Wright Field was a military installation and an airfield used as a World War I pilot, mechanic, and armorer training facility and, under different designations, conducted United States Army Air Corps and Air Forces flight testing. Lo ...

for testing on 27 July 1927, but it quickly became apparent that the Packard engine did not have sufficient power to compensate for the 800 lbs of extra weight, the craft performing more poorly than its predecessor, and the project was quickly abandoned.

Specifications (XP-4)

References

Notes

Bibliography

* Angelucci, Enzo. ''The American Fighter from 1917 to the present.'' New York: Orion Books, 1987. . * Dorr, Robert F. and David Donald. ''Fighters of the United States Air Force''. London: Temple, 1990. . * Jones, Lloyd S. ''U.S. Fighters: Army-Air Force 1925 to 1980s.''. Fallbrook, California: Aero Publishers, Inc., 1975. .

External links