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Douglas B-18 Bolo Bomber: The Plane that Bested the Flying Fortress

At the outset of World War II, the United States was largely unprepared for the conflict to come. Many of the planes in America’s inventory were obsolete, or close to it. One of those was the Douglas B-18 Bolo heavy bomber. 

This Douglas B-18 Bolo bomber is in flight over Hamilton Field, California on February 7, 1938. Soon, these planes were tested in the fiery crucible of combat. Note it’s relatively flat nose. Image: NARA

The Bolo was vastly inferior to the Boeing B-17 Flying Fortress, yet it still somehow beat the Boeing B-17 prototype in the military trials. Consequently, Douglas got the early contract for heavy bomber production.

Many Bolos were destroyed in the initial Japanese attacks against the USA in late 1941 and early 1942. However, the planes still played a small, but important, role in World War II. After military service, a number of surviving B-18s saw service in fighting fires and one was even caught running guns to Fidel Castro in Cuba. 

In this digital photo, we see a view of Hickam Field, now known as Hickam Air Force Base in Hawaii, from 4,000' in the air. B-18 bombers are clustered tightly together between the runway and aircraft hangars. Each aircraft pilot would learn to disperse its aircraft when parked on the tarmac. 
On May 3, 1940, nearly 30 B-18 bombers were closely packed together in this photo of Hickam Field in Hawaii. This parking method changed once the bullets began flying in December of 1941. Image: U.S. Navy

Even so, many people have never heard of the plane. Let’s take a look at this interesting bomber from the Douglas Aircraft Company.

Development of the B-18

Entering the mid-1930s, the United States had, arguably, one of the most advanced bombers to date: the Martin B-10. It was faster than any fighter of its era and introduced many new bomber design concepts that would be influential throughout the 20th century. However, it had a limited payload, and technology advancements quickly rendered it obsolete. The Douglas B-18 was intended to be a heavy bomber that would replace the B-10.

In this image, we see a flight of three B-18 bombers flying over the Pacific Ocean near the Hawaiian Islands in the early 1940s. Although the Boeing B-17 Flying Fortress was a superior bomber in almost every way, the B-18 beat the B-17 to enter production in 1937. By 1941, Boeing was starting to build B-17 bombers to replace the B-18. By the end of the war, virtually no B-18s were still operational, while the B-17 was the real workhorse of the American air power.
A flight of Douglas B-18 Bolo bombers fly in formation during exercises near Hawaii, taken in 1940-1941. Image: Harold Wahlberg

The United States Army Air Corps (later renamed to the United States Army Air Force) wanted a bomber to replace the B-10. They were looking for something with double the bomb capacity and range of the older plane. Douglas presented the DB-1, a company name for what would become the B-18.

It had stiff competition from the Boeing Model 299 and the Martin 146. The Model 299 would later be adopted as the magnificent B-17 while the Martin was a complete bust and was eventually scrapped. Interestingly, Martin was so disappointed with the performance of the Model 146 that it took a fresh look at bomber development and designed the very successful B-26 Marauder.

In this photo, we see the front of a B-18 while ground crew members work on the plane. This is an original plane without any variation modifier. By the time the B-18s ended production the country was involved in World War 2, production of all planes had ceased in favor of the more powerful B-17 bomber that offered longer range and a more precise bombardment capability.
U.S. Army Air Corps servicemen working a Douglas B-18 Bolo aircraft sometime in the 1930s. Image: Sgt. Lee R. Embree/U.S. Air Force

The B-18 design was based on the Douglas DC-2. The DC-2 was a commercial passenger plane that really proved civilian passenger air travel could be reliable and comfortable. Initially, the DC-2 commercial planes were flown by Transcontinental & Western Air (TWA). Both Pan American Airways (Pan Am) and the KLM Royal Dutch Airlines would also purchase the DC-2 airliners. The DC-2 was later developed into the DC-3, which was possibly the most successful aircraft ever created. 

