By the mid-1930s, the U.S. Army Air Corps (USAAC), superseded by the U.S. Army Air Forces (USAAF) on 20 June 1941, was ordering all-metal, single-engine, monoplane attack and pursuit aircraft with enclosed cockpits to replace the fabric-covered, open cockpit biplanes of the 1920s. Aircraft such as the Northrop A-17, Consolidated P-30 and Seversky P-35 were some of the aircraft in this category. However, the training aircraft used to train the pilots were still fabric covered biplanes and newer and more modern machines were necessary in the training role. One of the first of these was the USAAC's BT-9, a basic training aircraft designated NJ, q.v., in U.S. Navy (USN) service, built by North American Aviation, Incorporated (NAA) of Inglewood, California. (For a brief history of NAA, see NJ, North American.) To provide the necessary training, the USAAC defined a new category of training aircraft, Basic Combat (BC) in 1936; aircraft in this category would have the equipment and performance approaching the new first-line aircraft, e.g., retractable landing gear, armament, radios, instrumentation, etc.
The USAAC held a design competition for the first basic combat aircraft at Wright Field, Dayton, Ohio, in March 1937. NAA entered their Model NA-26, an all-metal, single-engined, two-seat, low-wing monoplane with a retractable main landing gear and steerable tail wheel. Like the BT-9, the wings were metal covered while the fuselage was all-metal with detachable fabric-covered aluminum alloy frames aft of the engine. The vertical and horizontal tail surfaces were metal while the control surfaces, i.e., ailerons, rudder, and elevators, were fabric covered. Power was provided by a 550-hp Pratt & Whitney R-1340 radial engine driving a two-bladed propeller. NAA's Model NA-26 won the competition and the USAAC placed an order for 177 production BC-1s with armament in June 1937, The BC-1s were built as Model NA-36s and were delivered between March and December 1938. One of the more visible identification marks of this aircraft was the squared-off lower portion of the rudder. Initially, these aircraft were used for courier service and general flying and proficiency flying by copilots, navigators and bombardiers detached for service at Army posts. In mid-1939, the BC-1s were assigned to the Air Corps Training Center at Randolph Field, San Antonio, Texas.
Early in 1938, NAA built the model NA-44, a private venture intended to serve as a light attack/dive bomber. This aircraft was similar to the BC-1 but featured an all-metal fuselage and a center wing section that was 12 inches (30.5 cm) longer in span to house 184 US gallon (697 liter) fuel tanks . Over 50 of these aircraft were delivered to foreign governments while the last three were accepted by the USAAC as BC-2s.
The USN faced the same problem as the USAAC, i.e., a need for newer, more modern training aircraft. In September 1938, the USN placed an order for 16 Model NA-52s, a version of the BC-1 incorporating the improvements from the Model NA-44 and BC-2s. These all-metal aircraft had a wider wing center section but used the same outer wing panels and square-bottom rudder of the BC-1. The USN designated them SNJ-1s and they were delivered between May and November 1939.
After taking delivery of the three BC-2s, the USAAC ordered 83 Model NA-55s, designated BC-1As, in June 1939. The final nine BC-1As were redesignated AT-6s when the BC category was eliminated in 1940. Unlike the BC-1, the BC-1As had a direct-drive engine giving the propeller tips a high speed causing a distinctive rasping noise unique to all SNJs.
The second SNJ was the SNJ-2 which had the BC-2 wing and the BC-1A's direct-drive engine. The USN ordered 61 aircraft; the first 36 were Model NA-65s; the remaining 25 were Model NA-79s. The last SNJ-2 was accepted in July 1940.
