The Boeing YP-29 was developed between the Model 248 (the prototype for the P-26) and the Model 266, the production version of the P-26, but despite being a rather more modern design it didn't enter production. The P-26 was the first monoplane fighter to join the USAAC, but it was very much a transitional design, with a fixed undercarriage, open cockpit and wing bracing. The Model 264 fixed all of these problems. Three prototypes were built, with a semi-retractable undercarriage, cockpit canopy and cantilevered wings.
The Model 264 used the same fuselage and tail as the P-26 and it used the same engine as the P-26A. It had fully cantilevered wings which contained the retractable undercarriage.
The first prototype began tests on 20 January 1934, with the USAAC designation of XP-940. This first prototype went back to Boeing in March 1934 to have the narrow cockpit canopy removed. In this configuration it became the YP-29A.
The second prototype had a remodelled 'glasshouse' canopy. It also had a less powerful R-1340-31 Wasp engine, and was given the designation YP-29. It was later given wing flaps and finally went to Langley Field as a research aircraft.
The third prototype was given more wing dihedral and a one-piece centre-section trailing edge flap.
All three prototypes underwent extensive trials with the USAAC, but it offered very little advantage over the P-26 and didn't enter production. The removal of the wing bracing and fixed undercarriage reduced drag and increased top speed, although only by 16mph. These new features increased the aircraft's weight, and reduced its ceiling and manoeuvrability.
Engine: Pratt & Whitney R-1340-35 Wasp; then -31 Wasp
Power: 570hp at 7,500ft (-35), 550hp at 10,000 (-31)
Span: 29ft 4.5in
Length: 24ft 11.75in
Height: 7ft 8in
Empty Weight: 2,502lb
Loaded Weight: 3,270lb
Maximum Speed: 242mph at 7,500ft
Climb rate: 1,840ft/ min
Guns: One 0.3in and one 0.5in machine guns