North American B-25 Mitchell

History of the North American B-25 Mitchell

The United States Army Air Corps (USAAC) operated two large medium bombers during World War II (1939-1945) - the Martin B-26 Marauder and the North American B-25 Mitchell. Both were designed during the same pre-war period, with a total production of 5,288 of the former and 9,816 of the latter before the end.

USS Mitchell's legacy was cemented through her service in the 1942 Doolittle Raid, which brought warfare to Japanese soil for the first time. The medium bomber became one of the classic American aircraft of the war, faithfully fulfilling its various roles on the battlefield.

Demand is growing

In the late 1930s, U.S. aircraft manufacturers were forced to deliver a new generation of fighters, bombers, and attack platforms in the face of new threats from Japan, Italy, and Germany. A March 1938 USAAC publication proposed a specification that called for designs capable of speeds in excess of 200 miles per hour, with a range of 1,200 miles and a bomb load of up to 1,200 pounds.

To be sure, the goals for this period are high, but the need to better help the U.S. military (and its allies) respond to new aircraft developments discovered abroad has become increasingly urgent.

XB-21

As early as 1936, North American Aviation (NAA) developed an intermediate bomber "XB-21" for USAAC evaluation. This entry is of the twin-engine type, with each nacelle connected to each wing main aircraft element outside the central fuselage.

The cockpit is layered with a glass nose for navigation/bombardier positions, and the crew consists of up to eight people. The fin contains a vertical fin with the horizontal plane set low. Trailing landing gear is used for ground operations.

Power comes from 2 x Pratt & Whitney R-1280-A "Twin Hornet" turbocharged air-cooled radial piston engines. Defensive armament is centered on a 5 x .30 M1919 caliber air-cooled machine gun, while the internal bomb bay can hold up to 10,000 lbs.

On December 22, 1936, only one prototype XB-21 was completed and flown for $122,000. The XB-21 competed directly with another twin-engine design of the time that was eventually adopted by the USAAC - the Douglas B-18 "Bolo" (detailed elsewhere on this site).

USAAC still had some interest in the XB-21 as they contracted several evaluation models but ended up only completing one form. Bolo continued to do bigger and better things in the pre-war world, with production reaching 350 units, leaving the XB-21 with no role or interested customers.

NA-40

The NA-21, North America's first twin-engine product, gave the company's engineers valuable experience designing, developing and selling fighter jets to the U.S. military. The company is more or less poised to deliver more modern and thorough aircraft over the next few years, and this new initiative ("NA-40") is moving so fast that the modified first flight proves it's already It was late January 1939. Until late March 1939, the aircraft was equipped with more powerful engines to provide a performance boost, and other aspects of its design were improved.

That same month, the current NA-40B was ready for USAAC evaluation and faced competition from designs provided by Douglas, Martin and Stillman. Over the next few weeks, the NA-40B failed to secure its future, and on April 11, 1939, the prototype was doomed to fail in a crash.

NA-62 becomes B-25

North American Airlines, undeterred, went ahead and started shaping the work already done on the NA-40B into the new "NA-62". The NA-62 was designed to meet recent USAAC requirements for a state-of-the-art medium bomber capable of speeds approaching 300 miles per hour, a range of up to 1,200 miles, and a war load of 2,400 pounds.

September 1939 USAAC authorities liked what they saw and committed to NA-62 - War in Europe (World War II) just broke out on September 1, 1939, so there is a sense of urgency now. The NA-62 will enter service with the USAAC as the "B-25" and will operate alongside the competing medium bomber design, the Martin B-26 Marauder (detailed elsewhere on this page).

Production of the new North American bomber increased, and after the completion of the ninth example, the company addressed the stability of its product by adding a negative angle to the outer wing panels (that is, the panels outside the engine nacelles). The surface area of ??the vertical tail has also been increased to improve stability and control.

Early Mitchell tags

The original production form, referred to simply as "B-25", was powered by 2 Wright R-2600-9 radial piston engines, each producing 1,350 hp. The bomb bay could hold up to 3,600 pounds of droppable supplies, and defense was provided by only three .30 caliber machine gunsone in the nose, one in the rump (beam) position, and finally in the ventral side.

A 0.50 caliber heavy machine gun was installed at the tail to better protect the aircraft's more vulnerable tail. Production ended after 24 prototypes, with the fleet serving more or less as a pre-production aircraft until the arrival of the B-25A model.

The B-25A was the first aircraft in the series to be considered combat capable. Better survivability like self-sealing fuel tanks and post-overhaul gunner station have been added to the base form.

However, the brand only achieved a total production of 40 before turning its attention to the upcoming B-25B.

The B-25B was upgraded with a dorsal turret with two guns (2 x .50 cal) and a remote-controlled, retractable ventral turret. Model B was the first authoritative brand in the series, with a production run of 120 units. Some of them were leased to the RAF and used locally under the name "Mitchell Mk.

I".

1942 Doolittle Raid

B-25B aircraft were selected for the famous Doolittle Raid in April 1942, which showed the Japanese that their homeland could be reached from the United States. Just four months after the Japanese attack on Pearl Harbor, 16 Model Bs were used in this daring mission. The bombers were launched from the aircraft carrier USS Hornet.

