Click on Picture to enlarge The B-25A

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All Photos And Text Courtesy Of The Air Force Museum

 

 

by Earl Swinhart

 

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North American B-25 Mitchell

Wednesday, July 28, 1943 was a warm day off the island of New Britain in the Bismarck Sea. Three Japanese destroyers were steaming on course 280° over the flat, mirror like water at 20 knots. Suddenly a lookout called "aircraft, low off the port beam!". Another lookout identified the planes as American B-25 bombers, notorious for their "skip bombing" against destroyers. All guns were trained on the interlopers. Suddenly, while the aircraft were still more than a mile (1.6 km) away, a great geyser of water shot up close by the destroyers. The lookouts began frantically searching the sea; there had to be a ship close by with cannon aboard. But there was none! Suddenly, one of the destroyers was hit. It exploded in flames and sank in just a few minutes. Was it possible these aircraft had some new and diabolical weapon?

On the contrary; it was the very same old 75 mm M-4 field cannon used to rout the Germans in WW1! A few months before the incident, Colonel Paul Gunn of the US Fifth Air Force in Australia, had experimented with the installation of a 20 mm cannon in the nose of a B-25. Colonel Gunn, abetted by a North American Aviation Company Tech Rep named Jack Fox, sent the idea to North American in Inglewood, California where it was promptly taken a step further and worked into the installation of the 75 mm cannon.

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B-25

General George Kenney called the North American B-25 Mitchell a "War Dog". He should know; he helped write the book on the B-25. General Kenney was commander of the Fifth Air Force in the South Pacific during WWII. Trying to fight off the Japanese in a "secondary combat theater" (as the Pacific war was regarded) meant "making do, with what you had". Prosecuting the war against Japan called for a lot of ingenuity. Kenney was forced to use what he could scrape together and make effective. He came up with the ideas and "Pappy" Gunn put the ideas to work. One of the first ideas was the installation of a machine gun "pack". The bombardiers compartment was removed and replaced with four .50 cal (12.7 mm) machine guns in the nose of the Mitchell and four more in blisters on the sides of the craft. The B-25 became an awesome strafing machine with eight forward firing guns. Later, they rigged a lock for the top turret making a total of ten .50 cal (12.7 mm) machine guns, all lit off simultaneously by one finger of the pilot!

Then came the installation of the 75 mm cannon. It required a crewman to load, fire and extract the casing. And when it fired it felt like the aircraft had "hit a brick wall", but with its 2.95 inch (75 mm) projectile, it could turn a tank into scrap metal and punch very large holes in Japanese destroyers and barges at a range of nearly 2 miles. The Japanese paid dearly for the ideas of Kenney and the ingenuity of Gunn.

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Take off from the deck of the USS HORNET of an Army B-25 on its way to take part in first U.S. air raid on Japan. Doolittle Raid, April 1942.

The North American B-25 Mitchell owed its beginnings to the Army's quest for a medium bomber. The B-18 "Bolo" was designed and built by Douglas Aircraft in 1937 and North American responded to this by designing and building the larger and more powerful B-21 "Dragon" that same year. Both of these aircraft were twin engine "tail dragger" types. Unsatisfied with performance only marginally better than single engine aircraft, the US Army Air Corps issued Proposal Circular #38-385 which was sent to all major aircraft manufacturers in March 1938. It contained the requirements for an "Aircraft - Bombardment Type - Medium". This would fill a gap in the bombing aircraft types between the light bomber and four engine heavy bomber. A total of 5 manufacturers submitted designs (North American, Douglas, Martin, Stearman and Bell) and all but one built prototypes. North American submitted their "Design NA-40" to the USAAC and shortly afterward built the NA-40B prototype. It was a sleek looking twin engine, twin tail machine with tricycle landing gear, not unlike the B-25 and fairly bristling with .30 Cal. (7.62 mm) machine guns. Unfortunately, while undergoing simulated "engine out" tests, the pilot lost control and the aircraft crashed. The pilot and crew escaped with minor injuries but the NA-40B was destroyed by fire and North American was disqualified, though the Army deemed the accident caused by pilot error and not by anything inherent in the design of the NA-40B. That left only 3 prototypes competing and shortly, one of these also crashed and burned (the Douglas 7B) and was disqualified, leaving less than half the original bidders still competing. The USAAC ruled no contest, and though Glenn Martin raised vigorous objections, new bids were ordered to be submitted in April, 1939.

The result from North American was a dramatically updated NA-40, redesignated the NA-62. The design was much more streamlined with the rear of the "greenhouse" canopy neatly faired into the fuselage (instead of the "upside down bathtub" of the NA-40), forming a straight line from the top of the windshield to the tail assembly. On August 10, the design was accepted by the USAAC as the B-25 and ordered into production straight off the drawing board, something not often done with new aircraft. The B-25 was fitted with two turbo supercharged Wright R-2600 Cyclone radial engines and though the dash numbers changed and modifications were made to it, the supercharged R-2600 Cyclone was standard through the final production model which was the B-25J.

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A landing gear, ready for assembly on a B-25 bomber, is rolled into place on the final assembly line of North American's Inglewood, Calif. plant.

The NA-62 had been designed with a noticeable dihedral to the wings, as were the first nine B-25s. Starting with the tenth aircraft, the outer wing panels were made horizontal to enhance stability and this modification gave the Mitchell its distinctive frontal silhouette. A total of twenty-four B-25s were built before the B-25As came into production.

