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B-47

B-47 "StratoJet"


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1. - Development


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2. - Serial #'s

B-47 Stratojet - Serials

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3. - Operational History

Early years

The USAF Strategic Air Command operated B-47 Stratojets (B-47s, EB-47s, RB-47s and YRB-47s) from 1951 through 1965.
When B-47s began to be delivered to the Air Force, most crews were excited about getting their hands on the hot new bomber, an aircraft whose performance was closer to that of jet fighters of the period than SAC's extant B-36 Peacemaker bomber. The B-47 was so fast that in the early days the aircraft set records with ease. The aircraft handled well in flight, with a fighter-like light touch to the controls. The large bubble canopy for the pilot and co-pilot enhanced the fighter-like feel of the aircraft with improved vision, but the design would also cause variations in internal temperatures for the 3-man crew.
It took the Air Force until 1953 to turn the B-47 into an operational aircraft. The aircraft was sluggish on takeoff and too fast on landings, a very unpleasant combination. If the pilot landed at the wrong angle, the aircraft would "porpoise", bouncing fore-and-aft. If the pilot didn't lift off for another go-round, instability would quickly cause the bomber to skid onto one wing and cartwheel. Because the wings and surfaces were flexible and bent in flight, low altitude speed restrictions were necessary to ensure effective flight control.
Improved training led to a good safety record, and few crews felt the aircraft was unsafe or too demanding, but apparently there were some aircrews who had little affection for the B-47. Crew workload was high, with only three officer crew members to keep the B-47 flying right. The B-52 Stratofortress, in contrast, generally had six crewmen, 5 officers and 1 enlisted, with far more internal cabin space.

Training and problems

The B-47's reliability and serviceability were regarded as good. The only major problem was poor avionics reliability, normal in this environment given the vacuum tube technology at the time, and the need to place some equipment outside the pressurized crew compartment. Much work was done to improve avionics reliability, but they remained problematic throughout the B-47's operational life.
Several models of the B-47 starting in 1950 included a fuel tank inerting system, in which dry ice was sublimated into carbon dioxide vapor while the fuel pumps operated or while the in-flight refueling system was in use. The carbon dioxide was then pumped into the fuel tanks and the rest of the fuel system, ensuring that the amount of oxygen in the fuel system was low, and thereby reducing the probability of an explosion. Ten carbon dioxide tanks and heaters were involved. The system was implemented largely to reduce risks from static electricity discharges occurring during in-flight refueling.


Strategic Air Command B-47 Stratojet bombers, the world's first swept-wing bomber.
Initial mission profiles included the loft bombing (Low Altitude Bombing System) of nuclear weapons. As the training for this imposes repeated high stress, the airframe lifetime would have been severely limited by metal fatigue, and this maneuver was eliminated.

Prime years

By 1956, the U.S. Air Force had 28 wings of B-47 bombers and five wings of RB-47 reconnaissance aircraft. The bombers were the first line of America's strategic nuclear deterrent, often operating from forward bases in the UK, Morocco, Spain, Alaska, Greenland, and Guam. B-47 bombers were often set up on "one-third" alert, with a third of the operational aircraft available sitting on hardstands or an alert ramp adjacent to the runway, loaded with fuel and nuclear weapons, crews on standby, ready to attack the USSR at short notice.
Crews were also trained to perform "minimum interval takeoffs (MITO)", with one bomber following the other into the air at intervals of as little as 15 seconds, to launch all bombers as fast as possible. MITO could be hazardous, as the bombers left turbulence and, with first generation turbojet engines with water injection systems, dense black smoke that blinded pilots in the following aircraft.
B-47 bombers apparently performed training missions in which they penetrated Soviet airspace in numbers. The facts behind these missions remain controversial, with some claiming that Curtis LeMay ordered them without presidential knowledge or approval.
The B-47 would be the backbone of SAC into 1959, when the B-52 began to assume nuclear alert duties and the number of B-47 bomber wings started to be reduced. B-47 production ceased in 1957, though modifications and rebuilds continued after that.
Operational practice for B-47 bomber operations during this time went from high altitude bombing to low altitude strike, which was judged more likely to penetrate Soviet defenses. Bomber crews were trained in "pop-up" attacks, coming in at low level at 425 knots (787 km/h) and then climbing abruptly near the target before releasing a nuclear weapon, and the similar "toss bombing" procedure, in which the aircraft released the weapon while climbing, and then rolled away to depart the area before bomb detonation.