In this photo we see the upgraded nose plexiglas used on the B-18A. B-18As also received more powerful radial engines to improve airspeed and runway length requirements. The fuselage of the aircraft remained the same, keeping the same about of cargo space as had been available since the first prototype was developed in 1934.
This B-18A features the relocated bomardier position and the corresponding nose alteration. This specific plane was in Canadian service. Image: Dept. of National Defence

Douglas’s twin engine DB-1 beat the Boeing based on three main points:

  1. The USAAC requested a twin engine bomber, and the Model 299 had four.
  2. The DB-1 was substantially cheaper than the Model 299.
  3. The Model 299 prototype crashed during take off. 

The U.S. Army Air Corps placed an order for 132 additional DB-1 bombers in January 1936 and designated it the B-18.

Armament on the B-18 was weak when compared to it’s eventual replacement, the B-17. However, it had a fair amount of defensive firepower for the time. Three .30-caliber (7.62mm) machine gun turrets were used on the plane: nose, dorsal and ventral positions. They were all manually operated by the crew of six men.

In this photo is the prototype Douglas DB-2. Functionally similar to the B-18A, the company experimented with the inclusion of a powered nose turret that promised better defensive use of the .30-caliber machine gun. Ultimately, the new turret experiment did not work out and no models we produced with it.
Douglas developed a DB-2 prototype that had a Tucker powered nose turret. These did not go into production and only one DB-2 was ever made. Image: U.S. Air Force

Douglas experimented with Tucker remote controlled gun turrets on the planes. One DB-2 was manufactured that used a Tucker powered nose gun turret. However, these were never adopted in production planes.

B-18A models received more powerful engines and relocated the bombardier position. Two orders of these were made — one for 177 bombers in 1937 and one for 40 airplanes in 1938. By 1939, however, it was obvious that the B-18 was vastly outmatched by other countries. Both the Japanese G3M Nell and Soviet Ilyushin DB-3 carried heavier bomb loads at faster speeds and over longer distances than the B-18.

The B-17 was the obvious replacement for the outdated bomber, but at the time of the Pearl Harbor attack on December 7, 1941, it was the B-18 that sat on the runways of most American bases. 

Douglas B-18 in World War II

During the initial Japanese onslaught, American forces were ill-prepared for combat. It is said many, if not most, B-18 bombers stationed in Hawaii and Philippines were destroyed on the ground. 

In this image, we see a pair of B-18 bombers making a simulated attack run on U.S. Army troops in the Philippines. This was part of war games to train the soldiers and pilots in tactics and combat. With the B-18s deployed outside the continental United States, they expected to see action when the inevitable war with Japan came about.
Two U.S. Army Air Corps B-18 bombers make a simulated attack run on infantry caught in the open during training maneuvers in the Philippines, July 1941. Image: U.S. Navy

Remaining B-18 bombers were split across multiple duties. In Hawaii and Alaska, they were used for armed reconnaissance patrols. In May of 1942, they joined the U.S. Navy in searching for the Japanese fleet approaching Midway. They were also used as transports to ferry troops throughout the Pacific. 

In this photo, we see a damaged B-18 Bolo in the foreground with smoke and fires burning in the distance. The bomber was hit while on the ground at Hickam Field. The black smoke in the background is from the U.S.S. Arizona, a battleship that was destroyed during the sneak Attack on Pearl Harbor. The attack on Pearl Harbor was a surprise military strike by the Imperial Japanese Navy Air Service upon the United States against the American naval base at Pearl Harbor in Honolulu, Hawaii, just before 8:00 a.m. on Sunday, December 7, 1941.
A damaged B-18 sits on Hickam Field during the Japanese attack on December 7, 1941. A large plume of smoke from the USS Arizona (BB-39) is visible behind the hangars. Image: Sgt. Lee R. Embree/U.S. Army

In a bit of an odd twist, the B-18 got a new lease on life from a general that tried to kill the project just a few years earlier.

