The Boeing P-12 was the US Army's version of the Navy's F4B, and was part of the last generation of biplane fighters to see service.
In 1928 Boeing developed two similar fighter prototypes, the Model 83 and the Model 89. The two aircraft used traditional construction methods, with a bolted aluminium tube structure for the rear fuselage and wooden structure for the wings, both fabric covered. The Model 83 and early production aircraft used steel tubing for the centre section and the engine area. They were powered by a Pratt & Whitney radial engine. They had equal chord, unequal span wings, with no sweep back (a change from the previous generation of Boeing biplane fighters). The upper wing was built in one piece, the lower wing in two halves which were then bolted together.
The main difference between the two designs was in the undercarriage - the Model 83 had a spreader-bar undercarriage and arrestor gear, the Model 89 had a split axle undercarriage. The Model 89 could also carry a 600lb bomb under the fuselage.
The Model 83 made its maiden flight on 25 June 1928 and went to the Navy on 28 June 1928. The Model 89 went to Anacostia by rail and made its maiden flight in Navy hands on 7 August 1928.
Both models were tested by the Navy, while the Army examined the Model 89 (The Army's Bolling Field bordered the Navy base at Anacostia). The Army was sufficiently impressed to place an order for ten P-12s (Model 102).
Eventually the Army received 366 P-12s - nine P-12s, one XP-12A, 90 P-12Bs, 95 P-12Cs, 36 P-12Ds, 110 P-12Es and 25 P-12Fs. The Army was thus the more important customer for the P-12/ F4B family, taking nearly twice as many aircraft as the Navy.
The P-12 saw widespread service with the USAAC. In the Continental United States it was used by the 1st, 8th, 17th and 20th Pursuit Groups as well as various training units. The 16th Pursuit Group was the main user in the Panama Canal Zone. On Hawaii the 5th Composite Group and 18th Pursuit Group used the type. Finally the 3rd Pursuit Squadron operated the P-12 on the Philippines.
The 1st Pursuit Group operated the P-12 from Selfridge Field, Michigan. All three of its squadrons received the type in 1930. The 17th and 94th Pursuit Squadrons kept it to 1932, the 27th to 1934.
The 8th Pursuit Group at Langley Field, Virginia, received the P-12 in 1932. The 33rd Pursuit Squadron kept it to 1935, the 35th and 36th squadrons to 1936.
The 17th Pursuit Group at March Field, California, received the P-12 in 1931. It converted to the P-26 in 1934 but it was then decided to turn it into an attack group. The 34th, 73rd and 95th Pursuit Squadrons all handed the P-26s on to the 20th Pursuit Group and reverted to the P-12 for another year before their attack aircraft were ready.
The 20th Pursuit Group (55th and 77th Pursuit Squadrons) operated the P-12 from 1930, when it was based at Mather Field, California. In 1932 it moved to Barksdale, Louisiana, where it gained a third P-12 squadron, the 79th. All three kept the P-12 until 1935.
The P-12 was also used by a detachment at Bolling Field, by the 43rd Pursuit Squadron, Air Corps Advancing Flying School at Kelly Field, Texas from 1932-36 and by the 48th Pursuit Squadron, Air Corps Technical School at Chanute Field, Ill from 1935 to 1936).
The first unit to receive the P-12 in the Panama Canal Zone was the 24th Pursuit Squadron (6th Composite Group) in 1930. This squadron then joined the 16th Pursuit Group, where it joined the 29th and 78th Pursuit Squadrons, both equipped with the P-12. The 78th lost its P-12s in 1936, but the other two squadrons kept them to 1939.
On Hawaii the P-12 was used by the 5th Composite Group. It was one of many types used by the 4th Observation (then Reconnaissance) Squadron in c.1929-1937 and then the 58th Observation Squadron (c.1936-38). The P-12 was also used by the 6th and 19th Pursuit Squadrons, both of the 18th Pursuit Group, from 1931-1938.
Finally the 3rd Pursuit Squadron used the P-12 on the Philippines from c.1930-1937, as part of the 1st then 4th Observation Group.
When the P-12 entered service it had a significantly higher service ceiling then previous American fighters. On 13 December 1929 2nd Lt Norman H. Ives of the 95th Pursuit Squadron set a altitude record for a fighter aircraft with full military load of 30,000ft, only to have it beaten by his colleague 2nd Lt George E. Price, who reached 31,200ft soon afterwards. The group also practised formation flying at high altitude.
The P-12 took part in the Air manoeuvres of 1931, forming part of a composite pursuit wing (130 P-12s, 58 P-1s and 17 P-6s), during a series of demonstrations around the United States.
The 94th Pursuit Squadron of the 1st Pursuit Group used its P-12s for experiments in high altitude interception, including a flight in October 1931 designed to test how long it would take to reach a target 100 miles away, another at 20,000ft, and long distance flights.
