B-25 Mitchell

B-25 Mitchell was a twin-engined, medium bomber manufactured by North American Aviation in the United States and used during World War II. By the time production of the plane ended, roughly 10,000 had been built, including PBJ-1 Navy Patrol Bomber and an F-10 reconnaissance version. It served in every combat theatre and was used by a number of countries other than the United States, including Australia, the United Kingdom (which received more than 900), China, The Netherlands, and Russia. It's nickname (and official RAF name) of 'Mitchell' was in honour of General Billy Mitchell, an early proponent of airpower.

While the B-25 was meant originally to bomb from medium altitudes in level flight, it was used frequently in the Pacific Theatre in treetop-level missions against Japanese airfields and for operations such as strafing and skip-bombing against enemy Japanese shipping.

The B-25 is most famous as the bomber used in the 1942 Doolittle Raid, where the raiders took off from the aircraft carrier USS Hornet, bombed Tokyo, and crashed in China; a B-25 also collided with the Empire State Building in 1945. The B-25 is the aircraft featured in the popular and influential novel Catch-22 and subsequent film.

Development

The B-25 was a descendant of the aborted XB-21 (N[orth]A[merican]-39) project of the mid-1930s. Experience gained in making the XB-21 was used by North American in designing the B-25 (NA-40). One NA-40 was built; several modifications were made on it to test a number of potential features, including the replacement of its Pratt & Whitney R-1830 radials with Wright R-2600 radials, the engine type that would become standard on the B-25.

The product of these experimentations, dubbed the NA-40B, was submitted to the United States Army Air Corps for evaluation near the end of the 1939. It was intended to be an attack bomber, to be exported to Britain and France, both of which had a pressing requirement for such aircraft in the early stages of World War II. However, the NA-40B was passed up in favour of the plane that would become the A-20 Havoc. Despite this loss, the NA-40B re-entered the spotlight when the Army evaluated it for use as a medium bomber. Unfortuantely, the plane was destroyed in a crash on 1939 April 11. Nonetheless, the NA-40B design was ordered for production in 1939.

Early Production

Along with the B-26 Marauder, the B-25 was ordered by the Army for production in 1939. An improvement on the NA-40B, dubbed the NA-62, was the basis for the first B-25 version. Due to a desperate need for medium bombers, no experimental or service-test versions were built. Any necessary modifications were made during production runs, or to existing aircraft at field modification centres.

The most significant change was a rearrangement of the wing. In the first nine aeroplanes of the production line, a dihedral wing was used. This design had some stability issues, so the dihedral angle was nullified on the outboard section of the wing, giving the B-25 a distinct 'gull wing' configuration. One less important change was an increase in the size of the vertical stabilisers and a decrease in the inward cant.

Operational History

Following a number of modifications, including improved engines, a sighting blister for the navigator, more nose armament, and de-icing and anti-icing equipment, the B-25C was released to the Army. It was the first mass-produced version of the B-25. The B-25D was identical, except in location: where the B-25C was built in Inglewood, California, the B-25D was built in Kansas City, Kansas. A total of 3915 B-25Cs and B-25Ds were built by North American during the course of the war.

Because of extreme need for durable aircraft to use in strafing missions, a version of the B-25 dubbed the B-25G was developed, in which the transparent nose was replaced by a solid nose. This housed two fixed .50-calibre machine guns and a 75 mm M4 cannon, the largest calibre weapon ever used on an American bomber. The B-25G’s successor, the B-25H, had even more firepower with the addition of 6 fixed .50-calibre machine guns. 1400 B-25Gs and B-25Hs were built.

The last produced version, the B-25J, was somewhere between the B-25C and the B-25H. It maintained much of the fixed armament of the B-25H, but the solid nose was replaced by a ‘greenhouse’ one seen on earlier models, though 800 B-25Js were converted to a solid nose version. It also featured improved engines. 4318 B-25Js were built.

References and external links

• Johnsen, Frederick A. North American B-25 Mitchell (Warbirdtech Series, Volume 12). Minnesota: Voyageur Press, 1997. (ISBN 0933424779)
• Scutts, Jerry. North American B-25 Mitchell. United Kingdom: Crowood Press, 2001. (ISBN 1861263945)
• Detailed historical overview