The Boeing B-47 Stratojet (Boeing company designation Model 450) is a retired American long-range, six-engined, turbojet-powered strategic bomber designed to fly at high subsonic speed and at high altitude to avoid enemy interceptor aircraft. The primary mission of the B-47 was as a nuclear bomber capable of striking targets within the Soviet Union.
Development of the B-47 can be traced back to a requirement expressed by the United States Army Air Forces (USAAF) in 1943 for a reconnaissance bomber that harnessed newly developed jet propulsion. Another key innovation adopted during the development process was the swept wing, drawing upon captured German research. With its engines carried in nacelles underneath the wing, the B-47 represented a major innovation in post-World War II combat jet design, and contributed to the development of modern jet airliners. Suitably impressed, in April 1946, the USAAF ordered two prototypes, designated "XB-47"; on 17 December 1947, the first prototype performed its maiden flight. Facing off competition such as the North American XB-45, Convair XB-46 and Martin XB-48, a formal contract for 10 B-47A bombers was signed on 3 September 1948. This would be soon followed by much larger contracts.
During 1951, the B-47 entered operational service with the United States Air Force's Strategic Air Command (SAC), becoming a mainstay of its bomber strength by the late 1950s. Over 2,000 were manufactured to meet the Air Force's demands, driven by the tensions of the Cold War. The B-47 was in service as a strategic bomber until 1965, at which point it had largely been supplanted by more capable aircraft, such as the Boeing B-52 Stratofortress. The B-47 was also adapted to perform a number of other roles and functions, including photographic reconnaissance, electronic intelligence, and weather reconnaissance. While never seeing combat as a bomber, reconnaissance RB-47s would occasionally come under fire near or within Soviet air space. The type remained in service as a reconnaissance aircraft until 1969. A few served as flying testbeds up until 1977.
The B-47 arose from an informal 1943 requirement for a jet-powered reconnaissance bomber, drawn up by the United States Army Air Forces (USAAF) to prompt manufacturers to start research into jet bombers. Boeing was among several companies to respond to the request; one of its designs, the Model 424, was basically a scaled-down version of the piston-engined B-29 Superfortress equipped with four jet engines. In 1944, this initial concept evolved into a formal request-for-proposal to design a new bomber with a maximum speed of 550 mph (480 kn; 890 km/h), a cruise speed of 450 mph (390 kn; 720 km/h), a range of 3,500 mi (3,000 nmi; 5,600 km), and a service ceiling of 45,000 ft (13,700 m).
In December 1944, North American Aviation, Convair, Boeing and the Glenn Martin Company submitted proposals for the new long-range jet bomber. Wind tunnel testing had shown that the drag from the engine installation of the Model 424 was too high, so Boeing's entry was a revised design, the Model 432, with the four engines buried in the forward fuselage. The USAAF awarded study contracts to all four companies, requiring that North American and Convair concentrate on four-engined designs (to become B-45 and XB-46), while Boeing and Martin were to build six-engined aircraft (the B-47 and XB-48). The powerplant was to be General Electric's new TG-180 turbojet engine.
In May 1945, the von Kármán mission of the Army Air Forces inspected the secret German aeronautics laboratory near Braunschweig.
General characteristics
Crew: 3
Length: 107 ft 1 in (32.64 m)
Wingspan: 116 ft 0 in (35.36 m)
Height: 28 ft 0 in (8.53 m)
Wing area: 1,428 sq ft (132.7 m2)
Aspect ratio: 9.42
Airfoil: NACA 64A(.225)12 mod (BAC145)
Empty weight: 80,000 lb (36,287 kg)
Gross weight: 133,030 lb (60,341 kg)
Max takeoff weight: 221,000 lb (100,244 kg)
Zero-lift drag coefficient: 0.0148 (estimated)
zero-lift drag coefficient area: 21.13 ft2 (1.96 m2)
Powerplant: 6 × General Electric J47-GE-25 turbojet engines, 7,200 lbf (32 kN) thrust each
Performance
Maximum speed: 607 mph (977 km/h, 527 kn)
Cruise speed: 557 mph (896 km/h, 484 kn)
Combat range: 2,013 mi (3,240 km, 1,749 nmi) with 20,000 lb (9,100 kg) bombload
Ferry range: 4,647 mi (7,479 km, 4,038 nmi) with underwing tanks
Service ceiling: 40,500 ft (12,300 m)
Rate of climb: 4,660 ft/min (23.7 m/s)
Wing loading: 93.16 lb/sq ft (454.8 kg/m2)
Thrust/weight: 0.22
Armament
Guns: 2 × 20 mm (0.787 in) M24A1 autocannon in a remote controlled tail turret with
Bombs: 25,000 lb (11,340 kg) of ordnance, including:
2 × Mk15 nuclear bombs (3.8 megaton yield each), or
4 × B28 nuclear bombs (1.1-1.45 megaton yield each), or
1 × B41 nuclear bomb (25 megaton yield), or
1 × B53 nuclear bomb (9 megaton yield), or
28 × 500 lb (227 kg) conventional bombs
#b47 #stratojet #aircraft
25 авг 2024
