The Boeing B-17 Flying Fortress is a four-engine 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 outperformed both competitors and exceeded the air corps' performance specifications. Although Boeing lost the contract 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.
The B-17 was primarily employed by the United States Army Air Forces (USAAF) in the daylight strategic bombing campaign of World War II against German industrial and military targets. The United States Eighth Air Force, based at many airfields in central and southern England, and the Fifteenth Air Force, based in Italy, complemented the RAF Bomber Command's nighttime 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 War in the Pacific, 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 developed a reputation as an effective bomber, dropping more bombs than any other U.S. aircraft in World War II. Of the 1.5 million tonnes of bombs dropped on Germany and its occupied territories by U.S. aircraft, 640,000 tonnes 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 May 2015, ten aircraft remain airworthy. None of them are combat veterans. Dozens more are in storage or on static display. The oldest of these is a D-series veteran of combat in the Pacific and the Caribbean.
On 8 August 1934, the U.S. Army Air Corps (USAAC) tendered a proposal for a multi-engine 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 that it would carry a "useful bombload" at an altitude of 10,000 ft (3,048 m) for ten 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 would be decided by a "fly-off" between Boeing's design, the Douglas DB-1, and the Martin Model 146 at 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 experimental Boeing XB-15 bomber with the Boeing 247 transport aircraft. The B-17's armament consisted of up to 4,800 lb (2,200 kg) of bombs on two racks in the bomb bay behind the cockpit, and initially possessed five .30 caliber (7.62 mm) machine guns. It was powered by four Pratt & Whitney R-1690 "Hornet" radial engines each producing 750 hp (600 kW) at 7,000 ft (2,100 m).
The first flight of the Model 299 was on 28 July 1935 with Boeing chief test-pilot Leslie Tower at the controls. Richard Williams, a reporter for the Seattle Times, coined the name "Flying Fortress" with his comment, "Why, it's a flying fortress!" when the Model 299 was rolled out bristling with multiple machine gun installations. The most unusual gun emplacement was the nose installation which allowed the single machine gun to be fired toward almost any frontal angle.
Boeing was quick to see the value of the name and had it trademarked for use.[N 1] Boeing also claimed in some of the early press releases that Model 299 was the first combat aircraft that could continue its mission if one of its four engines failed. On 20 August 1935, the prototype flew from Seattle to Wright Field in nine hours and three minutes at an average cruising speed of 252 miles per hour (406 km/h), much faster than the competition.
At the fly-off, the four-engine Boeing's performance was superior to those of the twin-engine DB-1 and Model 146. Major General Frank Maxwell Andrews of the GHQ Air Force believed that the long-range capabilities of four-engine large aircraft were more effective than shorter-ranged, twin-engine aircraft, and that the B-17 was better suited to new, emerging USAAC doctrine. His opinions were shared by the air corps procurement officers, and even before the competition had finished they suggested buying 65 B-17s.
Development continued on the Boeing Model 299, and on 30 October 1935, Army Air Corps test-pilot Major Ployer Peter Hill and Boeing employee Les Tower took the Model 299 on a second evaluation flight. The crew forgot to disengage the "gust locks", a system of devices integral to the design that held the bomber's movable control surfaces in place while the aircraft was parked on the ground. After takeoff, due to the failure to manually disengage all of the gust locks, the aircraft entered a steep climb, stalled, nosed over, and crashed, killing Hill and Tower (other observers survived with injuries).[N 2]
The crashed Model 299 could not finish the evaluation and, while the air corps was still enthusiastic about the aircraft's potential, army officials were daunted by the much greater expense per aircraft (Douglas quoted a unit price of $58,200 based on a production order of 220 aircraft, compared with a price of $99,620 from Boeing), and as the competition could not be completed Boeing was legally disqualified from consideration for the contract. Army Chief of Staff Malin Craig cancelled the order for 65 YB-17s, and ordered 133 of the twin-engine Douglas B-18 Bolo instead.
The loss was not total... but Boeing's hopes for a substantial bomber contract were dashed.
Though the crash of the prototype 299 in 1935 had almost wiped out Boeing, now it was seen as a boon. Instead of building models based on experimental engineering, Boeing had been hard at work developing their bomber and now had versions ready for production far better than would have been possible otherwise. One of the most significant weapons of World War II would be ready, but only by a hair.