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North American Aircraft’s B-25 Mitchell Medium Bomber

North American Aircraft’s B-25 Mitchell Medium Bomber

Named in honor of Major General William “Billy” Mitchell, the pioneer of U.S. military aviation, the North American Aircraft B-25 Mitchell medium bomber was used by many Allied air forces. The B-25 served in every theater of World War II and after the war ended many remained in service, operating in several civilian occupations for nearly 40 years. Produced in numerous variants, nearly 10,000 Mitchells rolled from NAA factories and today, the B-25 is used throughout the country and overseas as a very popular military airshow star

The Air Corps issued a specification for a medium bomber in March 1939: 2,400 lb., over 1,200 mi at 300 mph. NAA used the NA-40B design to develop the NA-62, which competed for the medium bomber contract. There was no YB-25 for prototype service tests. In September 1939, the Air Corps ordered the NA-62 into production as the B-25, along with the other new Air Corps medium bomber, the Martin B-26 Marauder “off the drawing board”.

Early into B-25 production, NAA incorporated a significant redesign to the wing dihedral. The first nine aircraft had a constant-dihedral, meaning the wing had a consistent, upward angle from the fuselage to the wingtip. This design caused stability problems. “Flattening” the outer wing panels by giving them a slight anhedral angle just outboard of the engine nacelles nullified the problem, and gave the B-25 its gull wing configuration. Less noticeable changes during this period included an increase in the size of the tail fins and a decrease in their inward tilt at their tops.

NAA continued design and development in 1940 and 1941. Both the B-25A and B-25B series entered USAAF service. The B-25B was operational in 1942. Combat requirements led to further developments. Before the year was over, NAA was producing the B-25C and B-25D series at different plants. Also in 1942, the manufacturer began design work on the cannon-armed B-25G series. The NA-100 of 1943 and 1944 was an interim armament development at the Kansas City complex known as the B-25D2. Similar armament upgrades by U.S-based commercial modification centers involved about half of the B-25G series.

Further development led to the B-25H, B-25J, and B-25J2. The gunship design concept dates to late 1942 and NAA sent a field technical representative to the SWPA. The factory-produced B-25G entered production during the NA-96 order followed by the redesigned B-25H gunship. The B-25J reverted to the bomber role, but it, too, could be outfitted as a strafer.

The Royal Air Force (RAF) was an early customer for the B-25 via Lend-Lease. The first Mitchells were given the service name Mitchell I by the RAF and were delivered in August 1941, to No. 111 Operational Training Unit based in the Bahamas. These bombers were used exclusively for training and familiarization and never achieved operational status. The B-25Cs and Ds were designated Mitchell II. Altogether, 167 B-25Cs and 371 B-25Ds were delivered to the RAF. The RAF tested the cannon-armed G series but did not adopt the series nor the follow-on H series.

By the end of 1942 the RAF had taken delivery of a total of 93 Mitchell marks I and II. Some served with squadrons of No. 2 Group RAF, the RAF’s tactical medium bomber force. The first RAF operation with the Mitchell II took place on 22 January 1943, when six aircraft from No. 180 Squadron RAF attacked oil installations at Ghent. After the invasion of Europe (by which point 2 Group was part of Second Tactical Air Force), all four Mitchell squadrons moved to bases in France and Belgium (Melsbroek) to support Allied ground forces. The British Mitchell squadrons were joined by No. 342 (Lorraine) Squadron of the French Air Force in April 1945.

Updated: October 8, 2018 — 10:34 AM
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