Two events occurred in 1940 that affected the production of the AT-6 for the USAAC and the SNJ for the USN. In May 1940, the Army and Navy appointed a Joint Air Advisory Committee to advise the Army and Navy chiefs on employment, requirements, and cooperation on aviation matters. This was followed on 23 July 1943, by an agreement between the American military and the British Purchasing Commission, which was responsible for the procurement of U.S.-built aircraft, stating that "the procurement of airplanes and engines during the next two fiscal years....should be coordinated to permit a unified effort." Finally, the Army-Navy-British Purchasing Commission Joint Committee was established on 13 September 1940 to "consider and decide matters pertaining to aircraft standardization and aircraft delivery schedules." This latter committee was renamed the Joint Aircraft Committee (JAC) in March 1941. For the first time, USAAC and USN aircraft could be built with standardized equipment, e.g., engines, propellers, communications equipment, pressure pumps, pipe fittings, nuts, bolts, etc. This became the Army-Navy (AN) standard. From this point on, the AT-6s and SNJs coming off the assembly line were essentially identical. Another result of this coordination effort was that the USAAC, and later the USAAF, was given responsibility for ordering all AT-6/SNJ/Harvards for both the U.S. and British Commonwealth.
The second event involved NAA. The BC-1s, BC-2s, SNJ-1s and SNJ-2s were all built at NAA's Inglewood, California plant but by 1940, NAA also had contracts for B-25 Mitchell medium bombers and Mustang fighters for the Royal Air Force (RAF). Even though it had been expanded, the Inglewood plant was not large enough to manufacture all three aircraft and NAA began looking for a new manufacturing site. NAA found a site at Hensley Field, Texas, a USAAC reserve base 11 miles (17.7 km) west-southwest of Dallas, and in late 1940, the U.S. government began construction of a 1-million square foot (92,900 square meter) factory on the site. The name Texan was applied to the aircraft built in Dallas and the name was retroactively applied to all AT-6/SNJ aircraft built in California.
The first aircraft that was produced after the standardization efforts was the Model NA-77 designed as an aerial gunnery trainer with the seat in the rear cockpit facing aft and provision for two 30-caliber (7.62 mm) machine guns, a flexible gun in the rear cockpit and another in the engine cowling. Provisions were also provided to carry ten 20-pound (9.1 kg) or four 100-pound (45.4 kg) bombs under the wings. This aircraft was the first in the series to be equipped with the standardized 600 hp (447 kW) Pratt & Whitney R-1340-AN-1 radial engine used in all later models, a Hamilton Standard two-bladed constant-speed propeller, removable fuel tanks in the wing center section, a triangular shaped vertical fin and rudder, and blunt wingtips.
Both the USAAC and USN placed orders with NAA for Model NA-77, all built in the Inglewood, California plant. The USAAC ordered 517 as AT-6A-NAs and the USN ordered 120 as SNJ-3s. Production of Model NA-78s began in the Dallas, Texas plant in March 1941; this was the first version that was ordered by the USAAC for the USN. The USAAC ordered 1,330 AT-6A-NTs and 150 of these aircraft were transferred to the USN as SNJ-3s. Subsequently, another 150 Model NA-85s were built as SNJ-3s.
As production of military aircraft increased in the U.S. in 1940-1941, the government feared a shortage of strategic materials might develop, especially aluminum. Aluminum was to be reserved for combat aircraft and the aircraft manufacturers were asked to manufacture all other aircraft using as much non-strategic materials as possible. NAA had begun work in 1940 when they refitted the wings and tail surfaces of a BC-1A with stainless steel but this became a problem when chromium and nickel, used in the manufacture of stainless steel, were also listed as strategic materials. NAA then experimented with low-alloy steel sheet which was spot welded and only added 150 pounds (68 kg) to the weight of the aircraft. Another innovation was the use of wood instead of metal. The strength of the wood was not a problem but the deterioration of the wood required frequent inspections.
The first aircraft built of non-strategic materials was the Model NA-88. The wings, center-section, fin, and the control surfaces, were made of spot-welded low-alloy steel while the side panels of the forward fuselage, the entire rear fuselage and the floorboards were made of mahogany plywood. The USAAF placed its first order for 5,370 AT-6C-NTs in June 1941; of these, 2,400 were transferred to the USN as SNJ-4s and 726 went to the RAF as Harvard Mk. IIAs under Lend Lease.
