The Boeing PW-9 was the first in a long series of successful Boeing biplane fighters that saw service with the USAAC and US Navy in the 1920s and early 1930s.
By the early 1920s Boeing had gained a great deal of experience in fighter construction, in particular with the Thomas-Morse MB-3A. Their engineers had also toured Europe, looking at First World War fighter aircraft, and had come to the conclusion that the Fokker D.VII was the most promising. They were particularly impressed by the mixed metal and wood construction methods used by Fokker. The fuselage was build around welded steel tubes while the wings were semi-cantilevered, eliminating some of the drag inducing bracing wires. Both fuselage and wing were fabric covered.
In the early 1920s the US Army didn't require any new fighter aircraft, but Boeing decided to begin design of a private venture fighter anyway.
The first version of the new Model 15 was to be powered by a 300hp Wright-Hispano engine, with a nose radiator mounted on the front of the aircraft. The wings were to be straight-chord but taper in thickness (something taken directly from the Fokker D.VII). The fuselage was built from welded steel tubes braced with piano wire, while the wings were made of plywood, spruce and mahogany. The tail was also of wooden construction. The wings and fuselage were both fabric covered.
The design saw a number of major changes before the first prototype was built. The Wright-Hispano engine was replaced with a 12-cylinder Curtiss D-12 that provided 435hp. The radiator was moved from the nose to a new position in a 'tunnel' below the engine, a design that was widely adopted by American aircraft manufacturers. The wings were tapered and the wing spars went from fully to partly-cantilevered with some wire bracing. The final design was a single bay biplane with wings of unequal span and chord. The first prototype had a though axle main landing gear.
The modified design was finalized on 10 January 1922. Boeing's gamble quickly began to pay off. The US Army agreed to provide the engine, military equipment and guns for the aircraft, and to test the aircraft, but for the moment both the design and the prototype remained the property of Boeing.
The Model 15 made its maiden flight on 2 June 1923. A further sign of army interest was that the flight was piloted by Captain Frank Tyndall, an army test pilot. After tests at Seattle the Model 15 was then sent to McCook Field for trials.
The prototype was soon given the military designation XPW-9. At McCook field it was tested against the Fokker XPW-7, Curtiss PW-8 and the Curtiss XPW-8A. After these trials Curtiss was asked to try out the tunnel radiators, and the design became standard on the Curtiss Hawk biplanes.
On 28 September 1923 the Army ordered two more XPW-9s, purchases the first prototype and officially gave the aircraft the XPW-9 designation. The second and third machines were delivered to the army on 1 May 1924. During this period Boeing also designed a divided-axle landing gear with oleo shock absorbers which became standard on production aircraft.
The US Army decided to order the PW-9. The first twelve were ordered on 19 September 1924, followed by another 18 in December 1924. The US Navy was also interested and placed its own order for the Model 15, as the Boeing FB-1. In both cases these were the first in a series of orders. The Army ordered twenty five PW-9As, of which twenty four were delivered in that format and one as the sole PW-9B. Another fifteen PW-9Bs were ordered, but they were delivered as the PW-9C. Another twenty five PW-9Cs were ordered and twenty four were delivered while the last was completed as the Model 15D, introducing changes that were made on the sixteen PW-9Ds.
The PW-9 entered service late in 1925. The first few aircraft remained in the US for further tests, but most of the production run of 29 aircraft went to Hawaii or the Philippines. As more aircraft were produced some US based units got the aircraft, but its main use was outside the Continental United States.
The PW-9 was used by the 3rd Pursuit Squadron on the Philippines in 1926-31. On Hawaii it equipped the 6th Pursuit Squadron (1927-30) and 19th Pursuit Squadron (1927-30). It was also one of several types used by the 24th Pursuit Squadron in the Panama Canal Zone.
