Description: Jet Eyes Boeing B-47 Stratojet Canopy Rail - Metal The B-47 Stratojet was a long-range, six-engined turbojet-powered strategic bomber designed to fly at high subsonic speeds and altitudes to avoid enemy detection and interception The primary mission of the B-47 was as a nuclear bomber capable of striking targets within the former Soviet Union This structured tag was cut from the canopy rail of a B-47It is a classic example of the bespoke qualities which speak volumes on each and every engineered piece released by Jet Eyes The patina of this multi-layered riveted piece and it’s design, materials and construction are a testament to an aircraft which forged the direction of the modern commercial jet airliner age Development of the B-47 can be traced back to a 1943 requirement expressed by the US Army Air Forces (USAAF) 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 engines carried in nacelles underneath the wing, the B-47 represented a major innovation in post–WWII combat jet design and contributed to the development of modern jet airliners In April 1946, the USAAF ordered two prototypes designated XB-47. On 17th 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 x10 B-47A bombers was signed on 3rd September 1948. This would be soon followed by much larger contracts During 1951 the B-47 entered operational service with the USAF Strategic Air Command (SAC) becoming a mainstay of its bomber strength by the late 1950s. Over 2000 were manufactured to meet Air Force demand 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 Boeing's own 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 Swept Wings In May 1945 the von Kármán mission of the Army Air Forces inspected the secret German aeronautics laboratory near Braunschweig. Von Kármán's team included the chief of the technical staff at Boeing, George S. Schairer. He had heard about the controversial swept-wing theory of RT Jones at Langley but after seeing German models of swept-wing aircraft and extensive supersonic wind-tunnel data the concept was decisively confirmed. He wired his home office: "Stop the bomber design" and changed the wing design. Analysis by Boeing engineer Vic Ganzer suggested an optimum sweepback angle of about 35 degrees. Boeing's aeronautical engineers modified the “Model 432” with swept wings and tail to produce the "Model 448" which was presented to the USAAF in September 1945. It retained the four TG-180 jet engines in its forward fuselage with two more TG-180s in the rear fuselage. The flush-mounted air intakes for the rear engines were inadequate while the USAAF considered the engine installation within the fuselage to be a fire hazard The engines were moved to streamlined pylon-mounted pods under the wings leading to the next iteration – the ”Model 450” which featured two TG-180s in a twin pod mounted on a pylon about a third of the way outboard on each wing plus another engine at each wingtip for good measure. The Army Air Force liked this new configuration so Boeing's engineers refined by moving the outer engines further inboard to about 3⁄4 of the wingspan. The thin wings provided no space for “tricycle main gear” to retract so it would have needed a considerable bulge in the fuselage aft of the bomb bay for lateral stability. The only technique to get a bomb-bay long enough for an A-bomb was a "bicycle landing gear" configuration. The two main gear assemblies were arranged in a tandem configuration with outrigger struts fitted to the inboard engine pods. As the landing gear arrangement made rotation impossible it was designed so that the aircraft rested on the ground at the proper angle for takeoff Pleased with the refined “Model 450” design the USAAF ordered two prototypes to be designated XB-47 in April 1946. Assembly began in June 1947 and the first XB-47 was rolled out on 12th September 1947 - six days before the USAAF became a separate service United States Air Force (USAF). According to aviation authors Bill Gunston and Peter Gilchrist, Boeing subjected the first prototype to "one of the most comprehensive ground-test programmes ever undertaken" Flight Test Phase The XB-47 prototype flew its first flight on 17th December 1947 (the anniversary of the Wright Brothers' first four flights in 1903) with test pilots Robert Robbins and Scott Osler at the controls. It lasted 27min flying from Boeing Field in Seattle to Moses Lake Airfield in central Washington State. While not experiencing major problems the emergency hot wire system was needed to raise the flaps and the engine fire warning indicators falsely illuminated. Robbins stated that it had good flight characteristics Robbins had been sceptical about the XB-47 saying