Despite the fact that the twin-engine Douglas B-18 fitted most of the United States Army Air Forces bombing squadrons before the start of World War II, the “Bolo”, as it was known, still remains one of the most overlook bombers in history. The Douglas Company new venture in the medium payload bomber platform is a direct descendant of the venerable DC-2 commercial transport plane. The B-18 was designed to replace another standard bear, the Martin B-10, as the US main medium attack bombing aircraft.
The aircraft conception and developing phase lasted between the spring and fall of 1934. By early 1935, Douglas’ engineering were placing the finishing touches in what they believed would be the world’s most stable medium platform. The craft first flew in the afternoon of April 11th 1935 and bombing trial began a just a few days after that. The trial pitted the Bolo against the new Martin design, the 146.
The 146 project was basically an upgraded B-10 with a larger bomb bay and extended operational range. There was another entry in the USAAF’s selecting bomber contest the four-engine Boeing 299, the forerunner of the historic B-17 Flying Fortress. Although the 299 was viewed in many circles at the clear favorite to win out, its step price (almost $ 100,000 per unit-1935 dollars) in comparison to the Bolo’s ($58,500 per) shifted the balance towards the Douglas’ entry.
In January 1936, the Army General Staff made it official when it ordered 133 Bolos. The order was followed a few month later with a larger, 217, one. The second batch ordered (217 samples) were known as the 18As. The main difference from the original version was its “shark” nose cone in which the bombardier’s position was extended forward over the nose gunner area. Twenty of these modified Bolos were dispatched to the Royal Canadian Air Force (RCAF) where they received a different designation: Digby 1s.
During the winter of 1939-40, 110 Bolos were upgraded to the 18B configuration. The new version included a sophisticated radio packaged for maritime reconnassaince missions over the US costal waters as well as in the Caribbean basin area where the type patrolled in search for German U-boats operating in the American hemisphere.
Because of its vast number, at least for pre-war American standards, Bolo stationed formations was one of the main target of Japanese medium altitude bomber attacks during Pearl Harbor on December 7th 1941. By the middle of 1942, the US began removing the B-18 from front line service. From that year until the plane was fully decommissioned in 1946, it served as transport and paratroop training platform.
In all, 350 Bolos were built in 10 versions (DB-1, B-18, 18m, DB-2, 18a, 18ma, 18b, 18c, Digby 1 and C-058). There was another proposed version, the XB-22, but this never made it out of the mockup phase. Beside the US and Canada, the Brazilian Air Force operated the B-18 during the war years. Today, only five samples of the Bolo remains in the world. All of them are in display at various American air museums.
|Power Plant:||Two Wright 1000hp R-1820.53 Cyclone, 9 cylinder radial engines|
|Total Wing Area:||89.65m square|
|Maximum Takeoff weight:||12,563kg|
|Climb Rate:||3048m in 9:54 minutes|
|Armament:||One 7.62mm heavy machine gun located in each, the nose, dorsal and ventral positions. Up to 2,951kg bomb load capability.|