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North American B-25 Mitchell

The North American B-25 Mitchell is an American medium bomber that was introduced in 1941 and named in honor of Brigadier General William "Billy" Mitchell, a pioneer of U.S. military aviation. 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 across four decades. Produced in numerous variants, nearly 10,000 B-25s were built. It was the most-produced American medium bomber and the third-most-produced American bomber overall. These included several limited models such as the F-10 reconnaissance aircraft, the AT-24 crew trainer, and the United States Marine Corps' PBJ-1 patrol bomber.

Design and development
On 11 March 1939, the US Army Air Corps issued Proposal No. 39-640 specifying a medium bomber capable of carrying a bombload over a range of at top speed in excess of . North American Aviation (NAA) used its NA-40B design to develop the NA-62 proposal. More state of the art compared to the competing Martin No. 179 proposal, the North American team included easy field maintenance and repair features, and according to Avery, "It promised to be an easy airplane to fly and placed no special requirements on pilot training programs." On 20 September. the Air Corps issued North American contract No. W353-ac-13258 for 184 B-25s powered by the Wright R-2600. The plane used the NACA 23017 airfoil at the wing root changing to a NACA 4409-R at the wingtip. On 19 August 1940, Vance Breese and NAA test engineer Roy Ferren flew the first flight test, when Ferren noted a severe roll-yaw condition. Preliminary flights by the Air Corps noted the Dutch roll characteristic, accentuated by wind and gusts and demanded a fix. NAA's first nine aircraft had a constant-dihedral, the wing having a consistent upward angle from the fuselage to the wingtip. "Flattening", or changing the outer wing panels dihedral to zero degrees, was a simple solution that solved the aerodynamic problem. This gave the B-25 its gull wing configuration. The 25 February 1941 flight test confirmed the change resulted in optimum flight characteristics. The vertical tail also went through five variations before being finalized. By the time of the attack on Pearl Harbor, 130 B-25s had been delivered. It produced B-25s at both its Inglewood main plant and an additional 6,608 aircraft at its Kansas City, Kansas, plant at Fairfax Airport. After the war, the USAF placed a contract for the TB-25L trainer in 1952. This was a modification program by Hayes of Birmingham, Alabama. Its primary role was reciprocating engine pilot training. A development of the B-25 was the North American XB-28 Dragon, designed as a high-altitude bomber. Two prototypes were built with the second prototype, the XB-28A, evaluated as a photo-reconnaissance platform, but the aircraft did not enter production. Flight characteristics The B-25 was 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 (230 km/h). The pilot had to remember to maintain engine-out directional control at low speeds after takeoff with rudder; if this maneuver were 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 its extremely noisy engines; as a result, many pilots eventually suffered from some degree of hearing loss. A Clayton S stack, introduced to quench the exhaust flame, was introduced in the B-25C series. These stacks protruded through the cowling, and though they weighed less than the replaced collector ring, they reduced aircraft speed by 9 mph due to the required aircraft fairings. According to Avery, "The increase in noise as compared to collector rings ported on the outboard side of the nacelles was a general crew complaint." == Operational history ==
Operational history