In 1932, at the end of the US Army 5-year expansion plan, the P-12E and P-12F were two of the three fighter types that the Air Corps designated 'standard', or suitable for front line service (along with the Curtiss P-6E).
By 1933 the P-12 was beginning to be left behind by more modern aircraft. During exercises in May a group of P-12s attempted to intercept a formation of Douglas B-7 bombers, but were simply outpaced. The P-12s were also used in some night fighting exercises, but without success.
In 1934 the Air Corps was given responsibility for carrying the air mail. Early in the venture the P-12 was used on shorter routes or on routes with little mail, but they weren't really suited to the task and were soon replaced with various observation aircraft.
The P-12 was also an excellent acrobatic aircraft. It was the equipment of 'Three Men on a Flying Trapeze', an acrobatic team formed by Captain Claire L. Channault that made its public debut over Miami in September 1934.
By the time of the 1935 air exercises the P-12 was no longer seen as a modern aircraft, and the groups still equipped with it (8th Pursuit and 17th Attack) didn't take part in the combat part of the manoeuvres.
Most of the surviving P-12Es and P-12Fs were grounded in 1941. They then went to Air Corps and mechanic's schools, although 23 went to the Navy as the F4B-4A.
P-12 (Model 102)
Ten P-12s were ordered although only 9 were completed in that format. They had the split-axle undercarriage of the Model 89, but used a less powerful engine than the Navy's F4B-1 - a 450hp Pratt & Whitney R-1340-7. As a result their top speed was slightly lower than that of the F4B. As with the F4B-1, the P-12 was built with individual cowlings for the engine cylinders. Both the P-12 and the F4B-1 used tapered ailerons.
The first P-12 was received by the Army in February 1929 and was flown from Brownsville, Texas, to France Field in the Panama Canal Zone, with Captain Ira C. Eaker at the controls. The last of the nine was delivered on 26 April 1929.
XP-12A (Model 101)
The tenth aircraft from the original order was completed as the experimental XP-12A. This had a more powerful 525hp R-1340-9 engine, with a long-chord NACA cowling in place of the individual cylinder cowlings. It had Frise-type ailerons (designed to reduce the effort needed to move the controls at high speeds). The main undercarriage had shorter struts while the fixed tail skid was replaced with a movable castoring unit. The XP-12A had a short life and was lost in a mid-air collision on 18 May 1929 after only four hours of flight, but many of its features were introduced on the P-12B and the F4B-2.
P-12B (Model 102B)
The P-12B was the first version of the aircraft to be ordered in large numbers by the USAAC. Ninety were ordered on 10 June 1929, with the first example making its maiden flight on 12 May 1930. At the time this was the biggest order for a single type of aircraft every placed by the Air Corps in peace time. The P-12B used the Frise-type ailerons of the XP-12A, but didn't use the NACA cowling. Instead they were built without any cylinder fairings, and were then given a ring cowling after entering service.
P-12C (Model 222)
An order for 131 P-12Cs was placed in June 1930. 95 of these aircraft were completed as the P-12C, the remaining 36 as the P-12D. The P-12C used a 525hp Pratt & Whitney R-1340-9 engine, was built with a ring cowling and had a new spreader-bar main landing gear in place of the split axle system of the older aircraft. The P-12Cs were later given the larger vertical tail surfaces introduced on the P-12E. The first P-12C made its maiden flight on 30 January 1931. They were later converted into P-12Ds.
P-12D (Model 227)
The last 36 aircraft from the P-12D order were completed as the P-12D, using a 525hp Pratt & Whitney R-1340-17 engine. The first P-12D made its maiden flight on 2 March 1931. The P-12Ds were later given the larger vertical tail surfaces introduced on the P-12E. All 36 were delivered between 25 February and 28 April 1931.
P-12E (Model 234)
In 1930 Boeing produced a new version of the P-12/ F4E, the Model 218. This was a private venture aircraft that featured a new metal semi-monocoque fuselage and that became the basis of the P-12E and the F4E-3. The sole Model 218 made its maiden flight on 29 September 1930 and was given the Air Corps designation XP-925. It was later sold to China where it was reported to have been shot down over Shanghai in 1932.
The US Army placed an order for 135 aircraft based on the Model 218 on 3 March 1931. The first 110 of these were delivered as the P-12E (Model 234) between 19 September and 15 October 1931, the remaining 25 as the P-12F. The first P-12E made its maiden flight on 15 October 1931, as the XP-12E. The P-12E also had larger vertical control surfaces, which were then fitted to older models.
The XP-12E was the first P-12E. It was given the new designation on 1 October 1931 because it was being used for test work. This aircraft (31-553) was later used as one of seven YP-12Ks with fuel-injected engines then as the turbo-supercharged XP-12L before reverting to P-12E standard.
