B-18 Bolo

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In the early 1930s, the development of military aviation in the United States was severely hampered by the effects of the Great Depression, which led to significant budgetary constraints, as well as widespread pacifist and isolationist sentiments among the American public. The prevailing attitude at the time was to limit the role of the Air Corps to supporting ground forces and coastal defense. The Baker Board, established in 1934 to assess the role of military aviation, even declared that “independent air missions have little effect upon the issue of the battle and none upon the outcome of the war.” This limited view of air power defined the context in which Army officers and War Department officials gathered at Wright Field in 1935 to select the next bomber for the Air Corps.

In May 1934, before the first Martin YB-10, the Air Corps’ first all-metal monoplane bomber, had even been delivered, the Air Corps announced a new competition for multi-engined bombers. These new bombers were required to carry 2,000 pounds (907 kg) of bombs over a distance of at least 1,020 miles (1,640 km) and, if possible, 2,200 miles (3,540 km), with a top speed of at least 200 mph (322 km/h) and ideally 250 mph (402 km/h). In response to this requirement, Douglas Aircraft developed the DB-1 (Douglas Bomber One), a twin-engined bomber based on its successful DC-2 transport aircraft. The DB-1 utilized the wings of the DC-2 but featured a deeper fuselage with a bomb bay, enlarged tail surfaces, and slightly increased wingspan with rounded tips. The aircraft was designed to be operated by a six-man crew and armed with three hand-held 0.30-caliber machine guns.

The DB-1 prototype, powered by two 850-horsepower Wright R-1820-G5 engines, was completed in April 1935 and underwent manufacturer trials before being sent to Wright Field in August 1935 for competitive testing. At Wright Field, the DB-1 was evaluated alongside the Martin 146, an improved version of the B-10, and the Boeing 299, the prototype of the B-17 Flying Fortress. Although the Boeing 299 was faster, had greater range, and carried more bombs, the DB-1 was significantly cheaper, priced at $58,500 compared to the Boeing’s $99,620 per aircraft. The decision ultimately came down to a choice between quality and quantity. The technical staff recommended purchasing a smaller number of Boeing bombers, but the General Staff, favoring the more affordable DB-1, opted for a larger number of these aircraft. The decision was further influenced by the crash of the Boeing 299 prototype, which bolstered the General Staff’s preference for the more conservative procurement approach.

In January 1936, the War Department ordered 133 Douglas B-18s and thirteen Boeing YB-17s. This decision has been widely criticized, both at the time and by later historians, given that the B-17 would go on to become one of the most effective bombers of World War II, while the B-18 was largely obsolete by the time the U.S. entered the war. However, it’s worth noting that even the early B-17 models were considered obsolete by 1941. On the other hand, the availability of a large number of B-18s during the late 1930s allowed the Air Corps to train enough bomber crews for the Army Air Forces, who would later fly the more advanced B-17 models with great success during the war.

The DB-1 prototype, after its evaluation by the Air Corps, was returned to Douglas to be upgraded to the B-18 production standard. It was then delivered back to the Air Corps in February 1937. Two years later, the prototype was modified to test the feasibility of firing large cannons from aircraft. An M1898 75 mm field-piece was mounted in the bomb bay, and the nose of the aircraft was altered to accommodate forward firing. Despite initial trials, excessive vibration when firing the cannon led to the discontinuation of the experiment. However, the lessons learned from these tests were invaluable in the development of later aircraft like the cannon-armed B-25G and B-25H Mitchell bombers. While the cannon-armed B-18 remained experimental, other production versions of the B-18 were produced in significant quantities, contributing to the training and operational readiness of U.S. bomber crews in the lead-up to World War II.

Specifications

variant
B-18
B-18A
crew
6
6
wingspan (m)
27,28
27,28
horizontal stabilizer overall span (m)
8,128
8,128
lenght (m)
17,27
17,63
height (m)
4,62
4,62
vertical stabilizer height (m)
4,064
4,064
wing area (m2)
89,09
89,09
wing flap area (m2)
5,96
5,96
aileron area (m2)
4,46 (each)
4,46 (each)
horizontal stabilizer total area (m2)
8,90
8,90
vertical stabilizer area (m2)
3,52
3,52
rudder area (m2)
4,33
4,33
empty weight (kg)
7130
7403
normal take-off weight (kg)
9584
10035
max take-off weight (kg)
12286
12552
engine
Wright R-1820-45 930 hp at 2100 rpm for take-off, 810 hp at 2100 rpm at 3140 m, air-cooled, radial
Wright R-1820-53 1000 hp at 0m, 850 hp at 2925 m, air-cooled, radial
propeller
Hamilton Standard Hydromatic, constant speed, 3-bladed, 2,59 m
Hamilton Standard Hydromatic, constant speed, 3-bladed, 2,59 m
fuel (l)
4429
4429
engine oil (l)
329
329
max speed (km/h)
349 at 3050 m
347 at 3050 m
cruising speed (km/h)
269
269
landing speed (km/h)
103
111
ceiling (m)
7375 – 7878
7285 – 7800
range (km)
max 3580
1850 with 1132 kg bombs
rate of climb
6,9 m/s
5,2 m/s
climbing time
9’6” at 3050 m
9’54” at 3050 m
bombs (kg)
1996
1996
armament
3×7,62 mm
3×7,62 mm

References

  • “Douglas B-18 Bolo – The Ultimate Look: from Drawing Board to U-boat Hunter” – William Wolf, Schiffer Publishing
  • Dan Hagedorn Sr., Dan Hagedorn Jr – The Douglas B-18 and B-23: America’s Forsaken Warriors, 2015
  • Michael O’Leary – DC-3 and C-47 Gooney Birds: Includes the DC-2, DC-3, C-47, B-18 Bolo, B-23 Dragon, the Basler turboprop Goonies, and many more, 1992
  • Rene J. Francillon – McDonnell Douglas Aircraft since 1920: Volume 1

Plastic model kits

1/72 Special Hobby SH72095 B-18 Bolo “Pre-War Service”
1/72 Special Hobby SH72228 B-18A Bolo “At War”
1/72 Special Hobby SH72251 Digby Mk.I Bolo in Canadian service
1/72 Special Hobby SH72265 B-18 Bolo “WWII Service”