B-18 Bolo
From Wikipedia, the free encyclopedia
| Douglas B-18 Bolo | |
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| Douglas B-18 Bolo, Castle Air Museum, Atwater, California. | |
| Type | Light bomber |
| Manufacturer | Douglas Aircraft Company |
| Maiden flight | 1935 |
| Retired | 1940s |
| Status | 5 surving models in museums |
| Primary users | United States Army Air Corps/United States Army Air Forces Royal Canadian Air Force |
| Produced | 1936- |
| Number built | 350 |
| Unit cost | US$58,500 (1935) |
| Variants | Douglas XB-22 C-58 Bolo |
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 based on the Douglas DC-2.
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[edit] History
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 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 engines.
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. 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 used them for patrols also. Bolos and Digbys sank four submarines during the course of the war.
[edit] Surviving aircraft
Only five B-18s still exist, preserved in museums in the United States:
- B-18 s/n 37-0029, at Castle Air Museum, Atwater, California.
- B-18A s/n 37-469, at National Museum of the United States Air Force, Wright-Patterson AFB, Ohio.
- B-18A s/n 39-25, at Wings Over the Rockies Air and Space Museum, Denver, Colorado.
- B-18B s/n 37-505, at McChord Air Museum, McChord AFB, Washington.
- B-18B s/n 38-593, at Pima Air & Space Museum Tucson, Arizona.
[edit] Variants and Design Stages
- DB-1—Prototype; first of B-18 production run. (×1)
- B-18—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—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—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 Mark I—Royal Canadian Air Force modification of B-18A.
[edit] Operators
[edit] Specifications (B-18A)
General characteristics
- Crew: 6
- Length: 57 ft 10 in (17.6 m)
- Wingspan: 89 ft 6 in (27.3 m)
- Height: 15 ft 2 in (4.6 m)
- Wing area: 959 ft² (89.1 m²)
- Empty weight: 16,321 lb (7,400 kg)
- Loaded weight: 22,123 lb (10,030 kg)
- Max takeoff weight: 27,500 lb (12,600 kg)
- Powerplant: 2× Wright R-1820-53 radial engines, 1,000 hp (750 kW) each
Performance
- Maximum speed: 215 mph (197 knots, 346 km/h)
- Combat radius: 999 nm (1,150 mi, 1,850 km))
- Ferry range: 1,800 nm (2,100 mi, 3,400 km)
- Service ceiling: 23,900 ft (7,280 m)
- Rate of climb: 1,030 ft/min (5.2 m/s)
- Wing loading: 23.1 lb/ft² (113 kg/m²)
- Power/mass: 0.09 hp/lb (150 W/kg)
Armament
- Guns: 3× .30 in (7.62 mm) machine guns
- Bombs: 4,500 lb (2,200 kg)
[edit] References
- Francillon, René (1979). McDonnell Douglas Aircraft Since 1920: Volume I.. London: Putnam. ISBN 0-87021-428-4.
[edit] External links
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