Named in honour of Major General William "Billy" Mitchell, a pioneer of U.S. military aviation, the North American B-25 Mitchell was an American twin-engine, medium bomber manufactured by North American Aviation (NAA).
Flown by numerous Allied air forces, the B-25 served in every theatre of World War II and after the war ended many remained in service, operating across four decades. Produced in numerous variants, nearly 10,000 Mitchells rolled from NAA factories.
In September 1939, the Air Corps ordered the B-25 into production, 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.
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 lead to further developments. Before the year was over, NAA was producing the B-25C and B-25D series at different plants.
The B-25 quickly gained a reputation as a safe and forgiving aircraft to fly. With one engine out, 60° banking turns into the dead engine were possible, and control could be easily maintained down to 145 mph. The pilot had to remember to maintain engine-out directional control at low speeds after takeoff with rudder; if this manoeuvre was attempted with ailerons, the aircraft could snap out of control. The tricycle landing gear made for excellent visibility while taxiing. The only significant complaint about the B-25 was the extremely high noise level produced by its engines; as a result, many pilots eventually suffered from varying degrees of hearing loss.
The sturdy aircraft that could withstand tremendous punishment. One B-25C of the 321st Bomb Group was nicknamed "Patches" because its crew chief painted all the aircraft's flak hole patches with the bright yellow zinc chromate primer. By the end of the war, this aircraft had completed over 300 missions, had been belly-landed six times and had over 400 patched holes. The airframe of "Patches" was so distorted from battle damage that straight-and-level flight required 8° of left aileron trim and 6° of right rudder, causing the aircraft to "crab" sideways across the sky.
The majority of B-25s in American service were used in the war against Japan in Asia and the Pacific. The Mitchell fought from the Northern Pacific to the South Pacific and the Far East. These areas included the campaigns in the Aleutian Islands, Papua New Guinea, the Solomon Islands, New Britain, China, Burma and the island hopping campaign in the Central Pacific. The aircraft's potential as a ground-attack aircraft emerged during the Pacific war. The jungle environment reduced the usefulness of medium-level bombing, and made low-level attack the best tactic. Using similar mast height level tactics and skip bombing, the B-25 proved itself to be a capable anti-shipping weapon and sank many enemy sea vessels of various types. An ever-increasing number of forward firing guns made the B-25 a formidable strafing aircraft for island warfare.
In Burma, the B-25 was often used to attack Japanese communication links, especially bridges in central Burma. later in the war, as the USAAF acquired bases in other parts of the Pacific, the Mitchell could strike targets in Indochina, Formosa and Kyushu, increasing the usefulness of the B-25. It was also used in some of the shortest raids of the Pacific War, striking from Saipan against Guam and Tinian.
The first B-25s arrived in Egypt and were carrying out independent operations by October 1942. Operations there against Axis airfields and motorised vehicle columns supported the ground actions of the Second Battle of El Alamein. Thereafter, the aircraft took part in the rest of the campaign in North Africa, the invasion of Sicily and the advance up Italy.
The RAF also received nearly 900 Mitchells, using them to replace Douglas Bostons, Lockheed Venturas and Vickers Wellington bombers. The Mitchell entered active RAF service on 22 January 1943. At first, it was used to bomb targets in occupied Europe. After the Normandy invasion, the RAF and France used Mitchells in support of the Allies in Europe. Several squadrons moved to forward airbases on the continent.
The B-25 first gained fame as the bomber used in the 18 April 1942 Doolittle Raid, in which 16 B-25s led by Lieutenant Colonel Jimmy Doolittle attacked mainland Japan, four months after the bombing of Pearl Harbour. The mission gave a much-needed lift in spirits to the Americans, and alarmed the Japanese, who had believed their home islands to be impenetrable by enemy forces. Although the amount of actual damage done was relatively minor, it forced the Japanese to divert troops for home defence for the remainder of the war.
The raiders took off from the carrier USS Hornet and successfully bombed Tokyo and four other Japanese cities without loss. Fifteen of the bombers subsequently crash-landed en route to recovery fields in eastern China. Of the 80 aircrew, 69 survived their historic mission and eventually made it back to American lines.
Following a number of additional modifications, including the addition of Plexiglas dome for navigational sightings to replace the overhead window for the navigator and heavier nose armament, de-icing and anti-icing equipment, the B-25C entered USAAF operations as the first mass-produced aircraft of its type.
Although the B-25 was originally designed to bomb from medium altitudes in level flight, it was used frequently in the Southwest Pacific theatre in treetop-level strafing and missions with parachute-retarded fragmentation bombs against
The USAAF Antisubmarine Command made great use of the B-25 in 1942 and 1943. Some of the earliest B-25 Bomb Groups also flew the Mitchell on coastal patrols after the Pearl Harbour attack, prior to the AAFAC organisation. Many of the two dozen or so Antisubmarine Squadrons flew the B-25C, D and G series in the American Theatre Antisubmarine campaign, often in the distinctive, white sea search camouflage.
In anti-shipping operations, the USAAF had urgent need for hard-hitting aircraft, and North American responded with the B-25G. In this series the transparent nose and bombardier/navigator position was changed for a shorter, hatched nose with two fixed .50 in machine guns and a 75 mm M4 cannon, one of the largest weapons fitted to an aircraft, similar to the British 57 mm gun-armed Mosquito Mk. XVIII and the German Henschel Hs 129B-3, and Ju 88P heavy cannon. The shorter nose placed the cannon breech behind the pilot where it could be manually loaded and serviced by the navigator; his crew station was moved to a position just behind the pilot. The navigator signalled the pilot when the gun was ready and the pilot fired the weapon using a button on his control wheel.
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