Of the 80 pilots involved, 69 eventually returned home although 15 of the bombers crashed en route to China.

The Mitchell model continues. .

The B-25C goes live as an improved version of the previous B-25B brand. The engines have now been changed to 2 x Wright R-2600-13 series air-cooled radial piston engines with additional much-needed power. The nose section has been improved by adding 2 x 0.50 cal HMG, making one trainable and the other fixed to prevent frontal attacks. A viewing bubble was provided for the navigator to better illustrate where the bomber was en route, and anti-icing equipment was installed for cold weather.

The Type C quickly differentiated itself from all other Mitchell bombers, with a total of 1,625 aircraft built to standard. Such was its scope that the British, Canadians, Chinese and Dutch were all recipients of this much-needed bombing platform. The British called this new model "Mitchell Mk.

II".

The B-25D was similar to the C model, but its production took place in Kansas City, Kansas (as opposed to Inglewood, California, where all other models came before it). The D-type aircraft was also converted into a photographic reconnaissance platform by installing photographic equipment (3 x K.17 cameras) and operated as an "F-10".

In 1944, at least four D-models were further modified for weather reconnaissance missions.

Developing Mitchell

The XB-25E is a B-25C used as a test bed for more advanced anti-icing/de-icing equipment. XB-25F-A is also used. The XB-25G is a Mitchell modified for an attack helicopter. Its nose is hooded and carries 2 x 0.50 caliber HMGs and a 75mm M4 autocannon for ground attack.

XB-25G successfully tested and led the development of B-25G. Four hundred production models completed this standard. In service, these aircraft carry more armor and fuel reserves to improve survivability and range.

The XB-28 "Dragon" (NA-63) (described elsewhere on this page) is an offshoot of the B-25 program. It was presented to the U.S. Air Force from two completed prototypes as a medium high-altitude bomber to serve over the vast Pacific theater of operations.

The aircraft lost the B-25's signature twin tail rudders, replaced by a single rudder unit. While the XB-28 proved to be a good entry point in testing, it was not adopted due to several factors including the U.S. shift to low-altitude bombing.

B-25H

The B-25H is an improved version of the G model. Added two additional 0.50 cal HMG to the nose. Before long, two sets of cannons were added to the sides of the forward hull, and four more .50 caliber HMGs were added. While these turrets were designed to only fire forward, they were extremely lethal to anyone unlucky enough to get in their way. The dorsal turret was moved forward on the fuselage spine for better visibility.

The original M4 cannon was replaced by the developing T13E1 model. Total production increased by another 1,000 Mitchells.

The B-25H has a crew of six, including two pilots, a navigator (also a bombardier), a turret gunner (also a flight engineer), a radio operator (also a beam gunner), and a rear gunner. Structurally, the aircraft has a barrel length of 52.10 feet, a wingspan of 67.6 feet, and a height of 16.3 feet.

Curb weight is 19,500 lbs and MTOW is 35,000 lbs. Power comes from 2 Wright R-2800-92 "Twin Cyclone" 14-cylinder air-cooled radial piston engines, each producing 1,700 horsepower to drive the three-bladed propellers. Performance includes a top speed of 272 mph, a cruising speed of 230 mph, a range of 1,350 miles and a service ceiling of up to 24,200 feet. Weapons range from 12 to 18 machine guns. 50 caliber and the aforementioned 75mm automatic cannon.

In addition to the traditional ?3,000 internal drop shop, the bomber can also be equipped with external tethers for carrying and releasing Mark 13 series torpedoes. Additionally, the wings can deploy eight 5-inch HVAR missiles for ground/ship attack.

B-25J

The B-25J is a mix of D and H variants and can be used as a medium bomber or attack helicopter. Made in Kansas City, the brand can carry up to 18 forward-facing machine guns for ground attack or for traditional bombing missions. 4,318 were eventually built, around 316 of which were shipped to England, where they were known as "Mitchell Mk. IIIs".

The J model is the most productive Mitchell in the entire family line.

Other Mitchell Forms

The Mitchell line also includes non-combat forms, such as the CB-25J converted into a transport role. Likewise, the VB-25J is also equipped with a military VIP transport role. Through the TB-25 variant family (including TB-25D to TB-25N), the airframe has also proven capable of pilot, bombardier, navigator, gunner and crew trainer.

The US Navy and Marine Corps also used medium bombers in various forms: the PBJ-1C was converted into an anti-submarine platform with a built-in airborne search radar. The PBJ-1J is Navy/Navy built for anti-submarine warfare and carries radar and missiles.

Operators

The B-25 was in service around the world, both during and after the war. Operators range from Argentina and Australia to Uruguay and Venezuela. Brazil, Canada, the Republic of China (Taiwan), France, Poland and the Soviet Union all used bombers of one form or another.

The RAF alone has a role in the story with more than 700 B-25s in nine squadrons.

B-25 in action

The B-25 series proved itself in global combat during World War II. Like other bombers of the time, it could be incredibly punishing and kept in the air. It can fly on one engine and is known for its excellent flight characteristics.

The aircraft is a viable candidate for a large number of approved and unapproved modifications, resulting in a large number of official and unofficial variants. The tricycle landing gear, coupled with the heavy glass and stepped cockpit, provides the pilot with excellent visibility from the cockpit during landing and takeoff.