B-18 Bolo

Douglas B-18A Bolo
Larger version
Description
Role	Medium bomber
Crew	6
First Flight	1935 April
Entered Service	1937 February 23
Manufacturer	Douglas Aircraft Company
Number built	133 B-18, 217 B-18A, 122 B-18B (cv.)
Dimensions
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
Weights
Empty	16,321 lbs	7,400 kg
Loaded	22,123 lbs	10,030 kg
Maximum takeoff	27,673 lbs	12,550 kg
Powerplant
Engine	Wright R-1820-53 (2)
Power (each)	1,000 hp	750 kW
Performance
Maximum speed	215 mph	346 km/h
Combat range	1,150 miles	1,850 km
Ferry range	2,100 miles	3,380 km
Service ceiling	23,900 ft	7,280 m
Rate of climb	1,030 ft/min	310 m/min
Wing loading	23.1 lb/ft²	112.6 kg/m²
Power/Mass	0.09 hp/lb	0.15 kW/kg
Armament
Guns	.303-calibre machine guns (3)
Bombs	4,500 lbs	2,200 kg

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.

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, the crash of the B-17 prototype (caused by taking off with the controls locked) removed it from consideration. 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 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

• USAF Museum description of B-18 (http://www.wpafb.af.mil/museum/research/bombers/b2-23.htm)