The B-25A was a bit more suited for combat than its predecessor, having self sealing fuel tanks and crew armor. However, most of the "A"s never saw combat but were used by the Army for coastal patrol and reconnaissance. Though the "A" had more armor, it was considered obsolete in a very short time because of its lack of provisions for self defense. A single thirty caliber (7.62 mm) machine gun was located at the waist and could be plugged into a ball socket on either side, another .30 cal. (7.62 mm) in the nose and one fired from a sockets in the top of the fuselage. Because of the opinion that most attacks would come from the rear, the prone tail gunner operated a .50 cal. (12.7 mm) machine gun. Forty B-25As were built by the end of production in August, 1941.

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Canadian B-25 Mitchell

At 8:20 AM on Saturday, April 18, 1942 the US Navy’s new carrier Hornet was approximately 650 miles (1,046 km) east of Tokyo, Japan, heading; 270°, speed; 20 knots (37 km/h). The original destination of the carrier was a launch point approximately 450 miles (724 km) east of Tokyo. But plans went awry earlier that morning when a Japanese picket boat (the "Nitto Maru" ) spotted them and sent a radio message to Tokyo. Though the message either was not received, or was ignored in Tokyo, the Americans had no way of knowing this. The aircraft were ordered launched immediately despite the fact they were 200 miles (322 km) further from the target than planned. Admiral William "Bull" Halsey aboard his flagship Enterprise had been informed of the message sent by the Nitto Maru. He couldn’t risk exposing the thin skinned carriers to a possible assault by a Japanese battlewagon, so he immediately flashed a message to the Hornet: "Launch Planes. To Colonel Doolittle and his gallant command Good Luck and God bless you". Intermittent rain squalls swept the flight deck and the sound of the Wright Cyclone engines warming up reverberated amongst the ships of Task Force 16. To an outside observer this would have appeared to be a standard naval combat mission except for two items: (1) This occurred a mere 4½ months after the Pearl Harbor disaster, and no one in their wildest dreams could have expected the US Navy to be able to attack Japan so soon. And: (2) These were definitely not naval aircraft thundering down the deck of the Hornet. They were US Army twin engine bombers!

The Doolittle raid was carried out by sixteen B-25B aircraft. The "B" was built with the advantage of a degree of combat experience. Dorsal and ventral gun turrets, each housing twin .50 cal. (12.7 mm) M-2 Browning machine guns were installed just behind the bomb bay. The .30 cal. (7.62 mm) was retained in the nose position. The tail gunners position was eliminated and an observers station installed. Although the turrets adversely affected the top speed of the B, firepower was greatly improved.

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Under the close supervision of a foreman, a new engine assembly is installed in a B-25 bomber at North American's Inglewood. Calif., plant.

The B-25C was an accumulation of the combat experience and the suggestions of the crews. The navigator had a new sighting blister installed in the roof just behind the pilots greenhouse. The bombardier received considerably more firepower in the form of a flexible .50 cal (12.7mm) M-2 to replace the .30 cal (7.62 mm) , and a fixed, forward firing .50 cal (12.7 mm) in the nose. Thereafter, all machine guns on this and succeeding models were .50 cal (12.7 mm) M-2 Colt-Brownings. Improvements in the trusty Cyclone engines were made with the installation of Holley carburetors and air filters. A new 24 volt electrical system replaced the 12 volt of earlier models. There were anteing provisions for the leading edges of the craft and fuel capacity was increased. The "C" was in reality the first mass produced Mitchell with over 1,600 copies rolling off the production lines. Many of the improvements found on later models were first tested on a "C".

The B-25D was identical to the "C", the only difference being the "D" was manufactured at the North American plant in Kansas City instead of the plant in Inglewood, California.

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Part of the cowling for one of the motors for a B-25 bomber is assembled in the engine department of North American's Inglewood, Calif. plant.

There was only one copy each of the "E" and "F" models. They were both taken directly off the "C" production line and used solely for the purpose of testing new anteing and de-icing equipment.

The first B-25G was serial #41-13296 which was taken off the "C" line and modified for the 75 mm M-4 cannon installation. The greenhouse nose was removed and replaced with a solid nose equipped with a pair of fixed, forward firing M-2 machine guns and the 75 mm M-4 cannon which ran under the pilots seat. Behind the pilot a gunner loaded, fired and extracted the empty shell casings. Twenty-one rounds were carried for the cannon. Armor was added to protect the gunner and the cannon rounds. Five of the "C"s were modified to the "G" configuration for testing before the production line started turning out "G"s. About 1,400 B-25Gs were produced.

The B-25H was considerably improved over the "G". The top Bendix turret was moved from behind the bomb bay forward to a position previously occupied by the navigator. The navigator was moved forward to the position of the cannon which was upgraded to the newer and lighter 75 mm model T13E1. The navigator acquired the duty of loading and firing the cannon in addition to his function as navigator and radio operator. Two additional M-2s were placed in the nose for a total of 4. The bottom turret was eliminated and replaced with an M-2 on each side in the waist position. Two more were placed in a power operated tail position.

The B-25J reverted to the greenhouse bombardier nose of the "C" model, but with far more firepower. Some variants had as many as 14 forward firing M-2 machine guns in front and four more at various other stations in the craft. The 75mm cannon was removed and a bombardier was again added as the sixth crewman. B-25Js were by far the largest production run of the Mitchell bomber with more than 4,300 copies delivered before the war ended and production lines of the B-25 were shut down for good.

