Douglas B-18 Bolo

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 developed into the Boeing B-17 Flying Fortress) and Martin 146.

While the Boeing design was clearly superior, the crash of the B-17 prototype (caused by taking off with the controls still 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 that of 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 due to the deeper fuselage. Added armament included nose, dorsal, and ventral gun turrets.

Preston Tucker's firm received a contract to supply a remote controlled gun turret for the aircraft.[3]

Douglas B-18 formation during exercises over Hawaii, 1940–1941.

A Douglas B-18 deployed at Aguadulce Army Airfield, Panama

The initial contract called for 133 B-18s (including DB-1), 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. 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.

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 fitted, had a maximum speed of 217 mph, cruising speed of 167 mph, and combat range of 850 miles. By 1940, most USAAC bomber squadrons were equipped with B-18s or B-18As.

However, the deficiencies in the B-18/B-18A bomber were becoming readily apparent to almost everyone. In range, in speed, in bomb load, and particularly in defensive armor and armament, the design came up short, and the Air Corps conceded that the aircraft was obsolete and totally unsuited in the long-range bombing role for which it had originally been acquired. To send crews out in such a plane against a well-armed, determined foe would have been nothing short of suicidal.

However, in spite of the known shortcomings of the B-18/B-18A, the Douglas aircraft was the most numerous American bomber type deployed outside the continental United States at the time of the attack on Pearl Harbor. It was hoped that the B-18 could play a stopgap role until more suitable aircraft such as the Boeing B-17 Flying Fortress and Consolidated B-24 Liberator became available in quantity.

World War II

A B-18 operated by Australian National Airways on behalf of the USAAF, flying over the Brisbane River in 1943

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 (MAD) 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 German submarine U-512 north of Cayenne, French Guiana.[4]

Two aircraft were transferred to Força Aérea Brasileira in 1942 and 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 charge at the end of the war. In 1940 the Royal Canadian Air Force acquired 20 B-18As (as the Douglas Digby Mark I), and also used them for patrol duties, being immediately issued to 10 Squadron to replace the squadron's Westland Wapitis.[5]

Bolos and Digbys sank an additional two submarines during the course of the war. RCAF Eastern Air Command (EAC) Digbys carried out 11 attacks on U-boats. U-520 was confirmed sunk by Flying Officer F. Raymes' crew of No. 10 (BR) Squadron, on 30 October 1942.[6] east of Newfoundland.[7] However, the antisubmarine role was relatively short-lived, and the Bolos were superseded in this role in 1943 by Consolidated B-24 Liberators which had a much heavier payload and a substantially longer range which finally closed the mid-Atlantic gap.

Surviving USAAF B-18s ended their useful lives in training and transport roles within the continental United States, 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, those bombers that were left were sold as surplus on the commercial market. Some postwar B-18s of various models were operated as cargo or crop-spraying aircraft by commercial operators.

Some of the Douglas Digbys in Canadian service were converted to either C-58s or used for training.[8]

DB-1

Manufacturer's designation for prototype, first of B-18 production run, 1 built.

B-18

Initial production version, 131 or 133 built.[9]

B-18M

Trainer B-18 with bomb gear removed.

DB-2

Manufacturer's designation for prototype with powered nose turret; last of B-18 production run, 1 built.

B-18A

B-18 with more powerful Wright R-1820-53 engines and relocated bombardier's station, 217 built.[10]

B-18AM

Trainer B-18A with bomb gear removed.

B-18B

Antisubmarine conversion, 122 converted by adding a radar and magnetic anomaly detector[11]

B-18C

Antisubmarine conversion, 2 converted. Fixed forward-firing .50 cal machine gun, starboard side of the fuselage near lower nose glazing.

XB-22

Improved version of B-18 using Wright R-2600-3 radial engines (1,600 hp/1,194 kW). Never built, largely due to better light bombers such as the B-23 Dragon.[12]

C-58

Transport conversion.

Digby Mark I

Royal Canadian Air Force modification of B-18A. Named after the RAF school of bombing at RAF Digby.

 Brazil

• Brazilian Air Force

1st Bomber Group (3 examples)

 Canada

• Royal Canadian Air Force

No. 10 Squadron RCAF, Halifax, Nova Scotia (Digby Mk.1)

 United States

• United States Army Air Corps/United States Army Air Forces

1st Search Attack Group, Langley Field, Virginia (B-18A/B/C)

2d Bombardment Group, Langley Field, Virginia (B-18A)

3d Bombardment Group, Barksdale Field, Louisiana (B-18)

5th Bombardment Group, Hickam Field, Hawaii (B-18)**

6th Bombardment Group, Rio Hato Airfield, Panama, (B-18/B-18A/B)

7th Bombardment Group, Hamilton Field, California, (B-18)

5th Bombardment Group, Luke Field, Oahu, Hawaii Territory (B-18)**

9th Bombardment Group, Caribbean; Panama and South American air bases (B-18/B-18A/B)

11th Bombardment Group, Hickam Field, Hawaii Territory (B-18)**

13th Bombardment Group, Langley Field, Virginia (B-18A/B)

17th Bombardment Group, McChord Field, Washington (B-18)

19th Bombardment Group, Clark Field, Philippines Commonwealth (B-18)**

22d Bombardment Group, Muroc Field, California (B-18)

25th Bombardment Group, Caribbean (B-18/B)

27th Bombardment Group, Barksdale Field, Louisiana (B-18)

28th Bombardment Group, California, (B-18)

28th Composite Group, Elmendorf Field, Alaska, (B-18A)

29th Bombardment Group, Langley Field (B-18A)

40th Bombardment Group, Panama, Puerto Rico (B-18/B)

41st Bombardment Group, California, (B-18)

42nd Bombardment Group, Portland, Oregon (B-18)

45th Bombardment Group, Savannah Airfield, Georgia (B-18A)

47th Bombardment Group, McChord Field, Washington (B-18)

479th Antisubmarine Group, Langley Field, Virginia (B-18A/B)

**Note: Most aircraft destroyed 7–8 December 1941 at outbreak of World War II

B-18B at Pima Air Museum

B-18B at Castle Air Museum

B-18A at Wings Museum

Douglas B-18A Bolo JBLM 37-505

B-18A Bolo 37-0469 from the 38th Reconnaissance Squadron on display at the National Museum of the U.S. Air Force.

