The Boeing XP-9 was an unsuccessful design for a shoulder-winged monoplane fighter designed in response to USAAC specification X-1623A. Boeing produced with the Model 96, an all-metal monoplane with shoulder mounted equal cord un-swept wings. The aircraft had a spreader bar main undercarriage and a tail wheel. The open cockpit was positions behind the wing trailing edge, nearer the tail than the nose. The aircraft was constructed around a semi-monocoque fuselage, with metal formers and dural covering behind the undercarriage struts and a welded steel tube framework for the nose. It was longer and with a wider span than either the P-12 or the experimental XP-15, and around 1,000lb heavier than the P-12 when full loaded.
The aircraft was powered by a Curtiss V-1570-15 Conqueror liquid cooled engine, which was meant to have provided 600hp but only produced 583hp. The aircraft received the XP-9 designation on 29 May 1928 and was originally meant to have been delivered in April 1929, but work was slow and it didn't make its maiden flight until 18 November 1930, at the Army Test Centre, Wright Field.
The XP-9 was a disappointing aircraft, with poor handling and a limited view from the cockpit. It was unpopular with the test pilots, partly because the controls were poorly designed. An attempt was made to improve the handling by installing larger vertical tail surfaces taken from a P-12, but the performance was still poor. The Air Corps had an option to take five service assessment Y1P-9s, but decided not to take them. The XP-9 only flew for 15 hours, then in August 1931 it was grounded for use as an instructional airframe.
Engine: Curtiss V-1570-15 liquid cooled engine
Power: Rated at 600hp, actual output 583hp
Span: 36ft 6in
Length: 25ft 1.75in
Height: 7ft 9in
Empty Weight: 2,669lb
Loaded Weight: 3,623lb
Maximum Speed: 213mph at 12,000ft
Cruising Speed: 180mph
Climb rate: 2,430ft/ min
Range: 425 miles
Guns: Two 0.5in machine guns
Bomb load: Two 122lb bombs, five 25lb bombs