In the United States it was used by the 14th Aero Squadron and 18th Squadron (Headquarters Squadron), both at Bolling Field, DC, the 95th Pursuit Squadron in California and alongside the P-1 by the 43rd School Squadron at Kelly Field Texas in 1929-31,
At the start of 1929 the PW-9Ds were used as 'blackboard planes' during the world endurance record attempt of the Question Mark. The sides of the aircraft were painted black and chalk messages for the crew of the Question Mark were written on them. The first message came at noon on New Year's Day and was a reminder to fly over the Rose Bowl at Pasadena during a game. The mission began on New Year's Day and ended on 7 January after a C-2A flown by Major Carl Spatz had been in the air for 150 hours, 40 minutes and 14 seconds.
PW-9 (Model 15)
The first 29 aircraft from the original two orders were delivered as the PW-9, the thirtieth as the Boeing XP-4 (Model 58).
The PW-9 was very similar to the third prototype XPW-9. It was powered by a 435hp Curtiss D-12 engine and had an improved engine cowling. The divided axle undercarriage developed during testing became standard. Deliveries began on 30 October 1925 and were complete by 18 December 1925. Most of the PW-9s went to units based in Hawaii and the Philippines.
PW-9A (Model 15A)
The army ordered 25 PW-9As on 26 October 1925. The PW-9A was powered by the Curtiss D-12C (V-1150-1), an improved version of the engine but with similar power to the basic D-12. The PW-9A also had duplicate flying and landing wires.
Twenty four aircraft were completed as the PW-9A. One was completed as the Model 15B, which became the basis of the PW-9B. Another aircraft was converted into a trainer and given the designation AT-3, Boeing Model 68.
PW-9B (Model 15B)
The last of the PW-9As was completed as the sole PW-9B. The PW-9B was powered by a new Curtiss D-12D (V-1150-3) engine. Fifteen were ordered, but they were completed as the PW-9C. The prototype PW-9B was later converted back to PW-9A standard.
PW-9C (Model 15C)
The fifteen PW-9Bs, ordered on 19 June 1926, were completed as the PW-9C. Another 25 PW-9Cs were ordered on 18 August 1926. The PW-9C was powered by the D-12D engine, had modified flying and landing wires and a heavier fuselage stricture. The first PW-9C was completed on 9 July 1927. They were later given a balanced rudder developed for the Navy Boeing FB-3. The final PW-9C was completed as the Model 15D, the prototype for the PW-9D.
PW-9D (Model 15D)
The prototype PW-9D introduced a series of detailed improvements. A larger balanced rudder was installed (developed for the FB-3). Wheel brakes were installed, the radiator was improved and a pressure fire extinguisher was installed. The prototype retained the D-12D engine of the PW-9C. The prototype was ready by 9 August 1927.
Sixteen production PW-9Ds were built, and fifteen of them were delivered between 25 April and 19 May 1928. The last of them was used as the basis of the XP-7 (Model 93).
PW-9E (Model 15E)
The PW-9E designation was allocated to a further version of the aircraft, and some work did begin, but in 1928 Boeing began work on the Model 83 and Model 89 fighters, which would enter service as the P-12. The Army decided that the new aircraft had more potential than the six year old PW-9, and the PW-9E was cancelled.
Engine: Curtiss D-12
Height: 8ft 2in
Empty Weight: 1,936lb
Loaded Weight: 3,120lb
Maximum Speed: 159.1mph
Cruising Speed: 142mph
Climb rate: 1,630ft/ min
Range: 390 miles
Guns: two 0.3in machine guns or one 0.3in and one 0.5in machine guns
Bomb load: Two 122lb bombs
Span: 32ft 0in
Length: 24ft 2in
Height: 8ft 8in
Empty Weight: 2,328lb
Loaded Weight: 3,234lb
Maximum Speed: 155mph at sea level, 152mph at 5,000ft
Cruising Speed: 124mph
Climb rate: 4 min to 5,000ft
Endurance: 2.87 hours