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Douglas B-18 Bolo

History of the Douglas B-18 Bolo

In 1934, the Douglas Aircraft Company developed the DB-1 (also known as the "Douglas Bomber 1") to meet the United States Army Air Corps (USAAC) requirements for a long-range medium bomber. USAAC attempted to replace its fleet of new, lanky Martin B-10 bombers with updated platforms with greatly increased capabilities.

Douglas developed their DB-1 from their existing "DC-2" series of commercial transport aircraft, a serviceable twin-engine development that first flew in May 1934, of which approximately 200 aircraft were produced. The DB-1 retains the former's wings (albeit slightly longer), uses a deeper fuselage for internal bomb bays, and adds appropriate defensive armament. As such, the DB-1 borrowed heavily from experience and technology in the form of the DC-2, essentially becoming a "militarized" version of the transport. The DB-1 prototype was completed in 1935 and entered a USAAC-sponsored competition in which the twin-engine Martin "Type 146" and Boeing "Type 299" participated.

The first flight of the Douglas prototype was recorded in April 1935.

Long Range Medium Bomber Competition

So far, Martin has received a US military contract to sell his original B-10 (introduced in November 1934), which was the USAAC's standard bomber. However, USAAC was already looking for a replacement, leading Martin to submit an enlarged version of his B-10 - the "Type 146" - to the competition.

Boeing developed and submitted its "Type 299," an expensive and large four-engine platform that seemed to fit well with USAAC's requirements for a new long-range bomber that eventually became the famous B-17 "Flying Fortress" itself.

The three aircraft were reviewed by USAAC during an assessment held at Wright Field in 1935. Delegates rated the Boeing 299 highly, arguing that the prototype was lost in an accident that was ultimately blamed on pilot error.

As a result, the crash completely disqualified the Type 299, making the Douglas B-18 a sort of front-runner (very little to say about the Martin design). Additionally, the Boeing 299 proved to be a cost-constrained machine for the still budget-conscious USAAC (when the Great Depression was still looming over the global economy), which drove the DB-1's effort to design an example for Douglas that cost almost Half the cost of purchasing a Boeing 299. As a result, the Douglas DB-1 design was officially accepted into U.S.

Air Force service as the B-18 "Bolo", with 99 of the initial B-18 variants contracted. Interestingly - despite losing a Boeing 299 in the race - USAAC also commissioned 13 YB-17 evaluation aircraft for additional research.

Notably, for Douglas, the B-18 became the first medium bomber design in the company's history (ironically, its history is tied to Boeing today).

Production and business use

In 1937, 35 more B-18 Bolos were signed, bringing the USAAC roster to over 100. All of these early forms were powered by Wright's R-1820 series radial piston engines. The last B-18 in this production was a single version with a powered nose turret, which Douglas designated the "DB-2". In the late 1930s, another contract was awarded for 217 B-18s, an upgraded B-18A with a forward bomber position above the nose gunner, delivered in 1937-1939.

Ultimately, approximately 350 to 370 production B-18s were procured.

Despite their rather declassified status in the early days of WWII, the B-18 bombers were still viable platforms for training aspiring bomber crews to deal with the nuisance and bombardment of large aircraft flying while they were accustomed to Flying at high altitudes. The B-18's presence was discovered within the United States and through various overseas deployments. In addition to being used as a conventional bomber and trainer, the B-18 (which was deprived of combat capability) was used as a makeshift transport. Some were further modified for use as anti-submarine (ASW) platforms and were actively used during maritime patrols off the coast of the United States and in the Caribbean.

In fact, on August 22, 1942, a B-18 is believed to be the first to sink a German U-boat (this one in Caribbean waters) - the U-boat identified as "U-654". Eventually, the B-18 was replaced in numbers by the better high-capacity Joint B-24 Liberator and (better known) the Boeing B-17 Flying Fortress - two aircraft of the USAAF's "Heavy Striker" Europe and the Pacific.

Variations

In general, there are some known variants of the B-18. Before becoming the 130's first "B-18" production form, the only prototype was the aforementioned "DB-1". After the bomb device was defused, the "B-18M" served as the team trainer. Douglas subsequently developed a "DB-2" prototype with a powered bow turret, one example of which was completed. The "B-18A" was the next major production version, of which about 217 were built using the more powerful Wright R-1820-53 series radial piston engines.

The bombardier position has also been reworked to improve visibility and has now been moved to the nose gunner's position. From this production form, the "B-18AM" became a team trainer. "B-18B" is a dedicated anti-submarine platform, 122 of which are converted from existing airframes. Only two similar "B-18C" submarine hunters were built, and they added two .50 caliber heavy machine guns on the right side of the fuselage as front-firing devices for strafing.

Development codenamed "XB-22", the B-18 prototypes were equipped with Wright R-2600-3 series radial piston engines, each rated at 1,600 horsepower, but this design never entered mass production. The USAAC transport version of the B-18 was called the "C-58". "Digby I" is Canada's designation for its small number of B-18s.

