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North American B-25 Mitchell

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Old August 1st 16, 03:32 PM posted to alt.binaries.pictures.aviation
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Default North American B-25 Mitchell


The North American B-25 Mitchell is an American twin-engine, medium bomber
manufactured by North American Aviation (NAA). It was named in honor of Major
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 Mitchells rolled from NAA
factories.[1] These included a few limited models, such as the United States
Marine Corps' PBJ-1 patrol bomber and the United States Army Air Forces' F-10
reconnaissance aircraft and AT-24 trainers.

The Air Corps issued a circular (Number 38-385) in March 1938 describing the
performance they required from the next bombers — a payload of 1,200 lb (540 kg)
with a range of 1,200 mi (1,900 km) at more than 200 mph (320 km/h).[2] Those
performance specifications led NAA to submit their NA-40 design. The NA-40 had
benefited from the North American XB-21 (NA-39) of 1936 which was the company's
partly-successful design for an earlier medium bomber that had been initially
accepted and ordered but then cancelled. However, the company's experience from
the XB-21 contributed to the design and development of the NA-40. The single
NA-40 built flew first at the end of January 1939. It went through several
modifications to correct problems. These improvements included fitting 1,600 hp
Wright R-2600 "Twin Cyclone" radial engines, in March 1939 which solved the lack
of power.

In March 1939, North American delivered the substantially redesigned and
improved NA-40 (as NA-40B) to the United States Army Air Corps for evaluation.
It was in competition with other manufacturers' designs (Douglas 7B, Stearman
X-100, and the Martin Model 167F) but failed to win orders. The aircraft was
originally intended to be an attack bomber for export to the United Kingdom and
France, both of which had a pressing requirement for such aircraft in the early
stages of World War II. However, the French had already opted for a revised
Douglas 7B (as the DB-7). Unfortunately, the NA-40B was destroyed in a crash on
11 April 1939 while undergoing testing. Although the crash was not considered
due to a fault with the aircraft design, the Army ordered the DB-7 as the A-20.

The Air Corps issued a specification for a medium bomber in March 1939: 2,400 lb
(1,100 kg) over 1,200 mi (1,900 km) at 300 mph (480 km/h)[4] 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".

Medium bomber

National origin
United States

North American Aviation

First flight
19 August 1940


1979 (Indonesia)

Primary users
United States Army Air Forces
Royal Air Force
Soviet Air Force
United States Marine Corps

Number built

Developed from
North American XB-21

Developed into
North American XB-28 Dragon

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. The strafer versions
were the B-25C1/D1, the B-25J1 and with the NAA strafer nose, the J2 sub-series.

Flight characteristics

The B-25 was a safe and forgiving aircraft to fly.[17] 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 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 high noise level was due to design and space restrictions in the engine
cowlings which resulted in the exhaust "stacks" protruding directly from the
cowling ring and partly covered by a small triangular fairing. This arrangement
directed exhaust and noise directly at the pilot and crew compartments. Crew
members and operators on the air show circuit frequently commented that "the
B-25 is the fastest way to turn aviation fuel directly into noise".[citation


The Mitchell was an exceptionally 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
high-visibility 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.

Specifications (B-25H)

General characteristics
Crew: 6 (one pilot, one co-pilot, navigator/bombardier, turret gunner/engineer,
radio operator/waist gunner, tail gunner)
Length: 52 ft 11 in (16.13 m)
Wingspan: 67 ft 7 in (20.60 m)
Height: 16 ft 4 in (4.98 m)
Wing area: 610 sq ft (56.7 m²)
Empty weight: 19,480 lb (8,855 kg)
Max. takeoff weight: 35,000 lb (15,910 kg)
Powerplant: 2 × Wright R-2600-92 Twin Cyclone 14-cylinder air-cooled radial
engine, 1,700 hp (1,267 kW) each

Maximum speed: 272 mph (237 kn, 438 km/h) at 13,000 ft (3,960 m)
Cruise speed: 230 mph (200 knots, 370 km/h)
Range: 1,350 mi (1,174 nmi, 2,174 km)
Service ceiling: 24,200 ft (7,378 m)


Guns: 12–18 × .50 in (12.7 mm) machine guns and 75 mm (2.95 in) T13E1 cannon
Hardpoints: 2,000 lb (900 kg) ventral shackles to hold one external Mark 13
Rockets: racks for eight 5 in (127 mm) high velocity aircraft rockets (HVAR)
Bombs: 3,000 lb (1,360 kg) bombs



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