B-25Bs aboard USS Hornet Asia-Pacific Most B-25s in American service were used in the war against Japan in Asia and the Pacific. The Mitchell fought from the North 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, as well as in the Doolittle Raid. 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. An ever-increasing number of forward firing guns made the B-25 a formidable strafing aircraft for island warfare. The Paul Gunn and Jack Fox modified strafer models with four .50 caliber guns were the B-25C1/D1, while the factory B-25J was equipped with a factory made eight gun strafer nose. Operations there against Axis airfields and motorized-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. In the Strait of Messina to the Aegean Sea, the B-25 conducted sea sweeps as part of the coastal air forces. In Italy, the B-25 was used in the ground attack role, concentrating on attacks against road and rail links in Italy, Austria, and the Balkans. The B-25 had a longer range than the Douglas A-20 Havoc and Douglas A-26 Invader, allowing it to reach further into occupied Europe. The five bombardment groups – 20 squadrons – of the Ninth and Twelfth Air Forces that used the B-25 in the Mediterranean Theater of Operations were the only U.S. units to employ the B-25 in Europe. Europe In October 1943, the Ninth Air Force 340th was transferred from the African and Mediterranean theater to England in support of the assault on Germany. In November 1944 the medium bombers eliminated the use of electric locomotives along Brenner Pass. Use as a gunship In antishipping operations, the USAAF had an 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 (12.7 mm) machine guns and a manually loaded 75 mm (2.95 in) M4 cannon. The B-25H series continued the development of the gunship version. NAA Inglewood produced 1000. The H had even more firepower; most replaced the M4 gun with the lighter T13E1, The H series normally came from the factory mounting four fixed, forward-firing .50 in (12.7 mm) machine guns in the nose; four in a pair of under-cockpit conformal flank-mount gun pod packages (two guns per side); two more in the manned dorsal turret, relocated forward to a position just behind the cockpit (which became standard for the J-model); one each in a pair of new waist positions, introduced simultaneously with the forward-relocated dorsal turret; and lastly, a pair of guns in a new tail-gunner's position. Company promotional material bragged that the B-25H could "bring to bear 10 machine guns coming and four going, in addition to the 75 mm cannon, eight rockets, and 3,000 lb (1,360 kg) of bombs." The H had a modified cockpit with single flight controls operated by the pilot. The co-pilot's station and controls were removed and replaced by a smaller seat used by the navigator/cannoneer, The radio operator crew position was aft of the bomb bay with access to the waist guns. Factory production totals were 405 B-25Gs and 1,000 B-25Hs, with 248 of the latter being used by the Navy as PBJ-1Hs. Return to medium bomber for World War II Weekend 2015 in Reading, Pennsylvania The final, and most numerous, series of the Mitchell, the B-25J, looked less like earlier series apart from the well-glazed bombardier's nose of nearly identical appearance to the earliest B-25 subtypes. was flown to Eglin AFB, Florida, from Turner Air Force Base, Georgia, on 21 May 1960, the last flight by a USAF B-25. It was presented by Brigadier General A. J. Russell, Commander of SAC's 822d Air Division at Turner AFB, to the Air Proving Ground Center Commander, Brigadier General Robert H. Warren. He in turn presented the bomber to Valparaiso, Florida, Mayor Randall Roberts on behalf of the Niceville-Valparaiso Chamber of Commerce. Four of the original Tokyo Raiders were present for the ceremony, Colonel (later Major General) David Jones, Colonel Jack Simms, Lieutenant Colonel Joseph Manske, and retired Master Sergeant Edwin W. Horton. It was donated back to the Air Force Armament Museum around 1974 and marked as Doolittle's 40-2344. U.S. Navy and USMC The U.S. Navy designation for the Mitchell B-25 was the PBJ-1, similarly the PBJ-1C and PBJ-1D reflected their AAF counterparts. Night search PBJs incorporated a retractable APS-3 radome scope. Under the pre-1962 USN/USMC/USCG aircraft designation system, PBJ-1 stood for Patrol (P) Bomber (B) built by North American Aviation (J), first variant (-1) under the existing American naval aircraft designation system of the era. In early 1943, the Navy took delivery of an initial 706 B-25s, assigned to the Marine Corps for patrol and anti-submarine duties initially, but then transitioning into an attack aircraft with bombs, torpedoes and radar directed