Fortunately for the U.S., the scarcity of aluminum did not materialize and the production of Model NA-88sas AT-6D-NTs continued using aluminum instead of low-alloy steel and wood. These aircraft also had a 24-volt electrical system and provision for three 30-caliber (7.62 mm) machine guns, one in the rear cockpit, one in the cowling and one in the right wing. The USAAF placed its first order for 3,961 Model NA-88s as AT-6D-NTs in April 1942; 1,357 were transferred to the USN as SNJ-5s and another 351 went to the RAF as Harvard Mk. IIIs under Lend Lease. A change in model number occurred in 1944 when the USAAC ordered 800 Model NA-121s delivered as AT-6D-NTs; 411 of these aircraft went to the USN as SNJ-5s.
The final version of these aircraft were Model NA-121s built as AT-6F-NTs. In the AT-6F-NT, the armament was omitted, the outer wing panels were strengthened; the rear fuselage was redesignated; the aircraft was equipped with a propeller spinner and a frameless, molded rear canopy; and there was a provision for a 20 U.S. gallon (76 liter) centerline drop tank. The USAAF ordered 956 AT-6F-NTs in April 1944 with 411 of them going to the USN as SNJ-6s.
In 1949, the USAF had over 2,000 T-6s, as the aircraft was redesignated in 1948, in service and a modernization program was undertaken by NAA to modify 2,068 of them. Each aircraft was equipped with a raised instructor's seat, a new standardized cockpit layout in both front and rear, increased fuel tankage, square tipped propellers, and F-51 Mustang-type landing gear and tail wheel. The new aircraft were given the designation T-6G and, because the modification was so extensive, all aircraft were given new serial numbers. The USN also began a modernization program in 1952, based on the USAF's modifications, to modernize six SNJ-4/-5/-6 aircraft. The work was performed at Naval Air Station Pensacola, Florida but the modifications were not as extensive as the USAF T-6Gs, e.g., the F-51 landing gear and tail wheel were not installed. The modified aircraft were designated SNJ-7s.
A projected SNJ-8, Model NA-198, similar to the T-6G, was cancelled.
SNJ-1: 16 Model NA-52s
SNJ-2: 61 aircraft; 36 Model NA-65s and 25 Model NA-79s
SNJ-3: 420 aircraft; 120 Model NA-77s, 150 Model NA-78s and 150 Model NA-85s
SNJ-3C: 12 SNJ-3s equipped with arrester gear for carrier landing training
SNJ-4: 2,400 Model NA-88s
SNJ-4C: About 40 SNJ-4s equipped with arrester gear for carrier landing training
SNJ-5: 1,568 aircraft; 1,357 Model NA-88s and 211 Model NA-121s
SNJ-5C: Unknown number of SNJ-5s equipped with arrester gear for carrier landing training
SNJ-6: 411 Model NA-121s
SNJ-7: One SNJ-5 and one SNJ-6 modified to near USAF T-6G standard
SNJ-7B: An SNJ-4 and an SNJ-6 modified to near USAF T-6G standard and equipped with machine guns
SNJ-7C: An SNJ-5 and an SNJ-6 modified to near USAF T-6G standard and equipped with arrester gear for carrier landing training
SNJ-8: Cancelled contract for 240 Model NA-198s
The first SNJ-1 was delivered on 15 May 1939 and was assigned to Naval Air Station (NAS) Pensacola, Florida. These aircraft were originally intended to be based at Naval Air Reserve Bases (NRABs) in the U.S. but they were retained for Naval use and SNJ-2s were used at the NRABs. On 31 December 1941, there were 353 SNJs in the Naval inventory, 14 SNJ-1s, 54 SNJ-2s and 285 SNJ-3s. Most were assigned to training bases, e.g., 96 at NAS Miami, 90 at NAS Jacksonville and 62 at NAS Pensacola, Florida; and 39 at NAS Corpus Christi, Texas. As the war progressed, large numbers of SNJs could also be found at auxiliary bases including Naval Auxiliary Air Station (NAAS) Barin Field, Foley, Alabama; NAAS Bronson Field, NAAS Corry Field and NAAS Saufley Field in Pensacola, Florida; and NAAS Chase Field in Beeville; NAAS Cuddihy Field and NAAS Waldron Field in Corpus Christi and NAAS Kingsville in Kingsville.