Later years
Stress and fatigue incurred in low altitude operations led to a number of wing failures and crashes and an extensive refit program was initiated in 1958 to strengthen the wing mountings. The program was known as "Milk Bottle", named after the big connecting pins that were replaced in the wing roots.
One of the more notable mishaps involving a B-47 occurred on 5 February 1958 near Savannah, Georgia. A B-47 based out of Homestead AFB, Florida was engaged in a simulated combat exercise with an F-86 Sabre, the bomber simulating an attacking aircraft and the fighter a defender. As was the practice at the time, the B-47 was carrying a single 7,600 lb (3,400 kg) Mark 15 thermonuclear weapon without its core. During this exercise, the F-86 collided with the B-47. The F-86 pilot ejected and the fighter crashed, while the B-47 suffered substantial damage, including loss of power on one of its outboard jet engines. The bomber pilot had to "safe" soft drop the Mark 15 weapon off the coast of Savannah, Georgia near Tybee Island after three unsuccessful landing attempts at Hunter Air Force Base. The bomb was successfully jettisoned and the aircraft landed safely. An extensive nine-month search was mounted for the unarmed bomb, but proved futile.
The only B-47s to see anything that resembled combat were the reconnaissance variants. They operated from almost every airfield that gave them access to the USSR, and they often probed Soviet airspace, and on occasion, B-47 pilots were caught in situations from which mostly speed and evasion in retreat saved them. At least five of these aircraft were fired on, and three of these were shot down. The B-47s fired back with their tail turrets, though it is uncertain if they scored any kills, but in any case these were the only shots fired in anger by any B-47. These missions became impractical upon the introduction by the Russians of the trans-sonic MiG-19.
Final phaseout of B-47 bomber wings began in 1963, and the last bombers were out of service by 1965. The very last USAF operational aircraft was grounded in 1969. The U.S. Navy kept specialized B-47 test aircraft in occasional use up to 1976. The final recorded flight of a B-47 was on 17 June 1986, when a B-47E was flown from the Naval Air Weapons Station China Lake, California, to Castle Air Force Base, California, for static display at the Castle Air Museum. There are at least 15 B-47s on static display, none flying.

Strategic operations

Strategic operations of the 2,000 B-47s required 800 KC-97 Stratotankers. On a typical RB-47H reconnaissance mission covering 5,984 mi (9,360 km), the aircraft would fly from Thule, Greenland to the Kara Sea to Murmansk and then return only to find Thule weathered-in, forcing the flight from the air-refueling/decision point near the northeast shore of Greenland to one of three equidistant alternates: Goose Bay, Labrador, London, or Fairbanks, Alaska. Five KC-97s at Thule were required to support this scenario. Two ground spares and one air spare insured two 20,000 lb (9,090 kg) fuel transfers at a distance of over 600 mi (965 km) from Thule. Tankers returned to Thule to refuel and again repeat the flight to intercept the returning RB-47H six hours later for another air refueling.
The first overflight of Soviet territory with an RB-47 took place on 15 October 1952, when an RB-47B flying out of Alaska overflew Soviet airfields in Eastern Siberia. The Soviets scrambled MiG-15s to intercept, but the fast RB-47B got away unharmed.citation needed
On 8 May 1954, after a top secret reconnaissance mission in the Kola Peninsula, a 4th Air Division 91 Strategic Reconnaissance Wing RB-47E reconnaissance aircraft, with Hal Austin at the controls, flew west from the Soviet Union. The RB-47E was flying at high altitude, out of reach of MiG-15s, but unknown to USAF intelligence some MiG-17s had been stationed in the area and they were able to intercept the intruder, so the plane was being chased by three Soviet MiG-17 jet fighters. The Soviet fighters tried to destroy the RB-47E with their guns in Soviet and Finnish airspace, but the damaged RB-47E managed to escape over Sweden back to RAF Fairford station in Gloucestershire, England, where it had taken off, thanks to its remarkable top speed and combat radius superior to the Soviet fighter jets. It was the first mission in which a jet airplane equipped with modern photography equipment was used by American military reconnaissance. The incident was kept secret by all parties.
One RB-47 flying out of Alaska was scouting out the Kamchatka Peninsula on 17 April 1955, when it was bounced by Soviet MiG-15s in international airspace. The RB-47 and its crew disappeared. Between 21 March and 10 May 1956, 16 RB-47Es and 5 RB-47Hs operating from Thule, Greenland, performed overflights the length of Siberia 156 times under Project HOME RUN. The Soviets filed an angry complaint with the US government, which attributed the overflights to "navigational difficulties". MiGs did bounce RB-47s on three separate occasions in the fall of 1958, with one incident over the Black Sea on 31 October, the second over the Baltic on 7 November, and the third over the Sea of Japan on 17 November. In all three cases, the RB-47s got away without serious injury.citation needed
On 1 July 1960, a PVO Strany MiG-19 shot down an RB-47H (AF Serial No. 53-4281) reconnaissance aircraft in the international airspace over the Barents Sea with four of the crew killed and two captured by the Soviets but released in 1961. The co-pilot reported that the MiG-19 jammed (whited-out) his MD-4 FCS scope rendering the RB-47H defenseless. It seems the Soviets were annoyed over recent overflights and wanted to send the Americans a message that such provocations would have consequences.
The last known confrontation between MiGs and RB-47s took place on 27 April 1965, when an ERB-47H was jumped by North Korean MiG-17s over the Sea of Japan. The MiGs gave the ERB-47H a working over, but it managed to make it back to Yokota Air Base in Japan with two engines out.
While a few of these aircraft performed special duties during the Vietnam War, such as relaying ELINT data from drones, they were eventually replaced by much more comfortable and capable Boeing RC-135 platforms. The last RB-47H was retired on 29 December 1967.
The final 15 RB-47Es built were fitted with additional equipment, including the AN/APD "side looking airborne radar (SLAR)" system, and gear to sample the air for fallout from nuclear tests. The Air Force judged them different enough on delivery, beginning in December 1955, to give them a new designation of RB-47K.