End of the road

Ultimately, technological reasons and advances in warfare itself inevitably made the B-18 an obsolete commodity. She proved insufficiently capable for the growing demands of USAAC, and her inherent network of defensive machine guns left much to be desired.

Its bomb load was largely surpassed by recent developments elsewhere, reducing the B-18's short-term tactical utility. Regardless, the B-18 was USAAC's standard medium bomber until 1941, as it handled reasonably well and proved adept at absorbing damage while still being airworthy (a common feature of nearly all WWII-era bombers...world wars ). In the early days of World War II, the explicit role of aircraft like the B-18 in building the American war machine proved extremely important.

The B-18 appeared (unfortunately as a ground target) during the Japanese surprise attack on Pearl Harbor on December 7, 1941, which officially drew the United States into World War II. Nearly all of the B-18s were killed in the attack at Hickam Airfield in the U.S. territory of Hawaii.

In early 1942, as America's war machine frantically accelerated, outdated designs like the B-18 gave way to more technologically advanced, modern equipment. Twenty B-18 Bolos served in the Canadian Air Force, designated "Digby Mk I" by the Royal Canadian Air Force, and were officially classified as "Reconnaissance Bombers" in inventory.

Brazil became the only other export operator of B-18s (under the banner of the "1st Bomber Group") and actively maintained three examples until their retirement in 1946 after the war. For the Americans, the B-18 served with no less than 22 bombers in groups from Virginia to Hawaii, as well as units in Panama, the Philippines, Puerto Rico and South America.

B-18 Bolo Walks

Externally, the Bolo creates a very robust look thanks to its oversized hull compartment. The positions of the cockpit and bombardier are located at the very forward end of the fuselage, and each area is characterized by the use of a heavy-duty frame, but all provide good outside visibility. Ammunition was housed in an internal bomb bay that formed the center of the hull. The wings were of a single-wing design, rounded in a typical 1930s fashion, and mounted on central brackets on either side of the fuselage. Each wing is fitted with an engine nacelle along its leading edge.

The center of the hull also contains aiming ports for the interior crew, as well as dorsal and ventral machine gun or viewing positions. An access door is found aft of the main wing assembly along the side of the fuselage. The tail is of a traditional design with a single circular vertical tail and a suitable circular horizontal plane. The B-18's landing gear is of the "tail" type, which means it uses two main gear legs and a small tail wheel.

This, combined with a deep torso, gives Boros a rather unique "nose up" look at rest. Each main landing gear leg has a large wheel, and the legs are embedded in flight under each engine nacelle. The bomb bay door was found in the belly of the aircraft behind the cockpit floor.

Two-piece doors were used to accommodate ordnance and complete the aerodynamic shape of the B-18. Each bomb bay door opens off-center in the form of a two-piece system that folds over each other. The Bolo is piloted by a crew of six, including two pilots, a dedicated bombardier and three machine gunners. Dimensionally, the aircraft has a wingspan of 89 feet 6 inches and a barrel length of 57 feet 10 inches.

She is 15 feet 2 inches tall. Total weight is 27,000 pounds with full internal bomb load.

B-18 Cockpit

The cockpit of the B-18 consists of two pilot seats arranged side by side. The instrument panel dominates the front view and contains nearly every available system gauge and switch. Each position incorporates a traditional flight yoke wheel for control from each seat. Engine controls are centralized on a center console for easy access from any location. Therefore, if the pilot becomes incapacitated in flight, the co-pilot can regain control of the aircraft without changing position.

Each position also has its own footrest. In addition to the extensive use of a frame consistent with other aircraft of the time, cockpit visibility was relatively good. Window panels provide a clear view forward, above and to the side of the aircraft.

The two engine nacelles are clearly visible from the pilot's position, allowing both personnel to respond to situations such as engine fires.

Armed

The B-18 was defended by 3 x .30 caliber machine guns. These lacked the general firepower inherent in the more powerful .50 caliber Browning M2 heavy machine guns, which were widely used on later American aircraft, ships and vehicles throughout the war. One machine gun was mounted on the nose and the other in the supine position.

The third is mounted in a ventral position. Aside from this defensive weapon, the real "bread and butter" of any bomber is of course its ability to carry bombs.

The B-18 will carry as much as 2,000 to 4,500 pounds of internal reserves for such work -- either conventionally dropped bombs or Navy depth charges, as needed.

Performance

Power for the B-18 was provided by two Wright R-1820 series air-cooled radial piston engines housed in streamlined nacelles along the wings. Each engine was rated up to 1,000 horsepower, depending on the powerplant model (various R-1820s were used in B-18 production). This allows for a top speed of 215 mph (about 15,000 feet) and a cruising speed of 167 mph.

Range is limited to 2,100 miles, while listed service is capped at a maximum of 24,000 feet. The engine drives a three-bladed metal propeller.

Today's B-18 Bolo

Of the hundreds to be produced, there are currently only six B-18s, with five serving as static museum displays and one currently undergoing refurbishment. Appropriately, one of them is located at the National Museum of the United States Air Force at Wright-Patterson Air Force Base in Dayton, Ohio - near Bolo's birthplace.