|P-12 / F4B|
|Boeing P-12E at the National Museum of the United States Air Force, in markings of 6th Pursuit Squadron, 18th PG, Wheeler Field, Hawaii|
|Manufacturer||Boeing Aircraft Company|
|First flight||25 June 1928|
|Retired||1949 Brazilian Air Force|
|Primary users||United States Army Air Corps|
United States Navy
Philippine Army Air Corps
Royal Thai Air Force
Developed as a private venture to replace the Boeing F2B and F3B with the United States Navy, the Boeing Model 99 first flew on 25 June 1928. The new aircraft was smaller, lighter and more agile than the ones it replaced but still used the Wasp engine of the F3B. This resulted in a higher top speed and overall better performance. As result of Navy evaluation 27 were ordered as the F4B-1; later evaluation by the United States Army Air Corps resulted in orders with the designation P-12. Boeing supplied the USAAC with 366 P-12s between 1929 and 1932. Production of all variants totaled 586.
F4B-1 (Boeing Model 99)
The F4B-1 was built using typical construction techniques of the day with a welded truss fuselage with formers and longerons to define the aerodynamic shape. Wings were of wood construction and covered by fabric. Ailerons were tapered, with corrugated aluminum covering. The Pratt & Whitney R-1340 nine-cylinder radial engine was uncowled and sported prominent cooling fairings behind each cylinder which were later removed in service.
F4B-2 (Boeing Model 223)
The F4B-2 was similar to the F4B-1 but incorporated a Townend ring cowling around the engine. The prominent cooling fairings behind each cylinder were not incorporated on this model. A spreader bar was incorporated between the landing wheels and the tail skid was replaced by a castoring tailwheel. Finally, the tapered ailerons were replaced by constant chord Frise ailerons. A total of 46 production F4B-2s were built. Bureau numbers included A-6813 through A8639 and A-8791 through A-8809. Some F4B-2s received F4B-4 style vertical fins and rudders to address poor directional stability.
F4B-3 (Boeing Model 235)
The F4B-3 represented a significant departure in design from the earlier versions of the F4B. While the F4B-1 and F4B-2 had fuselages constructed of welded steel tube truss, the F4B-3 used a combination of welded truss and semi-monocoque construction. From the engine mount aft to the rear of the fuel tank bay, the structure was welded steel truss, while the fuselage aft of the fuel tank bay was constructed of stressed skin, semi-monocoque aluminum alloy. Wings were constructed primarily of wood and covered in fabric. The F4B-3 was powered by a single-row, nine-cylinder Pratt & Whitney R-1340-D engine generating 500 hp. It had an internal supercharger and turned a 9 ft. two-blade Hamilton Standard propeller. The original configuration of the F4B-3 has a headrest fairing similar to the P-12E, but most were retrofitted with a headrest fairing capable of storing a liferaft. This later headrest fairing design was carried over to the F4B-4.
F4B-4 (Boeing Model 235)
The F4B-4 was nearly identical to the F4B-3, but incorporated a larger vertical fin to address the directional stability issues that plagued the F4B from its inception. The design was so similar to the F4B-3 that both aircraft had the same Boeing Model Number (235). The first nine aircraft (A-8912-8920) featured the same carburetor induction scheme as the F4B-3, but all following aircraft (A-8009-A-9053, 9226-9263 and 9719) featured a single oval carburetor intake on the port side only.
A detail specification was written for a follow-on variant of the F4B, known as the F4B-5. Based on the detailed specification, it would have been similar to the F4B-4.
U.S. Army Air Corps
P-12s were flown by the 17th Pursuit Group (34th, 73rd, and 95th Pursuit Squadrons) at March Field, California, and the 20th Pursuit Group (55th, 77th and 79th Pursuit Squadrons) at Barksdale Field, Louisiana. Older P-12s were used by groups overseas: the 4th Composite Group (3rd Pursuit Squadron) in the Philippines, the 16th Pursuit Group (24th, 29th, 74th, and 79th Pursuit Squadrons) in the Canal Zone, and the 18th Pursuit Group (6th and 19th Pursuit Squadrons) in Hawaii.
The P-12 remained in service with first-line pursuit groups until replaced by Boeing P-26s in 1934–1935. Survivors were relegated to training duties until 1941, when most were grounded and assigned to mechanic's schools. 23 P-12Cs, P-12Ds and P-12Es were transferred to the Navy for use as advanced trainers. Bureau numbers were 2489 through 2511. These aircraft were redesignated as F4B-4As
The production runs are shown below with the P-12 designations for Army aircraft and the F4B designations being for the Navy. The remaining aircraft are civilian or export.
|90||P-12B||R-1340-9||NACA cowl, shorter landing gear, larger wheels|
|96||P-12C||ring cowl, spreader-bar landing gear|
|110||P-12E||semi-monocoque metal fuselage, redesigned vertical tail, some with tailwheels replacing skids|
|27||F4B-1||split axle landing gear, ventral bomb rack|
|46||F4B-2||spreader bar landing gear, frise ailerons, tailwheel replacing skid|
|21||F4B-3||semi-monocoque metal fuselage,|
|92||F4B-4||R-1340-16||redesigned vertical tail, underwing racks (two 116 lb bombs), last 45 had mod. headrest w/life raft|
|5||100/100A||(civilian version of F4B-1)|
|14||256||(F4B-4, export to Brazil)|
|9||267||(F4B-3 fuselage/P-12E wings, export to Brazil)|
Data from 
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