Flying Fortress

B-17 Flying Fortress
B-17 "Sally B", England, 2001.
Description
Role	Heavy bomber
Crew	10—Pilot, copilot, bombardier, navigator, gunners (6): top turret gunner/flight engineer, dorsal gunner/radio operator, ball turret gunner, left waist gunner, right waist gunner, tail gunner
First Flight	1935 July 28
Entered Service	1938
Manufacturer	Boeing
Cost	$276,000 (1930s U.S.)
Dimensions
Length	74 ft 4 in	22.7 m
Wingspan	103 ft 10 in	31.6 m
Height	19 ft 1 in	5.8 m
Wing Area	1,527.4 ft²	141.9 m²
Weights
Empty	54,894 lb	24,900 kg
Loaded	72,134 lb	32,720 kg
Maximum Takeoff	74,134 lb	33,627 kg
Capacity
Powerplant
Engines	Wright R-1820 ‘Cyclone’ (4)
Power	1,200 hp	895 kW
Performance
Maximum Speed	287 mph	462 km/h
Combat Range	1,851 miles	2980 km
Ferry Range	miles	km
Service Ceiling	35,600 ft	10,850 m
Rate of Climb	ft/min	m/min
Wing Loading	47.2 lb/ft²	230.6 kg/m²
Power/Mass	.0665 hp/lb	.1094 kW/kg
Armament
Guns	Browning M-2 0.50-calibre (12.7 mm) machine guns (13)
Bombs	6,000 lb

The B-17 Flying Fortress was the first mass-produced, four-engine heavy bomber. It is still one of the most recognised aeroplanes ever built. It was most widely used for daylight strategic bombings of German industrial targets during World War II as part of the United States 8th Air Force.

The prototype B-17 first flew on 1935 July 28 as the Boeing Model 299. During a demonstration later that year at Wright Field in Dayton, Ohio, Model 299 competed with the Douglas DB-1 and Martin Model 146. While the Boeing design was obviously superiour, Army officials were daunted by the much greater expence per aircraft. It did not help that the Model 299 had during the demonstration, despite the fact that this crash was due to pilot error. In 1936, only 13 B-17s were ordered, next to 99 B-18s (successor of the DB-1).

The first B-17 went into service in 1938. By 1941 December 7, few B-17s were in use by the Army. Following the attack on Pearl Harbor, production was quickly accelerated. The aircraft served in every World War II combat zone. Production ended in 1945 May after 12,726 aircraft had been built.

Contrary to the common misperception that the aircraft was named the "Flying Fortress" because of the number of heavy machine guns it carried, it received that sobriquet from newspaper reporters in the 1930s based on its original mission as a coastal patrol bomber, a 'flying fortress' that would guard the nation's offshore limits beyond the range of the heavy guns sited at major harbours. Among the combat aircrews that flew bombers in World War II, noted aviation writer Martin Caidin reported that the B-17 was referred to as the "Queen of the Bombers."

The B-17 was noted for its ability to take battle damage, still reach its target and bring its crew home. It reportedly was much easier to fly than its contemporaries, and its toughness more than compensated for its shorter range and lighter bomb load when compared to the Consolidated B-24 Liberator or the British Avro Lancaster heavy bombers.

The design went through eight major changes over the course of its production, culminating in what some consider the definitive type, the B-17G, differing from its immediate predecessor by the addition of a chin turret with two 0.50-calibre (12.7 mm) machine guns under the nose. This eliminated the aeroplane's main defencive weakness.

