North American B-25 Mitchell B-25C

The B-25C was born of the leap in scale that the war in Europe forced on the American aircraft industry. After the short initial runs of the B-25, B-25A and B-25B, the first large Mitchell order was placed in September 1940: 1,025 aircraft of the C version, soon increased by a further 1,000. It was the first time North American had faced medium-bomber production on an industrial scale, and its main plant at Inglewood, California, became the centre of that effort.

On the B-25B airframe the new version brought together the improvements that defined the "standard" Mitchell. The Wright R-2600-9 engines gave way to R-2600-13s; de-icing and anti-icing equipment was added; the navigator received a sighting blister over his compartment; and the nose armament grew to two .50-calibre machine guns, one fixed and one flexible. By December 1941 the C also carried additional self-sealing fuel cells outboard of the wing centre section, extending its radius of action. The same series introduced the Clayton S exhaust stack, designed to quench the exhaust flame and make the aircraft less visible at night.

Compared with the B-25B, the Doolittle Raid version, the B-25C kept the manned dorsal turret and the remotely operated retractable ventral turret, each with a pair of .50-calibre guns, but added the R-2600-13 powerplant, the de-icing equipment, the navigator's blister and the re-armed nose. The Mitchell pilot training manual describes the de-icing system fitted to these aircraft: conventional inflatable boots on the leading edges of the wings and tail, operated by suction from the vacuum pumps on both engines, with a warning never to run them above 230 mph lest negative pressure expand and rupture the boots; and an isopropyl-alcohol anti-icing system with two nacelle tanks feeding the propellers, the bombardier's window and the carburettors.

Together with the B-25D, the B-25C became the basis for the field "strafer" conversions devised in New Guinea by Paul Gunn and Jack Fox. The B-25C1/D1 carried four .50-calibre guns in the nose for low-level strafing, a formula the factory eventually adopted with the eight-gun nose of the B-25J.

With 1,625 built, the B-25C was the first mass-produced Mitchell and one of the two great production blocks of 1942-43, the other being the Kansas City-built B-25D, identical except for its factory of origin. It was also the starting point for a string of experimental aircraft: the XB-25E and XB-25F, which tested hot-air and electrical de-icing systems respectively, and the XB-25G, whose solid nose with a 75 mm cannon opened the line of B-25G and B-25H gunships. Aircraft assigned to training were designated AT-24C, later TB-25C, and the US Navy operated an equivalent as the PBJ-1C, often fitted with search radar for anti-submarine work.

The B-25C reached the squadrons just as the United States entered the war, and it served in every theatre. In the South-West Pacific, General George Kenney, commanding the Fifth Air Force, ended 1942 frustrated by his bombers' poor results against Japanese shipping and tasked Major Paul Gunn of the 90th Bomb Squadron, 3rd Bomb Group, with turning A-20s and B-25s into strafers able to suppress anti-aircraft fire. Crews practised skip bombing and mast-height attacks against the wreck of the SS Pruth, a 4,700-ton steamer aground on a reef near Port Moresby, and perfected the tactics over the first two months of 1943. The payoff came at the Battle of the Bismarck Sea, where low-flying Mitchells and Havocs cut a Japanese convoy and its destroyer escort to pieces.

In Burma, the Tenth Air Force's 341st Bomb Group flew B-25Cs and Ds against bridges, using a combined glide-and-skip technique its crews called "glip" bombing. In the Mediterranean, the five bomb groups (twenty squadrons) of the Ninth and Twelfth Air Forces that flew the B-25 were the only US units to use the type against Europe; from February 1943 they came under General Carl Spaatz's Northwest African Air Forces, which carried the weight of the Tunisian campaign and the preparation of the Sicily landings in July of that year. One B-25C of the 321st Bomb Group, nicknamed "Patches", collected so many flak-hole patches, painted bright yellow by its crew chief, that its distorted airframe needed 8° of aileron trim and 6° of rudder to fly straight.

Beyond the USAAF, the B-25C was the first widely exported Mitchell. On 30 June 1941 the Netherlands Purchasing Commission, acting for the Dutch government-in-exile, signed a contract for 162 B-25Cs intended for the Netherlands East Indies; in February 1942 BOAC agreed to ferry 20 of them from Florida to Australia via Africa and India and another 10 by the South Pacific route, and by March five had reached Bangalore and twelve Archerfield. Those aircraft went on to equip No. 18 (Netherlands East Indies) Squadron RAAF. The RAF received 167 B-25Cs as the Mitchell II and flew its first operation with the type on 22 January 1943. The Soviet Union received 862 B-25s of the B, C, D, G and J versions under Lend-Lease via the Alaska-Siberia ALSIB ferry route, out of 870 dispatched, and well over a hundred B-25Cs and Ds went to Nationalist China.

By the end of the war most B-25Cs had been replaced by B-25Js, but some lived on with smaller air forces: Brazil operated 75 Mitchells of the B, C and J versions, and in 1950 the Indonesian Air Force inherited 25 ex-Dutch aircraft, including five B-25C photo-reconnaissance machines and one B-25C transport. The B-25C was, in short, the Mitchell that turned a good design into a mass-produced bomber, and the one that shaped the low-level attack tactics that came to define the family.