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102-528: 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

204-529: A η j {\displaystyle P_{br}={\frac {P_{a}}{\eta _{j}}}} The corresponding fuel weight flow rates can be computed now: F = c p P b r {\displaystyle F=c_{p}P_{br}} Thrust power is the speed multiplied by the drag, is obtained from the lift-to-drag ratio : P a = V C D C L W g ; {\displaystyle P_{a}=V{\frac {C_{D}}{C_{L}}}Wg;} here Wg

306-785: A = 7 5 R s T {\textstyle a={\sqrt {{\frac {7}{5}}R_{s}T}}} ; here R s {\displaystyle R_{s}} is the specific heat constant of air 287.16 J/kg K (based on aviation standards) and γ = 7 / 5 = 1.4 {\displaystyle \gamma =7/5=1.4} (derived from γ = c p c v {\textstyle \gamma ={\frac {c_{p}}{c_{v}}}} and c p = c v + R s {\displaystyle c_{p}=c_{v}+R_{s}} ). c p {\displaystyle c_{p}} and c v {\displaystyle c_{v}} are

408-542: 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

510-532: A thrust specific fuel consumption , so that rate of fuel flow is proportional to drag , rather than power. F = c T T = c T C D C L W {\displaystyle F=c_{T}T=c_{T}{\frac {C_{D}}{C_{L}}}W} Using the lift equation, 1 2 ρ V 2 S C L = W {\displaystyle {\frac {1}{2}}\rho V^{2}SC_{L}=W} where ρ {\displaystyle \rho }

612-508: A B-47 was on 17 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 , California, to Castle Air Force Base , California, for static display at the Castle Air Museum, where it presently resides. The only B-47s to see anything close to combat were the aerial reconnaissance variants. The first overflight of Soviet territory with

714-580: A B-47B, fitted with special radar and cameras in the bomb bay, occurred on 15 October 1952, overflying Soviet airfields in Northeastern 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

816-578: A B-47E, USAF Serial Number 53-2280, was used as a testbed for a newly developed fly-by-wire system. The U.S. Navy kept specialized 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

918-537: A farm near Hobart, Oklahoma , following engine problems. Four crewmen were killed in the incident. On 9 October 1957, B-47 serial number 51-2177A, of the 447th Bomb Squadron , 321st Bomb Wing at Pinecastle Air Force Base suffered wing failure and crashed northwest of Orlando, Florida , and west of Winter Park, Florida , while conducting a practice demonstration for the annual Strategic Air Command Bombing Navigation and Reconnaissance Competition at Pinecastle AFB. The wing commander, Colonel Michael Norman Wright McCoy,

1020-526: 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 L. Martin Company submitted proposals for

1122-481: 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. The USAF Strategic Air Command operated multiple B-47 models (B-47s, EB-47s, RB-47s and YRB-47s) from 1951 through 1965. Upon entry to service, its performance was closer to that of contemporary fighters than SAC's extant B-36 Peacemaker bomber, setting multiple records with ease. It handled well in flight,

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1224-639: A lift-to-drag ratio of 18:1, and a structural efficiency of 50%, the cruise range would be The range equation may be further extended to consider operational factors by including an operational efficiency ("ops" for flight operations) R = Z f η eng η aero η struc η ops {\displaystyle R=Z_{f}\eta _{\text{eng}}\eta _{\text{aero}}\eta _{\text{struc}}\eta _{\text{ops}}} The operational efficiency η o p s {\displaystyle \eta _{ops}} may be expressed as

1326-456: A near radioactive incident when it hit a storage igloo containing three MK-6 nuclear weapons . Although the bombs involved lacked their fissile cores , each carried about 8,000 pounds (3,600 kg) of high explosives for their trigger mechanism. The crash and ensuing fire did not ignite the high explosives and no detonation occurred. In November 1956, B-47E serial number 51-2421 of the 96th Bombardment Wing , flying from Altus AFB , crashed on

