Northrop A-17A

Last revised September 3, 2000


While production of the A-17 was underway, Northrop proposed the development of a version of the A-17 with a fully retractable main undercarriage. This retractable undercarriage consisted of a set of main wheels attached to the forward edge of the wing which retracted inwards into wheel wells underneath the fuselage. This retractable undercarriage was first tested on the Gamma 2J experimental advanced trainer. The A-17 design turned out to be readily adaptable to a retractable undercarriage, with relatively few changes being required. However, the use of the retractable undercarriage did require that the inboard leading edge wing roots be extended to provide space for the wheels.

On January 29, 1936, an initial order was placed for 100 retractable- undercarriage versions of the A-17, which were assigned the designation A-17A. Serials were 36-162/261. The first production A-17A (36-162) flew for the first time on July 16, 1936. There were some teething problems with the retractable undercarriage, which resulted in a delay of delivery to the USAAC until February 4, 1937. The aircraft was used for testing during this period, and two accidents caused by undercarriage failures caused the delivery of the second production aircraft to be delayed until April 1937. Once these difficulties were cleared up, the the 100 A-17As were delivered between April and December of 1937. A further 29 A-17As (38-327/355) were ordered during the second half of 1937, and these were delivered between June and September 1938.

All A-17As were powered by a 825 hp R-1535-13 Twin Wasp Junior engine. They were armed with four wing-mounted 0.30-inch machine guns and had a flexible 0.30-inch machine gun operated by the gunner in the rear cockpit. Normal bombload was four externally-carried 100-lb bombs or 20 30lb anti-personnel bombs carried internally. A maximum bombload was 1200 pounds.

The A-17As were delivered in 1937 to the 3rd Attack Group (8th, 13th, and 90th Squadrons) at Barksdale Field, Louisiana and to the 17th Attack Group (34th, 37th, and 95th Squadrons) based at March Field, California. They supplemented and later replaced the fixed-undercarriage A-17s serving with these units. The A-17A was fairly fast and had a fairly heavy forward-firing armament for its time, and during 1938-39 war games it was deemed to be the most effective ground attack aircraft yet devised. However, the Army decided that twin-engined attack aircraft offered substantial advantages over the single-engined types then in service, and the career of the A-17A with the Army was quite brief. After only three years of service with the Army, the A-17As were declared surplus.

Following the beginning of the Second World War with the German invasion of Poland, the French Armee de l'Air felt an urgent need for dive bombers, and since the US Army considered the A-17A to be obsolescent, the French Purchasing Commission that was touring the USA looking for aircraft was given permission to obtain 93 of the ex-USAAC A-17As.

The 93 A-17As ordered by France were withdrawn from USAAF service and were returned to the Northrop factory (which was by this time known simply as the El Segundo Division of Douglas) where they were refurbished and re-engined with 825 hp Pratt & Whitney Twin Wasp JrS2A5-G engines. Unfortunately, by the time that the planes were ready for delivery, France had fallen. The contract was then taken over by the British Purchasing Commission, which at that time was willing to buy just about anything that had wings. The British A-17As were given the RAF name Nomad. RAF serials were AS440/AS462, AS958/AS976, and AW420/AW438.

However, the RAF also deemed the Nomad to be obsolescent, and decided to restrict it from combat operations. 60 of the RAF Nomads were transferred to South Africa. 17 were lost at sea en enroute. The survivors were taken on charge in February 1941 by the SAAF, where they were used for training. None of these aircraft ever saw any combat. They remained in service until the end of 1942 when they were replaced by Fairey Battles. The last SAAF Nomads were struck off charge in 1944.

Those A-17As still in the USA were used during the early war years as advanced trainers or as squadron hacks before ending their lives in mechanics' schools. None of these aircraft ever saw any combat either. The last A-17A was struck off charge on October 31, 1944.

A-17A (36-184) was used by the National Advisory Committee for Aeronautics (NACA) during 1939 to test new types of engine cowlings. Initially, the aircraft was fitted with a large propeller spinner which completely covered the engine front air intake. Large ducts were built into the wing roots to provide air for engine cooling. However, before flight testing could begin ground tests indicated that the engine temperature rose too high and NACA decided not to try and fly the aircraft in such a configuration. NACA removed the wing ducts and replaced the oversized spinner with a ducted spinner with a large hole in its center that incorporated impeller blades which forced cooling air to the engine. Engine cooling while on the ground was much more effective than the NACA cowling used by the conventional A-17A--the engine could be operated at full throttle on the ground for 15 minutes without cylinder temperatures exceeding their limits. Although there was a slight decrease in speed with the nose blower, the results of the speed tests were considered inconclusive and the project was not pursued any further. 36-184 was de-modded to standard configuration and returned to the Air Corps on June 21, 1940.

A-17A 35-122 was used by NACA at Langley Field to test several aerodynamic innovations. At first it was used to test new exaust pipes. Later, it was used to test new laminar flow airfoils. The aircraft was eventually returned to the Air Corps.

A-17A 36-207 is on display at the USAF Museum in Dayton, Ohio.

Serials of Northrop A-17A:

36-162/261 		Northrop A-17A 
				c/n 189/288 
38-327/355 		Northrop A-17A 
				c/n 381/409 

Specification of Northrop A-17A:

Engine: One Pratt & Whitney R-1535-13 Twin Wasp Junior fourteen-cylinder air-cooled radial engine, rated at 825 hp at 2500 feet. Performance: Maximum speed 220 mph at sea level. Cruising speed 170 mph. Landing speed 64 mph. Initial climb rate 1350 feet per minute. An altitude of 5000 feet could be reached in 3.9 minutes. Service ceiling 19,400 feet. Normal range 730 miles with 654 pounds of bombs. Maximum range 1195 miles. Dimensions: Wingspan 47 feet 9 inches, Length 31 feet 8 inches, Height 12 feet 0 inches, Wing area 363 square feet. Weights: 5106 pounds empty, 7550 pounds loaded. Armament: Four wing-mounted 0.30-inch machine guns, plus one flexible 0.30-inch machine gun operated by rear cockpit gunner. Normal bombload was four externally-carried 100-lb bombs or 20 30lb anti-personnel bombs carried internally. Maximum bombload was 1200 pounds.

Sources:


  1. American Combat Planes, Third Enlarged Edition, Ray Wagner, Doubleday, 1982.

  2. United States Military Aircraft Since 1909, Gordon Swanborough and Peter M. Bowers, Smithsonian, 1989.

  3. McDonnell Douglas Aircraft Since 1920, Volume I, Rene J. Francillon, Naval Institue Press, 1988.

  4. Northrop's Connection--The Unsung A-17 Attack Aircraft and its Legacy, Alain J. Pelletier, Air Enthusiast, May/June 1998, No 75.

  5. E-mail from Charles Hinton on 13th Squadron having A-17s at Barksdale