Douglas B-18 Bolo


The Douglas B-18 Bolo is an American twin-engined medium bomber which served with the United States Army Air Corps and the Royal Canadian Air Force during the late 1930s and early 1940s. The Bolo was developed by the Douglas Aircraft Company from their DC-2 as a replacement for the Martin B-10.
By 1940 standards, it was slow, had an inadequate defensive armament, and carried too small a bomb load. By 1942, surviving B-18s were relegated to antisubmarine, training and transport duties. A B-18 was one of the first USAAF aircraft to sink a German U-boat, on 22 August 1942 in the Caribbean.

Design and development

In 1934, the United States Army Air Corps requested for a twin-engine bomber with double the bomb load and range of the Martin B-10 then entering service. During the evaluation at Wright Field the following year, Douglas offered its DB-1. It was competing against the Boeing Model 299 and Martin 146.
While the Boeing design was clearly superior, the 299's four engines eliminated it from consideration despite being the favorite, and the crash of the prototype — caused by taking off with the controls still locked — put its purchase on hold. The Martin 146 was a minor improvement on the B-10, and was never seriously considered. During the depths of the Great Depression, the lower price of the DB-1 at $58,500 compared to $99,620 for the Model 299 also favored the Douglas entry, and it was ordered into immediate production in January 1936 as the B-18.
The DB-1 design was modified from that of the DC-2. The wingspan was greater, the fuselage was narrower and deeper, and the wings were moved up to a mid-wing position to allow space under the spars for an enclosed bomb bay. Added armament included manually operated nose, dorsal, and ventral gun turrets.
At one point, Preston Tucker's firm received a contract to supply Tucker [gun turret|Tucker remote controlled gun turrets] but these were unsuccessful, and were never used in service.

Operational history

The initial contract called for 133 B-18s, 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 in a redesigned nose but this did not become standard. Additional contracts in 1937 and 1938 were for the B-18A, which had the bombardier's position further forward over the nose-gunner's station in a wedge shaped nose and the B-18A was fitted with more powerful engines.
Deliveries of B-18s to Army units began in the first half of 1937, with the first examples being test and evaluation aircraft being turned over to the Materiel Division at Wright Field, Ohio, the Technical Training Command at Chanute Field, Illinois, the Aberdeen Proving Ground, Maryland, and Lowry Field, Colorado. Deliveries to operational groups began in late 1937, the first being the 7th Bombardment Group at Hamilton Field, California.
Production B-18s, with full military equipment, had a maximum speed of, cruising speed of, and combat range of. By 1940, most USAAC bomber squadrons were equipped with B-18s or B-18As.
However, the B-18/B-18A's deficiencies were made apparent when an all-red Soviet Ilyushin TsKB-30 named Moskva made a non-stop flight from Moscow to North America in April 1939, a distance of, which was well beyond the capabilities of the B-18. The TsKB-30/DB-3 was also 25% faster, was capable of carrying a bomb load 2.5 times as large as the B-18, and carried a heavier defensive armament. In August of the same year, a Japanese Mitsubishi G3M2 named Nippon flew from Tokyo to the US, and then around the world, with the stage from Chitose, Hokkaido to Nome, Alaska being over. The military version could also carry more than the B-18, further, faster, and was also better armed. Both types had roughly higher service ceilings as well.
The Air Corps conceded that the Bolo was obsolete and unsuitable for its intended role. However, in spite of this, the B-18/B-18A was still the most numerous American bomber type deployed outside the continental United States at the time of the attack on Pearl Harbor. The B-18 would be a stopgap until the more capable Boeing B-17 Flying Fortress and Consolidated B-24 Liberator became available in quantity.

World War II

When war came to the Pacific, most of the B-18/B-18A aircraft based overseas in the Philippines and in Hawaii were destroyed on the ground in the initial Japanese onslaught. The few Bolos that remained played no significant role in subsequent operations.
The B-18s remaining in the continental US and in the Caribbean were then deployed in a defensive role in anticipation of attacks on the US mainland. These attacks never materialized. 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 equipment was sometimes housed in a tail boom. These aircraft, designated B-18B, were used in the Caribbean on anti-submarine patrol. On 2 October 1942, a B-18A, piloted by Captain Howard Burhanna Jr. of the 99th Bomb Squadron, depth charged and sank the north of Cayenne, French Guiana.
Two aircraft were transferred to the Brazilian Air Force in 1942, and were used with a provisional conversion training unit set up under the provisions of Lend-Lease. They were later used for anti-submarine patrols. They were struck off at the end of the war.
In 1940 the Royal Canadian Air Force acquired 20 B-18As, and also used them for patrol duties, being immediately issued to 10 Squadron to replace the squadron's Westland Wapitis.
Bolos and Digbys sank an additional two submarines during the course of the war. RCAF Eastern Air Command Digbys carried out 11 attacks on U-boats. was confirmed sunk by Flying Officer F. Raymes' crew of No. 10 Squadron, on 30 October 1942. east of Newfoundland. However, the antisubmarine role was relatively short-lived, and the Bolos were superseded in this role in 1943 by B-24 Liberators, which had a much heavier payload and a substantially longer range, which finally closed the mid-Atlantic gap. Some of the Douglas Digbys in Canadian service were converted into transports or used for training.
Surviving USAAF B-18s ended their useful lives in training and transport roles, and saw no further combat action. Two B-18As were modified as unarmed cargo transports under the designation C-58. At the end of the war, remaining examples were sold as surplus on the commercial market. Some postwar B-18s were operated as cargo or crop-spraying aircraft by commercial operators.

Variants

;DB-1
;B-18
;;B-18M
; DB-2
;B-18A
;B-18AM
;B-18B
;B-18C
;XB-22
;C-58
;Digby Mark I

Operators

Six B-18s are known to exist, five of them preserved or under restoration in museums in the United States, and one is a wreck still located at its crash site:
;B-18
  • 36-446 – Kohala Mountains, Hawaii. Tail code "81 50R". Crashed in 1941 and abandoned. The Air Force recovered the nose turret for 37-029 and the dorsal turret for 37-469. The Pacific Air Museum in Honolulu has had plans to recover the airframe.
  • 37-029 – Castle Air Museum at the former Castle Air Force Base in Atwater, California. Dropped from USAAF inventory in 1944, it was registered as NC52056 in 1945, later to N52056. The B-18 was used by Avery Aviation and then Hawkins and Powers, as a firebomber, dropping borate for many years.
;B-18A
;B-18A/B
;B-18B
  • 38-593 – Pima [Air & Space Museum] adjacent to Davis-Monthan Air Force Base in Tucson, Arizona. This Bolo spent the early part of WWII on anti-submarine patrol. In 1943 began use a light transport. She was retired and struck from the inventory in 1945. Was operated as a firebomber as N66267, 1954–1970. In storage at Phoenix Goodyear Airport, Litchfield Park, Arizona by September 1969, then delivered to Pima on 5 September 1976. The aircraft sat outside in the desert for many years, before being restored and moved indoors for display. The aircraft is still equipped with an antisubmarine search radar dome.

    Specifications (B-18A)

Notable appearances in media