Other aircraft were larger, faster, "prettier" and produced in greater quantities. But none could surpass the colorful career of the North American B-25 Mitchell bomber.

 

 The Aviation History On-Line Museum.

 

The B-25 & The Empire State Building

 

 

The North American B-25

 

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North American B-25 Mitchell taking-off or landing. Note the Canadian markings, and the Squadron's emblem under the cockpit window

North American B-25 Mitchell during the last stages of landing.

North American B-25 Mitchell in full flight (looks like it's an original War color photo)

The North American B-25 Mitchell was a compact and powerful puppy, used for tactical bombing. The Mitchell was named after the USAAC Colonel 'Billy' Mitchell, who was court-martialed in the 1920's because of his insistence with respect to tactical and strategic bombing.

The type originates in 1938, when North American gambled that the US Army Air Corps’ circular proposal of January for a three-seat twin-engine attack bomber would soon lead to a full requirement for a medium attack bomber, and started work as a private venture on its NA-40 design that was evolved under the design leadership of R.H.Rice.

The NA-40 was based on an all-metal structure combining a semi-monocoque fuselage and cantilever stressed-skin flying surfaces, and in configuration was a monoplane with a rectangular-section fuselage with rounded corners, a high-set tail unit with endplate vertical surfaces, shoulder-set dihedral wing that was tapered in thickness and chord and carried on its trailing edge the standard combination of outboard ailerons and inboard flaps, and tricycle landing gear whose single nose and twin main units retracted respectively into the underside of the forward fuselage and the underside of the nacelles for the two wing-mounted engines. Initially these engines were 2 × Pratt & Whitney R-1830-56C3-G Twin Wasp radials, rated at 1,100 hp (820 kW) for take-off each. Provision was made for a disposable weapons load in a lower-fuselage weapons bay, and the gun armament comprised 7 × 0.3 inch (7,62 mm) Browning machine guns installed as four fixed forward-firing weapons in the wing leading edges outboard of the engine nacelles, one trainable forward-firing weapon in the glazed nose position, one trainable rearward-firing machine gun in the dorsal position, and one trainable rearward-firing weapon in the ventral tunnel position.

The NA-40 prototype made its maiden flight in January 1939, and in that month the USAAC announced a requirement for a new attack bomber. The requirement called for design submissions to be made by July 1939, and North American decided to revise the NA-40 into the NA-40B (otherwise NA-40-2) with a powerplant of 2 × Wright GR-2600-A71 Cyclone 14 radial, rated at 1,500 hp (1118 kW) for take-off and 1,275 hp (951 kW) at 12,000 ft (3660 m) each, and driving a three-blade Hamilton Standard metal propeller of the constant-speed type. North American delivered the NA-40B for trials in March 1939, but the aeroplane was lost in an accident only two weeks later. The type ordered to satisfy the attack bomber requirement was the Douglas Model 7 that was ordered as the A-20. Nevertheless, the NA-40B had impressed the USAAC, and when the service issued a March 1939 circular proposal for a five-seat medium bomber North American was well placed to respond with its NA-62 design evolved from the NA-40B. The various submissions were evaluated from July 1939, and the USAAC then contracted with North American for ‘off the drawing board’ production of 184 B-25 aircraft of the NA-62 type that was basically the NA-40B with a wider fuselage that allowed a doubling of the weapons load to 3,600 lb (1633 kg), the wing moved down to the mid-set position that permitted the upper line of the fuselage to be straightened, the powerplant changed to 2 × R-2600-9 radial, rated at 1,700 hp (1.267,5 kW) for take-off and 1,350 hp (1.007 kW) at 13,000 ft (3.960 m) each, and supplied with fuel from an internal capacity of 759 Imp gal (912 US gal, 3.452 liters), the crew increased from three to five, and the defensive armament altered to one 0.5 inch (12,7 mm) Browning trainable rearward-firing machine gun operated by a prone gunner in the tail position, two 0.3 inch (7,62 mm) Browning trainable lateral-firing machine guns in single-gun beam positions operated by waist gunners, and one 0.3 inch (7,62 mm) Browning trainable forward-firing machine gun in any of three nose positions operated by the bombardier.
The B-25 initial production model was used a a service trials type, and deliveries amounted to 24 NA-62 aircraft that were delivered from February 1941 after a first flight in August 1940. The type revealed a lack of directional stability, and from the 10th aircraft onward was delivered with the flat outer wing panels that gave the Mitchell its final and highly distinctive gull-wing appearance.