1428-630: A non-stop flight to Ben Guerir Air Base in Morocco. After descending through clouds to begin their second round of aerial refueling over the Mediterranean Sea at 14,000 feet, one of the four aircraft, serial number 52-0534 , failed to make contact with the tanker; neither the aircraft, its two nuclear weapon cores , nor its personnel were ever found. On 28 March 1956, a B-47 exploded near Wichita, Kansas , with an instructor and two student pilots on board. It crashed four miles northeast of

1530-510: A number of airplane weights from the equilibrium condition P a = P r {\displaystyle P_{a}=P_{r}} is noted . To each flight velocity, there corresponds a particular value of propulsive efficiency η j {\displaystyle \eta _{j}} and specific fuel consumption c p {\displaystyle c_{p}} . The successive engine powers can be found: P b r = P

1632-413: 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

1734-439: 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

1836-461: A ride in the XB-47. A formal contract for 10 aircraft was signed on 3 September 1948. The total number of B-47s built was 2,042. The XB-47, which looked nothing like contemporary bombers, 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

1938-593: A separate service, the United States Air Force (USAF), on 18 September 1947. 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". The XB-47 prototype flew its first flight on 17 December 1947 (the anniversary of the Wright Brothers ' first four flights on 17 December 1903), with test pilots Robert Robbins and Scott Osler at

2040-615: A specific range and fuel weight flow rate can be related to the characteristics of the airplane and propulsion system; if these are constant: R = η j g c p C L C D ln ⁡ W 1 W 2 = V ( L / D ) I s p L n ( W i / W f ) {\displaystyle R={\frac {\eta _{j}}{gc_{p}}}{\frac {C_{L}}{C_{D}}}\ln {\frac {W_{1}}{W_{2}}}=V(L/D)IspLn(Wi/Wf)} An electric aircraft with battery power only will have

2142-428: A stable center of gravity was a critical copilot duty. The aircraft was so aerodynamically clean that rapid descent ("penetration") from high cruise altitude 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 180 kn (330 km/h). To shorten the landing roll, USAF test pilot Major Guy Townsend promoted

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2244-557: Is d W d R = d W d t d R d t = − F V , {\displaystyle {\frac {dW}{dR}}={\frac {\frac {dW}{dt}}{\frac {dR}{dt}}}=-{\frac {F}{V}},} where V {\displaystyle V} is the speed), so that d R d t = − V F d W d t {\displaystyle {\frac {dR}{dt}}=-{\frac {V}{F}}{\frac {dW}{dt}}} It follows that

2346-566: Is a Federal Advisory Committee that provides independent advice on matters of science and technology relating to the Air Force mission, reporting directly to the Secretary of the Air Force and Chief of Staff of the Air Force . In the past, it has provided advice on technologies such as: supersonic aircraft, weather forecasting , satellite communications, medical research, crewless airplanes, and defenses against aircraft and missiles. Today,

2448-1235: Is a height that a quantity of fuel could lift itself in the Earth's gravity field (assumed constant) by converting its chemical energy into potential energy. Z f {\displaystyle Z_{f}} for kerosene jet fuel is 2,376 nautical miles (4,400 km) or about 69% of the Earth's radius . There are two useful alternative ways to express the structural efficiency η struc = ln ⁡ W ^ 1 W ^ 2 = ln ⁡ ( 1 + W fuel W ^ 2 ) = − ln ⁡ ( 1 − W fuel W ^ 1 ) {\displaystyle \eta _{\text{struc}}=\ln {\frac {{\widehat {W}}_{1}}{{\widehat {W}}_{2}}}=\ln \left(1+{\frac {{W}_{\text{fuel}}}{{\widehat {W}}_{2}}}\right)=-\ln \left(1-{\frac {{W}_{\text{fuel}}}{{\widehat {W}}_{1}}}\right)} As an example, with an overall engine efficiency of 40%,

2550-526: Is again mass. When cruising at a fixed height, a fixed angle of attack and a constant specific fuel consumption, the range becomes: R = 2 c T C L C D 2 2 g ρ S ( W 1 − W 2 ) {\displaystyle R={\frac {2}{c_{T}}}{\sqrt {{\frac {C_{L}}{C_{D}^{2}}}{\frac {2}{g\rho S}}}}\left({\sqrt {W_{1}}}-{\sqrt {W_{2}}}\right)} where