The General and Submarines

Lt. Gen. Frank Maxwell Andrews was in charge of the Caribbean Defense Command, and he had a problem: German U-boats. With much of the U.S. Navy deployed to the Pacific Theater, the British Royal Navy was heavily relied on for anti-submarine efforts in the Atlantic. Unfortunately too many German subs were slipping past and threatening shipping off of the U.S. coast.

In this digital image, we see a Douglas B-18 launching depth charges at a German U-boat. A depth charge is an anti-submarine warfare weapon designed to destroy submarines by detonating in the water around the target and subjecting it to a destructive hydraulic shock.
This B-18A Bolo fires rocket-powered depth charges at a target to its rear. Later “B” models would have a radar system that dominated the plane’s nose. Image: U.S. Navy

Lt. Gen. Andrews knew the strengths and weaknesses of the B-18 platform as he had been an outspoken advocate for the adoption of the Boeing B-17 over the B-18 several years prior. With more B-17 and Consolidated B-24 bombers coming online, Lt. Gen. Andrews was able to collect many of the remaining B-18 bombers and have them upgraded for anti-submarine warfare (ASW).

[Interested in other ways America fought the German U-boats? Read about how these WW2 blimps took on the Nazi submarines.]

Designated the B-18B, the new bombers were upgraded -18s and -18As that used radar to scan the ocean’s surface for German underwater boats. Additionally, many of the B-18B bombers were fitted with magnetic anomaly detection gear to locate submerged German boats. Bombs were replaced with depth charges. 

In this photograph, we see a B-18B bomber fitted with MAD gear on a sponson. Sponsons are projections extending from the sides of land vehicles, aircraft or watercraft to provide protection, stability, storage locations, mounting points for weapons or other devices, or equipment housing.
This is a B-18B bomber with a radar array (nose) and MAD gear (sponson aft of the tail) for submarine hunting. It was converted from an “A” model for its new mission. Image: NARA

Between 1942 and 1943, B-18B Bolos flew regular ASW patrols over the Atlantic Ocean and Caribbean Sea. The crews prosecuted multiple contacts and were credited with sinking four U-boats: U-512, U-520, U-615, and U-654. 

[Read about Hitler’s nuclear U-boat in this article about the U-234 submarine.]

In this photograph, we see a post-WWII B-18 in civilian use. These planes were often used for cargo or crop spraying aircraft by commercial operators  — a much different position that its role in 1943. This one sprayed DDT. Dichlorodiphenyltrichloroethane, commonly known as DDT, is a colorless, tasteless, and almost odorless crystalline chemical compound, an organochloride. Originally developed as an insecticide, it became infamous for its environmental impacts. DDT was first synthesized in 1874 by the Austrian chemist Othmar Zeidler. DDT's insecticidal action was discovered by the Swiss chemist Paul Hermann Müller in 1939.
After World War II, surviving B-18 bombers were sold to the public. This plane found a new career in Oregon, spraying 1,000 gallons of DDT pesticide in each run. Image: NARA

In 1943, B-24 Liberators began replacing the B-18 for sub hunting duties. As the war wound down, the B-18s continued to be used as transports and training planes. After the war, they were surplussed and used for a range of things including crop dusting and fire fighting.

Primary Users of the Bomber

The United States was the primary user of the B-18. It’s impact in the Second World War are described above. However, two additional countries also used the B-18: Brazil and Canada. 

In this photo, we see a Douglas Digby in flight over Canada in 1941. Canada purchased 20 of the B-18A bombers for use in its No. 10 Squadron based in Nova Scotia.
A Royal Canadian Air Force Douglas Digby bomber flies over Nova Scotia in July 1941. Canada purchased 20 B-18A bombers from the United States. Image: Dept. of National Defence

The Royal Canadian Air Force acquired 20 B-18A bombers and designated them the Douglas Digby Mark I. They were assigned to No. 10 Squadron to replace the aging Westland Wapitis biplanes. Based in Halifax, Nova Scotia, the Digby Mk. 1 was used to carry out about a dozen attacks on German submarines.

