Boeing B17 flying fortress
The Boeing B17 flying fortress was designed in the 1930's as a relatively fast, high-flying, long-range bomber, with heavy defensive armament (at the expense of bomb load, which was 4,800 lb (2,200 kg)). In 1937, it was powered by four Wright R-1820-39 Cyclone engines with superchargers to compress the intake air for more engine power at higher altitude. The B-17 Flying Fortress became the third-most produced bomber of all time, (12,731 B17's were built between 1938 and 1945). Only the four-engined Consolidated B-24 Liberator and the twin-engined Junkers Ju 88 were produced in larger numbers.
During WW-2, B-17s, dropped more than 640,000 tons on Nazi targets while all U.S. aircraft dropped about 1.5 million tons of bombs.
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.B-17F variants were the main versions flying against Germans in 1943. They had Sperry ball gun turrets for ventral defence and a larger plexiglas bombardier's nose enclosure for improved forward vision.
The YB-40 gunship, used before the North American P-51 Mustang became available, was a heavily armed escort version of the standard B-17 with an extra dorsal turret in the radio room, a remotely operated and fired "chin turret" directly below the bombardier's position, and twin .50 in (12.7 mm) guns in each of the waist positions. The ammunition load was over 11,000 rounds and all this made the YB-40 more than 10,000 lb (4,500 kg) heavier than a fully loaded B-17F.The bombardier used a Norden bombsight, a top secret, gyro-stabilized analogue computer, that could calculate the point when bombs should be released. The required the bombardier to control the aircraft during the final moments before release.
On August 17, 1942, 12 B-17Es of the 97th, with a close escort of four squadrons of RAF Spitfires IXs, launched the first USAAF heavy bomber raid on the railroad marshalling yards at Rouen-Sotteville in France. Only one B-17 was slightly damaged and half the bombs landed in the target area.
As the number of American bombing raids increased, so did German the number of anti-aircraft guns and fighter aircraft, and losses increased.
British and American air forces targeted ball-bearing factories in 1943, hoping to limit the German production of war material. The first raid on Schweinfurt, caused little damage but 300 German fighter aircraft intercepted the 230 attacking B-17's shooting down 36 B-17's with the loss of 200 aircrew.
A second raid, on October 14, 1943, was more successful but 60 of the 291 attacking Fortresses were shot down over Germany and another 17 damaged beyond repair. Only 33 bombers survived with no damage and 650 aircrew were lost, some as prisoners of war.
Daylight bomber raids were suspended until the arrival of long range escort fighters that could protect the bombers all the way to the target and back. Night bombing was also hazardous as the German night-fighters began using radar to locate the bombers in October 1943, when 176 American bombers were shot down.
The B-17 could survive incredible battle damage. One collided with a Focke-Wulf 190, that severely damaged the tail plane and knocked out an engine, but it brought its crew home without injury. Other B-17's returned with engines destroyed, shredded tails and missing large areas of wings. Luftwaffe pilots found that an average of 20 hits with 20 mm (0.79 in) shells were required to bring them down, while an average pilot had to fire 1000 shells at a bomber. The first Fw 190's in action, were armed with only two 20 mm (0.79 in) MG FF cannons and carried only 500 rounds of ammunition. Later versions carried four or even six MG 151/20 cannon plus two 13 mm machine guns. The German fighters discovered that attacking from the front (head on) was the most effective, typically taking only four or five hits to bring a bomber down. With this approach, there were fewer defensive guns, the B-17 pilot was not protected by armour, and the relative speed made accurate return fire difficult.
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