that before his first flight he had prayed "Oh God, please help me through the next two hours" Robbins soon realized that he had an extraordinary aircraft. Chuck Yeager also flew the XB-47 noting it was so aerodynamically clean, so much so that he had difficulty landing on the Edwards lakebed. In February 1949 Russ Schleeh and Joe Howell "broke all coast-to-coast speed records" flying between Moses Lake and Andrews AFBs averaging 607.8mph. During an early test flight the canopy came off at high speed killing pilot Scott Osler. The aircraft was safely landed by the co-pilot and the accident resulted in a canopy redesign and hiring of pilot Tex Johnston as chief test pilot The second XB-47 (46-066) prototype first flew on 21st July 1948 and following its delivery to the USAF in December of that year served as a flying test bed until 1954. Its final destination was Chanute AFB where it was used as a maintenance and familiarisation aircraft. The second prototype was equipped with more powerful General Electric J47-GE-3 turbojets with 5,200 lbf of static thrust each. The J47 or "TG-190" was a redesigned version of the TG-180/J35. The first prototype was later retrofitted with these engines Flight testing of the prototypes was careful and methodical since the design was new in so many ways. They initially suffered from "Dutch roll" - an instability that caused it to weave in widening S turns and remedied by the addition of a "yaw damper" control system to automatically deflect the rudder to damp out the weaving motion. Wind tunnel tests had shown it would pitch up at maximum speed due to wing stall on the outboard section of the wing. This was confirmed during flight tests so small vanes called "vortex generators" were added to prevent airflow separation Both XB-47 prototypes were test flown at Edwards AFB. The first XB-47 (46-065) was disassembled and scrapped in 1954 making the second prototype (46-066) the sole surviving XB-47. Upon retirement, XB-47 (46-066) was restored and placed on display at the Octave Chanute Aerospace Museum in Rantoul, IL remaining there until the museum announced its closure due to financial difficulties in April 2015. In late 2015 the Flight Test Historical Foundation began fundraising to purchase XB-47 (46-066) for relocation to the Flight Test Museum at Edwards AFB. The purchase was completed in August 2016 and on 21st September 2016 the aircraft arrived at Edwards AFB for reassembly, restoration and eventual display at the Flight Test Museum Overview The XB-47 looked nothing like contemporary bombers and was described by Boyne as a "sleek, beautiful outcome that was highly advanced". The 35 degree swept wings were shoulder-mounted, the inboard turbojet engines mounted in twin pods at about a third of the span and the outboard engines singly near the wing tip. This arrangement reduced the bending moment at the wing roots, saving structural weight. Powerplant mass acted as counter-flutter weights The wing airfoil was identified by Boeing as the BAC 145, also known as NACA 64A (.225) 12 mod. Wing flexibility was a concern, flexing as much as 17.5’ at the tip. Major effort was expended to ensure that flight control could be maintained as the wing moved up and down, these worries proved to be mostly unfounded. Its maximum speed was limited to 425kn IAS to avoid control reversal, where aileron deflections would cause the wings to twist and produce a roll in the opposite direction to that desired by the pilot. The wings were fitted with a set of Fowler flaps that extended well behind the wing to enhance lift at slow speeds. The flight control surfaces were powered, augmenting the pilot's inputs and reducing the exertion required to overcome the forces involved The XB-47 was designed to carry a crew of three in a pressurised forward compartment: a pilot and co-pilot in tandem in a long fighter-style bubble canopy and a navigator/bombardier in a compartment in the nose. The co-pilot doubled as tail gunner (using a remotely controlled, radar-directed tail gun) and the navigator as bombardier. The bubble canopy which provided a high level of visibility to the pilots, pitched up and slid backward as the cockpit was high off the ground, the crew entered via a door and ladder on the underside of the nose. The extreme front of the nose was initially glazed for visual navigation and bomb sighting but this requirement was soon deleted together with the glazing. Most production versions had a metal nose with no windows. A K series bombsight provided integrated radar navigation and visual navigation the optical portion extending through the nose in a small dome. For greater comfort both heaters and refrigeration systems