The Boeing Boeing Model 66, XP-8, was a prototype American biplane fighter of the 1920s, notable for its unusual design incorporating the engine radiator into the lower wing.
Army testing of the aircraft began in January 1928, and it handled well, but performance was lacking, achieving only a maximum speed of 173.2 mph.
Even so, the prototype continued in Air Corps service until June 1929, after which it was scrapped.
The airframe design lived on in the Navy’s Boeing F2B.