The Douglas B-18 Bolo
was a United States Army Air Corps
and Royal Canadian Air Force bomber
of the late 1930s and early 1940s. The Bolo
was built by Douglas Aircraft Company
and based on its DC-2
. Although not the latest or most advanced design, the B-18
was pressed into service where it performed wartime patrol duties early in World War II
Design and development
In 1934, the United States Army Air Corps
put out a request for a bomber
with double the bomb load and range of the Martin B-10
, which was just entering service as the Army's standard bomber.
In the evaluation at Wright Field
the following year, Douglas showed its DB-1
. It competed with the Boeing Model 299
(later the B-17 Flying Fortress
) and Martin Model 146
. While the Boeing design was clearly superior, the crash of the B-17 prototype (caused by taking off with the controls locked) removed it from consideration. During the depths of the Great Depression
, the lower price of the DB-1 ($58,500 vs. $99,620 for the Model 299) also counted in its favor. The Douglas design was ordered into immediate production in January 1936 as the B-18.
The DB-1 design was essentially the same as the DC-2, with several modifications. The wingspan was 4.5 ft (1.4 m) greater. The fuselage was deeper, to better accommodate bombs and the six-member crew; the wings were fixed in the middle of the cross-section rather than to the bottom, but this was due to the deeper fuselage. Added armament included nose, dorsal, and ventral gun turrets.
The initial contract called for 133 B-18s (including DB-1), using Wright R-1820 radial engines
. The last B-18 of the run, designated DB-2
by the company, had a power-operated nose turret
. This design did not become standard. Additional contracts in 1937 (177 aircraft) and 1938 (40 aircraft) were for the B-18A
, which had the bombardier
's position further forward over the nose-gunner
's station. The B-18A also used more powerful engines.
By 1940, most US Army Air Force bomber squadrons were equipped with B-18s or B-18As. Many of those in the 5th Bomb Group and 11th Bomb Group in Hawaii were destroyed in the attack on Pearl Harbor.
B-17s supplanted B-18s in first-line service in 1942. Following this, 122 B-18As were modified for anti-submarine warfare. The bombardier was replaced by a search radar with a large radome. Magnetic anomaly detection (MAD) equipment was sometimes housed in a tail boom. These aircraft, designated B-18B, were used in the Caribbean on anti-submarine patrol. Two aircraft were transferred to Força Aérea Brasileira in 1942. The Royal Canadian Air Force acquired 20 B-18As (designated the Douglas Digby Mark I), and also used them for patrol duties.
On 2 October 1942, a B-18A depth charged and sank the German u-boat U-512 north of Cayenne, French Guiana. Bolos and Digbys sank an additional two submarines during the course of the war. RCAF Eastern Air Command (EAC) Digbys carried out 11 attacks on U-boats. U-520 was confirmed sunk by Flying Officer F. Raymes' crew of No 10 (BR) Sqn, on 30 October 1942 east of Newfoundland.
- Prototype, first of B-18 production run, 1 built.B-18
- Initial production version, 131 or 133 built.;B-18M
- Bomb gear removed from B-18 to serve as trainer.;DB-2
- Powered nose turret prototype; last of B-18 production run, 1 built.B-18A
- B-18 with more powerful Wright R-1820-53 engines and moved bombardier's station, 217 built.B-18AM
- Bomb gear removed from B-18A to serve as trainer.B-18B
- Antisubmarine conversion, 122 converted.B-18C
- Antisubmarine conversion, 2 converted.XB-22
- Improvement on B-18 using Wright R-2600-3 radial engines (1,600 hp, 1194 kW). Never built, largely due to better light bombers such as the B-23 Dragon.C-58
- Transport conversion.Digby I
- Royal Canadian Air Force modification of B-18A.
Only five B-18s still exist, preserved in museums in the United States:B-18 s/n 37-0029
- On display at Castle Air Museum, Atwater, California.B-18A s/n 37-469
- On display at National Museum of the United States Air Force, Wright-Patterson AFB, Ohio.B-18A s/n 39-25/64
- On display at Wings Over the Rockies Air and Space Museum, Denver, Colorado.
- See the Wings' B-18 Bolo Walk Around Site with aircraft history.B-18B s/n 37-505
- On display at McChord Air Museum , McChord AFB, Washington.B-18B s/n 38-593
- On display at Pima Air & Space Museum Tucson, Arizona.B-18 s/n 36-446
- Sitting in a gulch on Laupahoehoe Nui LLC property, Hamakua, Hawai'i.
- Hopefully soon to be rescued by the Pearl Harbor Aviation Museum.
- Francillon, René. McDonnell Douglas Aircraft Since 1920: Volume I. London: Putnam, 1979. ISBN 0-87021-428-4.
- Kostenuk, Samuel and Griffin, John. RCAF Squadron Histories and Aircraft: 1924–1968. Toronto: Samuel Stevens, Hakkert & Company, 1977. ISBN 0-88866-577-6.