Temporary designation for a P-12E being used for engine tests, later reverts to P-12E standard.
The last twenty-five aircraft from the P-12E order were completed as the P-12F. They were powered by an R-1340-19 engine that produced 600hp at take-off and 500hp at 11,000ft (up from 7,000ft in the P-12E). Top speed increased by 5mph but the climb rate and service ceiling saw more significant improvements. The last of the P-12Fs was used to test a sliding cockpit canopy.
XP-12G (Model 102B)
The first P-12B was later used to test a turbo-supercharged Pratt & Whitney R-1340G/H engine, driving a three bladed propeller. In this configuration the aircraft was given the designation XP-12G. It was tested during 1932 and then converted back into a standard P-12B.
The 33rd P-12D was used to test a geared Wasp engine (XGRS-1340-E) was the designation XP-12H. The engine was not a great success and the aircraft was converted back to P-12D standard in June 1932.
The P-12J was the designation given to a single P-12E when it was equipped with a 575hp SR-1340-H engine. The same aircraft was later converted into one of the seven YP-12Ks, before reverting to P-12E standard.
The YP-12K was the designation given to seven aircraft that were given a fuel-injected SR-1340E engine. The seven aircraft consisted of the P-12J, the XP-12E and five normal P-12Es. All seven eventually reverted to P-12E standard in June 1938. In the gap the XP-12E was also used as the XP-12L.
The XP-12L was the designation given to one of the YP-12K (the XP-12E) when it was given a F-7 turbo-supercharger to go with the fuel injected SR-1340E engine. The new designation was assigned on 2 January 1934. The aircraft was converted back to the YP-12K standard in February 1937 then to the P-12E standard in June 1938.
The Model 100 was a civil version of the F4B-1 with all military equipment removed. Four were built and had varied careers. The second was used as an engine test bed at Pratt & Whitney and was used with the R-985 Wasp Jr, R-1535 Twin Wasp Jr and R-1690 Hornet.
The sole Model 100A was a convertible two-seater built for Howard Hughes and that survived until 1957.
No aircraft were built with this designation, but it would have been used for any export versions of the P-12D.
The Model 100E was equivalent to the P-12E, but due to US government restrictions couldn't use the same model number. Two were exported to Thailand. They were delivered on 10 November 1931. One was taken by the Japanese, survived the Second World War and became an exhibit at the Thai Aeronautical Museum at Bangkok.
The Model 100F was equivalent to the P-12F. One was built for Pratt & Whitney where it was used as an engine test bed. The aircraft was lost during a high altitude test flight after a weight that had been installed to balance the aircraft when different engines were used broke loose and destroyed the controls.
One Model 218 was built. It had a metal semi-monocoque fuselage and was the prototype for the P-12E and F4B-3. It was later exported to China and probably lost over Shanghai in 1932.
The Model 256 was the designation for fourteen aircraft sold to Brazil in 1932. They were built using the first fourteen airframes from the F4B-4 order, but with Naval equipment removed. They were delivered to Brazil between 14 September and 8 October 1932.
The first Brazilian order was quickly followed by a second order for nine aircraft. This was filled by the Model 267, which had the F4B-3 fuselage, tail and landing gear and the P-12E wings. All nine aircraft were delivered on 21 February 1933.
Engine: Pratt & Whitney R-1340-7
Span: 30ft 0in
Length: 20ft 1in
Height: 9ft 7in
Empty Weight: 1,758lb
Loaded Weight: 2,536lb
Maximum Speed: 171mph at 5,000ft, 158mph at sea level
Cruising Speed: 135mph
Climb rate: 2,080ft/min
Guns: Two 0.3in machine guns
Engine: Pratt & Whitney R-1340-7
Span: 30ft 0in
Length: 20ft 3in
Height: 8ft 10in
Empty Weight: 1,945lb
Loaded Weight: 2,638lb
Maximum Speed: 166mph at 5,000ft, 157mph at sea level
Climb rate: 2,040ft/min
Range: 540 miles
Guns: Two 0.3in machine guns
Engine: Pratt & Whitney R-1340-77
Span: 30ft 0in
Length: 20ft 3in
Height: 8ft 8in
Empty Weight: 1,956lb
Loaded Weight: 2,648lb
Maximum Speed: 188mph at 7,000ft
Cruising Speed: 163mph
Range: 475 miles
Engine: Pratt & Whitney R-1340-17
Span: 30ft 0in
Length: 20ft 3in
Height: 9ft 0in
Empty Weight: 1,999lb
Loaded Weight: 2,690lb
Maximum Speed: 189mph at 7,000ft
Cruising Speed: 160mph
Climb rate: 5.8mins to 10,000ft