In addition to performing its designed duty as a training aircraft, the SNJ was also used as a squadron utility aircraft so that aircrew could maintain their proficiency. Many were also used as station utility aircraft for personnel on the base.
The last SNJ was removed from the inventory in June 1968.
U.S. Marine Corps
The USMC received its first SNJ-2 in 1940 followed by SNJ-3s in 1941. By 7 December 1941, the USMC had 3 SNJ-2s and 15 SNJ-3s; the SNJ-2s and two SNJ-3s were assigned to Base Air Detachment One (BAD-1) at Marine Corps Air Station (MCAS) Quantico, Virginia; the remainder of the SNJ-3s were assigned to Marine Fighting Squadron One Hundred Eleven (VMF-111) and VMF-121 at MCAS Quantico; VMF-211 at MCAS Ewa, Territory of Hawaii; and VMF-221 and Marine Observation Squadron Two Hundred Fifty One (VMO-251) at NAS San Diego, California.
Like the USN, the USMC operated SNJs throughout the war as squadron and station utility aircraft permitting assigned personnel to maintain their proficiency.
U.S. Coast Guard
The USCG received 15 USN SNJ-5/-6s beginning in 1943. One or two aircraft were assigned to each Coast Guard Air Station (CGAS), e.g., CGAS Biloxi, Mississippi; CGAS Elizabeth City, North Carolina; CGAS Port Angeles, Washington; CGAS San Francisco, California; and CGAS St. Petersburg, Florida. Five other SNJs were used for cross-country navigation training.
SNJ-1: One 550 hp (410 kW) Pratt & Whitney R-1340-6 nine-cylinder, single-row, air-cooled, radial engine.
SNJ-2: One 550 hp (410 kW) Pratt & Whitney R-1340-56 nine-cylinder, single-row, air-cooled, radial engine.
SNJ-3 to SNJ-6: One 600 hp (447 kW) Pratt & Whitney R-1340-AN-1 nine-cylinder, single-row, air-cooled, radial engine.
Wing Span: 42 feet (12.80 meters)
Length: 27 feet 11.6 inches (8.52 meters)
Height: 8 feet 6.3 inches (2.60 meters)
Wing Area: 248.3 square feet (23.07 square meters)
SNJ-1: 3,250 pounds (1,474 kg)
SNJ-3: 3,900 pounds (1,769 kg)
SNJ-4: 4,143 pounds (1,879 kg)
SNJ-5: 4,082 pounds (1,852 kg)
SNJ-6: 4,050 pounds (1,837 kg)
Maximum Speed: 178 mph (286 km/h) at 5,100 feet (1,554 meters)
Cruiser Speed: 140 mph (225 km/h)
Service Ceiling: 24,900 feet (759 meters)
Range: 944 miles (1,519 km)
SNJ-3/-4: Two 30-caliber (7.62 mm) machine guns, one flexible in the rear compartment with 500 rounds per gun (rpg), one fixed in the cowling and one fixed in the right wing, both with 200 rpg. The aircraft could also carry ten 20-pound (9.1 kg) or four 100-pound (45.4 kg) bombs under the wings.
SNJ-5: Same as SNJ-3/-4 except provision for a 30-caliber (7.62) machine gun in the right wing.