Curtiss A-12

The Curtiss A-12 was the first monoplane attack aircraft to serve in substantial numbers with the US Army Air Corps. It formed the bulwark of Army attack plane strength throughout the early to mid-1930s. However, the A-12 was rapidly made obsolescent by advances in aviation technology, and its service with front-line units of the Army Air Corps was quite brief. By the late 1930s, it had been relegated largely to training units. Except for 20 export versions which were sent to China, the A-12 took no part in aerial combat during World War 2.

The name Shrike was quite often applied to this aircraft, but this was actually a Curtiss company name, and was not used by the US Army for the A-12

The A-12 was a development of the Conqueror-powered A-8 via the experimental YA-10. A small number of Curtiss YA-8 and Y1A-8 monoplane attack planes had been delivered to the Army in 1932. They were powered by the Curtiss V-1570 Conqueror V-12 liquid-cooled engine. As an experiment, the first YA-8 (32-344) was modified at the Curtiss factory in Buffalo, New York where the Conqueror engine was replaced by a Pratt & Whitney R-1690D 9-cylinder air-cooled radial engine. The aircraft was redesignated YA-10.

Flight tests with the YA-10 proved the advantage of an air-cooled radial engine for attack aircraft. The Army found the radial engine less expensive to operate than the liquid-cooled V-12, and it had no complex cooling radiators exposed to enemy fire. Consequently, the Army immediately requested that the 46 A-8Bs then on order be delivered as radial-engined aircraft. This resulted in a change in designation to A-12. Serials were 33-212/257. The engine was the Wright R-1820-21 Cyclone air-cooled radial, rated at 160 hp at 1900 rpm.

It had been found that the wide separation between the two cockpits of the A-8 hindered communication and cooperation between the two crew members, so on the A-12 the rear cockpit was moved forward to share a common location with the pilot's cockpit. The rear gunner's cockpit had a sliding canopy which did not fully enclose it, whereas the pilot's cockpit was now fully open and was protected only by a windshield.

The forward section of the A-12 fuselage was of welded tubular steel construction with two wing stubs supported by two heavy struts on each side. The rear section was of monocoque construction with smooth dural skin, J section stringers and bulkheads. The two sections were joined by longeron stubs. The landing gear was attached to the underside of the wing stubs, with the rigid portion being bolted to the underside of the front and rear wing hinge fittings and braced sideways by an adjustable streamlined strut that ran to the center of the fuselage. The wheel was held by a horizontal jointed yoke, hinged at the rear to allow the wheel to move up and down. Each landing gear and wheel were completely spatted. It was possible to latch the wheels before takeoff so that they would not drop down the last six inches of their travel while in the air. However, the wheels were lowered by the pilot before landing so that the full 10-inch wheel motion was available to absorb landing shock.

The main wings were attached to the fuselage wing stub by front and rear hinge pins. They were braced at outboard points by double front and rear wires running to a strongpoint on top of the fuselage just behind the strut bracing points. On the bottom of the wing there were double front and rear bracing wires which were attached to the landing gear.

The wings of the A-12 were of all-metal construction, but with the ailerons being covered with fabric. The A-12 had a set of full-span leading edge slats which opened automatically at high angles of attack. They had shock absorbers which prevented them from opening or closing too suddenly. The A-12 also had a set of trailing edge wing flaps. The trailing edge flaps could be cranked down by as much as 35 degrees by the pilot.

The tail surfaces were of all metal construction, but the rudder and elevators were fabric-covered. The angle of incidence of the stabilizer could be adjusted in flight from +3 degrees to -6 degrees. The vertical stabilizer had a fixed offset of 21/2 degrees to the left.

The forward-firing armament consisted of four 0.30-inch Browning machine guns installed in the main landing gear spats, two guns in each member. Each gun was supplied by a 600 round magazine. These guns were aimed by a C-4 gunsight that was mounted just forward of the pilot's windshield. A single flexible 0.30-inch machine gun was provided for the observer. The A-12 could carry ten 30-lb bombs internally in a pair of N-2 bomb racks just aft of the pilot's seat and on either side of the main fuel tank. These bombs were carried in a vertical position. Alternatively, an external rack capable of carrying up to four 100-pound bombs could be installed underneath the fuselage. A 52-gallon auxiliary tank could be carried in place of the bombs. The auxiliary tank could be dropped in flight. In fact, the main fuel tank could also be jettisoned in flight by means of a special release handle.

