<p>When viewing this earlier generation of Boeing classics, even the most skeptical observer cannot divorce the B-17 from the wartime fields of East Anglia, the strains of Glenn Miller and the monumental air battles fought over German cities from late 1942. However, there was a lot more to the B-17 than just its 8th Air Force service.
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<p>The vast armadas of the US 8th Air Force, equipped mainly with the Boeing B-17, ranged far and wide over Germany and occupied Europe in 1942-45, bombing individual factories and other precision targets and also whittling away at the fighter strength of the Luftwaffe in some of the largest and bloodiest air battles in all history. In 1934, such battles could not have been foreseen. The only targets within range of US bombers were in such unlikely places as Canada, Mexico and small British islands. In the Depression, money was tight, and the new monoplane Martin Bomber appeared to be all that was needed.
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<p>When the US Army Air Corps put out a request for a new multi-engined bomber, a few far-sighted engineers at the Boeing Airplane Company decided to interpret 'multi-engined' as meaning not two engines (as had generally been done before) but four. Admittedly, they did this mainly in order to get more height over the target, but it had the effect of making the Boeing Model 299 significantly larger than its rivals. Design began on 18 June 1934, and the prototype made a very successful first flight in the hands of Les Tower at Boeing Field on 28 July 1935. The main purpose of the new bomber was to defend the United States by bombing an invasion fleet (the only plausible kind of target) and it was the nature of this mission, rather than heavy defensive armament, that resulted in Boeing eventually registering the name 'Flying Fortress'.
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<hi style=hdr1>Triumph and Disaster</hi>
<p>On 20 August 1935 the impressive aircraft, unpainted except for US Army Air Corps rudder stripes and civil registration NX13372, flew nonstop to Wright Field at an average speed faster than the maximum possible speed of its twin-engined rivals. On the first officially observed flight before the USMC evaluation officers, on 30 October 1935, the great bomber took off, climbed far too steeply, stalled and dived into the ground, bursting into a ball of fire. The accident was caused entirely by someone having omitted to remove the external locks on the elevators, and although the immediate winner of the official trials had to be the Douglas B-18, the much greater potential of the great Boeing bomber resulted in a service-test order for 13, designated Y1B-17, placed on 17 January 1936.
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<p>These had many changes, especially to the landing gear, armament and in having 930-hp (694-kW) Wright Cyclone engines instead of 750-hp (560-kW) Pratt & Whitney Hornets. In 1937 the machines were delivered to the 2nd Bombardment Group at Langley Field, which subsequently flew almost 10,000 hours with no serious trouble and did more than any other unit in history to solve the problems of long-distance bombing, especially at high altitude. A 14th aircraft was built as the Y1B-17A with engines fitted with General Electric turbosuperchargers, which increased the speed from 256 mph (412 km/h) to 311 mph (500 km/h) and raised the operating height to well over 30,000 ft (9,145 m).
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<p>Results with the B-17 (as the Y1B was called after its test period was complete) were so good the USMC not only fought for massive production numbers, in the teeth of opposition from the US Navy, but also with Boeing collaboration even planned a next-generation bomber which became the B-29. US Navy anger was so intense that production numbers had to be scaled down, and the production batch of the first series model, the B-17B, numbered only 39. These had numerous minor changes as well as a redesigned nose and large rudder. They were the first aircraft in the world to enter service with turbocharged engines. The B-17B entered service in 1939 and was the fastest, as well as the highest-flying, bomber in the world. The US Army Air Corps had by this time embarked on a major program of perfecting long-range strategic bombing by day, using the massed firepower of a large formation to render interception hazardous. It was expected that, because of the B-17's speed and height, opposing fighters would be hard-pressed to keep up and would present an almost stationary (relative to the bombers) target that could be blasted by the fire from hundreds of machine guns.
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<hi style=hdr1>Further Power and Speed</hi>
<p>Boeing and Wright Field continued to improve the B-17 and in 1939 an additional 39 were ordered under the designation B-17C. These were much heavier, weighing 49,650 lb (22,520 kg) compared with about 43,000 lb (19,505 kg) for a B-17, because of increased armor, self-sealing tanks, heavier defensive armament (with twin 0.5-in/12.7-mm guns above and in a new ventral 'bathtub', twin 0.3-in/7.62-mm guns in the nose and new flush side gun positions) and extra equipment. Despite the greater weight, the fitting of 1,200-hp (895-kW) engines made this the fastest of all versions, with a maximum speed of 320 mph (515 km/h). In spring 1941 a batch of 20 was assigned to the RAF, following 15 months of negotiations which finally resulted in the aircraft being supplied in exchange for complete information on their combat performance (this was prior to the 1940 Lend-Lease Act). As RAF Fortress Is they had a disastrous and mismanaged career which dramatically reduced their numbers to a handful (about nine) which were transferred to Coastal Command and the Middle East.
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<p>Further extensive internal improvements, a new electrical system and engine-cowl cooling gills led to the B-17D, of which 42 were ordered in 1940. This was the latest model in service at the time of Pearl Harbor (7 December 1941), when 30 were destroyed on the ground at Hickam Field and at Clark Field, Philippines, the following day.