In this photo we get an excellent view of the B-18A nose. Used by the Canadian Air Force, the Douglas Digby was successful in prosecuting attacks on multiple U-boat submarines u-boot from Nazi Germany during the Second World War.
The Royal Canadian Air Force No. 10 Squadron based in Halifax replaced its bi-planes with the Douglas Digby. Image: Dept. of National Defence

Reports vary on exactly how many, but Brazil acquired either two or three B-18 bombers from the United States. It is believed two were B-18C variants. The possible third model is undetermined. They were part of the Brazilian Air Force 1st Bomber Group.

B-18 Model Variants

As with most military airplanes, there were a number of model variations in the B-18 bomber line. Roughly 130-135 of the original Douglas B-18 planes were manufactured. A single DB-18M was made that was designed as a trainer. It was essentially the same plane, but with the bomb gear removed.

Here we see a B-18 crash at Hickam Airfield in 1943. The crash, while serious, was still one that people were able to walk away from.
This original B-18 crash landed at Hickam Field on May 22, 1943. The bullnose indicates this is a pre “A” model. Image: NARA

The last DB-18 was made as a prototype designated as DB-2 by Douglas. This bomber used a powered nose turret for advanced air defense. 

Douglas B-18A

The DB-18A was the most produced version of the aircraft with 217 examples delivered to the U.S. Army Air Corps. It was a welcome upgrade to the original, sporting more powerful engines that shortened take-off distances and improved the maximum air speed.

The Douglas B-18A model used the Wright R-1820-53 radial engine rated at 1,000 horsepower. It had nine cylinders and was normally aspirated. Wright R-1820 Cyclone engines powered many aircraft of the era including the Boeing B-17, Douglas SBD Dauntless and various versions of the Douglas C-47 Skytrain. Believe it or not, but Caterpillar actually modified these engines to run on diesel and used them to power the M4A6 Sherman tank.

This unit photograph shows a squadron of B-18A pilots and crews.
This United States Army Air Corps unit photograph was taken in front of a Douglas B-18A Bolo. The updated bombardier position is visible through the upper nose. Image: Museum of Flight/Public Domain

Another change to the Douglas B-18A Bolo was the relocation of the bombardier’s station. This is immediately visible to the casual observer as the plane’s nose was significantly altered. Original B-18 bombers had a flat-ish glassed nose. The B-18A’s nose became markedly more pronounced which allowed the bombardier to be out over the nose gun position.

The plane’s development was ahead of the great bombing campaigns in Europe, so many of the theories regarding bombers were untested. Moving the bombardier’s location in the plane was not, on the whole, an unreasonable modification to a plane’s evolution.

A trainer with the bomb gear removed was also made for the U.S. Army Air Force. It was designated as the B-18AM. 

B-18A Specifications

Here are the specs of a standard B-18A bomber:

  • Crew: Six
  • Length: 57′ 10″ (17.63 m)
  • Wingspan: 89′ 6″ (27.28 m)
  • Height: 15′ 2″ (4.62 m)
  • Wing Area: 959 sq. ft. (89.1 m2)
  • 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: Three-bladed fully-feathering Hamilton Standard Hydromatic propeller
  • 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)
  • Service Ceiling: 23,900 ft (7,300 m)
  • Guns: 3 × 0.30 in (7.62 mm) machine guns
  • Bombs: 2,000 lb (910 kg) normal; 4,400 lb (2,000 kg) maximum

Douglas B-18B

Completely replaced by the B-17 in 1942, the remaining B-18 and B-18A Bolos had no clear role for the United States. To make use of them, the USAAF had 122 of the planes — nearly all that remained — converted to anti-submarine aircraft. These conversion planes were renamed to the B-18B.

The “new” B-18B planes were fitted with radar and MAD gear.