2652-429: Is assumed that the thrust specific fuel consumption is constant as the aircraft weight decreases. This is generally not a good approximation because a significant portion (e.g. 5% to 10%) of the fuel flow does not produce thrust and is instead required for engine "accessories" such as hydraulic pumps , electrical generators , and bleed air powered cabin pressurization systems. This can be accounted for by extending

2754-404: Is assumed. The relationship D = C D C L W {\displaystyle D={\frac {C_{D}}{C_{L}}}W} is used. The thrust can now be written as: T = D = C D C L W ; {\displaystyle T=D={\frac {C_{D}}{C_{L}}}W;} here W is a force in newtons Jet engines are characterized by

2856-441: Is generally recommended at a slightly higher airspeed. Most long-range cruise operations are conducted at the flight condition that provides 99 percent of the absolute maximum specific range. The advantage of such operation is that one percent of the range is traded for three to five percent higher cruise speed. United States Air Force Scientific Advisory Board The United States Air Force Scientific Advisory Board ( SAB )

2958-451: Is the air density , and S the wing area , the specific range is found equal to: V F = 1 c T C L C D 2 2 ρ S W {\displaystyle {\frac {V}{F}}={\frac {1}{c_{T}}}{\sqrt {{\frac {C_{L}}{C_{D}^{2}}}{\frac {2}{\rho SW}}}}} Inserting this into ( 1 ) and assuming only W {\displaystyle W}

3060-628: Is the energy per mass of the battery (e.g. 150-200 Wh/kg for Li-ion batteries), η total {\displaystyle \eta _{\text{total}}} the total efficiency (typically 0.7-0.8 for batteries, motor, gearbox and propeller), L / D {\displaystyle L/D} lift over drag (typically around 18), and the weight ratio W battery / W total {\displaystyle {W_{\text{battery}}}/{W_{\text{total}}}} typically around 0.3. The range of jet aircraft can be derived likewise. Now, quasi-steady level flight

3162-412: Is the speed, and F {\displaystyle F} is the fuel consumption rate, is called the specific range (= range per unit mass of fuel; S.I. units: m/kg). The specific range can now be determined as though the airplane is in quasi-steady-state flight. Here, a difference between jet and propeller-driven aircraft has to be noticed. With propeller-driven propulsion, the level flight speed at

Boeing B-47 Stratojet - Misplaced Pages Continue

3264-607: Is the weight (force in newtons, if W is the mass in kilograms); g is standard gravity (its exact value varies, but it averages 9.81 m/s ). The range integral, assuming flight at a constant lift to drag ratio, becomes R = η j g c p C L C D ∫ W 2 W 1 d W W {\displaystyle R={\frac {\eta _{j}}{gc_{p}}}{\frac {C_{L}}{C_{D}}}\int _{W_{2}}^{W_{1}}{\frac {dW}{W}}} To obtain an analytic expression for range,

3366-503: Is the zero-fuel mass and W f {\displaystyle W_{f}} the mass of the fuel, the fuel consumption rate per unit time flow F {\displaystyle F} is equal to − d W f d t = − d W d t . {\displaystyle -{\frac {dW_{f}}{dt}}=-{\frac {dW}{dt}}.} The rate of change of aircraft mass with distance R {\displaystyle R}

3468-600: Is uncertain if they scored any kills; these were the only shots fired in anger by any B-47. On 8 May 1954, after a top secret reconnaissance mission near the Kola Peninsula , a 4th Air Division / 91st Strategic Reconnaissance Wing RB-47E, flown by then-Capt (later Col) 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

3570-490: Is varying, the range (in kilometers) becomes: R = 1 c T C L C D 2 2 g ρ S ∫ W 2 W 1 1 W d W ; {\displaystyle R={\frac {1}{c_{T}}}{\sqrt {{\frac {C_{L}}{C_{D}^{2}}}{\frac {2}{g\rho S}}}}\int _{W_{2}}^{W_{1}}{\frac {1}{\sqrt {W}}}dW;} here W {\displaystyle W}

3672-809: 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 28 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 in Japan with three engines out. A few operated during

