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| Douglas B-18A Bolo
|
|
| Description
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| Role | Medium bomber
|
| Crew | 6
|
| First Flight | 1935 April
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| Entered Service | 1937 February 23
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| Manufacturer | Douglas Aircraft Company
|
| Number built | 133 B-18, 217 B-18A, 122 B-18B (cv.)
|
| Dimensions
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| Length | 57 ft 10 in | 17.6 m
|
| Wingspan | 89 ft 6 in | 27.3 m
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| Height | 15 ft 2 in | 4.6 m
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| Wing Area | 959 ft² | 89.1 m²
|
| Weights
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| Empty | 16,321 lbs | 7,400 kg
|
| Loaded | 22,123 lbs | 10,030 kg
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| Maximum takeoff | 27,673 lbs | 12,550 kg
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| Powerplant
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| Engine | Wright R-1820-53 (2)
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| Power (each) | 1,000 hp | 750 kW
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| Performance
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| Maximum speed | 215 mph | 346 km/h
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| Combat range | 1,150 miles | 1,850 km
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| Ferry range | 2,100 miles | 3,380 km
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| Service ceiling | 23,900 ft | 7,280 m
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| Rate of climb | 1,030 ft/min | 310 m/min
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| Wing loading | 23.1 lb/ft² | 112.6 kg/m²
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| Power/Mass | 0.09 hp/lb | 0.15 kW/kg
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| Armament
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| Guns | 0.303-calibre machine guns (3)
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| Bombs | 4,500 lbs | 2,200 kg
|
The Douglas B-18 Bolo was a U.S. Army and Royal Canadian Air Force bomber of the late 1930s and early 1940s based on the Douglas DC-2.
History
In 1934, the Army Air Corps put out a request for a bomber with double the bomb load and range of the Martin B-10, then 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, Army officials held it too expensive to build at that time; the Douglas design was ordered into immediate production in 1936 January 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 bomber used two Wright R-1820-45 ‘Cyclone 9’s, of 930 hp (694 kW) each.
The initial contract called for 133 B-18s (including DB-1), using Wright radials. 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 Wright R-1820-53 engines of 1,000 hp (746 kW).
By 1940, most Army 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. The Royal Canadian Air Force acquired 20 B-18As (designated the Douglas Digby Mark I), and used them for patrols also.
Variants and Design Stages
- DB-1—Prototype; first of B-18 production run. (×1)
- B-18 (http://www.wpafb.af.mil/museum/research/bombers/b2-23.htm)—Initial production version. (×131, or 133)
- 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)
- B-18A (http://www.wpafb.af.mil/museum/research/bombers/b2-24.htm)—B-18 with more powerful Wright R-1820-53 engines, bombardier’s station moved. (×217)
- B-18AM—Bomb gear removed from B-18A to serve as trainer.
- B-18B (http://www.wpafb.af.mil/museum/research/bombers/b2-25.htm)—Antisubmarine conversion. (×122)
- B-18C—Antisubmarine conversion. (×2)
- XB-22 (http://www.wpafb.af.mil/museum/research/bombers/b2-30.htm)—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 Mark I—Royal Canadian Airforce modification of B-18A.
References and External links
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