Technical data on the North American B-25C Mitchell
Powerplant	2 × Wright R-2600-13 radial, rated at 1700 hp (1267.33 kW) each		Role during war	(Ground) Attack Fighter Medium Bomber U-boat Destroyer Maritime/Coastal patrol reconnaissance Bomber Anti-shipping Aircraft
Length	52 ft 11 inch		Height	15 ft 9 inch
Empty weight	20000 lb		Operational weight	26208 lb typical, 28460 lb max
Wing Span	67 ft 7 inch		Wing Aspect ratio	7.49
Wing Area	610 sq ft		Service ceiling	21200 ft
Maximum speed	284 mph at 15000 ft		Cruising speed	233 mph at optimum altitude
Initial climb rate	Climb to 15,000 ft in 16 min 30 sec		Range	1500 miles typical
Fuel capacity internal	811 Imp gal (974 US gal), plus provision for a weapons-bay mounted tank of 487 Imp gal (585 US gal) of auxiliary fuel that could be dropped		Fuel capacity external	-
Machine guns	2 × 0.50 inch Browning trainable in a power operated dorsal Bendix turret, 400 rounds each 2 × 0.50 inch Browning trainable in a power operated retractable ventral Bendix turret, 350 rounds each 1 × 0.3 inch Browning trainable forward-firing in the nose, 600 rounds		Cannons	-
Bomb load	Up to 3,200 lb, carried in a under fuselage weapons bay rated at 3,200 lb. General disposables load consisted of: 1 × 2,000 lb bomb, or 2 × 1,600 lb bombs, or 3 × 1,000 lb bombs, or 6 × 500 lb bombs, or 8 × 250 lb bombs, or 12 × 100 lb bombs		Torpedoes/rockets	-
Crew	5: pilot, navigaotr/radio operator, flight engineer/gunner, gunner/camera operator, gunner		Naval or ground based	Ground
First flight (prototype)	January 1939		Operational Service	1941 - 1960's
Manufacturer	North American Aviation, Inc		Number produced	9.817 total, 1.619 this version

Metric system
Length	16.13 m		Height	4.8 m
Empty weight	9072 kg		Operational weight	11888 kg typical, 12909 kg max
Wing Span	20.6 m		Wing Aspect ratio	7.49
Wing Area	56.67 m²		Service ceiling	6462 m
Maximum speed	457 km/h at 4572 m		Cruising speed	375 km/h at optimum altitude
Initial climb rate	Climb to 4.570 m in 16 min 30 sec		Range	2414 km typical
Fuel capacity internal	3.687 liters, plus provision for a weapons-bay mounted tank of 2.214 liters of auxiliary fuel that could be dropped		Fuel capacity external	-
Machine guns	2 × 12,7 mm Browning trainable in a power operated dorsal Bendix turret, 400 rounds each 2 × 12,7 mm Browning trainable in a power operated retractable ventral Bendix turret, 350 rounds each 1 × 7,62 mm Browning trainable forward-firing in the nose, 600 rounds		Cannons	-
Bomb load	Up to 1.452 kg, carried in a under fuselage weapons bay rated at 1.452 kg. General disposables load consisted of: 1 × 907 kg bomb, or 2 × 726 kg bombs, or 3 × 454 kg bombs, or 6 × 227 kg bombs, or 8 × 113 kg bombs, or 12 × 45 kg bombs		Torpedoes/rockets	-

Technical data on the North American B-25H Mitchell
Powerplant	2 × Wright R-2600-13 radial, rated at 1700 hp (1267.33 kW) each		Role during war	(Ground) Attack Fighter Medium Bomber U-boat Destroyer Maritime/Coastal patrol reconnaissance Bomber Anti-shipping Aircraft
Length	51 ft 0 inch		Height	15 ft 9 inch
Empty weight	19975 lb		Operational weight	36047 lb max
Wing Span	67 ft 7 inch		Wing Aspect ratio	7.49
Wing Area	610 sq ft		Service ceiling	23800 ft
Maximum speed	275 mph at 13000 ft		Cruising speed	230 mph at optimum altitude
Initial climb rate	Climb to 15,000 ft in 19 min 0 sec		Range	2700 miles max
Fuel capacity internal	811 Imp gal (974 US gal), plus provision for up to 591 Imp gal (710 US gal) of auxiliairy fuel in a 487 Imp gal (585 US gal) weapons-bay mounted tank that could be dropped and a 104 Imp gal (125 US gal) waist tank		Fuel capacity external	-
Machine guns	4 × 0.50 inch Browning fixed forward-firing, two on each side of the nose 2 × 0.50 inch Browning trainable in a power operated dorsal Bendix turret, 400 rounds each 2 × 0.50 inch Browning trainable rearward-firing in the tail position 2 × 0.50 inch Browning trainable lateral-firing, one in each of the beam positions		Cannons	1 × 2.95 inch T13E1 fixed forward-firing in the port lower side of the nose.
Bomb load	Up to 5,400 lb, carried in a under fuselage weapons bay rated at 3,000 lb and on four underwing hardpoints rated at 600 lb each. General disposables load consisted of: free-fall bombs		Torpedoes/rockets	8 × 5 inch air-to-surface rockets in stead of external bombs 1 × 2,150 lb torpedo in stead of internal load
Crew	5: pilot, navigaotr/radio operator, flight engineer/gunner, gunner/camera operator, gunner		Naval or ground based	Ground
First flight (prototype)	January 1939		Operational Service	1941 - 1960's
Manufacturer	North American Aviation, Inc		Number produced	9.817 total, 1.000 this version

Metric system
Length	15.54 m		Height	4.8 m
Empty weight	9061 kg		Operational weight	16351 kg max
Wing Span	20.6 m		Wing Aspect ratio	7.49
Wing Area	56.67 m²		Service ceiling	7254 m
Maximum speed	443 km/h at 3962 m		Cruising speed	370 km/h at optimum altitude
Initial climb rate	Climb to 4.570 m in 19 min 0 sec		Range	4345 km max
Fuel capacity internal	3.687 liters, plus provision for up to 2.687 liters of auxiliairy fuel in a 2.214 liters weapons-bay mounted tank that could be dropped and a 473 liters waist tank		Fuel capacity external	-
Machine guns	4 × 12,7 mm Browning fixed forward-firing, two on each side of the nose 2 × 12,7 mm Browning trainable in a power operated dorsal Bendix turret, 400 rounds each 2 × 12,7 mm Browning trainable rearward-firing in the tail position 2 × 12,7 mm Browning trainable lateral-firing, one in each of the beam positions		Cannons	1 × 75 mm T13E1 fixed forward-firing in the port lower side of the nose.
Bomb load	Up to 2.449 kg, carried in a under fuselage weapons bay rated at 1.361 kg and on four underwing hardpoints rated at 272 kg each. General disposables load consisted of: free-fall bombs		Torpedoes/rockets	8 × 127 mm air-to-surface rockets in stead of external bombs 1 × 975 kg torpedo in stead of internal load