rockets. The PBJ had its origin in an inter-service agreement of mid-1942 between the Navy and the USAAF exchanging the Boeing Renton plant for the Kansas plant for B-29 Superfortress production. The Boeing XPBB Sea Ranger flying boat, competing for B-29 engines, was cancelled in exchange for part of the Kansas City Mitchell production. On 1 March 1943, VMB-413 was the first of sixteen USMC squadrons equipped with PBJs, all commissioned at MCAS Cherry Point. The large quantities of B-25H and J series became known as PBJ-1H and PBJ-1J, respectively. Royal Air Force Great Britain received 910 B-25s during WWII, but many were returned afterwards. No 418 (Auxiliary) Squadron received its first Mitchell IIs in January 1947. It was followed by No 406 (auxiliary), which flew Mitchell IIs and IIIs from April 1947 to June 1958. No 418 operated a mix of IIs and IIIs until March 1958. No 12 Squadron of Air Transport Command also flew Mitchell IIIs along with other types from September 1956 to November 1960. In 1951, the RCAF received an additional 75 B-25Js from USAF stocks to make up for attrition and to equip various second-line units. Royal Australian Air Force The Australians received Mitchells by the spring of 1944. The joint Australian-Dutch No. 18 (Netherlands East Indies) Squadron RAAF had more than enough Mitchells for one squadron, so the surplus went to re-equip the RAAF's No. 2 Squadron, replacing their Beauforts. Dutch Air Force in 1943 During World War II, the Mitchell served in fairly large numbers with the Air Force of the Dutch government-in-exile. They participated in combat in the East Indies, as well as on the European front. On 30 June 1941, the Netherlands Purchasing Commission, acting on behalf of the Dutch government-in-exile in London, signed a contract with North American Aviation for 162 B-25C aircraft. The bombers were to be delivered to the Netherlands East Indies to help deter any Japanese threatened expansion into the region. via the Alaska–Siberia ALSIB ferry route. A total of 870 B-25s were sent to the Soviets, meaning that 8 aircraft were lost during transportation. Other damaged B-25s arrived or crashed in the Far East of Russia, and one Doolittle Raid aircraft landed there short of fuel after attacking Japan. This lone airworthy Doolittle Raid aircraft to reach the Soviet Union was lost in a hangar fire in the early 1950s while undergoing routine maintenance. In general, the B-25 was operated as a ground-support and tactical day bomber (as similar Douglas A-20 Havocs were used). It saw action in fights from Stalingrad (with B/C/D models) to the German surrender during May 1945 (with G/J types). The B-25s that remained in Soviet Air Force service after the war were assigned the NATO reporting name "Bank". China Well over 100 B-25Cs and Ds were supplied to the Nationalist Chinese during the Second Sino-Japanese War. An unknown number were abandoned with the retreat to Formosa. Indonesia Indonesian Air Force received 25 ex-Dutch B-25 Mitchells after the end of Indonesian National Revolution in 1950, consisting of 5 B-25C photo-reconnaissance, 1 B-25C transport, 10 B-25J bombers and 9 B-25J gunship/strafer variants. A pair of B-25J were used to attack a radio station in Ambon during South Maluku rebellion in August 1950. They were used to bomb rebel targets during the PRRI and Permesta rebellions in 1958, where one was hit by anti-aircraft fire and three were damaged by strafing run from rebel-flown B-26 Invader. To extend its service life, the B-25s were sent to Hong Kong for major overhaul in 1959–1960. The last Indonesian B-25s were retired in 1974. == Variants ==
Variants