To make room for the SCR-517-T-4 air-to-surface vessel radar, the bombardier’s position in the nose was replaced with a large radome. This helped the plane’s crew spot any subs operating on the surface. Keep in mind that submarines and U-boats of this era were all diesel-powered, and had to spend the majority of its time at sea on the ocean’s surface. 

This photo, taken on the day of the Pearl Harbor attack, shows a damaged B-18 Bolo in a hanger. The hangar is damaged. Soldiers in the foreground are setting up a crew served machine gun in a crater left by a Japanese bomb.
Bomb damage to the hangars at Hickam Field is obvious at 1700 hours December 7, 1941. A damaged Douglas B-18 bomber is visible inside the badly damaged hangar. Image: NARA

MAD gear was used for pinpointing the location of a sub underwater. MAD stands for magnetic anomaly detector (or detection depending on the context.) This sensitive equipment could detect the disruption in the earth’s magnetic field caused by a large metal submarine. Crews could fly over an area in a search pattern and plot the speed and direction of subs using multiple passes. This information would then be used to fire rocket-propelled depth charges from the bomb bay to sink the sub.

MAD gear is completely passive, so there was no way the submarines could detect its use. Of course the shadow of a passing plane combined with the noise of its engines were a pretty good tip for subs on or near the surface.

B-18B Specifications

Here are the specs for the B-18B Bolo:

  • Crew: Six
  • Length: 57′ 10″ (17.63 m)
  • Wingspan: 89′ 6″ (27.28 m)
  • Height: 15′ 2″ (4.62 m)
  • Wing Area: 959 sq. ft. (89.1 m2)
  • 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: Three-bladed fully-feathering Hamilton Standard Hydromatic propeller
  • 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)
  • Service Ceiling: 23,900 ft (7,300 m)
  • Guns: 3 × 0.30 in (7.62 mm) machine guns
  • Bombs: Rear-firing, rocket-propelled depth charges

Douglas B-18C

Only two B-18C Bolos were made. Like the B-18Bs, these were designed for anti-submarine duty. The major change on these models was the addition of a pair of forward-facing Browning .50-caliber machine guns. These models were eventually sold to Brazil. Their final disposition is unknown. They are unlikely to have survived the past 7+ decades.

Where Can You See a B-18 Today?

Relatively few B-18 Bolos have been restored and are preserved for history. Excluding unrecovered B-18 wrecks or scrap, the following planes can still be seen today.

In this photograph, we see the only restored B-18 Bolo on the planet. It is located in California at the Castle Air Museum.
On display at Castle Air Museum, this is one of only five preserved Bolos. It is unique as the only straight B-18; the others are either B-18A or B-18B models. Image: Alan Wilson/CC BY-SA 2.0 DEED

B-18: A single B-18 can be seen at the Castle Air Museum in Atwater, California. Tail number N52056 (originally NC52056) was used for fighting fires after World War II.

B-18A: Three B-18A Bolos are available for viewing. The first, tail number N56947, is located at the National Museum of the United States Air Force. Located in Dayton, Ohio at Wright-Patterson AFB, this is a must-visit museum for any aviation enthusiast. 

A second B-18A is in the collection at Wings Over the Rockies Air and Space Museum in Denver, Colorado. This example was sold as surplus after WWII, eventually ending up in Cuban hands. Federal agents, however, seized the plane in Florida when it was caught running guns to Fidel Castro. It eventually went to the National Museum of the United States Air Force before being transferred to Wings Over the Rockies.

The third B-18A is tail number N67947 which is currently at the McChord Air Museum. Located at McChord Field (formerly McChord AFB) near Lakewood, Washington, the museum is accessible to the public. This plane is believed to be the last Bolo to have flown — it’s final flight was in 1971. At the time of this writing, McChord Air Museum states the plane is “currently undergoing an extensive restoration.”

B-18B: One Douglas B-18B is believed to have been restored and can be viewed at the Pima Air & Space Museum in Tucson, Arizona. It still has a search radar dome in the nose, making it unique.

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