Technical data on the North American B-25J Mitchell
Powerplant	2 × Wright R-2600-92 radial, rated at 1850 hp (1379.16 kW) each		Role during war	(Ground) Attack Fighter Medium Bomber U-boat Destroyer Maritime/Coastal patrol reconnaissance Bomber Anti-shipping Aircraft
Length	52 ft 11 inch		Height	15 ft 10 inch
Empty weight	21100 lb		Operational weight	33500 lb typical, 41800 lb max
Wing Span	67 ft 7 inch		Wing Aspect ratio	7.49
Wing Area	610 sq ft		Service ceiling	24200 ft
Maximum speed	272 mph at 13000 ft		Cruising speed	230 mph at optimum altitude
Initial climb rate	1,110 ft per minute		Range	1275 miles typical
Fuel capacity internal	811 Imp gal (974 US gal), plus provision for up to 591 Imp gal (710 US gal) of auxiliairy fuel in a 487 Imp gal (585 US gal) weapons-bay mounted tank that could be dropped and a 104 Imp gal (125 US gal) waist tank		Fuel capacity external	-
Machine guns	2 × 0.50 inch Browning fixed forward-firing, on the (port?) side of the nose 1 × 0.50 inch Browning trainable forward-firing in the nose 8 × 0.50 inch Browning fixed forward-firing, in the nose in stead of the former two gun positions (solid nose configuration) 2 × 0.50 inch Browning trainable in a power operated dorsal Bendix turret, 400 rounds each		Cannons	-
Bomb load	Up to 2,000 lb, carried in a under fuselage weapons bay rated at 2,000 lb. General disposables load consisted of: 1 × 2,000 lb bomb		Torpedoes/rockets	8 × 5 inch air-to-surface rockets 1 × 2,000 lb torpedo in stead of internal load
Crew	6: pilot, navigaotr/radio operator, flight engineer/gunner, gunner/camera operator, 2 gunners		Naval or ground based	Ground
First flight (prototype)	January 1939		Operational Service	1941 - 1960's
Manufacturer	North American Aviation, Inc		Number produced	9.817 total, 4.318 this version

Metric system
Length	16.13 m		Height	4.83 m
Empty weight	9571 kg		Operational weight	15196 kg typical, 18960 kg max
Wing Span	20.6 m		Wing Aspect ratio	7.49
Wing Area	56.67 m²		Service ceiling	7376 m
Maximum speed	438 km/h at 3962 m		Cruising speed	370 km/h at optimum altitude
Initial climb rate	338 m per minute		Range	2052 km typical
Fuel capacity internal	3.687 liters, plus provision for up to 2.687 liters of auxiliairy fuel in a 2.214 liters weapons-bay mounted tank that could be dropped and a 473 liters waist tank		Fuel capacity external	-
Machine guns	2 × 12,7 mm Browning fixed forward-firing, on the (port?) side of the nose 1 × 12,7 mm Browning trainable forward-firing in the nose 8 × 12,7 mm Browning fixed forward-firing, in the nose in stead of the former two gun positions (solid nose configuration) 2 × 12,7 mm Browning trainable in a power operated dorsal Bendix turret, 400 rounds each		Cannons	-
Bomb load	Up to 907 kg, carried in a under fuselage weapons bay rated at 907 kg. General disposables load consisted of: 1 × 907 kg bomb		Torpedoes/rockets	8 × 127 mm air-to-surface rockets 1 × 907 kg torpedo in stead of internal load

 

 

Here is a quick overview of all different versions, without the full technical specifications:

Different versions of the North American B-25  Mitchell
North American NA-40/NA-62 prototypes	In 1938 North American decided to enter a competition for a three-seat twin-engined attack bomber. This was a big step for North American, since it was familiar with single-engined trainers, not twin-engined attack aircraft or bombers. Nevertheless, the resulting design had merits, but in the end had to concede to the Douglas Model 7, also known as the Douglas A-20 Havoc/Douglas Boston. Nevertheless, North American was now ready to enter a competition for an advanced tactical medium bomber. Based on the experience gained, an new requirements for the new aircraft several features were changed. The new prototype to emerge was designated NA-62 by North American, and differed from the preceding prototypes NA-40 and NA-40B with respect to: a wider fuselage to enable a greater war load, the wing moved down from high-set to the mid-set position to straigthen the upper line of the fuselage, changed powerplant from 2 × Wright GR-2600-A71 Cyclone 14 radials to 2 × Wright R-2600-13 radials, the crew increased from three to five, the fuel capacity increased to 759 Imp gal (912 US gal, 3.452 liters) and improved/increased guns armament (offensive and defensive). this type was ordered 'off the drawing board', and an order for 24 service trials aircraft was placed by the USAAC Number built: 3
North American B-25	The initial version of the B-25 was identical to the NA-62 prototype. Service trials with the aircraft showed a lack in directional stability, and from the 10th aircraft onwards all Mitchells with the flat outer wing panels that give the wings a gull-shaped apearance. Number built: 24
North American B-25A	This first updated version was modified to suit operational needs in the European Theatre. Changes include protective armor for the crew, and a revised fuel system that comprised four self-sealing tanks in the wings for 578 Imp gal (694 US gal, 2627 liters) of fuel that could be supplemented by an additional 348 Imp gal (418 US gal, 1.582 liters) of fuel in a droppable tank carried in the weapons bay. Other technical details include: a length of 54 ft 1 in (16,485 m), empty weight of 17,870 lb (8.105 kg), normal take-off weight of 25,322 lb (11.486 kg), max take-off weight of 27,100 lb (12.293 kg), max level speed of 315 mph (507 km/h) at 15,000 ft (4.570 m), typical range of 1,350 miles (2.172 km) with a weapons load of 3,000 lb (1.361 kg), climb to 15,000 ft (4.570 m) in 8 minutes 24 seconds, and a service ceiling of 27,000 ft (8.230 m). Number built: 40
North American B-25B	The original contract was signed for 184 aircraft, and the B-25B fulfilled the remainder of the batch which started with the B-25. This version saw the addition of power-operated Bendix turrets, each armed with 2 × 0.50 inch (12,7 mm) Browning trainable guns. The dorsal turret had 400 rounds for each gun, the retractable ventral turret had 350 rounds for each gun. The single 0.3 in (7,62 mm) Browning trainable gun in the nose was retained, but the 0.50 inch (12,7 mm) in the tail was removed. Other technical details include: a length of 52 ft 11 in (16,13 m), empty weight of 20,000 lb (9.072 kg), normal take-off weight of 26,208 lb (11.888 kg), max take-off weight of 28,460 lb (12.909 kg), max level speed of 300 mph (483 km/h) at 15,000 ft (4.570 m), typical range of 1,350 miles (2.173 km) with a weapons load of 3,000 lb (1.361 kg), and a service ceiling of 23,500 lb (10.660 m). Number built: 120
North American B-25C Mitchell	This version was the first to officially receive the name Mitchell. Also it was the first version to be built in large numbers. It was based on the B-25B, and changes were made only on the 'inside' of the aircraft: it had the same external features and armament, but it's electrical system was chenged from a 12-Volt to a 24-Volt system. The powerplant was changed to 2 × Wring R-2600-13 radials, rated at at 1,700 hp (1.268 kW) for take-off and 1,400 hp (1.044 kW) at 13,000 ft (3.960 m) each, and driving a three-blade Hamilton Standard metal propeller of the constant-speed type. From the 384th aircraft onward there was additional fuel tankage, and the weapons bay was revised to enable the B-25 to carry greater loads and heavier bombs. Apart from the standard B-25C Mitchel, several blocks were built: B-25C-1 Mitchell Starting with the 606th aircraft, 258 aircraft were delivered with provision for external racks that allowed the Mitchell to carry a 2,000 lb (907 kg) torpedo under the fuselage instead of the internally carried bombs (although the weapons bay could still carry the jettisonable auxiliary fuel tank) or 8 × 250 lb (113 kg) bombs under the wings in addition to the internally carried bombs, thereby increasing the maximum possible disposable load from 3,200 lb (1.452 kg) to 5,200 lb (2.359 kg) on short-range missions. Another change was the replacement of the bombardier’s 0.3 in (7,62 mm) Browning machine gun by a 0.5 inch (12,7 mm) Browning trainable forward-firing machine guns with 300 rounds, B-25C-5 Mitchell 162 examples of the B-25C-5 Mitchell (NA-92 originally ordered in June 1941 by the Netherlands) that followed between October and December 1942 the pilot was provided with a 0.50 inch (12,7 mm) Browning fixed forward-firing machine gun with 300 rounds on the starboard side of the nose. B-25C-10 Mitchell 150 examples of the B-25C-10 Mitchell (NA-94) were destined for the UK under the Lend-Lease Act, and had an improved compass and better winterisation equipment. B-25C-15 Mitchell 150 examples of the B-25C-15 Mitchell (NA-93) were destined for China under the Lend-Lease Act appeared in January 1943, and were fitted with individual flame-damped exhausts. B-25C-20 Mitchell 200 examples of the B-25C-20 Mitchell (NA-96), a variant basically similar to the B-25C-15 were not bought under the Lend-Lease Act, but had been ordered by the USAAC for its own use. B-25C-25 Mitchell 100 aircraft were built according to the B-25C-25 Mitchell standard that differed from the B-25C-20 in having a 192 Imp gal (230 US gal, 871 liter) self-sealing fuel tank in the weapons bay, and provision for a 270.6 Imp gal (325 US gal, 1230 liter) auxiliary tank carried in the weapons bay. Number built: 1.619