fitted to the nose ;B-25 :The initial production version of B-25s, they were powered by R-2600-9 engines. and carried up to 3,600 lb (1,600 kg) of bombs and defensive armament of three .30 machine guns in nose, waist, and ventral positions, with one .50 machine gun in the tail. The first nine aircraft were built with constant dihedral angle. Due to low stability, the wing was redesigned so that the dihedral was eliminated on the outboard section (number made: 24). ;B-25A :This version of the B-25 was modified to make it combat ready; additions included self-sealing fuel tanks, crew armor, and an improved tail-gunner station. No changes were made in the armament. It was redesignated obsolete (RB-25A) in 1942 (number made: 40). ;B-25B :The tail and gun position were removed and replaced by a manned dorsal turret on the rear fuselage and retractable, remotely operated ventral turret, each with a pair of .50 in (12.7 mm) machine guns. A total of 120 were built (this version was used in the Doolittle Raid). A total of 23 were supplied to the Royal Air Force as the Mitchell Mk I. ;B-25C :An improved version of the B-25B, its powerplants were upgraded from Wright R-2600-9 radials to R-2600-13s; de-icing and anti-icing equipment were added; the navigator received a sighting blister; and nose armament was increased to two .50 in (12.7 mm) machine guns, one fixed and one flexible. The B-25C model was the first mass-produced B-25 version; it was also used in the United Kingdom (as the Mitchell Mk II), in Canada, China, the Netherlands, and the Soviet Union (number made: 1,625). ;ZB-25C ;B-25D :Through block 20, the series was near identical to the B-25C. The series designation differed in that the B-25D was made in Kansas City, Kansas, whereas the B-25C was made in Inglewood, California. Later blocks with interim armament upgrades, the D2s, first flew on 3 January 1942 (number made: 2,290). ;F-10 :The F-10 designation distinguished 45 B-25Ds modified for photographic reconnaissance. All armament, armor, and bombing equipment were stripped. Three K.17 cameras were installed, one pointing down and two more mounted at oblique angles within blisters on each side of the nose. Optionally, a second downward-pointing camera could also be installed in the aft fuselage. Although designed for combat operations, these aircraft were mainly used for ground mapping. ;B-25D weather reconnaissance variant :In 1944, four B-25Ds were converted for weather reconnaissance. One later user was the 53d Weather Reconnaissance Squadron, originally called the Army Hurricane Reconnaissance Unit, now called the "Hurricane Hunters". Weather reconnaissance first started in 1943 with the 1st Weather Reconnaissance Squadron, with flights on the North Atlantic ferry routes. ;ZB-25D ;XB-25E :A single B-25C was modified to test de-icing and anti-icing equipment that circulated exhaust from the engines in chambers in the leading and trailing edges and empennage. The aircraft was tested for almost two years, beginning in 1942; while the system proved extremely effective, no production models were built that used it before the end of World War II. Many surviving warbird-flown B-25 aircraft today use the de-icing system from the XB-25E (number made: 1, converted). ;ZXB-25E ;XB-25F-A :A modified B-25C, it used insulated electrical coils mounted inside the wing and empennage leading edges to test the effectiveness as a de-icing system. The hot air de-icing system tested on the XB-25E was determined to be the more practical of the two (number made: 1, converted). ;XB-25G :This modified B-25C had the transparent nose replaced to create a short-nosed gunship carrying two fixed .50 in (12.7 mm) machine guns and a 75 mm (2.95 in) M4 cannon, then the largest weapon ever carried on an American bomber (number made: 1, converted). ;B-25G :The B-25G followed the success of the prototype XB-25G and production was a continuation of the NA96. The production model featured increased armor and a greater fuel supply than the XB-25G. One B-25G was passed to the British, who gave it the name Mitchell II that had been used for the B-25C. The USSR also tested the G (number made: 463; five converted Cs, 58 modified Cs, 400 production). , Colorado ;B-25H :An improved version of the B-25G, this version relocated the manned dorsal turret to a more forward location on the fuselage just aft of the flight deck. It also featured two additional fixed .50 in (12.7 mm) machine guns in the nose and in the H-5 onward, four in fuselage-mounted pods. The T13E1 light weight cannon replaced the heavy M4 cannon 75 mm (2.95 in). Single controls were installed from the factory with navigator in the right seat (number made: 1000; two airworthy ). ;B-25J-NC : Follow-on production at Kansas City, the