The A-20C was introduced on the production line during early 1941. It was an attempt to standardize on a common British and American version of the Douglas attack bomber. Based on combat reports from the field, self-sealing fuel tanks and additional armor were added. The A-20C reverted back to the slanted diagonal glass nose arrangement of the A-20A instead of the stepped arrangement of the A-20B. A teardrop-shaped blister was used to add an additional gun on the side of the nose. 0.30-inch (0.303-inch guns on British versions) machine guns were used in all positions. The impractical rear-aimed nacelle guns were finally deleted. The aircraft was powered by Wright R-2600-23 engines instead of the earlier R-2600-3 or -11 versions. The extra weight resulted in a drop in top speed from 350 mph on the A-20A to 342 mph on the A-20C.
The Lend-Lease version of the A-20C was known as the Boston IIIA. The Boston IIIAs differed from the A-20C primarily in being armed with 0.303-inch machine guns instead of 0.30-inch guns. The Boston IIIA also had extended carburetor air intakes above the cowling to include tropical filters. The USAAF A-20Cs were generally identical to the British Boston IIIA, but US 0.30-inch guns were substituted for for British 0.303-inch weapons and the exhaust collector ring for the 1600 hp R-2600-23 engines was replaced by individual exhaust stacks which resulted in an increase in top speed of 15 mph.
The A-20C featured the ability to carry a standard 2000-lb naval torpedo externally underneath the bomb bay. This capability was not often used by the USAAF, but was extensively exploited by Russian-flown A-20Cs with some considerable success.
808 A-20Cs were built at Douglas-Santa Monica (41-19088/19462 and 42-32951/33383) under Lend Lease Contract DA2, and 140 were built under Lend-Lease Contract DA934 by Boeing at its Seattle facility (41-19589 to 41-19728).
Back in June of 1940, Boeing had acquired a license from Douglas for DB-7 manufacture to fulfill foreign orders, and this company continued for a while afterwards to build A-20s to fulfill Lend-Lease contracts. Boeing was furnished with complete detailed designs and master tooling to ensure interchangeability of parts between aircraft built by the two companies. However, the Douglas-built A-20Cs had a new collector-ring exhaust that replaced the large single stack of the DB-7B and A-20A, with the Boeing-built machines retaining the exhaust arrangement of the DB-7B.
The A-20C was the first A-20 version to be covered by the Block Number and Factory Designation systems. However, the Boeing A-20 machines were all built before the system went into effect, as were the first 375 built by Douglas.
The A-20C-1-DO (42-32951/33050) were all intended for the Army and delivered with USAAF camouflage and armament.
The A-20C-5-DO (42-33051/33200) added provisions for tow-target reels, had revised wing flap controls, and had an electric gunsight and a bulletproof windshield.
The A-20C-10-DO (42-33201/33383) were the same as the -5 except for an additional radio.
Most of the A-20Cs that were ordered were intended for delivery to Britain or the Soviet Union under Lend-Lease. 200 went to Britain as the Boston IIIA (BZ196 to BZ352, BZ355 to BZ378 and BZ381 to BZ399), while others were taken over by the RAF in the field from the USAAF, with some machines retaining their original USAAF serials and others being assigned new RAF serials (HK896, HK870, HK872 to HK879, HK912, HK918, HK923, HK924, HK934, HK960, HK962, HK964, HK967, HK969, HK970, HK972 and HK973). It turned out that most of the British order was actually diverted to the USSR under Lend-Lease.
The last 433 A-20C production aircraft were fitted with an extra 140-gallon self-sealing fuel tank in the bomb bay, which raised the total fuel capacity to 540 gallons. All A-20Cs could be fitted with a ferry tank underneath the belly.
Following Pearl Harbor, a substantial number of the A-20Cs were taken over by the USAAF from Lend-Lease contracts in order to establish A-20 training groups in the US. In USAAF service, the A-20C was used primarily as a trainer and test aircraft, and very few of them actually saw combat. Various armament and turret arrangements were tried out on USAAC A-20Cs, along with various other unusual configurations. At least 56 A-20Cs taken over by the USAAF were fitted with racks for a torpedo under the belly. Several A-20Cs were modified in the field to mount a battery of six 0.50-inch machine guns in the glazed nose, which was either painted over or covered with light metal.
An experimental caterpillar track main undercarriage was tested on A-20C serial number 41-19158. The second A-20C-5-DO (43-33201) was fitted with a Martin twin-gun dorsal turret similar to that later fitted to all aircraft beginning with the A-20G-20-DO block. At least one A-20C (41-19205) was used to test an aircraft's ability to withstand frangible bullets when used as a gunnery target. The entire top fuselage from the cockpit back to the gunner's area was removed and covered over. The center section of the fuselage, wings, and engine area was then covered with armor. The cockpit area was heavily shielded by armor, and special glass was used.
41-19088/19462 Douglas A-20C Havoc - Lend-lease contract for RAF and for Soviet Air Force - Substantial numbers were taken over by USAAF after Pearl Harbor. 41-19589/19728 Boeing A-20C-BO Havoc - license built Havoc intended for Lend-Lease with RAF, but most were diverted to USAAC. 42-32951/33050 Douglas A-20C-1-DO Havoc - Built under lend-lease contract for delivery to RAF and Soviet Air force. Substantial numbers retained by USAAF. 42-33051/33200 Douglas A-20C-5-DO Havoc - Built under lend-lease contract for delivery to RAF and Sov AF. Substantial numbers retained by USAAF. 33134 to RAAF as A28-27. Lost in action 1/44. 33142 to RAAF as A28-28. converted to components 5/45. 33154 to RAAF as A28-23 - crash landed 9/43, converted to components. 33163 to RAAF as A28-24, crashed in sea 3/44. 33168 to RAAF as A28-31. Converted to components 5/45. 33172 to RAAF as A28-25, converted to components 4/45. 33174 to RAAF as A28-30. Damaged in accident 8/44. converted to components. 33180 to RAAF as A28-26. Crashed and burned 10/43. 33143, 33148, 33152, 33164, 33165, 33170, 33177, 33179 modified as P-70A-1 night fighter. 42-33201/33383 Douglas A-20C-10-DO Havoc - Built under lend-lease contract for delivery to RAF and Soviet Air force. Substantial numbers retained by USAAF. 33211 to RAAF as A28-29. shot down 11/43. 33221 modified as P-70A-1 night fighter
Engines: Two Wright R-2600-23 Double Cyclone air-cooled radial engines, each
rated at 1600 hp for takeoff and 1275 hp at 11,500 feet.
Performance: Maximum speed 342 mph at 13,000 feet, 314 mph at sea
level. Cruising speed 280 mph. Landing speed 100 mph. Service
ceiling 25,320 feet. An altitude of 10,000 feet could be attained in
6.3 minutes. Range 745 miles with 1000 pounds of bombs. Maximum
ferry range 2300 miles.
Dimensions: Wingspan 61 feet 4 inches, length 47 feet 3 5/8 inches,
height 17 feet 7 inches, wing area 464 square feet.
Weights: 15,625 pounds empty, 21,000 pounds gross, 24,500 pounds
Armament: Four 0.30-inch machine guns machine guns in the nose, two
in lower nose and one in a teardrop-shaped blister mounted on each
side of the nose. Two flexible 0.30-inch machine guns in flexible
dorsal position. One flexible 0.30-inch machine gun in ventral tunnel