Boeing P - 29 The Boeing P - 29 and XF7B - 1 were an attempt to produce a more advanced version of the highly successful P - 26 . 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 , developed as a private venture under a bailment contract negotiated with the U . S . Army . Development of three prototypes was initiated in the interval between the testing of the XP - 936 ( P - 26 prototype , company Model 248 ) and the delivery of the first P - 26A ( Model 266 ) to the U . S . Army . The Model 264 was an updated and modernized P - 26 , differing in having fully cantilever wings , wing flaps , enclosed " greenhouse " canopy , and retractable undercarriage . The landing gear was similar to the Boeing Monomail , the main wheels retracting backwards about halfway into the wings . The fuselage and the tail 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 , used in the P - 26 . The 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 canopy , essentially a transparent continuation of the P - 26 ' s protective headrest , extending all the way to the windshield frame . The Wasp radial was enclosed in a full NACA cowling rather than the narrow Townend ring of the P - 26 . One final variant was considered by Boeing , the Model 273 , which was intended for the U . S . Navy as the XF7B - 1 . Aside from slight dimensional variations , military equipment carried , and the performance 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 an open cockpit , which was considered more acceptable in the era . 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 XP - 940 five days later . During testing , the XP - 940 achieved a maximum speed of 220 mph at 10 , 000 ft ( 354 km / h at 3 , 050 m ) . After testing , the XP - 940 was returned to the factory in March for modifications . Due to the tight - fitting canopy and restricted pilot vision from the cockpit enclosure , Boeing reverted to an open cockpit design , retaining the long headrest all the way to the tail . The engine was replaced by a 600 hp ( 450 kW ) R - 1340 - 35 with a drag ring , similar to the P - 26A ' s . It was also fitted with flaps , which the XP - 940 lacked . Upon completion of testing of the XP - 940 , the Army decided on 29 June 1934 to purchase it and two sister ships . The designation P - 29 was assigned . After the modified XP - 940 was returned to the Army in April 1934 , it was assigned the designation YP - 29A ( serial number 34 - 24 ) . It eventually was redesignated the P - 29A after an engine change to an R - 1340 - 27 in place of the - 35 . The cleaner design of the P - 29A resulted in a speed increase of 16 mph over the P - 26A , but its greater weight cut down on the aircraft ' s ceiling and maneuverability . Consequently , the Army cancelled an intended P - 29A order . The three prototypes were subsequently used strictly for experimental purposes . The second prototype 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 an 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 244 mph at 10 , 000 ft . Initial climb was 1 , 600 ft per minute . Service ceiling was 26 , 000 ft , and absolute ceiling was 26 , 700 ft . 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 . An additional variant with a 700 hp ( 520 kW ) R - 1535 ( civil Twin Wasp Junior ) was proposed , as the XP - 32 , but was never constructed . Flying for the first time in September 1933 , the XF7B - 1 ( BuNo 9378 ) was the first monoplane fighter to be tested by the U . S . 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 .