In February 1934 William E. Boeing, a renowned aviation pioneer, won a USAAC tender and was authorized to build a prototype of his four-engined bomber. The XB-15 was a huge aircraft, with wingspan of 149 feet (45.52 m) – about one third more than the B-17 it preceded. However, the engines it was to be equipped with never materialized, hence the XB-15 proved underpowered.
In May 1934 the Army issued another request for proposals for a multi-engined bomber. Unlike his competitors, Martin and Douglas companies, Boeing came up with another four-engined aircraft. The Model 299 – B-17 prototype – was basically a scaled-down version of the XB-15. After a rollout ceremony a local Seattle newspaper called it a “flying fortress” and the name stuck. The aircraft first flew on 28th July 1935.
The first serial-production version was B-17B, equipped with the top-secret Norden bombsight, which was regarded as a marvel of technology at that time. In late July 1940 the first B-17C was ready to fly. Twenty aircraft were supplied to the Great Britain (where the type was known as Fortress I) under Lend-Lease provisions. They were grouped in No. 90 Sqn RAF. On 8th July 1941 the British B-17s, three aircraft in all, carried out their first bombing raid, targeting the Kriegsmarine base at Wilhelmshaven. The early operational service revealed some serious deficiencies of the design. First and foremost, the aircraft’s defensive capabilities were far from adequate. On 8th September 1941 German fighters easily shot down two of the four Fortress Is of No. 90 Sqn RAF dispatched to bomb the German pocket battleship Admiral Scheer docked in Oslo, Norway. By September 1941 the British lost, in combat and accidents, nearly half of their 20 B-17s. Somewhat disappointed, they relegated the remaining aircraft to Coastal Command for long-range patrols.
Meanwhile, in spring 1941 Boeing commenced deliveries of the B-17D. The crew and vital parts of the aircraft were now protected by more armor and the fuel tanks were self-sealing. Most of the D models were sent to the Hawaii and Philippines, where the war caught up with them in December 1941.
In September 1941 the first B-17E rolled off the assembly line. It was a major redesign. The tail section, lengthened by six feet (1.8 m), housed a tail gunner station armed with twin-mounted .50 inch (12.7 mm) machine guns. Two powered fully traversable turrets were added, one mounted ventrally and the other in dorsal position, directly behind the cockpit, both armed with twin ‘fifties’. Waist gunner stations on either side of the fuselage were fitted with bigger, rectangular windows. Enlarged tail surfaces much improved the aircraft’s handling. Since the remote-controlled Bendix turret, mounted under the belly, proved impractical, it was soon replaced with Sperry ball turret – a hydraulically lowered and raised ball with a gunner inside; it was electrically operated and armed with twin-mounted .50 inch machine guns.
In service with the US 8th Army Air Force (ETO)
The Flying Fortresses were the core and the main striking force of the 8th AF stationed in England. This most powerful of the USAAF air forces had over 2,000 heavy bombers, 1,000 escort fighters and about 200,000 personnel at the peak of its strength.
The first American Flying Fortresses (B-17Es) arrived in England in July 1942. They debuted on 17th August 1942, when 12 aircraft of 97th BG headed for Rouen-Sotteville to strike the largest marshalling yards and engine shed in northern France. Before the month was out, a new Flying Fortress model arrived in England. The B-17F was equipped, among other improvements, with wider paddle-bladed propellers and uprated engines. The B-17F received a long series of minor modifications with successive production blocks. Overall, 3,405 aircraft of this model were produced (some under licence by Douglas and Lockheed-Vega plants).
Although initially B-17s didn’t venture beyond the range of their Spitfire escorts, losses were only to be expected. On 6th September 1942 the inevitable happened – B-17F (s/n 41-24445) of 97th BG flown by 2/Lt. Clarence Lipsky went down north of Amiens, France. The first American Flying Fortress shot down over Europe was credited to Hptm. Karl-Heinz Meyer, the commander of II./JG 26.