B-25J could be called a cross between the B-25D and the B-25H. It had a transparent nose, but many of the delivered aircraft were modified to have a strafer nose (J2). Most of its 14–18 machine guns were forward-facing for strafing missions, including the two guns of the forward-located dorsal turret. The RAF received 316 aircraft, which were known as the Mitchell III. The J series was the last factory series production of the B-25 (number made: 4,318). ;CB-25J :Utility transport version ;VB-25J :A number of B-25s were converted for use as staff and VIP transports. Henry H. Arnold and Dwight D. Eisenhower both used converted B-25Js as their personal transports. The last VB-25J in active service was retired in May 1960 at the Eglin Air Force Base in Florida. Trainer variants Most models of the B-25 were used at some point as training aircraft. ;TB-25D :Originally designated AT-24A (Advanced Trainer, Model 24, Version A), trainer modification of B-25D often with the dorsal turret omitted, in total, 60 AT-24s were built. ;TB-25G :Originally designated AT-24B, trainer modification of B-25G ;TB-25C :Originally designated AT-24C, trainer modification of B-25C ;TB-25J :Originally designated AT-24D, trainer modification of B-25J, another 600 B-25Js were modified after the war. ;TB-25K :Hughes E1 fire-control radar trainer (Hughes) (number made: 117) ;TB-25L :Hayes pilot-trainer conversion (number made: 90) ;TB-25M :Hughes E5 fire-control radar trainer (number made: 40) ;TB-25N :Hayes navigator-trainer conversion (number made: 47) U.S. Navy / U.S. Marine Corps variants ;PBJ-1C :Similar to the B-25C for the U.S. Navy, it was often fitted with airborne search radar and used in the antisubmarine role. ;PBJ-1D :Similar to the B-25D for the U.S. Navy and U.S. Marine Corps, it differed in having a single .50 in (12.7 mm) machine gun in the tail turret and waist gun positions similar to the B-25H. Often it was fitted with airborne search radar and used in the antisubmarine role. ;PBJ-1G :U.S. Navy/U.S. Marine Corps designation for the B-25G, trials only ;PBJ-1H :U.S. Navy/U.S. Marine Corps designation for the B-25H :One PBJ-1H was modified with carrier takeoff and landing equipment and successfully tested on the USS Shangri-La, but the Navy did not continue development. ;PBJ-1J :U.S. Navy designation for the B-25J (Blocks −1 through −35), it had improvements in radio and other equipment. Beside the standard armament package, the Marines often fitted it with 5-inch underwing rockets and search radar for the antishipping/antisubmarine role. The 11.75 inch Tiny Tim rocket-powered warhead was used in 1945 on PBJ-1H. == Operators ==
Operators
; • An ex-USAAF TB-25N (s/n 44-31173) was acquired in June 1961 and registered locally as LV-GXH, it was privately operated as a smuggling aircraft. It was confiscated by provincial authorities in 1971 and handed over to Empresa Provincial de Aviacion Civil de San Juan, which operated it until its retirement due to a double engine failure in 1976. Currently, it is under restoration to airworthiness. ; on a training flight near Canberra in 1942. • Royal Australian Air Force – 50 aircraft, including three joint units with Military Aviation – Royal Dutch East Indies Army (ML-KNIL): • No. 2 Squadron RAAF; • No. 18 (Netherlands East Indies) Squadron RAAF; • No. 19 (Netherlands East Indies) Squadron RAAF and; • No. 119 (Netherlands East Indies) Squadron RAAF. ; • Biafran Air Force operated two aircraft. ; • Bolivian Air Force operated 13 aircraft ; • Brazilian Air Force operated 75 aircraft, including B-25B, B-25C, and B-25J. ; • Royal Canadian Air Force operated 164 aircraft in bomber, light transport, trainer, and special mission roles. • No. 13 (P) Squadron Mitchell II at RCAF Station Rockcliffe • No. 406 Auxiliary Squadron Mitchell III ; • Republic of China Air Force operated more than 180 aircraft. ; • People's Liberation Army Air Force operated captured Nationalist Chinese aircraft. ; • Chilean Air Force operated 12 aircraft. ; • Colombian Air Force operated three aircraft. ; • Cuban Army Air Force operated six aircraft. • Fuerza Aérea del Ejército de CubaCuerpo de Aviación del Ejército de Cuba ; • Dominican Air Force operated