Boeing P-29
The Boeing P-29 and the XF7B-1 developments were an attempt to produce a more advanced version of the highly successful P-26 pursuit aircraft. Although slight gains were made in performance, the U.S. Army Air Corps and U.S. Navy did not order the aircraft.
Design and development
The Boeing YP-29 originated as the Model 264 project developed as a private venture by Boeing at company expense under a bailment contract that was negotiated with the US Army. Development of three prototypes was initiated in the interval between the testing of the XP-936 (P-26 prototype, company designation of Model 248) and the delivery of the first P-26A (Model 266) to the US Army.
Basically, the Model 264 was an updated and modernized P-26, differing from the P-26 in having fully-cantilever wings, wing flaps, enclosed "greenhouse" canopy and a retractable undercarriage. The undercarriage was similar to Boeing Monomail landing gear, in which the main wheels retracted backwards about halfway into the wings. The fuselage and the tail unit were basically the same as those of the P-26. The 264 retained the proven 550 hp Pratt & Whitney R-1340-31 Wasp air-cooled radial, basically the same type of engine which powered the P-26. Armament of one 0.30-cal and one 0.50 cal machine guns mounted in the fuselage sides and firing between the cylinder heads of the radial engine was the same as the P-26A.
The first Model 264 featured a long, narrow sliding cockpit enclosure, essentially a transparent continuation of the P-26's protective headrest all the way to the windshield frame. The Pratt & Whitney Wasp was enclosed in a full NACA cowling rather than the narrow Townend-Ring that was used on the P-26.
One final variant was considered by Boeing, the Model 273 which was intended for the US Navy as the XF7B-1. Aside from slight dimensional variations, military equipment carried and the altitude ratings of its Wasp engine, the naval fighter was very similar to its Army antecedents. Like the other variants, its enclosed cockpit was eventually modified into a more conventional open cockpit.
Testing
The airplane made its maiden flight on 20 January 1934 and was flown to Wright Field for Army testing under the experimental military designation of XP-940 five days later. During testing, the XP-940 achieved a maximum speed of 220 mph at 10,000 feet. The gross weight was 3814 pounds. After testing, the XP-940 had been returned to the factory in March for modifications. Due to the tight-fitting canopy and restricted pilot vision from the cockpit enclosure, Boeing reverted back to a standard open cockpit installation, retaining the long headrest that extended all the way to the tail. The engine was replaced by a 600 hp Pratt & Whitney R-1340-35 and a drag ring similar to that on the P-26A was introduced.
Upon completion of the successful testing of the XP-940, the Army decided on 29 June 1934 to purchase it and its two sister ships. The pursuit designation of P-29 was assigned. After the modified XP-940 was returned to the Army in April 1934, it was assigned the designation YP-29A with serial number 34-24. It eventually was redesignated the P-29A after an engine change to a 600 hp Pratt & Whitney R-1340-27 in place of the R-1340-35.
The cleaner design of the P-29A resulted in an increase of 16 mph over the P-26A, but its greater weight cut down on the ceiling and the maneuverability, consequently the US Army reevaluated its priorities and cancelled an intended P-29A order. The three prototypes were subsequently used strictly for experimental purposes.
The second prototype ordered by the Army was completed with a large and roomy glasshouse enclosure around the cockpit and, in addition, the tailwheel was housed in a different fairing. Other changes included using a 600 hp Pratt and Whitney R-1340-35, enclosed in an anti-drag ring. The aircraft was delivered to the Army on 4 September 1934 under the designation YP-29 with serial number 34-23.
Despite its earlier Army designation and serial number, it was actually the second Model 264 to fly. During tests, the following data was obtained: Weights were 2509 lbs. empty, 3518 lbs. gross. Maximum speed was 250 mph at 10,000 feet. Initial climb was 1600 feet per minute. Service ceiling was 26,000 feet, and absolute ceiling was 26,700 feet. Range was 800 miles.
This new cockpit enclosure satisfied the requirement for pilot protection at 250 mph operating speeds. Nevertheless, the landing speed of the YP-29 was considered too high for Army operational use and the YP-29 was returned to the factory for the installation of wing flaps. Following service testing by the Army and Boeing, which included trials with controllable pitch propellers, the service test designation was dropped and changed to P-29 after the engine was changed to a Pratt & Whitney R-1340-39.
The third Model 264 was completed as the YP-29B with an open cockpit configuration similar to that of the YP-29A. The serial number was 34-25. The only outward differences between it and the YP-29A were the addition of a one-piece wing flap similar to that of the YP-29, an additional one degree of dihedral in the wing and an oleo tail wheel assembly similar to that of the YP-29. The YP-29B was sent to Chanute Field in Illinois for service testing. It was eventually redesignated P-29B, adding to the bewildering succession of designations for essentially the same model.
Flying for the first time in September 1933, the XF7B-1 (s/n 9378) was the first monoplane fighter to be tested by the US Navy, although concerns over its high landing speed rendered it unsuitable for carrier operations.
All the P-29 and XF7B-1 aircraft were ultimately scrapped.
Specifications (XF7B-1)
General characteristics
- Crew: 1
Performance
Armament
- Guns: 2× .30 in (7.62 mm) machine guns
- Bombs: 1× 200 lb (90 kg) bomb
References
- Pedigree of Champions: Boeing Since 1916, Third Edition. Seattle, WA: The Boeing Company, 1969.
External links
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