In early 1939, prior to the signing of the first contract for the French DB-7, Douglas had begun a major redesign of the 7B to meet US Army Air Corps requirements. On June 30, 1939, the US Army rewarded Douglas's efforts by placing an order for the DB-7 under the designation A-20.
The Air Corps version of the Douglas bomber corresponded roughly to the DB-7B version that had been ordered by Britain. As compared to the French DB-7A, the A-20 differed in using steel forgings instead of dural for its main wing attachment fittings, in having a strengthened wing and fuselage structure to cope with a 3750-pound increase in gross weight, and in being fitted with a six-inch longer nose offering 25 percent more glazed area, and in having self-sealing fuel tanks with a total capacity of 394 US gallons. It differed from the DB-7B in having American armament, which consisted of four forward-firing 0.30-inch machine guns--mounted two each inside external side nose blisters instead of inside the lower nose section. In addition, twin flexible 0.30-inch guns were installed in an open dorsal position, and one flexible 0.30-inch machine gun was carried in a ventral tunnel position. Provision was made for a fixed rearward-firing 0.30-inch machine gun mounted in each engine nacelle. These rearward-pointing guns were fired by the rear gunner by means of a foot pedal.
Two separate versions were ordered by the Air Corps-- the A-20 which was to be a high-altitude version, and the A-20A which was intended for low- and medium-altitude operations.
Originally, 63 A-20s were ordered (serial numbers 39-735/797). The A-20 was to be be powered by turbosupercharged Wright R-2600-7 radials. The large turbosupercharger was mounted internally on the outer flanks of the engine nacelle, directly under the wing. The A-20 was intended as a high-altitude light bomber with a performance sufficient to make it essentially immune from interception.
Only one aircraft was destined to be completed as an A-20. This was the first aircraft on the A-20 order (39-735). It was fitted with the turbosupercharged R-2600-7 engine which offered a power of 1700 hp at 20,000 feet. Unfortunately, the turbosupercharger installation was large and bulky, and the engines developed serious cooling problems. In the meantime, Air Corps requirements were changing, and there was no longer a perceived need for a high-altitude light bomber. Consequently, a decision was made to convert all the other A-20s on the order to A-20A configuration with 1600 hp Wright R-2600-11 engines without turbosuperchargers.
39-735 later became the prototype of the P-70 night fighter series, and most of the A-20 order was actually completed as P-70s rather than A-20As. The remaining three aircraft on the A-20 order were delivered as reconnaissance aircraft under the designation F-3.
Serials of Douglas A-20 Havoc:
39-735 Douglas A-20 Havoc -modified as XP-70 night fighter. 39-736/740 Douglas P-70 Havoc 39-741 Douglas XF-3 Havoc - transferred to US Navy as BD-1 BuNo 4251 39-742/744 Douglas P-70 Havoc 39-745 Douglas YF-3 Havoc 39-746/747 Douglas P-70 Havoc 39-748 Douglas YF-3 Havoc 39-749/797 Douglas P-70 Havoc
Specification of Douglas A-20 Havoc:
Engines: Two Wright R-2600-7 Double Cyclone air cooled radials equipped with
turbo superchargers, rated at 1700 hp at 20,000 feet.
Performance (estimated): Maximum speed 388 mph at 20,000 feet.
Cruising speed 218 mph. Landing speed 93 mph. Service ceiling 31,500
feet. An altitude of 10,000 feet could be attained in 5 minutes.
Range 767 miles with 1200 pound bombload. 1100 miles maximum range.
Dimensions: wingspan 61 feet 4 inches, length 47 feet 7 inches,
height 17 feet 7 inches, wing area 464 square feet.
Weights: gross weight 20,329 pounds.
Armament: Four forward-firing 0.30-inch machine guns mounted two each
on external side blisters. In addition, twin flexible 0.30-inch guns
were installed in an open dorsal position, and one flexible 0.30-inch
machine gun was carried in a ventral tunnel position. Provision was
made for a fixed rearward-firing 0.30-inch machine gun mounted in each
engine nacelle. These guns were fired by the rear gunner by means of
a foot pedal.
Sources:
-
American Combat Planes, Third Enlarged Edition, Ray Wagner, Doubleday,
1982.
-
McDonnell Douglas Aircraft Since 1920, Vol 1, Rene J. Francillon,
Naval Institute Press, 1988
-
United States Military Aircraft Since 1909, Gordon Swanborough and
Peter M. Bowers, Smithsonian, 1989.
-
A-20 Havoc in Action, Aircraft Number 144, Squadron/Signal Publications,
Jim Mesko, 1994.
-
Famous Bombers of the Second World War, William Green, Doubleday, 1960
-
Boston, Mitchell and Liberator In Australian Service, Stewart Wilson,
Aerospace Publications, 1992.
- Jane's Fighting Aircraft of World War II, Military Press, 1989.
