The Boeing B-17 Flying Fortress is a four-engined heavy bomber developed in the 1930s for the United States Army Air Corps (USAAC). Competing against Douglas and Martin for a contract to build 200 bombers, the Boeing entry (prototype Model 299/XB-17) outperformed both competitors and exceeded the Air Corps' performance specifications. Although Boeing lost the contract (to the Douglas B-18 Bolo) because the prototype crashed, the Air Corps ordered 13 more B-17s for further evaluation. From its introduction in 1938, the B-17 Flying Fortress evolved through numerous design advances, becoming the third-most produced bomber of all time, behind the four-engined Consolidated B-24 Liberator and the multirole, twin-engined Junkers Ju 88.
The B-17 was primarily employed by the USAAF in the daylight strategic bombing campaign of World War II against German industrial, military and civilian targets. The United States Eighth Air Force, based at many airfields in central, eastern and southern England, and the Fifteenth Air Force, based in Italy, complemented the RAF Bomber Command's night-time area bombing in the Combined Bomber Offensive to help secure air superiority over the cities, factories and battlefields of Western Europe in preparation for the invasion of France in 1944. The B-17 also participated to a lesser extent in the Pacific War, early in World War II, where it conducted raids against Japanese shipping and airfields.
From its prewar inception, the USAAC (by June 1941, the USAAF) promoted the aircraft as a strategic weapon; it was a relatively fast, high-flying, long-range bomber with heavy defensive armament at the expense of bombload. It developed a reputation for toughness based upon stories and photos of badly damaged B-17s safely returning to base. The B-17 dropped more bombs than any other U.S. aircraft in World War II. Of approximately 1.5 million tons of bombs dropped on Nazi Germany and its occupied territories by U.S. aircraft, over 640 000 tons (42.6%) were dropped from B-17s. In addition to its role as a bomber, the B-17 was also employed as a transport, antisubmarine aircraft, drone controller, and search-and-rescue aircraft.
As of October 2019, nine aircraft remain airworthy, though none of them were ever flown in combat. Dozens more are in storage or on static display. The oldest of these is a D-series flown in combat in the Pacific on the first day of the United States' involvement in World War II.
On 8 August 1934, the USAAC tendered a proposal for a multiengine bomber to replace the Martin B-10. The Air Corps was looking for a bomber capable of reinforcing the air forces in Hawaii, Panama, and Alaska. Requirements were for it to carry a "useful bombload" at an altitude of 10,000 ft (3,000 m) for 10 hours with a top speed of at least 200 mph (320 km/h).
They also desired, but did not require, a range of 2,000 mi (3,200 km) and a speed of 250 mph (400 km/h). The competition for the air corps contract was to be decided by a "fly-off" between Boeing's design, the Douglas DB-1, and the Martin Model 146 at Wilbur Wright Field in Dayton, Ohio.
The prototype B-17, with the Boeing factory designation of Model 299, was designed by a team of engineers led by E. Gifford Emery and Edward Curtis Wells, and was built at Boeing's own expense. It combined features of the company's experimental XB-15 bomber and 247 transport.
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[218]
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
Empty weight: 36,135 lb (16,391 kg)
Gross weight: 54,000 lb (24,500 kg)
Max takeoff weight: 65,500 lb (29,700 kg)
Aspect ratio: 7.57
Powerplant: 4 × Wright R-1820-97 "Cyclone" turbosupercharged radial engines, 1,200 hp (895 kW) each
Propellers: 3-bladed Hamilton-Standard constant-speed propeller
Performance
Maximum speed: 287 mph (462 km/h, 249 kn)
Cruise speed: 182 mph (293 km/h, 158 kn)
Range: 2,000 mi (3,219 km, 1,738 nmi) with 6,000 lb (2,700 kg) bombload
Ferry range: 3,750 mi (6,040 km, 3,260 nmi)
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)
Armament
Guns: 13 × .50 in (12.7 mm) M2 Browning machine guns in 9 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; Internal load only (400 mi): 8,000 lb (3,600 kg)
Long range missions; Internal load only (≈800 mi): 4,500 lb (2,000 kg)
Max Internal and External load: 17,600 lb (7,800 kg)
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