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Boeing 299 / B-17 Flying Fortress

Boeing B-40 / C-108 / F-9



Of the B-17C which followed, a batch of 20 were supplied to the RAF (designated Fortress I) and used operationally in Europe for evaluation, leading to improved B-17D and B-17E aircraft with self-sealing fuel tanks and revised armour and armament.

America's USAAC had been a little ahead of Britain in specifying their need for a four-engined bomber, and the prototype Boeing Model 299 / XB-17 designed to meet this require-ment flew for the first time on 28 July 1935. Powered by four 750 hp Pratt & Whitney Hornet engines, the prototype crashed three months later at Wright Field when the control locks were inad-vertently left engaged before takeoff.

A pre-production batch of 13 Y1B-17s was bought for evaluation.

It was not until 1938 that the USAAC was able to place an order for 39 production B-17B, the last of this batch entering service in March 1940. These were the first B-17 production aircraft to be equipped with turbocharged Wright Cyclone engines, providing a higher maximum speed and much increased service ceiling.

The United States had made twenty B-17Cs available to the Royal Air Force. They used them to bomb the German naval base at Wilhelmshaven on July 8th, 1941, marking the B-17's first hostile action.

Following an extensive redesign, to increase armour and armament, new versions were introduced and were widely used by the Americans, both in Europe and the Pacific.




Many changes were made as a result of combat experience first by the RAF and then by the USAAF in Europe. Even the B-17E , armed with one 7.62mm and 12 12.7mm machine-guns for defence and able to carry a maximum 7,983kg of bombs, was given a mauling by the Luftwaffe when it first ventured over Europe in daylight: but the Ame-ricans stood by their beliefs in the effectiveness of day bombing added still more guns, learned new tactics and eventually made possible the crushing round-the-clock bomber offensive.

Well over 3,000 of the B-17F were built.

A further modification programme, this time to improve the bomber's ability to repel air attacks from the front, produced the B17G with its twin-gun 'chin' turret which you can see clearly on this example.

Most extensively built variant was the B-17G (8,680), built by Douglas and Lockheed Vega as well as at the Boeing plant, Seattle. The B-17G model, the seventh variation of the origi-nal design, was equipped Pratt & Whitney R-1820-97 radial engines with super-chargers that allowed the airplane to cruise at 35,000 feet at a maximum speed of 285 miles per hour. It also carried up to thirteen .50-caliber machine guns and 6,000 pounds of bombs. The addition of a chin turret below the nose (containing two 12.7mm machine-guns) provided better defence against the head-on attacks. U.S.forces used it primarily for high-level daylight bombing over Europe. The for-midable machine gun placement en-abled B-17s to develop a highly effective defensive tactical formation.

The B-17 flew the 8th Air Force’s first combat mission out of England in August 1942. The British were skeptical about daylight bombing, but the American strategy was made possible by the ruggedness built into high-flying bombers like the B-17 and by the deadly accuracy of the Norden bombsight. Used as the spearhead of the U.S. Army Air Force’s attacks in Europe, the aircraft also saw combat duty in all theaters of war. Three days after Pearl Harbor, the Japanese convoys en route to Luzon in the Philippines were met by Flying Fortresses.

They flew high in huge formations, protecting each other with cross-fire, and dropped 640,036 tons of bombs in Europe for a loss of 4,750 aircraft.

Special variants included the B-40 with up to 30 machine-guns/cannons, which was intended as a B-17 escort, but proved to be an operational failure; BQ-7 pilotless aircraft packed with explosives to be deployed against German targets by radio control, which failed due to unreliable control equipment; CB-17 and C-108 transports; and F-9 long-range B-17 equipped to serve as an air-sea rescue aircraft and able to deploy a lifeboat carried beneath the fuselage.

At the height of production Boeing's Seattle plant alone produced a completed aircraft every ninety minutes.  A total of 12,731 built by Boeing, Douglas, and Lockheed Vega of which just over two-hundred were supplied to the RAF.


Versions of the wartime Flying Fortress were still in service in 1955 include lhe U.S.A.F.'s QB-17G drone, SB-17 with an airborne lifeboat and CB-17G V.I.P. transport; and the U.S. Navy's PB-1G air-sea rescue and PB-1W radar early-warning aircraft. All have four Wright R-1820-97 piston engines.



Boeing QB-17G Fortress


In New Mexico in 1950, Project Cirrus involved seeding rain clouds with dry ice from a B-17.
Project Cirrus


Project Cirrus
Project Cirrus




Allison Engines Testbed Gallery



 Engines: 4 x P&W Hornet, 750 hp
 Wingspan: 103 ft 9 in
 Length: 68 ft 9 in
 Take-off weight: 43,000 lb
 Bombload: 2570 lb
 Loaded range: 2000 mi at 204 mph


Gross weight: 49,650 lb
Empty weight: 30,620 lb
Fuel capacity: 1,700 Usgals
Engines: four 1,200 hp Wright Cyclone radials.
Top speed: 323 mph
Cruise speed: 250 mph
Climb to 25,000 ft.: 41 min
Range: 3,400 nm
Ceiling: 37,000 ft.

Engines: 4 x Wright R-1820-97, 1,200 hp, 885kW
Length 73.9 ft. (22.5 m)
Height: 5.8 m / 19 ft 0 in
Wing span: 103 ft 8 in (31.6 m)
Wing area: 141.9 sq.m / 1527.40 sq ft
Weight empty 32,250 lb. (14,630 kg)
Max. bomb load: 9,600 lb (4,350 kg)
Max. Speed 317 mph (510 kph)
Cruise speed: 250 km/h / 155 mph
Range 2,000 miles (3,220 km) with 4,000 lb. of bombs
Ceiling: 10700 m / 35100 ft
Crew: 10
Armament: Up to thirteen 0.30 and 0.50 in. machine-guns

Engine: 4 x Wright R-1850-65 Cyclone, 1200 hp
Wing span: 103 ft 9 in (31.62 m)
Length: 73 ft 10 in (22.5 m)
Height: 19 ft 2 in (5.84 m)
Engines: 4 x Wright, 1200 hp
Max TO wt: 53,000 lb (24,040 kg)
Max level speed: 275 kts / 317 mph / 510 kph
Service ceiling: 36581 ft / 11150 m
Range: 2592 nm / 4800 km
Crew: 9
Armament: 13x MG 12,7mm, 7985 kg Bomb

Engines: 4 x Wright Cyclone R-1820-97, 1,200 hp
Wing span: 103 ft. 9.5 in / 31.62m
Length: 74 ft. 9 in / 22.78m
Height: 19 ft. 1 in / 5.82m
Wing area: 1,420.0 sq ft / 131.92 sq.m
Loaded weight: 66,000 lb
Empty Weight: 36,136lbs (16,391kg)
Maximum Take-Off Weight: 72,003lbs (32,660kg)
Maximum Speed: 287mph / 462kmh; 249kts at 25,000 ft / 7,620 m
Cruise speed: 182 mph
Rate-of-Climb: 541ft/min (165m/min)
Climb to 20,000 ft / 6,095 m: 37 min 0 sec
Service Ceiling: 35,597ft (10,850m)
Armament: 13 x 0.5in Browning mg
Bombload: 8000 lb / 17,600 lb
Crew: 10
Range: 3,400 miles / 5,470 km
Range with 500lb load: 2100 miles / 3,220km



QB-17G Fortress
Engines: four Wright R-1820-97
Span: 103 ft. 9 in
Weight: 49,500 lb
Max Speed: 295 m.p.h.







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