Forty-two more B-17Cs were ordered on April 17, 1940. However, these planes were sufficiently different from the original batch of B-17Cs that the Army decided on September 6, 1940 to give them a new designation of B-17D. In reality, the B-17D was only slightly different from the B-17C and bore the same company model number (299H). Externally, the B-17D differed from the C in having a set of engine cowling flaps to improve the cooling. Internal changes included electrical system revisions and the addition of a tenth crew member. The B-17D had paired guns in the belly and top positions, bringing the total armament to one 0.30-inch and six 0.50-inch machine guns. The external bomb racks were deleted.
The first B-17D flew on February 3, 1941. The B-17Ds were delivered to the Army from February to April of 1941. First priority was given to overseas units, with most of the B-17Ds going to units based in Hawaii or in the Philippines. The batch of B-17Cs which did not get sent to Britain were later modified to B-17D standards and redesignated B-17D.
Starting in March of 1941, the Army began to paint its B-17s in olive drab and grey camouflage paint. By the time of Pearl Harbor, virtually all B-17Cs and Ds were in warpaint.
The only "shark-fin" B-17 known to still remain in existence is B-17D 40-3097 (known as *Swoose*). It is currently in storage at the Paul Garber facility at Silver Hill, Maryland.
Boeing B-17D Fortress 40-3059/3100
Specification of B-17D:
Four Wright GR-1820-65 (G-205A) Cyclone radials rated at 1200 hp for takeoff, 1000 hp at 25,000 feet. Performance: Maximum speed 318 mph at 25,000 feet. Service ceiling 37,000 feet. Dimensions: wingspan 103 feet 9 3/8 inches, length 67 feet 10.6 inches, height 15 feet 5 inches, wing area 1420 square feet. Weights: 30,963 pounds empty, 39,319 pounds gross. Armament: Armed with six 0.50-inch machine guns and one 0.30-inch machine gun. A single 0.50-inch gun was carried in each of the two waist positions, and a pair of 0.50-inch machine guns were mounted in each of the dorsal and ventral positions. There was one 0.30-inch machine gun which could be fired from any one of six sockets in the nose. A maximum of 4800 pounds of bombs could be carried in an internal bomb bay.