Curtiss A-12

Curtiss A-12

By Joe Baugher

The A-12 was the first monoplane attack aircraft to serve in substantial numbers with the USAAC, forming the bulwark of attack plane strength in the early- to mid-1930s. However, A-12 was fast made obsolescent by advances in aviation technology, and its service with front-line units of the Air Corps was quite brief. By the late 1930s, it had been relegated largely to training units. Except for 20 export versions sent to China, the A-12 had no part in aerial combat during WW2.

    The name Shrike was quite often applied to this aircraft, but it was actually a Curtiss name and never officially used by the Army.

As a development of the Conqueror-powered A-8, via the experimental YA-10, a small number of Curtiss YA-8/Y1A-8 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 Buffalo factory with a P&W R-1690D air-cooled radial and redesignated YA-10, and flight tests proved the advantage of an air-cooled radial for attack aircraft as less expensive to operate than the liquid-cooled V-12 and with no complex cooling radiators vulnerable to enemy fire. Consequently, the Army immediately requested that 46 A-8Bs then on order be delivered with 160hp Wright R-1820-21 Cyclones, redesignated as A-12 [33-212/257].

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

    The forward section of the fuselage was of welded tubular steel construction with 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 the last six inches of their travel while in the air. However, the wheels were lowered fully by the pilot before landing to absorb landing shock.

    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 were of all-metal construction, but ailerons were covered with fabric. The A-12 had a set of full-span leading edge slats which opened automatically at high angles of attack, and had shock absorbers which prevented them from opening or closing too suddenly. Trailing edge flaps could be cranked down by as much as 35° by the pilot. The tail surfaces were of all-metal construction with fabric-covered rudder and elevators. Angle of incidence of the stabilizer could be adjusted in flight from Ʊ to -6°. The vertical fin had a fixed offset of 2-1/2° left.

    Forward-firing armament consisted of four .30 Browning machine guns installed in the landing gear spats, two in each gear; each gun had a 600-round magazine, and were aimed by a C-4 gunsight mounted just forward of the pilot's windshield. A single flexible .30 machine gun was provided for the observer. The A-12 could carry ten 30# bombs carried in a vertical position internally in a pair of N-2 bomb racks aft of the pilot's seat and on either side of the main fuel tank. Alternatively, an external rack could carry up to four 100# bombs underneath the fuselage, or a jettisonable 52-gallon auxiliary tank could replace the bombs. The main fuel tank, as well, could also be jettisoned in flight by means of a special release handle.

The first A-12 [33-212] arrived at Wright Field on Nov 21, 1933, and remained there until scrapped in Oct 1936. The second A-12 [33-213] went to Edgewood Arsenal MD on Nov 23, and the third [33-214] went to Aberdeen MD on Nov 29. The remaining 43 A-12s went to the 3rd Attack Group at Fort Crockett TX between Dec 1933 and Feb 1934. Their unit cost was $19,483, minus government-furnished equipment. The 3rd AG was commanded by LtCol Horace M Hickam, who was killed Nov 5, 1934 when his A-12 [33-250] flipped over on its back in landing at Fort Crockett.

    First operational test of USAAC A-12s was to come from a completely unexpected source. In Feb 1934, the government canceled all air mail contracts with private carriers and turned over the mission of flying the air mail to the Army, which was completely unsuited for this task. The 3rd Attack Group was given the assignment of covering the Central Zone with headquarters in Chicago, and 41 A-12s from the 3rd AG were assigned air mail duty. When flying mail, the A-12s had a lockable cover placed over their rear cockpits, and some replaced the rear cockpit glass with metal. By the end of the Air Mail Emergency in May 1934, when new contracts were signed with civil carriers, 2 A-12s had been lost in fatal crashes while carrying the mail.

    The 3rd AG moved to its new permanent base at Barksdale Field LA in Feb 1935, where A-12s 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 AL and one went to Edgewood Arsenal MD, replacing [33-213], which went into a depot. Ten went to Kelly Field TX to serve as trainers. During 1937, 5 more A-12s were sent to Kelly Field, 4 of them from Maxwell Field and 1 [33-214] from Aberdeen. [33-214] had been assigned from May through Nov 1934 to the 37th Attack Squadron of the 8th Pursuit Group at Langley Field VA—where it had served alongside the A-8s—and had been returned to Aberdeen.

    Fifteen of the 3rd AG's A-12s were sent to Wheeler Field in Hawaii in 1936. They were joined by 6 more A-12s in 1937—including [33-213], which had been at Edgewood—and 5 from Maxwell Field. They were assigned to the 26th Attack Squadron as 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 Dec 7, 1941; however, they did not participate in any combat. Of the 9, one was scrapped in May 1942 and 8 were returned to the mainland to be used as instructional airframes.

Of the 16 A-12s remaining on the mainland in 1937, [33-237] stayed at Edgewood until scrapped there in Jan 1942, and the others 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 stayed there until removed from service. The last 2 [33-223/252] became instructional airframes in March 1942.

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

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