Douglas B-18 Bolo
Technical Information

Background
Designed and developed by Douglas as a bomber for the U.S. Army Air Corps (USAAC) to replace the Martin B-10. The design was based on the Douglas DC-2 airliner. During 1935, Air Corps bombing trials at Wright Field the Douglas DB-1, the prototype of the B-18 competed against the twin engine Martin 146, an improved version of the B-10 and the four-engine Boeing Model 299 prototype of the B-17 Flying Fortress. Although many Air Corps officers judged the Boeing design to be superior, the Army General Staff preferred the DB-1 because it was less expensive.

B-18
The B-18 was developed from the successful DC-2 commercial airliner. In 1935 a design competition and "fly-off" was held to select a replacement for the Martin B-10/12 then in service with the USAAC. Competitors were the Douglas DB-1, Martin 146 (an improvement of the B-10 design) and Boeing Model 299. The Douglas design was selected, designated B-18 and contracts awarded for 82. The order was increased to 132 by June of 1936.

B-18A
The second version, designated B-18A, appeared in 1937 with a revised nose with extensive glazing in which the bomb-aimer/navigator sat above and ahead of the nose gun, which was housed in a ball-type turret. 255 of this version were ordered. Only 217 were delivered as B-18As; the final 38 were delivered as B-23s, an almost total redesign.

Wartime History
The B-18 Bolo was the primary U.S. Army Air Corps (USAAC) bomber when it became the U.S. Air Force (USAF) on June 20, 1941 and remained in use in the early months of World War II. Thirty-three B-18s were based in Hawaii with the 5th Bombardment Group (5th BG) and 11th Bombardment Group (11th BG). In the Philippines, twelve were assigned to the 28th Bombardment Squadron (28th BS). Other B-18s were based in Panama and the Caribbean and three airfields in the United States.

At the start of the Pacific War, Japanese air raids destroyed some B-18s in the Philippines. The few remaining played no significant role in later operations. By early 1942, replaced by the B-17 Flying Fortress as the USAAF first-line bombardment aircraft. Afterwards, many B-18s remained in use as transports, or modified as the B-18Bs for anti-submarine duty.

Production
Douglas built a total of 350 B-18s including 133 B-18s and 217 B-18A between 1936–1939.

Technical Details
Crew  Six
Engines  Two Wright R-1820-53s of 1,000 hp
Span  89 ft. 6 in
Length  57 ft. 10 in
Height  15 ft. 2 in
Maximum Speed  215 mph at 15,000'
Range  2,100 miles
Armament  Three .30-cal. guns (in nose, ventral and dorsal positions)
Bombload   4,500 lbs internally