North American B-25D Mitchell	An initial order for 1,200 B-25D (NA-87) bombers, identical in all respects to the early-production B-25C, was placed with a new bomber production plant established in Kansas City facility in June 1941. this facility was part of a bigger production plan empowered and set in motion by the US government in December 1940. The idea was to create additional production capacity in the less industrialised mid-west, where the new plants could tap in new sources of workers, and spreading the work in stead of concentrating it on the East and West coasts. Inglewood, the original North American production facility for the B-25, provided knock-down kits for the first six aircraft and then all the detail parts for the following 94 as a means of kick-starting Kansas City production, and the first of these aircraft was delivered in February 1942. From the 10st aircraft parts from the Fisher Body Division (a General Motors Corporation Division) were used, outer wing panels and fuselage side panels from this source being added to assemblies produced in Kansas City. The first 200 B-25D aircraft were basically similar to the B-25C with the exception of provision for 104 Imp gal (125 US gal, 473 liters) of auxiliary fuel in a waist tank for a maximum range of 2,650 miles (4265 km), but from November 1942 there followed a number of blocks that deviated from this standard: Number built: 2.290
North American B-25G Mitchell	Delivered to the extent of 405 aircraft including five B-25C conversions, this NA-96 variant was a dedicated anti-ship model evolved for use in the Pacific theater with a four-man crew and a 75 mm (2.95 in) M4 gun installed in the nose, where it was complemented by 2 × 0.50 inch (12,7 mm) Browning fixed forward-firing machine guns, 400 rounds each. Also, four ‘package’ guns on the sides of the forward fuselage augmented the offensive gun armament. The last 221 aircraft omitted the ventral turret, which was deemed superfluous for the low-level anti-ship role. The type was not notably successful because of the weight of the 75 mm (2.95 in) gun installation, in the lower port side of the forward fuselage, and the slow rate at which the 20 lb (9,1 kg) shells, carried in a 21-round tray, could be loaded by hand. The B-25G had the same powerplant, dimensions and weights as the B-25C, but differed in details such as: max level speed of 281 mph (452 km/h) at 15,000 ft (4.570 m) declining to 268 mph (431 km/h) at sea level, max range of 2,200 miles (3541 km) with auxiliary fuel, typical range of 1.525 miles (2.454 km) with a weapons load of 3,000 lb (1.361 kg), and a service ceiling of 24,300 ft (7405 m). Number built: 400 plus 5 conversions
North American B-25H Mitchell	The NA-98 was a development of the B-25G with a five-man crew, the lighter 75 mm (2.95 in) T13E1 gun, 8 × 0.50 inch (12,7 mm) Browning fixed forward-firing machine guns (four in the nose and four on the fuselage sides), 6 × 0.50 inch (12,7 mm) Browning trainable machine guns (two weapons each in the dorsal and tail positions and single weapons in the two beam positions), provision for 3,000 lb (1.361 kg) of bombs in the weapons bay, and provision for 8 × 5 inch (127 mm) air-to-surface rocket under the wings. Even the 8 rockets alone were said to be equal to the broadside salvo of a destroyer, so you can imagine the huge firepower of this version. Number built: 1.000
North American B-25J Mitchell	This final (production) version of the Mitchell was a reversion to the medium-bomber role, as opposed to the attack aircraft role it's predecessors more or less had. The NA-108 was a six-crew development of the B-25H with a glazed nose carrying one trainable and two fixed forward-firing 0.50 inch (12,7 mm) Browning machine guns. The dorsal turret was moved farther forward to a position just to the rear of the flightdeck, and the first 150 aircraft were completed with provision for a 2,000 lb (907 kg) bomb or torpedo. Many of the aircraft were later adapted with a ‘solid’ nose accommodating a fixed forward-firing battery of 8 × 0.50 inch (12,7 mm) Browning machine guns, again more suited for the Attack aircraft role.. Number built: 4.318
North American AT-24A Mitchell	An number of B-25D Mitchells were converted to act as crew trainers Number converted: unknown out of 60
North American AT-24B Mitchell	An number of B-25G Mitchells were converted to act as crew trainers Number converted: unknown out of 60
North American AT-24C Mitchell	An number of B-25C Mitchells were converted to act as crew trainers Number converted: unknown out of 60
North American AT-24D	An number of B-25J Mitchells were converted to act as crew trainers Number converted: unknown out of 60
North American CB-25J Mitchell	Conversion of B-25J Mitchells, used as utility transport. Number converted: unknown
North American RB-25D Mitchell	Redesignation of the F-10 Mitchell Redesignated aircraft
North American TB-25C Mitchell	Redesignation of the AT-24C Mitchell Redesignated aircraft
North American TB-25D Mitchell	Redesignation of the AT-24A Mitchell Redesignated aircraft
North American TB-25G Mitchell	Redesignation of the AT-24B Mitchell Redesignated aircraft
North American TB-25J Mitchell	Redesignation of the AT-24D Mitchell Redesignated aircraft
North American TB-25K Mitchell	Conversion from B-25J aircraft for training purposes for the E1 radar fire-control system Number converted: 117
North American TB-25L Mitchell	Conversion from B-25J aircraft for training purposes for pilots Number converted: 90
North American TB-25M Mitchell	Conversion from B-25J aircraft for training purposes of operators in the E5 radar fire-control system Number converted: 40
North American TB-25N Mitchell	Conversion from B-25J aircraft for training purposes for pilots, slightly differeing from the TB-25L Mitchell. Number converted: 47
North American VB-25J Mitchell	Conversion from B-25J aircraft to be operated as staff transport. Number converted: unknown
North American F-10	This designation was accorded to 10 examples of the B-25D which were converted as photo-reconnaissance aircraft with additional fuel and a three-camera installation in the chin and ventral positions for trimetrogon photography. Number converted: 10
North American PBJ-1C	This designation was accorded to 50 B-25C aircraft transferred to the US Navy for use in the patrol bomber role. Number transferred: 50
North American PBJ-1D	This designation was accorded to 152 B-25D aircraft transferred to the US Navy for use in the patrol bomber role. Number transferred: 152
North American PBJ-1G	This designation was accorded to one B-25G aircraft transferred to the US Navy for use in the patrol bomber role. Number transferred: 1
North American PBJ-1H	This designation was accorded to 248 B-25H aircraft transferred to the US Navy for use in the patrol bomber role. Number transferred: 248
North American PBJ-1J	This designation was accorded to 255 B-25J aircraft transferred to the US Navy for use in the patrol bomber role. Number transferred: 255
North American Mitchell Mk I for the RAF	This designation was accorded to 23 examples of the B-25B transferred to the UK under the terms of the Lend-Lease Act. Number transferred: 23
North American Mitchell Mk II for the RAF	This designation was accorded to 571 examples of the B-25C and B-25D transferred to the UK under the terms of the Lend-Lease Act Number transferred: 571
North American Mitchell Mk III for the RAF	This designation was accorded to 316 examples of the B-25J transferred to the UK under the terms of the Lend-Lease Act. Of these aircraft 20 were later passed back to the USAAF. Number transferred: 316