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<p>By this time Boeing had developed a visually different model which incorporated all the lessons learned in World War II in Europe. Called Boeing 2990, it entered US Army Air Force service in December 1941 as the B-17E. Its most striking change was the much larger tail, with a giant dorsal fin and long-span tailplane giving better control and stability at high altitude. Armament was completely revised, with paired 0.5-in (12.7-mm) guns in a powered turret behind the cockpit, in a ventral turret at the trailing edge, and in a new manual turret in the tail. Another pair of guns could be fired by hand from the roof of the radio compartment, and with a single hand-aimed gun at each waist position this made a total of 10 heavy machine guns, plus two 0.3-in (7.62-mm) guns aimed from the nose.
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<p>Further improvements in armor and equipment all helped to increase gross weight to 54,000 lb (24,494 kg), so cruising speed inevitably fell from 231 to only 210 mph (372 to 338 km/h). This was the first B-17 in large-scale production, and deliveries totalled 512 including 45 sent to the RAF as Fortress IIAs.
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<hi style=hdr1>Massive Production</hi>
<p>On 30 May 1942 Boeing flew the first B-17F incorporating many changes which allowed gross weight to soar to 65,000 lb (29,484 kg) with a potential bomb load for short ranges of 20,800 lb (9,435 kg), although on normal combat missions the load seldom exceeded 5,000 lb (2,268 kg). The only obvious external change on the F model was the more pointed nose molded in one piece of Plexiglas. This type went into production not only at Boeing but also in a great nationwide pool with assembly lines at Douglas (Long Beach) and Vega (a Lockheed subsidiary at Burbank). Boeing built 2,300 of this model, and Douglas and Vega added 605 and 500, respectively.
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<p>With the B-17E and B-17F the US 8th Air Force built up its early strength in England. The first combat mission was flown on 17 August 1942 by 12 B-17Es of the 97th Bomb Group against a marshalling yard near Rouen. This was the small beginning to the greatest strategic striking force ever created, which was to lead to a three-year campaign in the course of which 640,036 tons of bombs were dropped on German targets and, at the cost of grievous losses, supremacy was eventually obtained even over the heart of Germany in daylight.
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<p>By far the most numerous model of B-17 was the last one. The B-17G was the final result of bitterly won combat experience and among other changes it introduced a chin turret firing ahead with twin accurately aimed 0.5-in (12.7-mm) guns. Previously, German fighters had brought down many B-17s with head-on attacks, but the B-17G, with the chin turret plus two more 0.5-in (12.7-mm) cheek guns (and possibly the dorsal turret) firing ahead was a tougher proposition. The B-17G had enclosed waist positions, much greater ammunition capacity and, like most B-17Fs, paddle-blade propellers to handle the greater weight and prevent too much deterioration in performance. Most B-17Gs had improved turbochargers which actually increased service ceiling to 35,000 ft (10,670 m), but these bombers were so heavy the cruising speed fell to 182 mph (293 km/h). This increased the time the gigantic formations were exposed to rocket and cannon attack by the German fighters; conversely, of course, it lengthened the time the B-17 guns could destroy those fighters.
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<hi style=hdr1>Electronic Versions</hi>
<p>Boeing built 4,035 B-17Gs, Douglas 2,395 and Vega 2,250, a total of 8,680. The total of all versions was 12,731, of which 12,677 were formally accepted by the USAAF. The B-17F was used by the RAF as the Fortress II and the B-17G as the Fortress III, the main user being Coastal Command. Some were modified with a radar in place of the chin or ball turret, and for use against surfaced U-boats a 40-mm Vickers S gun was fitted in a nose mount. The B-17G was also the chief heavy carrier of special electronics for the RAF's No. 100 Group, Nos 214 and 233 Sqns being the pioneers of spoofing, decoy, jamming and intelligence missions with 19 distinct types of electronic or related device, including the super-power emitters coded 'Jostle' and 'Piperack'. The only electronic device often carried by USAAF B-17s was the early H2X or Mickey Mouse radar used for bombing through cloud. This set's scanner was normally housed in a retractable radome under the nose or in place of the ball turret.
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<p>The ball turret, a retractable installation on the B-24 Liberator, was fixed on the B-17. Originally the B-17E had been fitted with a drum-type ventral turret aimed by a gunner in the fuselage, sighting via a periscope. This was soon replaced by the aptly-named spherical ball-turret made by the Sperry company. The gunner had to climb into this and squat with his knees fully bent for perhaps five or six hours. A belly landing could flatten the ball-turret and its occupant, and there were many occasions when—because of combat damage—the turret doors jammed and a belly landing would have killed the ball-turret gunner. Normal procedure for a belly landing was to get the gunner out and then, using special tools, disconnect the whole turret from the aircraft and let it fall free. On one occasion a B-17 returned with severe combat damage and jammed landing gears, and near its home airfield it was found that the special tools were not on board. The executive officer of the station was notified by radio; within minutes he had grabbed a set of tools and taken off. For more than two hours he circled in close formation with the stricken B-17 trying to pass the tools on the end of a cable. He succeeded.