The first A-12 (33-212) arrived at Wright Field on November 21, 1933. It remained at Wright Field until scrapped in October of 1936. The second A-12 (33-213) went to Edgewood Arsenal, Maryland on November 23, and the third (33-214) went to Aberdeen, Maryland, on November 29. The remaining 43 A-12s went to the 3rd Attack Group at Fort Crockett, Texas between December 1933 and February 1934. Their unit cost was $19,483, minus government-furnished equipment. The 3rd Attack Group was commanded by Lt. Col. Horace M. Hickam.

The first operational test of the USAAC A-12s was to come from a completely unexpected source. In February of 1934, the US Government canceled all air mail contracts with private carriers and turned over the mission of flying the air mail to the US Army. The Army was completely unsuited for this task. The 3rd Attack Group given the assignment of covering the Central Zone with headquarters in Chicago. 41 A-12s from the 3rd Attack Group were assigned air mail duty. When flying the mail, the A-12s had a lockable cover placed over their rear cockpits, and some replaced the rear cockpit glass with metal. By the time of the end of the Air Mail Emergency in May of 1934 when new contracts were signed with civilian carriers, two A-12s had been lost in fatal crashes while carrying the mail.

On November 5, 1934, Colonel Hickam was killed when his A-12 (serial number 33-250) flipped over on its back after touching down short and hitting the lip of the concrete runway while landing at Fort Crockett.

The 3rd Attack Group moved to its new permanent base at Barksdale Field in Louisiana in February of 1935. The A-12s of the 3rd Attack Group began to be replaced by Northrop A-17s in the middle of 1936. They were then dispersed to various training units. Nine A-12s went to the USAAC Tactical School at Maxwell Field, Alabama. One A-12 went to Edgewood Arsenal, replacing 33-213 which went into a depot. Ten went to Kelly Field, Texas to serve as trainers. During 1937, five more A-12s were sent to Kelly Field, four of them from Maxwell Field and one (33-214) from Aberdeen. 33-214 had been assigned from May through November of 1934 to the 37th Attack Squadron of the 8th Pursuit Group at Langley Field, Virginia (where it had served alongside the A-8s) and had been returned to Aberdeen. 15 of the 3rd Group's A-12s were sent to Wheeler Field in Hawaii in 1936. They were joined by six more A-12s in 1937, including 33-213 which had been at Edgewood and five from Maxwell Field. They were assigned to the 26th Attack Squadron which was part of the 18th Composite Group. The A-12s were transferred to Hickam Field in 1940. Nine A-12s were still there when Pearl Harbor was attacked on December 7, 1941. However, they did not participate in any combat. One of the nine Pearl Harbor-based A-12s was scrapped in May of 1942, and 8 were returned to the mainland where they were used as instructional airframes.

Of the 16 A-12s that stayed on the mainland in 1937, 33-237 stayed at Edgewood until scrapped there in January 1942. The other 15 remained at Kelly Field, where there were scrapped in 1937 and 1938. The 12 remaining A-12s were then sent to Maxwell Field during 1938 and remained there until removed from service. The last two, 33-223 and 33-252, became instructional airframes in March of 1942. No US Army A-12s saw any combat during World War 2.

20 export versions of the A-12 were sold to China in 1936. The Export Shrikes had a more powerful engine, a Wright SR-1820F-52 radial rated at 775 hp at full throttle and 890 hp for takeoff. Armament and fuel capacity was the same as that of the A-12. The Export Shrike had a maximum speed of 182 mph at sea level, 6 mph faster than the A-12. When the Japanese opened hostilities against China in 1937, these planes were soon involved in combat. It appears that few if any of the Chinese Shrikes survived the first year of the war.

I do not know if any A-12s survive today.

Serials of Curtiss A-12:

33-212/257

Specification of Curtiss A-12:

Powerplant: One 670 hp Wright R-1820-21 air-cooled radial engine. Performance: Maximum speed 177 mph at sea level. Cruising speed 151 mph at sea level. Stalling speed 67 mph. Initial climb rate 1170 feet per minute. Service ceiling 15,150 feet. Range 450 miles. Dimensions: Wingspan 44 feet 0 inches, length 32 feet 3 inches, height 9 feet 4 inches, wing area 284.5 square feet. Weights: 3898 pounds empty, 5736 pounds loaded. Armament: Four forward-firing 0.30-inch machine guns. One flexible 0.30-inch machine gun operated by rear observer. Ten 30-pound bombs could be carried internally, or four 100 pound bombs externally.

Sources:

1. American Combat Planes, Third Enlarged Edition, Ray Wagner, Doubleday, 1982.
   
   
2. Kenn C. Rust and Walter M. Jefferies, Jr., The Curtiss Shrike, Aircraft in Profile, Doubleday, 1969.
   
   
3. United States Military Aircraft Since 1909, Gordon Swanborough and Peter M. Bowers, Smithsonian, 1989.