 

Operational remarks:

The B-25 Mitchell proved to be an outstanding aircraft right from the start. The aircraft entered service in the early summer of 1941 with the 34th, 37th and 95th Bombardment Squadrons and 89th Reconnaissance Squadron of the 17th Bombardment Group (Medium). The type's first kill was scored when in December 1941 a B-25A of the 17th BG claimed the sinking of a Japanese submarine off the coast of California only a short time after the Japanese attack on Pearl Harbor.
The first action during which the B-25 gained real fame was during the famous and American celebrated Doolittle Raid. It was 16 B-25B's that undertook the raid in April 1942. They took off from the aircraft carrier USS Hornet and attacked Tokyo before the survivors attempted to fly on to airfields in China. Although there was not much damage done, the psychological impact was enormous. Until then Japan had believed to be immune to attacks on the homeland, so after the attacks the Japanese had to take into consideration counter measures against exactly these kind of raids and others. More effort had to be put into defensive measures, hampering the offensive Japanese onslaught. Historians even believe the raid was the direct cause for the Battle of Midway. This Battle, fought over a strategically very important island in the middle of the Pacific was the first big defeat for the Japanese, who lost four aircraft carriers. Japan never really recovered from this blow, and it was the beginning of the end of Japan's success story.
Many of the B-25C and B-25D aircraft were operated in the South-West Pacific Area by units of the US 5th Army Air Force, most notably the 3rd, 22nd and 345th Bombardment Groups. It turned out that while the airframe/powerplant combination of the B-25 was well suited to this theater, there was frequent demand for attacks on shipping and small targets dispersed in jungle for which the armament was not ideal. By September 1943, therefore, some 175 examples of the B-25C and B-25D had been modified by the depot at Townsville in Australia for low-level strafing, with a crew of three. The ventral turret was removed, and the bombardier position was replaced by two pairs of 0.5 inch (12,7 mm) Browning machine guns and supplemented by two additional pairs of 0.5 inch (12,7 mm) Browning machine guns on the sides of the forward fuselage for a fixed forward-firing armament of eight heavy machine guns. The weapons bay was adapted to carry 60 small fragmentation bombs and six 100 lb (45 kg) demolition bombs.
The B-25C and B-25D were also operated by the 7th and 341st Bombardment Groups of the 10th Air Force in the China-Burma-India theater, the 1st Bombardment Group of the Chinese-American Composite Wing of the US 14th Army Air Force in China, the 28th Bombardment Group of the 11th Army Air Force in the Aleutian Islands, the 41st and 42d Bombardment Groups of the 13th Army Air Force in the Central Pacific, and the 12th, 310th, 321st and 340th Bombardment Groups of the 12th Army Air Force in North Africa and Italy.
The NA-96 variant (B-25G) was a dedicated anti-ship model evolved for use in the Pacific theater with a four-man crew and a 75 mm (2.95 inch) M4 cannon installed in the nose, where it was complemented by two 0.5 inch (12,7 mm) Browning fixed forward-firing machine guns, and by the four ‘package’ guns on the sides of the forward fuselage; the last 221 aircraft omitted the ventral turret, which was deemed superfluous for the low-level anti-ship role. The type was not notably successful because of the weight of the 75 mm (2.95 inch) cannon installation, in the lower port side of the forward fuselage, and the slow rate at which the 20 lb (9,1 kg) shells, carried in a 21-round tray, could be loaded by hand. A later version of this anti-shipping type was the more succesfull B-25H, or NA-98. The NA-98 was based on the B-25G with a five-man crew, the lighter 75 mm (2.95 inch) T13E1 gun, eight 0.5 inch (12,7 mm) Browning fixed forward-firing machine guns (four in the nose and four on the fuselage sides), six 0.5 inch (12,7 mm) Browning trainable machine guns (two weapons each in the dorsal and tail positions and single weapons in the two beam positions), provision for 3,000 lb (1.361 kg) of bombs in the weapons bay, and provision for eight 5 inch (127 mm) rocket under the wings. This was the most heavily armed version of the B-25, and it could really deliver a Big Punch.
The Mitchell was used in almost all Theatres of Operation during the War, and succesfully so. During and after the War it was used by the USA, Australia, Brazil, Canada, China, France, Great Britain, the Netherlands and the USSR.

Strengths:

• Good performance

• Excellent defensive armament

• Excellent offensive armament

Weaknesses:

• None

 

 

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