The North American NA-16 basic training monoplane of 1935 was the ancestor of a whole series of military trainers, culminating in the fabulously successful AT-6 Texan of World War 2 fame. Less well-known is the fact that there was a single-seat fighter aircraft based on this design which actually served for a brief period of time with the USAAF.
The series of single-seat fighters based on the NA-16 trainer were originally developed by North American Aviation for export to the air forces of smaller nations which required relatively simple and inexpensive aircraft but which also wanted aircraft with such advanced features as enclosed cockpits and retractable undercarriages. To meet this need, North American evolved the single-seat NA-50A, a single-seat fighter adaptation of the company's two-seat NA-26 advanced trainer, the first development of the NA-16 which featured a retractable undercarriage. The philosophy used by North American was more-or-less the same as that used much later by Northrop in the F-5 fighter which was based on the T-38A Talon two-seat trainer.
The NA-50A was powered by an 870 hp Wright R-1820-77 Cyclone nine-cylinder air-cooled radial engine driving a three-bladed propeller. The NA-50A was armed with a pair of 0.30-inch machine guns. Maximum speed was 295 mph at 9500 feet, range was 645 miles, and service ceiling was 32,000 feet.
The only customer for the NA-50A was the Peruvian Air Force. Seven examples were delivered to Peru in 1938-1939. The Peruvians fitted racks underneath the fuselage for light bombs. During the brief war between Peru and Ecuador in 1941, the Peruvian NA-50As actually flew a number of operational sorties, two examples being lost in action.
On December 30, 1939, Thailand ordered six examples of a design basically similar to the NA-50A. Designated NA-68 by the company, these planes differed from the NA-50A in having redesigned tail surfaces with a more angular rudder and a modified undercarriage. It had heavier armament, consisting of a pair of 0.30-inch machine guns in the wings and two 20-mm cannon in underwing gondolas. The engine was the same as that of the NA-50A, namely a Wright R-1820-77 Cyclone. The increased weight caused the performance to suffer--maximum speed was only 270 mph at 8700 feet, normal range was 635 miles, and service ceiling was 27,500 feet. Weights were 4660 pounds empty, 5990 pounds normal loaded, and 6800 pounds maximum. Dimensions were wingspan 37 feet 3 inches, length 27 feet 0 inches, height 19 feet 8 inches, and wing area 227.5 square feet.
The six NA-68s were on their way to Thailand via ship when Japan invaded that country. The ship was detained at Hawaii by the U.S. government and the six NA-68s were seized to prevent them from falling into enemy hands. They were requisitioned by the Army and assigned the designation P-64. The serials assigned were 41-19082/19087.
The P-64s were obviously not suited for front-line combat duty, and when they were returned to the USA they had their cannon armament removed and were assigned to advanced fighter training schools at Luke Field in Arizona. While the P-64s were serving with the Army as advanced fighter trainers, the Thai national insignia were replaced with USAAC insignia, but the planes kept their original Thai camouflage paint job. The P-64s rounded out their brief service lives as liaison aircraft aircraft with Trainer Command. In 1943, surviving P-64s were redesignated RP-64, where the R stood for "Restricted", meaning that they were to be excluded from combat duties. Most of the P-64s were eventually scrapped, but one survives today in the collection of the Experimental Aircraft Association of Oskosh, Wisconsin. It is 41-19085, which bore civilian registrations of NX37498, XB-KUU and N68622 during its postwar years.
It is interesting to compare the P-64 to the Commonwealth CA-12 Boomerang of Australia, which was a fighter adaptation of the Wirraway trainer (license-built North American NA-33).