Only six B-18s still exist, five of them preserved or under restoration in museums in the United States:[13]

B-18

• 36-446 – Kohala Mountains, Hawaii. Tail code "81 50R". Crash-landed due to engine failure on February 25, 1941. Crew was rescued and the aircraft was abandoned; it remains in a gulch on private land. The Air Force later recovered the nose turret for 37-029 and the dorsal turret for 37-469. There have been plans to recover the aircraft for the Pacific Air Museum in Honolulu.[14][15]
• 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.[16]

B-18A

• 37-469 – National Museum of the United States Air Force at Wright-Patterson Air Force Base in Dayton, Ohio. One of the first production Bolos, was delivered to Wright Field in 1937 for evaluation testing. Sold as N56847, converted to crop sprayer; by May 1969 stored derelict at Tucson, Arizona. It sat outdoors for many years before being restored to static display condition. This aircraft has an incorrect dorsal turret. The museum has been attempting to locate a correct turret for this aircraft for many years.[17]
• 39-025 – Wings Over the Rockies Air and Space Museum at the former Lowry Air Force Base in Denver, Colorado. This Bolo spent World War II at several airfields as a bombardier trainer and as a light transport. It was dropped from inventory on 3 November 1944, and was later sold, acquiring the civil registry NC62477. It spent 14 years on the civil registry before going to Cuba in 1958. In November 1958 the aircraft was seized in Florida by US Treasury agents when it was hauling guns to Fidel Castro. In 1960, the aircraft was parked at Cannon AFB, New Mexico, until being presented to the National Museum of the United States Air Force at Wright-Patterson AFB. It flew to the museum in April 1961. In 1988, the aircraft was transferred to the Wings Over The Rockies Aviation and Space Museum where it was restored though the 1990s. It is displayed there as AAC Ser. No. 39-522.[18]

B-18B

• 37-505 – At the McChord Air Museum, McChord AFB, Washington. Sold as N67947, then Mexican registration XB-JAJ. Acquired by Tucson Air Museum Foundation of Tucson, Arizona and stored at Watsonville, California. This was the last flyable B-18, making its final flight to Tucson on 10 April 1971. At Pima Air & Space Museum in 1973, it was subsequently acquired by the National Museum of the United States Air Force in 1981 and moved to Davis-Monthan AFB, Arizona for storage, then in 1983 put on display at the McChord Air Museum. Access to the McChord Air Museum is currently restricted to military personnel (active, reserve, national guard, retired), and their dependents unless a base visitor pass is acquired in advance.[19]
• 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.[20]

Data from McDonnell Douglas aircraft since 1920 : Volume I[21]

General characteristics

• Crew: 6
• Length: 57 ft 10 in (17.63 m)
• Wingspan: 89 ft 6 in (27.28 m)
• Height: 15 ft 2 in (4.62 m)
• Wing area: 959 sq ft (89.1 m²)
• Airfoil: root: NACA 2215; tip: NACA 2209[22]
• Empty weight: 16,320 lb (7,403 kg)
• Gross weight: 24,000 lb (10,886 kg)
• Max takeoff weight: 27,673 lb (12,552 kg)
• Powerplant: 2 × Wright R-1820-53 Cyclone 9-cylinder air-cooled radial piston engines, 1,000 hp (750 kW) each
• Propellers: 3-bladed fully-feathering Hamilton Standard Hydromatic propellers

Performance

• Maximum speed: 216 mph (348 km/h, 188 kn) at 10,000 ft (3,000 m)
• Cruise speed: 167 mph (269 km/h, 145 kn)
• Range: 900 mi (1,400 km, 780 nmi)
• Ferry range: 2,100 mi (3,400 km, 1,800 nmi)
• Service ceiling: 23,900 ft (7,300 m)
• Time to altitude: 10,000 ft (3,000 m) in 9 minutes 54 seconds
• Wing loading: 25 lb/sq ft (120 kg/m²)
• Power/mass: 0.0833 hp/lb (0.1369 kW/kg)

Armament

• Guns: 3 × 0.30 in (7.6 mm) machine guns
• Bombs: 2,000 lb (910 kg) normal; 4,400 lb (2,000 kg) maximum

Avionics

• SCR-517-T-4 ASV radar B-18B
• Mark IV Magnetic anomaly detector (MAD) B-18B

Related development

• Douglas DC-2
• Douglas B-23 Dragon

Related lists

• List of aircraft of World War II
• List of bomber aircraft
• List of military aircraft of the United States

Wikimedia Commons has media related to Douglas B-18 Bolo.

• B-18 Bolo (factsheet with gallery), USAF Museum, archived from the original on 2007-03-15.
• Baugher, Joseph ‘Joe’ (ed.), "Douglas B-18 Bolo", USAF bombers, Baughers.
• "Douglas B-18 Bolo / B-23 Dragon", Douglas DC-1 / DC-2 Military Series.