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The Curtiss A-18 Shrike was the service-test version of the XA-14 twin-engined ground attack aircraft. Like the XA-14 it was of all-metal construction apart from fabric covers on the movable control surfaces and the rear of the wing. The two crewmen were carried in rather widely separated cockpits. On the XA-14 part of the reason for the gap had been to make space for the internal fuselage bomb bay, but on the A-18 the bombs were carried in two bomb bays in the wings, each capable of carrying 200lb of bombs, while more bombs could be carried under the wings. The main change made to the A-18 was the use of Wright Cyclone R-1820-47 engines and three-bladed propellers. The more powerful engines compensated for an increase in gross weight of over 1,000lb and gave the A-18 a top speed of 247mph, 4mph faster than the XA-14.
The US Army placed an order for thirteen Y1A-18 service test machines on 23 July 1936 (Y1 indicating the use of F-1 funding to pay for the aircraft). These aircraft were delivered in July-October 1937, and were tested by the 8th Attack Squadron of the Third Attack Group. In tests against the single-engined Northrop A-17 the A-18 proved to be slightly faster and have a higher service ceiling, but lacked the range of the A-17, and so did not receive a production contract. The existing Y1A-18s were transferred to the Third Bombardment Group in 1940, to be used for operational training, and as the service test period was over were redesignated as plain A-18s. They remained in use until 1940.
Although the A-18 Shrike was not a success itself, the concept of a twin-engined attack aircraft had impressed the Air Corps, and late in 1937 they invited companies to submit designs for an aircraft with twice the range and bomb load of the A-18. Out of this contest came the Martin Maryland, Douglas A-20 Havoc/ Boston and the North American B-25 Mitchell.
Engine: Wright R-1820-47 Cyclone
Power: 850hp
Span: 59ft 6in
Length: 41ft
Height: 11ft
Empty Weight: 9,580lb
Gross Weight: 12,849lb
Maximum Speed: 247mph at 2,500ft
Cruising Speed: 217 mph
Ceiling: 25,000ft
Range: 651 miles
Guns: Four .30in machine guns fixed in nose, one flexible in rear cockpit
Bomb load: 200lb of bombs in each wing bomb bay
Suggested Reading
Curtiss Aircraft, 1907-1947, Peter M Bowers (Amazon.co.uk)
Curtiss Aircraft, 1907-1947, Peter M Bowers (Amazon.com)