On the same day that the US Army ordered the A-20 high-altitude light bomber, it also ordered the A-20A, which was a low- and medium-altitude version of the Douglas attack bomber. A May 20, 1939 contract approved on June 30 called for 123 A-20As.
The A-20A was essentially similar to the A-20 except for the omission of the trouble-prone turbosupercharger. The A-20A was powered by a pair of Wright R-2600-3 Double Cyclone radials with two-state mechanical superchargers. This engine was similar to those fitted to the French DB-7A and British DB-7B, and produced 1600 hp for takeoff.
In general, the A-20A corresponded to the British DB-7B except for differences in the internal equipment and in the caliber of the armament. The A-20A carried two 0.3-inch forward-firing Browning machine guns installed in the lower nose. These could be supplemented by a teardrop-shaped gun blister carrying a single 0.30-inch machine mounted on each side of the lower nose. Two 0.30-inch machine guns were mounted on a flexible rear gunner's position, and a 0.3-inch ventral tunnel gun was provided for protection against attacks from below. A Browning gun could be mounted in the tail of each engine nacelle, pointing directly aft and operated by a foot pedal installed in the rear gunner's cockpit. However, these fixed rearward-firing guns were felt to be of little use and were rarely actually fitted.
Like the British DB-7A, early A-20As were fitted with cooling vents along the sides of the engine cowling, but these were later deleted since they were found to be of little use.
The initial order for 123 A-20A aircraft was later increased by 20, these being fitted with the more powerful Wright R-2600-11 engines, although these were still designated A-20A. They were added to the order in exchange for the A-17As that Douglas resold to Britain.
All A-20As were built at the Douglas plant in El Segundo, California. The first A-20A flew on September 16, 1940, the aircraft being delivered on November 30. The first deliveries to the USAAC took place in December. The A-20A went into service in the spring of 1941 with the 3rd Light Bombardment Group (formerly known as the 3rd Attack Group) at its new Savanna, Georgia base. USAAC units based Hawaii and the Canal Zone got 12 A-20As each, and the remainder were delivered to new Light Bombardment units, the 15th Bomb Squadron (Light) at Lawson Field, the 46th Bombardment Group (light) at Bowman Field, and the 48th Bombardment Group (Light) at Will Rogers Field.
The Army liked the A-20A because of its excellent performance and because it had no adverse handling characteristics. Early aircraft were delivered in natural metal finish, with US insignia being carried only on the upper and lower wings.
In July 1941, one A-20A airframe was experimentally fitted with three remotely-controlled power-operated turrets, above and below the fuselage, and in the nose. The designation XA-20B was applied to the project. The experiment was not successful, and was discontinued.
In late 1942, the surviving A-20As were redesignated RA-20A, the R prefix meaning that they were restricted from combat use.
39-721/734 Douglas A-20A Havoc 40-071/179 Douglas A-20A Havoc 077 to RAAF as A28-36 11/43. Converted to components 04/45. 085 to RAAF as A28-32 11/43. Converted to components 04/45. 118 to RAAF as A28-37 11/43. Converted to components 04/45. 139 to RAAF as A28-38 11/43. Converted to components 04/45. 143 to RAAF as A28-33 11/43. Converted to components 5/44 144 to RAAF as A28-39 11/43. Converted to instructional airframe. SOC 10/46. 162 to RAAF as A28-35 11/43. Converted to components 3/45. 40-3143/3162 Douglas A-20A Havoc 3159 to RAAF as A28-40 11/43. Converted to components 04/45. 3160 to RAAF as A28-34 11/43. Converted to components 04/45.
Engines: Two Wright R-2600-11 Double Cyclone air-cooled radial engines, each
rated at 1600 hp for takeoff and 1275 hp at 12,000 feet.
Performance: Maximum speed 347 mph at 12,400 feet. Cruising speed
295 mph. Landing speed 85 mph. Service ceiling 28,175 feet. An
altitude of 10,000 feet could be attained in 5.1 minutes. Range 525
miles with 2400 pounds of bombs. 675 miles range with 1200 pounds of
bombs. Maximum range 2000 miles.
Dimensions: Wingspan 61 feet 4 inches, length 47 feet 7 inches,
height 17 feet 7 inches, wing area 464 square feet.
Weights: 15,165 pounds empty, 19,750 pounds gross, 20,711 pounds
Armament: Two 0.3-inch forward-firing Browning machine guns installed
in the lower nose. These could be supplemented by a teardrop-shaped
gun blister carrying a single 0.30-inch machine mounted on each side
of the lower nose. Two 0.30-inch machine guns were mounted on a
flexible rear gunner's position, and a 0.3-inch lower tunnel gun was
provided for protection against attacks from below. A Browning gun
could be mounted in the tail of each engine nacelle, pointing directly
aft and operated by a foot pedal The A-20A could carry a single
1100-lb bomb in the bomb-bay, or a similar weight of fragmentation,
chemical, or smaller general-purpose bombs.