were present in the cockpit to manage the cockpit environment. There was little vibration compared to prior bombers powered by reciprocating engines Engines and Performance During the late 1940s the bomber was hailed as the fastest of its class in the world. The first prototypes were fitted with GE J35 turbojets, the production version of the TG-180 with 3970 lbf of thrust. Early jet engines did not develop good thrust at low speeds so to assist take off when heavily loaded the B-47 had provisions for fitting solid-fuel rocket-assisted takeoff (RATO) rockets, each generating roughly 1000 lbf of static thrust. Early aircraft had mounts for nine RATO units built into each side of the rear fuselage arranged in three rows of three bottles. Most of the space within the upper fuselage was taken up by self-sealing fuel tanks, the wing having been deemed unsuitable for storing fuel The performance of the “Model 450” was projected to be so good that the bomber would be as fast as fighters then on the drawing board thus the only defensive armament was to be a tail turret with two .50” AN/M2 Browning machine guns which would in principle be directed by an automatic fire-control system. The two XB-47s were neither fitted with combat equipment nor tail turrets as they were engineering and flight test aircraft only. The total bombload capacity was to be 25000lb. Production aircraft were to be equipped with modern electronics for navigation, bombing, countermeasures and turret fire control. Navigation was more difficult than on earlier aircraft due to the higher speed involved One problem with the aircraft was that higher altitudes where the pure turbojet engines could produce good fuel economy, the wing became compromised. At the top of the B-47s envelope of 35000’ it entered "coffin corner". At an altitude permitting optimal range efficiency over most payloads, there was an envelope of 5kn between maximum MACH and stall speed. For the B-47 to cross the Atlantic Ocean it had to be flown this high. Due to its rudimentary autopilot the pilot had to leave it turned off and spend up to eight hours diligently monitoring the airspeed and adjusting the throttles to avoid going into a stall. For perspective a B757 has a split of over 50kn for the heaviest loads at 41000’. Fuel capacity was enormous at 17000 USG, more than triple the 5000 USG of the B-29 Superfortress. This meant that maintaining fuel trim to ensure a stable centre of gravity was a critical co-pilot duty Drogue Chutes The aircraft was so aerodynamically clean that rapid descent "penetration" from high cruise altitudes to the landing pattern required dragging the deployed rear landing gear. The relatively high wing loading (weight/wing area) required a high landing speed of 180kn. To shorten the landing roll USAF test pilot Major Guy Townsend promoted the addition of a 32’ German-invented "ribbon" drag chute (thrust reversers had not then been developed). For the same reason the B-47 was the first mass-produced aircraft to be equipped with an anti-skid braking system A related problem was engine thrust reduction on landing approach. Since it could take as long as 20 sec to throttle back to full power the bomber could not easily do a "touch and go" momentary landing. A 16’ "approach chute" (drogue parachute) provided aerodynamic drag so that the aircraft could be flown at approach speeds with the engines throttled at ready-to-spool-up medium power. On the ground the pilots used the 32’ "brake chute" which could be deployed to stop the aircraft from "porpoising" or bouncing after a hard landing on the front nose gear. Training typically included an hour of dragging the approach chute around the landing pattern for multiple practice landings Early Years The USAF Strategic Air Command operated multiple B-47 models between 1951 and 1965. Upon entry to service its performance was closer to that of contemporary fighters than SAC's including the B-36 Peacemaker bomber setting multiple records with ease. It handled well in flight, the controls had a fighter-like light touch. The large bubble canopy enhanced flight crew visibility and gave a fighter-like feel. It did however cause internal temperature variations for the crew. The three-man crew consisted of the commander, copilot and a navigator/bombardier or a crew chief The B-47 became operational in 1953 having the unfortunate characteristics of being sluggish on takeoff and too fast on landings. If landed at the wrong angle the B-47 would "porpoise", bouncing fore-and-aft. If the pilot did not lift off for another go-around instability would quickly cause it to skid onto one wing and cartwheel. Because the wings and surfaces flexed in