Douglas B-18 Bolo

Douglas B-18 Bolo
Name	B-18 Bolo
Type	Medium bomber
Manufacturer	Douglas Aircraft Company
Designer	Donald Douglas
First flight	April 1935
Introduced	1936
Retired	1946
Primary user	United States Army Air Corps
Number built	350
Developed from	Douglas DC-2
Variants with their own articles	Douglas B-23 Dragon

Douglas B-18 Bolo. The Douglas B-18 Bolo was an American medium bomber developed in the mid-1930s as the primary bomber for the United States Army Air Corps. Derived from the civilian Douglas DC-2 transport, it was selected over competing designs from Martin and Boeing. Though obsolescent by the outbreak of World War II, it served in various roles including anti-submarine warfare and training, with several surviving examples preserved in museums.

Development and design

The B-18 originated from a 1934 United States Army Air Corps competition to find a modern bomber to replace the Martin B-10. The Douglas Aircraft Company, led by Donald Douglas, submitted a militarized version of its successful Douglas DC-2 airliner. This design was chosen over the more advanced Boeing Model 299, which later evolved into the Boeing B-17 Flying Fortress, partly due to its significantly lower cost. The prototype, designated DB-1 by Douglas, first flew in April 1935 from Clover Field in Santa Monica, California. The production B-18 featured a lengthened fuselage compared to the Douglas DC-2, a Bomb bay in the lower fuselage, and defensive gun positions in the nose, dorsal, and ventral locations. Power was provided by two Wright R-1820 Cyclone radial engines. An improved model, the B-18A, introduced more powerful engines mounted further forward on the wing to improve center-of-gravity and single-piece cowlings.

Operational history

Upon entering service in 1936, the B-18 equipped the majority of United States Army Air Corps bomber squadrons, including units in the Philippines and Panama Canal Zone. By the time of the Attack on Pearl Harbor, the B-18 was considered hopelessly outclassed by modern fighters and bombers used by the Luftwaffe and Imperial Japanese Navy Air Service. During the early years of World War II, many B-18s based in the Continental United States and the Caribbean were hastily modified for anti-submarine warfare, equipped with magnetic anomaly detection gear and depth charges. They served with the United States Army Air Forces and the Royal Canadian Air Force on convoy patrol duties over the Atlantic Ocean and the Gulf of Mexico. Others were relegated to transport, training, and utility roles within the Continental United States. A small number were transferred to the Força Aérea Brasileira under the Lend-Lease program.

Variants

The primary production variant was the initial B-18, with 133 built. The main improved version was the B-18A, featuring more powerful Wright R-1820 engines and a redesigned nose, with 217 produced. The B-18M was a designation for B-18s modified as unarmed trainers. The B-18B was a conversion of approximately 122 B-18A aircraft for anti-submarine warfare, fitted with search radar and a Magnetic anomaly detector. The sole XB-22 was a proposed version with more powerful Wright R-2600 engines, but it was not pursued. The design was further developed into the significantly different Douglas B-23 Dragon, which featured a larger wing and a tail gun position.

Operators

The primary military operator was the United States Army Air Corps, which later became the United States Army Air Forces. The Royal Canadian Air Force operated 20 B-18A aircraft, designated as the Digby Mk. I, for anti-submarine warfare duties over the Atlantic Ocean. The Força Aérea Brasileira received a small number of B-18As for coastal patrol along the South Atlantic. Following the war, a few aircraft saw service with the Uruguayan Air Force.

Specifications (B-18A)

* Crew: 6 * Length: 57 ft 10 in * Wingspan: 89 ft 6 in * Height: 15 ft 2 in * Wing area: 965 sq ft * Empty weight: 16,321 lb * Max takeoff weight: 27,673 lb * Powerplant: 2 × Wright R-1820-53 Cyclone 9-cylinder air-cooled radial piston engines, 1,000 hp each * Maximum speed: 215 mph * Cruise speed: 167 mph * Range: 1,200 mi * Service ceiling: 23,900 ft * Armament: ** Guns: 3 × .30 in Browning machine guns (nose, dorsal, ventral) ** Bombs: 4,400 lb internal ordnance

Surviving aircraft

Several B-18/B-18A airframes are preserved. A B-18A is on display at the National Museum of the United States Air Force at Wright-Patterson Air Force Base in Ohio. Another B-18A is part of the collection at the Pima Air & Space Museum in Tucson, Arizona. The wreckage of a Royal Canadian Air Force Digby Mk. I that crashed in 1942 is displayed at the Atlantic Canada Aviation Museum in Halifax, Nova Scotia. A B-18B used for anti-submarine warfare training is stored at the McChord Air Museum on Joint Base Lewis-McChord in Washington.

Category:United States bomber aircraft 1930–1939 Category:Douglas aircraft Category:World War II American bombers