Variants/Design stages

• —Competed at the Wright Field evaluation in 1935; crashed due to pilot error. (×1)
• —(The Y1B- prefix indicates a funding source outside normal fiscal year procurement.) The prefix was changed to YB- on 1936 November 20 before it first flew. While meant for flight testing, General Andrews of the Army General Head Quarters Air Force decided to push development of heavy bomber techniques, and assigned twelve YB-17s to the Second Bomb Group based in Langley Field, Virginia. The thirteenth was the only of the order used for flight testing. It was assigned to Material Division at Wright Field. (×13)
• —The aircraft that became the sole Y1B-17A was originally ordered as a static test bed for engine types; results study of a variety of configurations led to the use of a bottom-mounted turbo-supercharger. This turbo-supercharge became standard on the B-17B, and allowed it to fly higher and faster than the YB-17. When testing was complete the Y1B-17A was renamed the B-17A. (×1)
• —The B-17B was essentially a B-17A with a larger rudder, larger flaps, and a redesigned nose. Used Wright R-1820-51 engines of 1,000 hp (746 kW) each. (×39)
  • RB-17B. Redesignation of the B-17B, occurring in 1942 October. RB- indicates ‘restricted’; it was used for training, transport, messenger, and liason duties.
• —B-17B with more powerful machine gun used in the B-17E was replaced by a .50-calibre gun, and two cheek guns were added, bringing the total guns to 11. The maximum bomb capacity was increased from 4,200 lb to 8,000 lb; this reduced the cruise speed by 70 mph (113 km/h). A number of other modifications were made, including adding a Bendix chin turret and external bomb racks. The Memphis Belle was a B-17F. (×3405: 2300 Boeing, 605 Douglas, 500 Lockheed-Vega)
• —Final B-17 version. The changes made in the course of the B-17F production run were all incorporated into the final, defining, B-17G design. (×8680). A number of were made to the B-17G design:
  • CB-17G. Troop transport capable of carrying 64 troops.
  • DB-17G. Drone variant.
  • JB-17G. Engine test-bed. (×3)
  • RB-17G. Reconnaissance variant.
  • —Rescue version, originally designed as B-17H. Featured A-1 lifeboat under fuselage. After World War II, armament on the SB-17G was removed; it was reinstated when the Korean conflict began.
  • VB-17G. VIP transport.
• —A modification project undertaken by Boeing and Lockheed-Vega on the ninth B-17E built; one major change was use of Allison V-1710-89 engines. It was meant as an improved version of the B-17, and a variant that could be used if the Wright R-1820 engine became scarce. Completing the modifications took less than a year, and the XB-38 made its first flight on 1943 May 19. While it showed a slightly higher top speed, after a few flights it had to be grounded due to a problem with engine manifold joints leaking exhaust. Following the fixing of this problem, testing continued until the ninth flight on 1943 June 16. During this flight, the third (right inboard) engine caught fire, and the crew was forced to bail out. The XB-38 was destroyed and the project cancelled, in part because the V-1710 engines were needed for other projects.
• —Prior to the introduction of the P-51 Mustang, a B-17 escort variant called the YB-40 was introduced. This aircraft differed from the standard B-17 in that a second dorsal turret was installed between the top turret and the waist guns; and the single 0.50-calibre (12.7 mm) machine gun at each waist station was replaced by a pair of 0.5-calibre (12.7 mm) guns. In addition, the bombardier’s equipment was replaced with two 0.50-calibre (12.7 mm) machine guns in a ‘chin’ turret to augment the existing ‘cheek’ machine guns, and the bomb bay itself was converted to a magazine. The concept was twofold. First, the YB-40 would provide a heavily-gunned escort capable of accompanying the bombers all the way to the target and back. Second, they were used as decoys; a YB-40 would leave the bomber stream with one engine feathered, apparently in distress. Enemy fighters would close for the kill and discover that the 'cripple' was nothing of the kind. The aircraft was used with some success in the Mediterranean, but was overall a failure because it could not keep up with standard B-17Fs once they had dropped bombs. It was withdrawn from service after less than ten missions. (×25: 1 XB-40, 20 YB-40, 4 TB-40)
• BQ-7. Late in WWII, at least 25 B-17s were loaded with 12,000 lb (5443 kg) of high explosives, fitted with radio controls, dubbed "BQ-7 Aphrodite missiles," and used against U-boat pens and bomb-resistant fortifications. Because few (if any) BQ-7s hit their target, the Aphrodite project was scrapped in early 1945. (×24)

Units Using the B-17

United States Army Air Force

Royal Air Force

• Number 59 Squadron
• Number 90 Squadron
• Number 206 Squadron
• Number 214 Squadron
• Number 220 Squadron
• Number 223 Squadron
• Number 251 Squadron
• Number 517 Squadron
• Number 519 Squadron
• Number 521 Squadron

Israeli Air Force