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<p>In 1942 various special versions of B-17 were produced by Vega to serve as escort fighters. The first was the second Vega-built B-17F, which was rebuilt as an XB-40 with many armament changes including a second dorsal turret and a bomb bay full of ammunition. It was followed by 20 YB-40s with even heavier armament including quadruple gun mounts at nose and tail and a total of as many as 30 guns of up to 37- or 40-mm caliber. So heavy were these 'fighters' that they could not even keep formation with the B-17 bombers, and although they flew nine combat missions in 1943 they were judged unsuccessful.
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<p>In 1943 Boeing converted the ninth production B-17E to have liquid-cooled Allison engines of 1,425 hp (1,063 kW) each; these naturally resulted in improved performance but it remained a one-off prototype (designated XB-38). Another unique machine was the plush XC-108 VIP transport which began life as a B-17E (41-2593) but was converted for General Douglas MacArthur, Supreme Commander in the Pacific, with a comfortable interior for 38 passengers. The XC-108A was a similar conversion but for cargo, with a large door on the left side. The YC-108 was a VIP conversion of a B-17F, and the XC-108B was a B-17F tanker which ferried fuel over the 'Hump' from India to China.
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<hi style=hdr1>Oddities and Other Developments</hi>
<p>The F-9s were a batch of 16 B-17Fs rebuilt by United Airlines at Cheyenne as strategic reconnaissance machines with from six to 10 cameras in fuselage installations. Another 45 B-17Fs were converted as F-9As or F-9Bs, while 10 B-17Gs were turned into F-9Cs, the postwar designation for survivors being FB-17 up to 1947 and RB-17 thereafter. One B-17F served with the US Navy, and late in the war 40 B-17Gs were transferred to the US Navy to pioneer the technique of AEW (airborne early warning) with the newly developed APS-120 radar in a vast chin blister; this variant was designated PB-1W.
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<p>A strange wartime rebuild was the Aphrodite cruise missile conversion in which war-weary B-17Fs and B-17Gs were stripped of everything that could be removed and packed with 10 tons of Torpex, a British explosive with 50 per cent greater blasting power than Amatol. Under the project names 'Perilous' and 'Castor' many tests were made, the take-off being made by two pilots in an open cockpit who then baled out to leave the Fortress (official designation BQ-7) under radio control from an accompanying aircraft such as a B-17 or PV-1. Though 11 combat launches were made on German targets the idea was judged too perilous after one BQ-7 had made a crater over 100 ft (30 m) in diameter in England and another had broken radio link and orbited a British city before heading out to sea.
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<p>In 1944 British experience was used in converting B-17Gs into B-17H air/sea rescue aircraft with an airborne lifeboat and search radar; postwar, these were designated SB-17G. Other postwar variants included the CB-17 and VB-17 transports, TB-17 trainers, radio-guided QB-17 versions and DB-17 radio director aircraft. These soldiered on with the USAF after its formation in 1947, and also with various minor air forces. Many others became civil airliners. Seven of the 68 which landed in Sweden during the war entered service as airliners with AB Aerotransport, and another was used as an executive transport by TWA. One fire-fighting conversion was powered by Rolls-Royce Dart turboprops, and the B-17 was a popular testbed for experimental jet and turboprop engines in the late 1940s.
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<p>No history of the B-17 would be complete, however, without reference to its exciting cloak-and-dagger operations with I/KG 200, the clandestine Gruppe of the Luftwaffe whose story has only recently come into the open. The B-17, mainly the G model, was its most important captured type, used for numerous long-range missions under the cover designation Dornier Do 200. These machines carried out daring operations throughout Europe, from Norway to Jordan and the Western Desert. They were not specifically intended to deceive the Allies, and wore German markings; they were used just because they were better for the job than any German aircraft.
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<hi style=hdr1>Specification</hi>
<hi style=hdr2>Boeing—B-17F-25-BO</hi>
<list style=aflst>
<item><hi format=bold>Type:</hi> heavy bomber with crew of eight to 10
<item><hi format=bold>Performance:</hi> maximum speed 295 mph (475 km/h); initial climb rate 900 ft (274 m) per minute; service ceiling 36,000 ft (10,975 m); combat radius with 5,000-lb (2,270-kg) bomb load 800 miles (1,287 km)
<item><hi format=bold>Dimensions:</hi> span 103 ft 9 in (31.6 m); length 74 ft 9 in (22.8 m); height 19 ft 2 in (5.85 m); wing area 1,420 sq ft (131.92 m<su>2</su>)
<item><hi format=bold>Armament:</hi> maximum bomb load 9,600 lb (4,355 kg), later increased to 17,600 lb (7,983 kg); defensive firepower normally 11 guns of 0.5-in (12.7-mm) caliber and one of 0.30-in (7.62-mm) caliber