flight, low-altitude speed restrictions were necessary to ensure effective flight control. While the B-47 was regarded as a maintenance "hog", general reliability was good. The only major issuing related to the vacuum tube technology avionics. Positioning equipment outside the pressurised crew compartment provided increased cooling which enhanced some aspects of reliability but further work was still required. Advancements in electro-technology were slow during this era which plagued the B-47 throughout its operational life From 1950 several models of the B-47 included a fuel tank inerting system in which dry ice was sublimed into carbon dioxide vapour while the fuel pumps operated or while the in-flight refuelling system was in use. The carbon dioxide was pumped into both the fuel tanks and the fuel system to ensure low oxygen levels throughout. It was implemented largely to reduce the probability of an explosion from static electricity discharges Initial mission profiles included the loft bombing of nuclear weapons. As the training for this imposes repeated high stress on the aircraft, the airframe lifetime would have been severely limited by metal fatigue and this manoeuvre was eliminated. Improved training led to a good safety record and few crews felt the aircraft was unsafe or too demanding. Despite this some aircrews had little affection for the B-47. With only three crew members workload was high. In contrast Boeing's B-52 Stratofortress generally had six crew, five officers and one enlisted with more internal cabin space Prime Years B-47 variants flew multiple nuclear weapons test flights throughout the 1950s and “reflex” missions proved endurance (up to 18hrs) long range capability of the B-47 and aircrews. These were also "simulated strike missions against the then Soviet enemy" Three B-47s flew cross country from March AFB to Philadelphia International Airport as participants in the 1955 Labor Day race. In the 1956 event three B-47s participated in the GE Trophy race for Jet Bombers flying from Kindley Field, Bermuda to Oklahoma City, one setting a course speed record of 522.417kn By 1956 the USAF had x28 B-47 bombers and x5 RB-47 reconnaissance aircraft. The B-47 was the first line of America's strategic nuclear deterrent often operating from forward bases in the UK, Morocco, Spain, Alaska, Greenland and Guam. B-47s were often set up on "one-third" alert where a third of operational aircraft available would sit on hardstands or alert ramps adjacent to runways loaded with fuel and nuclear weapons with crews on hot standby ready to attack the USSR at short notice. Crews were trained to perform "Minimum Interval Take Offs” (MITO) one bomber following another into the air at intervals of as little as 15s to launch as fast as possible. MITO could be hazardous as the bombers left wingtip vortices and general turbulence behind them. The first generation turbojet engines fitted with water-injection systems also created dense black smoke The B-47 was the backbone of SAC into 1959 when the B-52 began to assume nuclear alert duties and the number of B-47s started to reduce. Production ceased in 1957 though modifications and rebuilds continued. Operational practice for B-47 bomber during this time went from high-altitude bombing to low-altitude strike which was judged more likely to penetrate Soviet defenses. Crews were trained in "pop-up" attacks coming in at low level at 425kn then climbing abruptly near the target before releasing a nuclear weapons Reconnaissance The only B-47s to see anything resembling combat were the aerial reconnaissance variants. The first overflight of Soviet territory with a B-47B fitted with special radar and cameras in the bomb bay occurred on 15th October 1952, overflying Soviet airfields in North-eastern Siberia. RB-47s operated from almost every airfield that gave them access to the USSR and routinely probed Soviet airspace. Occasionally they would avoid confrontations with speed and evasion. At least five aircraft were fired upon and three were shot down. The RB-47s returned fire with their tail turrets although it is uncertain if they scored any kills. These were the only shots fired in anger by any B-47 On 8th May 1954 after a top secret reconnaissance mission near the Kola Peninsula, a 4th Air Division/91st Strategic Reconnaissance RB-47E flown by then Captain Harold "Hal" Austin overflew the Soviet Union at high altitude out of reach of MiG-15s. Unknown to USAF intelligence MiG-17s capable of intercepting it had been stationed nearby. The RB-47E was chased by several MiG-17s, firing upon it with their guns over Soviet and Finnish airspace. While taking damage the RB-47E escaped over Sweden to