Boeing XP-8

The Boeing XP-8, company Model 66, was a prototype American biplane fighter of the 1920s, notable for building the engine radiator into the lower wing. Boeing developed it in 1926 as a private venture aiming at the Army Air Corps competition announced in 1925; the airframe was essentially a PW-9 fitted with an experimental 600 hp Packard 2A-1500 engine, with the radiator moved back so its opening coincided with the front edge of the lower wing and left an unusually narrow profile around the engine. Army testing began in January 1928 and it handled well, but performance was lacking, reaching only 173.2 mph. The prototype stayed in Air Corps service until June 1929 and was then scrapped, although its airframe design lived on in the Navy's Boeing F2B.