Boeing B-17 Flying Fortress

Responding to the specification released by the United States Army Air Corps in May 1934 calling for a multi-engined bomber that was able to carry a bomb load of 2,000lb between 1,020 and 2,200 miles, at a speed of 200 - 250 mph, with a deadline of August 1935 for a prototype of the aircraft to be ready for testing. Boeing submitted their Model 299, which would be powered by four engines. Design of the aircraft began midway through June 1934, and just over a year later, on the 16th July 1935 at Boeing Field, the aircraft was introduced to the press, with the headlines the next day proclaiming a '15-ton Flying Fortress' leading to Boeing registering it as the Model 299 name.

Twelve days later on the 28th July 1935 the B-17 made its first flight, before being flown to Wright Field for testing and evaluation a few weeks later. By making this flight the B-17 met two objectives of the United States Army Air Corps specification, the journey was 2,100 miles long and was done at an average speed of 252 mph. The prototype comprised armament of five machine guns and could carry more than double the required bomb load of 2,000lb with a 4,800lb maximum load and was powered by four 750-hp Pratt & Whitney R-1690 radial engines. However during testing a setback occurred on the 30th October 1935, when the prototype crashed on take-off, an investigation was to later conclude that the controls had been locked when take-off was attempted. Despite this setback the United States Army Air Corps ordered thirteen YB-17s, later to be called Y1B-17s, as a result of the successful testing before the accident.

The 2nd December 1936 saw the first Y1B-17 fly, with a few improvements compared to the prototype, the aircraft would now be powered by 930-hp Wright GR-1820-39 Cyclone radials and could accommodate nine crew members. The United States Army Air Corps 2nd Bombardment Group based at Langley Field received twelve aircraft during the first eight months of 1937. The other Y1B-17 of the thirteen originally ordered was sent for further testing at Wright Field. The first variant to enter operational service was designated the B-17A. Following shortly after was the B-17B, which, whilst almost identical to the B-17A, featured a larger rudder. This first flew on the 27th June 1939 and just over a year later, on the 21st July 1940, the new B-17C flew with 1,200-hp engines.

It was with the Royal Air Force that the B-17 was to first experience combat during the Second World War (1939 - 1945) when No. 90 Squadron, which reformed on the 7th May 1941 at RAF Watton, received the B-17C, designated Fortress I that same month. On the 8th July 1941 they took part in their first RAF raid against the naval barracks at Wilhelmshaven, Germany, however, bombing from 30,000 ft they failed to hit the target. Over the next two months another 26 attacks were made on various German targets, and with eight Fortress Is lost due to combat or accidents the Fortress I proved unsatisfactory for use by Bomber Command for daylight bombing. The remaining Fortress Is were transferred to Coastal Command. As a result of the poor performance of the B-17 over Europe a number of areas where the aircraft could be improved were found, these included more defensive armament to combat attacks from German fighters and a higher service celling. By the end of 1941, the United States was drawn into the Second World War after the Japanese attack on Pearl Harbor on the 7th December 1941.

The introduction of the B-17D, with additional armour and self-sealing tanks, and the B-17E, which flew for the first time on the 5th September 1941. The United States Army Air Force used the B-17 for the first time over Europe on the 17th August 1942, when twelve B-17Es escorted by Supermarine Spitfires of the Royal Air Force attacked the marshalling yards at Rouen in France, only two aircraft sustained minor damage and the mission was a success.

Flying for the first time on the 30th May 1942, the B-17F featured a redesigned nose, more armour and increased fuel capacity. Along with the B-17E it would be the Flying Fortress versions most extensively used by the Eighth Air Force. However mounting losses during the daylight raids were to show that the B-17, either on its own or flying in formation, could not defend themselves. Although the B-17G appeared with a gun turret in the nose section to limit the aircraft's vulnerability to head on attacks, daylight raids deep into Germany saw heavy losses. The introduction of the North American P-51 Mustang and Republic P-47 Thunderbolt equipped with external fuel tanks saw losses reduced.

The Boeing B-17 Flying Fortress was used wherever US forces were. In the Pacific theatre of war they were used for close-support bombing, patrol and reconnaissance. A few B-17's were produced for special operations and purposes and despite production totalling 12,731, only a few hundred would stay in service at the conclusion of the Second World War.