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Info

The Boeing B-17 Flying Fortress is a four-engine heavy bomber developed in the 1930s for the United States Army Air Corps (USAAC).

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Design

The aircraft went through several alterations in each of its design stages and variants. Of the 13 YB-17s ordered for service testing, 12 were used by the 2nd Bomb Group of Langley Field, Virginia, to develop heavy bombing techniques, and the 13th was used for flight testing at the Material Division at Wright Field, Ohio. Experiments on this aircraft led to the use of a quartet of General Electric turbo-superchargers which would become standard on the B-17 line. A 14th aircraft, the YB-17A, originally destined for ground testing only and upgraded with the turbochargers, was re-designated B-17A after testing had finished.

As the production line developed, Boeing engineers continued to improve upon the basic design. To enhance performance at slower speeds, the B-17B was altered to include larger rudders and flaps. The B-17C changed from three bulged, oval shaped machine gun blisters to two flush, oval-shaped machine gun window openings and, on the lower fuselage, a single "bathtub" machine gun gondola housing which resembled the similarly configured and located ventral defensive emplacement on the German Heinkel He 111P-series medium bomber.

While models A through D of the B-17 were designed defensively, the large-tailed B-17E was the first model primarily focused on offensive warfare. The B-17E was an extensive revision of the Model 299 design: The fuselage was extended by 10 ft (3.0 m); a much larger rear fuselage, vertical tailfin, rudder, and horizontal stabilizer were added to the design; a gunner's position was added in the new tail; the nose (especially the bombardier's well-framed, ten-panel nose glazing) remained relatively the same as the earlier B through D versions had, but with the addition of a Sperry electrically powered manned dorsal gun turret just behind the cockpit, and the similarly powered (also built by Sperry) manned ventral ball turret just aft of the bomb bay – replacing a relatively hard-to-use, Bendix-designed remotely operated ventral turret on the earliest examples of the Evariant, that had also been used on the earlier marks of the North American B-25 Mitchell – resulted in a 20% increase in aircraft weight.The B-17's turbocharged Wright R-1820Cyclone 9 engines were upgraded to increasingly more powerful versions of the same powerplants multiple times throughout its production, and similarly, the number of machine gun emplacement locations was increased to enhance the aircraft's combat effectiveness.

The B-17F variants were the primary versions flying for the Eighth Air Force to face the Germans in 1943, and had standardized the manned Sperry ball turret for ventral defense, replacing the earlier, ten-panel well-framed bombardier's nose glazing from the B subtype with an enlarged, nearly frameless plexiglas bombardier's nose enclosure for improved forward vision.

By the time the definitive B-17G appeared, the number of guns had been increased from seven to thirteen, the designs of the gun stations were finalized, and other adjustments were completed. The B-17G was the final version of the Flying Fortress, incorporating all changes made to its predecessor. Many B-17Gs were converted for other missions such as cargo hauling, engine testing and reconnaissance. Initially designated SB-17G, a number of B-17Gs were also converted for search-and-rescue duties, later to be redesignated B-17H.

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Specifications

General Characteristics

Crew: 10: Pilot, co-pilot, navigator, bombardier/nose gunner, flight engineer/top turret gunner, radio operator, waist gunners (2), ball turret gunner, tail gunner

Length: 74 ft 4 in (22.66 m)

Wingspan: 103 ft 9 in (31.62 m)

Height: 19 ft 1 in (5.82 m)

Wing area: 1,420 sq ft (131.92 m2)

Airfoil: NACA 0018 / NACA 0010

Aspect ratio: 7.57

Empty weight: 36,135 lb (16,391 kg)

Loaded weight: 54,000 lb (24,500 kg)

Max. takeoff weight: 65,500 lb (29,700 kg)

Powerplant: 4 × Wright R-1820-97 "Cyclone"turbosupercharged radial engines. 1,200 hp(895 kW) each

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Performance

Maximum speed: 287 mph (249 kn, 462 km/h)

Cruise speed: 182 mph (158 kn, 293 km/h)

Range: 2,000 mi (1,738 nmi, 3,219 km) with 2,700 kg (6,000 lb) bombload

Service ceiling: 35,600 ft (10,850 m)

Rate of climb: 900 ft/min (4.6 m/s)

Wing loading: 38.0 lb/sq ft (185.7 kg/m2)

Power/mass: 0.089 hp/lb (150 W/kg)

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Armaments

Guns: 13 × .50 in (12.7 mm) M2 Browning machine guns in 8 positions (2 in the Bendix chin turret, 2 on nose cheeks, 2 staggered waist guns, 2 in upper Sperry turret, 2 in Sperry ball turret in belly, 2 in the tail and one firing upwards from radio compartment behind bomb bay)

Bombs:

Short range missions (<400 mi): 8,000 lb (3,600 kg)

Long range missions (≈800 mi): 4,500 lb (2,000 kg)

Overload: 17,600 lb (7,800 kg)

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