Front view of the first Northrop A-17 built. Note that this aircraft was initially the Northrop Gamma 2F and lacked the dive brakes -- flaps with holes in them -- of the production A-17s. (U.S. Air Force photo)
Northrop developed the A-17 in the early 1930s to fill an Army Air Corps requirement for an attack bomber. The aircraft provided ground support for infantry, attacking at tree-top level with its four forward-firing .30-cal. machine guns and fragmentation or chemical bombs carried internally. Powered by the 750-hp Pratt & Whitney R-1535-11 radial engine, the A-17 could also carry up to four 100-pound bombs on the underside of the wing center section. In its day, the A-17 had more firepower than its contemporaries: the P-35, the P-36 and the early P-40. Delivery of 110 A-17s began in August 1935.
The first A-17 (S/N 35-51) was initially built as a company demonstrator with the designation Northrop Gamma 2F. The 2F was an improved version of the Northrop Gamma 2C. The 2C was also a company-funded demonstrator aircraft that was later modified, purchased by the Air Corps and redesignated YA-13.
The YA-13 was initially fitted with a 710-hp radial engine, but proved to be under-powered during flight testing. The aircraft was refitted with a 950-hp radial engine and re-designated YA-16, but was over-powered with the new engine. The Gamma 2F (a different, but similar airplane) had a 750-hp radial engine that proved satisfactory. After initial prototype testing, the Gamma 2F was returned to Northrop for some modifications.
The Air Corps purchased the aircraft after the modifications were complete and designated it A-17. An order for 110 aircraft was placed in the spring of 1935. The modified Gamma 2F was delivered as the first A-17 in the summer of 1935 with the initial production aircraft arriving in December of that year.
The remaining 109 production aircraft had the modifications done to the first aircraft on the assembly line. The most notable change was the addition of three dive brakes located on the lower trailing edge of the wing. The dive brakes reduced aircraft speed during steep dive bombing attacks and were perforated to reduce buffeting and unwanted lift. The A-17 was also fitted with partial wheel spats -- aerodynamic covers for the landing gear. Throughout the late 1920s and early 1930s fixed landing gear aircraft sometimes had full wheel spats (or pants) fitted. Invariably the outer half of these covers would be removed in the field. This made maintenance much easier -- changing tires, cleaning mud and debris and strut servicing.
The A-17 was initially tested at Wright Field by the Material Division. Initially, the 3rd and 17th Attack Groups received the A-17. When the improved A-17A was delivered, the A-17 was taken out of first line service and used for secondary duties like staff transport and training.
The A-17 could carry 20 30-pound bombs internally in small fuselage bomb compartments. The aircraft could also carry four 100-pound bombs on external wing racks. The A-17 was also capable of carrying gas canisters on wing pylons.
Although the A-17 formed the major part of the Air Corps attack capability in the mid- to late-1930s, none were ever used in combat. The improved A-17A replaced the A-17 in first line attack units by mid-1938.
Improved version of Gamma 2F
TECHNICAL NOTES: Armament: Four forward-firing .30-cal. machine guns and one flexible .30-cal. machine gun for the rear gunner, plus provisions for four 100 lbs. bombs externally mounted and 20 17-30 lbs. bombs internally carried in four dispensers (1,000 lbs. maximum bomb load) Engine: Pratt & Whitney R-1535-11 Twin Wasp Junior radial of 750 hp Maximum speed: 206 mph
Cruising speed: 170 mph Range: Approx. 1,250 miles maximum ferry range Service ceiling: 20,700 ft. Span: 47 ft. 9 in. Length: 31 ft. 9 in. Height: 11 ft. 11 in. Weight: 7,350 lbs. gross takeoff weight Crew: Two (pilot and observer/rear gunner) Serial number: 35-51 to 35-160