its home base at RAF Fairford, Gloucestershire. Its top speed and combat radius superiority to the fighter jets were decisive factors. The mission marked the first time a jet aircraft equipped with modern K-17 and K-38 aerial photographic equipment was used for USAF reconnaissance over the Soviet Union. The incident was kept secret by all parties Other interceptions resulted in losses. An RB-47 flying from Alaska was scouting the Kamchatka Peninsula on 17th April 1955 when it was intercepted by Soviet MiG-15s in international airspace before disappearing. Between 21st March and 10th May 1956, x16 RB-47Es and x5 RB-47Hs operating from Thule performed overflights the length of Siberia 156 times under Project HOMERUN. The Soviets filed a complaint with the US government which attributed the overflights to "navigational difficulties". MiGs intercepted RB-47s on three separate occasions over the Black Sea on 31st October, the Baltic on 7th November and the Sea of Japan on 17th November 1958 On 1st July 1960 a PVO Strany MiG-19 shot down an RB-47H (USAF S/N 53-4281) in international airspace over the Barents Sea killing four of the crew while two were captured by the Soviets and released in 1961. The co-pilot reported that the MiG-19 jammed his MD-4 FCS (that aimed the tail guns) rendering it defenseless. The last known confrontation between MiGs and RB-47s occurred on 28th April 1965 when an ERB-47H was intercepted by two North Korean MiG-17s over the Sea of Japan. While hit by the MiGs it returned to Yokota Air Base, Japan with three engines out. A few operated during the Vietnam War on missions such as relaying ELINT data but were replaced by more efficient and capable Boeing RC-135s. The last RB-47H was retired on 29th December 1967 The final x15 RB-47s built from December 1955 were fitted with additional equipment including AN/APD "side looking airborne radar" (SLAR) and equipment to sample air from the fallout of nuclear tests. These were given the designation RB-47K and generally used for weather reconnaissance missions carrying a load of eight "dropsonde" weather sensors that were released at various checkpoints along the flight path. Reflected RF data was logged by the navigator. The RB-47Ks were in service until 1963, succeeded by dedicated reconnaissance aircraft such as the Lockheed U-2 Later Years Stress and fatigue incurred in low-altitude operations led to a number of wing failures, crashes and an extensive refit program to strengthen the wing mountings beginning in 1958. The program was known as "Milk Bottle" named after the big connecting pins that were replaced in the wing roots A more notable mishaps occurred on 5th February 1958 near Savannah, GA when a B-47 based at Homestead AFB, FL was engaged in a simulated combat exercise against an F-86 fighter. As was the practice at the time the B-47 was carrying a single 7600lb Mark 15 nuclear bomb without its core. During this exercise the two aircraft collided. The F-86 crashed after the pilot ejected while the B-47 suffered substantial damage including loss of power in one outboard engine. After three unsuccessful landing attempts at Hunter AFB the bomber pilot had to "safe" soft drop the Mark 15 weapon off the coast of Savannah near Tybee Island after which a safe landing was performed. Despite an extensive nine-month search the unarmed bomb was never found In 1963 the Kennedy administration offered x24 B-47E bombers as an interim Canberra Mk 20 replacement for the Royal Australian Air Force (RAAF) pending delivery of the much delayed F-111C. Three B-47E aircraft flew to Australia for demonstration purposes but the RAAF wisely declined stating the aircraft was technically outdated and too resource-intensive During 1963 final phase-out of B-47s the last were out of SAC service by 1966. The last USAF operational aircraft were WB-47Es assigned to the Air Weather Service and were withdrawn from use in September 1969. Shortly before B-47E USAF S/N 53-2280 was used as a testbed for a newly developed fly-by-wire system. The US Navy kept specialized the EB-47E test aircraft from USAF inventory in occasional use to support the Fleet Electronic Warfare Systems Group (FEWSG) until December 1977 being replaced by government owned/contractor operated (GOCO) NKC-135 modified Stratotankers also loaned from the USAF The final recorded flight of a B-47 was on 17th June 1986 when a B-47E was restored to flightworthy condition for a one-time ferry flight. This aircraft was flown from Naval Air Weapons Station China Lake, CA to Castle AFB, CA for static display at the Castle Air Museum, where it presently resides So there y’all have it!
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