five aircraft. ; • French Air Force operated 11 aircraft. • Free French Air Force operated 18 aircraft. ; • Indonesian Air Force in 1950, received 25 B-25C and B-25J Mitchells previously operated by the Royal Netherlands East Indies Army Air Force (ML-KNIL). • Eight Mexican civil registrations were allocated to B-25s, including one aircraft registered to the Bank of Mexico, but used by the President of Mexico. ; , formed in 1946, during the Indonesian War of Independence. These aircraft were used in the ground attack role, leading to the dorsal turret being removed. • Military Aviation – Royal Dutch East Indies Army (ML-KNIL; 1942–1950): 149 aircraft (initially in three joint units with the Royal Australian Air Force) during World War II and the Indonesian War of Independence: • No. 18 Squadron (NEI) RAAF/18 Squadron ML-KNIL (1942–1950) – bomber • No. 119 (Netherlands East Indies) Squadron RAAF (1943–1943) – bomber • No. 19 Squadron (NEI) RAAF/19 Squadron ML-KNIL (1944–1948) – transport • 16 Squadron ML-KNIL (1946–1948) – ground attack • 20 Squadron ML-KNIL (1946–1950) – transport • Naval Aviation Service (MLD) – 107 aircraft; initially in a joint unit with the UK Royal Air Force: • No. 320 (Netherlands) Squadron RAF (1942–1946) ; • Peruvian Air Force received eight B-25Js in 1947, which formed Bomber Squadron N° 21 at Talara. ; • Polish Air Forces on exile in Great BritainNo. 305 Polish Bomber Squadron ; • Spanish Air Force operated one ex-USAAF example interned in 1944 and operated between 1948 and 1956. ; • Soviet Air Force (Voyenno-Vozdushnye Sily. VVS) received a total of 866 B-25s of the C, D, G*, and J series. * trials only (5). ; • Royal Air Force received just over 700 aircraft. • No. 98 Squadron RAF – September 1942 – November 1945 (converted to the Mosquito • United States Marine Corps ; • Uruguayan Air Force operated 15 aircraft. ; • Venezuelan Air Force operated 24 aircraft. == Accidents and incidents ==
Accidents and incidents
Training mission incident On 1 November 1941, a B-25 on a training mission flying out of Wright-Patterson Air Force Base, crashed near Benton Ridge, Ohio. West Chester B-25 crash On 7 May 1944, a B-25C crashed and exploded around north of West Chester, Pennsylvania, killing all seven military passengers and crew members on board. Caught in stormy weather, the plane nose-dived into the woods at Oaklands Cemetery and burst into flames. Empire State Building crash At 9:40 on 28 July 1945, a USAAF B-25D crashed in thick fog into the north side of the Empire State Building between the 79th and 80th floors. Fourteen people died — 11 in the then world’s tallest building and the three occupants of the aircraft, including the pilot, Colonel William F. Smith. Betty Lou Oliver, an elevator attendant, survived the impact and the subsequent fall of the elevator cage 75 stories to the basement. General Leclerc's aviation accident French general Philippe Leclerc was aboard his North American B-25 Mitchell, Tailly II, when it crashed near Colomb-Béchar in French Algeria on 28 November 1947, killing everyone on board. Lake Erie skydiving disaster A bit after 16:00 on 27 August 1967, a converted civilian B-25 mistakenly dropped eighteen skydivers over Lake Erie, four or five nautical miles (7.5–9.3 km) from Huron, Ohio. The air traffic controller had confused the B-25 with a Cessna 180 Skywagon that was trailing it to take photographs, causing the B-25 pilot to think he was over the intended drop site at Ortner Airport. Sixteen of the jumpers drowned, while two were rescued. A National Transportation Safety Board report faulted the pilot, and to a lesser extent the skydivers, for executing a jump when they could not see the ground, and faulted the controller for the misidentification. The United States was subsequently held liable for the controller's negligence. == Surviving aircraft ==
Surviving aircraft
, of the Canadian Warplane Heritage Museum during the Brantford Air Show at Brantford, Ontario, Canada in 2010 Many B-25s are currently kept in airworthy condition by air museums and collectors. == Specifications (B-25H) ==
Specifications (B-25H)
== Notable appearances in media ==
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