The B-25D was the version of the B-25C built by the North American factory at Kansas City, Kansas.
In 1940, American military planners recognized that the war in Europe would create such an increased need for military aircraft that existing manufacturing facilities would be unable to keep up with the demand. Consequently, the US government approved the construction of of a series of entirely new aircraft plants. These new plants would be located mainly in the Midwest, well isolated, it was hoped, from the threat of bombing raids from either German or Japanese aircraft. Ownership of these plants would be retained by the government, but they would be leased to private aircraft manufacturers for the purpose of fulfilling military contracts.
One of these government-owned plant was in Kansas City, Kansas. Its construction was authorized in December of 1940 for the production of B-29 Superfortress bombers by North American Aviation. However, the Boeing Renton plant was added to the B-29 production program in exchange for the Navy cancellation of the SeaRanger flying boat, and this freed up the Kansas City plant for the manufacture of Mitchell medium bombers for both the Army and the Navy.
The Fisher Body Division of the General Motors Corporation was named as a major subcontractor. It was initially planned that Fisher would perform most of the manufacturing, with North American/Kansas doing most of the final assembly. However, the program at the Kansas facility was later expanded to include manufacture as well, and at the period of peak production, Kansas City was performing 71 percent of the effort.
An initial order for 1200 B-25D (NA-87) bombers was approved on June 28, 1941. North American Inglewood manufactured and supplied the parts for the first 100 B-25Ds built at Kansas City. The first two B-25Ds were accepted in February of 1942. Subsequent B-25Ds were built almost entirely by Fisher and by North American/Kansas. Beginning with B-25D serial number 41-29748, Fisher supplied outer wings, fuselage side panels, control surfaces, and transparent enclosures to Kansas City for mating with center sections and with other parts manufactured there.
The first B-25D was accepted by the USAAF in February of 1942. Initially, the B-25D was virtually identical to the B-25C, and many of the early innovations introduced on the B-25D production line at Kansas City paralleled those introduced on the B-25C line at Inglewood. The key external difference between the early B-25D and the B-25C was in the demarcation of the underside paint, with the B-25D using a deep wave pattern. However, it was generally impossible to tell the difference between a B-25C and a B-25D without a knowledge of the serial numbers.
Beginning with the B-25D-1 production block, external wing bomb racks were provided, additional self-sealing tanks were installed in the outer wing panels (adding 304 US gallons to the fuel capacity), carburetor air filters were installed, self-sealing oil tanks were provided, provisions were made for the installation of torpedo racks, a scanning blister was installed over the navigator's compartment, Bendix Amplidyne turrets were installed, and the flame-dampening "finger"-type engine exhausts were installed. The external bomb racks could carry six to eight bombs in the 100-325 pound range.
In the B-25D-5 production block, the 0.30-inch machine gun in the nose was replaced with a pair of fixed 0.50-inch and a single flexible 0.50-inch machine guns. This made them different from the B-25C's, which had only a single 0.50-inch fixed gun in the nose. An improved scanning lens for the sighting system for the retractable ventral turret was provided, and provisions for a 585-gallon droppable bomb-bay fuel tank were installed on every third airplane through 41-30532. Provisions for additional cabin heating were added on B-25D-5 No. 41-30057 onward.
On the B-25D-10 production block, additional provisions were made for better winterization, a remote reading compass was installed, emergency hydraulic landing gear lowering mechanisms were provided, and the conduit shielding box was eliminated.
Effective on B-25D-15 and subsequent production blocks, the flame-dampening "finger"-type stack exhaust collector was replaced with individual Clayton "S"- shaped exhaust stacks connected to each cylinder, with individual cutouts and fairings being provided in the cowling where the stacks protruded.
