North American B-25 Mitchell

The roots of the B-25 can be traced back to North American's NA-40 aircraft. This had been undergoing flight tests with the United States Army Air Corps when the aircraft crashed on the 11th April 1939, with all crew members escaping. However, the design showed potential. With the release of the United States Army Air Corps Proposal No 39-640 on the 11th March 1939, which called for a medium bomber capable of a top speed of at least 300 mph, with a range of 2,000 miles with a bomb load of 3,000lb, North American submitted their design, based on the NA-40, the NA-62, with 184 aircraft ordered on the 10th August 1939.

Now known as the B-25, the 19th August 1940 would see the first production example fly. The aircraft would normally have a crew of five, comprising, pilot, co-pilot, bombardier, wireless operator and gunner. Powered by a pair of 1,700-hp Wright R-2600-9 Double Cyclone engines, the B-25 had a top speed of 322 mph, range of 2,000 miles with a service ceiling of 30,000 ft. Armament was one 0.50-in machine-gun and three 0.30-in machine-guns, bomb load was 3,600lb. The B-25 entered service when the 17th Bombardment Group based at McChord Field took delivery of the first example in February 1941.

The B-25A was next and featured armour plating for the crew and self-sealing fuel tanks, with the first example flying on the 24th February 1941. Powered by the same 1,700-hp Wright R-2600-9 Double Cyclone engines as its predecessor, the B-25A had a top speed of 315 mph, range of 1,350 miles and a service ceiling of 27,000 ft. Armament consisted of one 0.50-in machine-gun and three 0.30-in machine-guns, with a bomb load of 3,600lb. The B-25A would enter service as part of the 17th Bombardment Group based at McChord Field, who would also achieve the aircraft's first operational success, when a B-25, flown by Second Lieutenant Everett W. Holstrom, attacked and sunk a Japanese submarine off the West Coast of the United States on the 24th December 1941.

The B-25B, also known as the Mitchell Mk I, followed, and like the two variants before it, was powered by the 1,700-hp Wright R-2600-9 Double Cyclone engine. This had a top speed of 300 mph, range of 1,300 miles with a service ceiling of 25,000 ft. Armament was four 0.50-in machine-guns and one 0.30-in machine-gun. Bomb load was 5,000lb. It was the B-25B that was chosen to take part in an attack on mainland Japan on the 18th April 1942. Sixteen aircraft, led by Lieutenant Colonel James Doolittle, featuring modifications such as autopilot and a 60% increase in fuel capacity, would take-off from the carrier USS Hornet (CV-8) to attack various targets in Japan, including Tokyo and Yokohama. This would become known as the 'Doolittle Raid'.

The 1,700-hp Wright R-2600-13 Double Cyclone powered B-25C, also called the Mitchell Mk II, was the next variant. Its top speed was 284 mph, range 1,500 miles and a service ceiling of 24,000 ft. Armament was six 0.50-in machine-guns, with a bomb load of 5,200lb. This was followed by the B-25D which had the same top speed, range, service ceiling and armament of its predecessor, but was powered by the 2,000-hp Pratt & Whitney R-2600-27 engine. With the first B-25D, with Paul Balfour at the controls, making its maiden flight on the 3rd January 1942.

A pair of B-25Cs would be used to test de-icers. One would become the XB-25E, with the other known as the XB-25F-A.

Entering service in July 1943 the B-25G was designed to attack shipping and was fitted with a 75mm cannon in the nose. Powered by the 1,700-hp Wright R-2600-13 Double Cyclone engine, it had a top speed of 284 mph, range of 1,560 miles and a service ceiling of 24,300 ft. As well as the 75mm cannon the B-25G had armament of five 0.50-in machine-guns and had a bomb load of 3,000lb.

The next variant was the B-25H, which was powered by the 1,700-hp Wright R-2600-13 Double Cyclone engine. This gave the aircraft a top speed of 280 mph, range of 1,350 miles with a service ceiling of 24,300 ft. Armament was one 75mm cannon and twelve 0.50-in machine-guns, bomb load was 3,000lb.

The last production version was the B-25J, also known as the Mitchell Mk III. The 1,700-hp Wright R-2600-13 Double Cyclone engine powered the aircraft giving it a top speed of 272 mph, range of 1,250 miles whilst its service ceiling was 29,000 ft. Armament consisted of twelve 0.50-in machine-guns and its bomb load was 3,000lb.

As well as serving with the United States, the Royal Air Force would also use the B-25 Mitchell, and the type entered operational service with the RAF on the 22nd January 1943, when six aircraft from No. 180 Squadron attacked the oil installations at Ghent, Belgium, three would fail to return. B-25s would serve with various air forces around the world, including Canada, Netherlands and China.

By the time production had finished 9,884 B-25s had been built and served in various roles including reconnaissance and wing de-icing experiments and continued in service outside of the US until 1960.