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BOEING B-17 FLYING FORTRESS
Variants - B-17F/Fortress II
The B-17F was an upgrade of the B-17E, although outwardly the types were distinguished only by exchanging the bombardier's ten panel, well-framed nose glazing that had originated with the B-17B, for a molded one-piece or two-piece plexiglas cone, the two-piece version having a nearly-transparent diagonal seam. Late production "F" series aircraft received substantially enlarged mounts for the "cheek"-mounted guns on each side of the nose, offset in their horizontal placing, still with the starboard "cheek" emplacement further forward, and fully feathering paddle-bladed propellers. Numerous internal changes were made to improve the effectiveness, range, and load capacity of the B-17. However, once placed in combat service, the "F" series was found to be tail heavy. The weight of gunners and ammunition when combat-loaded moved the center of gravity rearward from its design point and forced the constant use of elevator trim tab, stressing this component.
B-17F Flying Fortress/41-24639 of the 91st BG/322nd BS.
[Source: USAF Photo]
In combat the B-17F proved almost immediately to have inadequate defensive protection when attacked from the front. Various armament configurations of two to four flexible guns were utilized in the field, as sometimes cannibalized from damaged B-17s' tail gun positions (as one example), but the problem was not adequately addressed until the introduction of a powered, Bendix-designed remotely operated "chin" turret in the final production blocks of the F-series Fortresses — starting with the last 86 B-17Fs built by Douglas of the 605 B-17F-DL bombers built, from the B-17F-75-DL production block — directly derived from its debut on the
YB-40 experimental "gunship" version.
By using a stronger undercarriage, the maximum bomb capacity was increased from 4,200 lb (1,900 kg) to 8,000 lb (3,600 kg). Though this modification reduced cruise speed by 70 mph (110 km/h), the increase in bomb capacity was a decided advantage. A number of other modifications were made, including re-integrating external bomb racks, but because of its negative impact on both rate-of-climb and high altitude flight the configuration was rarely used and the racks were removed.
Range and combat radius were extended with the installation in mid-production of additional fuel cells in the wings. Called "Tokyo tanks", nine self-sealing rubber-composition tanks were mounted inside each wing on each side of the joint between the inner and outer wing sections. With an extra 1,080 US gal (4,100 l) to the 1,700 US gal (6,400 l) available on the first B-17Fs, the Tokyo tanks added approximately 900 mi (1,400 km) to the bomber's range.
3,405 were built: 2,300 by Boeing, 605 by Douglas, and 500 by Lockheed (Vega). These included the famous Memphis Belle. 19 were transferred to the RAF, where they served with RAF Coastal Command as the Fortress II.
First Flight: May 30, 1942
Produced: 3,405 (-BO x 2,300/-DL x 605/-VE x 500)
Sources:
Wikipedia
U.S.A.A.F. RESOURCE CENTER > BOMBERS > FLYING FORTRESS > VARIANTS > PREVIOUS PAGE