Beginning with B-25D-15 No. 41-30533, a clear vision windshield was installed. A 230-US gallon self-sealing bomb bay fuel tank was installed, and a 325-gallon metal bomb bay fuel tank was installed on every other plane. Additional armor plate was installed behind the copilot. In the late Spring, 1943, the Army Air Forces ordered an interim configuration of the B-25D and the B-25G with a major upgrade of the armament package. This change to the B-25D was known as the B-25D2 series and bridged the gap until the so-called 2081 change introduced the B-25J in December 1943. The B-25D2 modification program roughly coincides with the production of the B-25D-20 block and soon many B-25D headed for the combat zones were in the interim configuration. The AAF, the USN, and the Allies all received B-25D2. The B-25D production was extended with the NA100 and eventually the interim configuration was built on the factory assembly line.
On the B-25D-25 production block, a portable oxygen system was added.
The last (B-25D-30) production block introduced more winterization changes, including a windshield defroster.
The first B-25D was accepted by the USAAF in February 1942, with the last being accepted in March of 1944 as a B-25D-35-NA. Production B-25Ds were identified as being Kansas City products by their series designator and did not use the NC factory code on their originaal data block stenciling. The NC plant designator did not appear until the B-25J.
41-29648/29847 North American B-25D Mitchell c/n 87-7813/8012 41-29848/29947 North American B-25D-1 Mitchell c/n 87-8013/8112 41-29948/30172 North American B-25D-5 Mitchell c/n 87-8113/8337 41-30173/30352 North American B-25D-10 Mitchell c/n 87-8338/8517 41-30353/30532 North American B-25D-15 Mitchell c/n 87-8518/8697 41-30533/30847 North American B-25D-20 Mitchell c/n 87-8698/9012 42-87113/87137 North American B-25D-20 Mitchell c/n 100-20606/100-20630 42-87138/87452 North American B-25D-25 Mitchell 87138/87312 c/n 100-20631/100-20805 87313/87452 c/n 100-23306/23445 42-87453/87612 North American B-25D-30 Mitchell c/n 100-23446/100-23605 43-3280/3619 North American B-25D-30 Mitchell c/n 100-23606/100-23945 43-3620/3869 North American B-25D-35 Mitchell c/n 100-23946/100-24195
Engines: Two Wright R-2600-13 Double Cyclone fourteen-cylinder air-cooled radials, each rated at 1700 hp each for takeoff, 1500 hp at 2400 rpm. Equipped with Holley 1685HA carburetors. Performance: Maximum speed 284 mph at 15,000 feet. Cruising speed 233 mph at 15,000 feet. Initial climb rate 1100 feet per minute. An altitude of 15,000 feet could be reached in 16.5 minutes. Service ceiling 24,000 feet, Range 1500 miles with 3000 pounds of bombs. Weights: 20,300 pounds empty, 34,000 pounds maximum loaded. Dimensions: wingspan 67 feet 67.7 inches, length 53 feet 0 inches, height 15 feet 9 inches, wing area 610 square feet. Fuel: The fuel capacity consisted of four tanks in the inner wing panels, with a total capacity of 670 US gallons. In addition, a 515-gallon tank could be installed in the bomb bay for ferrying purposes, bringing total fuel capacity to 1255 US gallons. Later versions had additional auxiliary fuel tanks in the outer wing panels. Later versions could also have 125-gallon tanks fitted in side waist positions, a 215-gallon self-sealing fuel tank installed in the bomb bay, and provisions could be made for a droppable 335-gallon metal bomb-bay fuel tank. Armament: Two 0.50-inch machine guns in dorsal turret. Two 0.50-inch machine guns in retractable ventral turret. One 0.30-inch machine gun in flexible mount in the nose. Starting with B-25D-5 the 0.30-inch nose gun was removed and replaced by a flexible 0.50-inch machine gun in the extreme nose and two fixed 0.50-inch machine mounted in the nose and firing through holes cut into the side of the Plexiglas glazing. Normal bomb load was 3000 pounds but could be increased on the B-25D-1-NA with external underwing racks to a maximum of 5200 pounds.