The RB-47Ks were generally used for weather reconnaissance missions, carrying a load of eight "dropsonde" weather sensors that were released at various checkpoints along the aircraft's flight path. Data radioed back from the dropsondes was logged using equipment operated by the navigator. The RB-47Ks stayed in service until 1963.
Incidentally, there were B-47F, B-47G, and B-47J variants, but these were all one-shot conversions of B-47Bs or B-47Es, to be discussed later. There never was a B-47I variant. The Air Force never designated a B-47I, because the "I" suffix was too easily confused with the numeral "1."

Production numbers
The total number of B-47s built was 2,032.

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4. - Variants


XB-47 - 2
B-47A - 10
B-47B - 399
B-47E - 1,341
RB-47E- 240
RB-47H- 32
ERB-47H - 3
RB-47K - 15

Total 2,042

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5. - Technical Specifications

  • General characteristics

Crew: 3
Length: 107 ft 1 in (32.6 m)
Wingspan: 116 ft 0 in (35.4 m)
Height: 28 ft 0 in (8.5 m)
Wing area: 1,428 ft² (132.7 m²)
Airfoil: NACA 64A(0.225)12 mod root and tip
Empty weight: 79,074 lb (35,867 kg)
Loaded weight: 133,030 lb (60,340 kg)
Max takeoff weight: 230,000 lb (100,000 kg)
Powerplant: 6× General Electric J47-GE-25 turbojets, 7,200 lbf (32 kN) each
Zero-lift drag coefficient: 0.0148 (estimated)
Drag area: 21.13 ft² (1.96 m²)
Aspect ratio: 9.42

  • Performance

Maximum speed: 606 mph11 (527 kn, 977 km/h)
Cruise speed: 557 mph (484 kn, 896 km/h)
Combat radius: 2,013 mi (1,749 nmi, 3,240 km) with 20,000 lb (9,000 kg) bombload
Ferry range: 4,647 mi (4,037 nmi, 6,494 km)
Service ceiling: 33,100 ft (10,100 m)
Rate of climb: 4,660 ft/min (23.7 m/s)
Wing loading: 93.16 lb/ft² (454.8 kg/m²)
Thrust/weight: 0.22
Lift-to-drag ratio: 20.0 (estimated)

  • Armament

Guns: 2 × 20 mm M24A1 autocannons
Bombs: 25,000 lb (11,000 kg) of ordnance, including:
2 × nuclear bombs, or
28 × 500 lb (230 kg) conventional bombs


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6. - Operators


  • United States
    • United States Air Force
    • United States Navy

  • Canada
    • Royal Canadian Air Force

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7. - Survivors


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8. - Links


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9. - Markings


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10. - References



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