3774-733: The Flight Test Museum at Edwards AFB. The purchase was completed in August 2016 and on 21 September 2016 the aircraft arrived at Edwards AFB for reassembly, restoration and eventual display at the Flight Test Museum. By mid-1948, the USAF's bomber competition had already been through one iteration, pitting the North American XB-45 against the Convair XB-46. The North American design won that round of

3876-480: 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 15 seconds 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

3978-523: 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 29 December 1967. The final 15 RB-47s, built from December 1955, 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 . These were given

4080-517: The great-circle distance divided by the actual route distance η route = D GC D actual {\displaystyle \eta _{\text{route}}={\frac {D_{\text{GC}}}{D_{\text{actual}}}}} Off-nominal temperatures may be accounted for with a temperature efficiency factor η temp {\displaystyle \eta _{\text{temp}}} (e.g. 99% at 10 deg C above International Standard Atmosphere (ISA) temperature). All of

4182-728: The thrust specific fuel consumption has been adjusted down and the virtual aircraft weight has been adjusted up to maintain the proper fuel flow while making the adjusted thrust specific fuel consumption truly constant (not a function of virtual weight). Then, the modified Breguet range equation becomes R = a M g c ^ T C L C D ln ⁡ W ^ 1 W ^ 2 {\displaystyle R={\frac {aM}{g{\widehat {c}}_{T}}}{\frac {C_{L}}{C_{D}}}\ln {\frac {{\widehat {W}}_{1}}{{\widehat {W}}_{2}}}} The above equation combines

Boeing B-47 Stratojet - Misplaced Pages Continue

4284-508: 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 Boeing's own B-52 Stratofortress . The B-47

4386-536: The French aviation pioneer, Louis Charles Breguet . It is possible to improve the accuracy of the Breguet range equation by recognizing the limitations of the conventionally used relationships for fuel flow: F = c T T = c T C D C L W {\displaystyle F=c_{T}T=c_{T}{\frac {C_{D}}{C_{L}}}W} In the Breguet range equation, it

4488-594: The SAB performs in-depth reviews of the Air Force Research Laboratory 's science and technology research, and performs studies on topics tasked by the Secretary and Chief of Staff. Members are appointed by the Secretary of Defense . The board was established in 1944 under the name Scientific Advisory Group with General Henry H. Arnold as the military director and Dr. Theodore von Kármán as

4590-528: The USAF had 28 wings of B-47 bombers and five wings of 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, with a third of 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

4692-432: The addition of a 32 ft (9.8 m) 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 that the aircraft's engines would have to be throttled down on landing approach. Since it could take as long as 20 seconds to throttle them back up to full power,

4794-492: The airspeed and adjusting the throttles to avoid going into a stall. For perspective, a modern Boeing 757 has over 50 kn (93 km/h) of difference at even a very heavy weight at 41,000 feet (12,000 m). Fuel capacity was enormous, at 17,000  US gal (64,000 L), more than triple the 5,000 US gal (19,000 L) on the B-29 Superfortress, and meant that maintaining fuel trim to ensure

4896-686: The assumed fuel flow formula in a simple way where an "adjusted" virtual aircraft gross weight W ^ {\displaystyle {\widehat {W}}} is defined by adding a constant additional "accessory" weight W acc {\displaystyle W_{\text{acc}}} . W ^ = W + W acc {\displaystyle {\widehat {W}}=W+W_{\text{acc}}} F = c ^ T C D C L W ^ {\displaystyle F={\widehat {c}}_{T}{\frac {C_{D}}{C_{L}}}{\widehat {W}}} Here,

4998-412: The bomber could not easily do a " touch and go " momentary landing. A 16-foot "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-foot "brake chute". The brake chute could be deployed to stop the aircraft from "porpoising", or bouncing, after

5100-584: The bomber pilot had to "safe" soft drop the Mark 15 weapon off the coast of Savannah, Georgia near Tybee Island , after which the B-47 landed safely. Despite an extensive nine-month search, the unarmed bomb was never found. In 1963, the Kennedy administration offered 24 B-47E bombers as an interim Canberra Mk 20 replacement for the Royal Australian Air Force (RAAF), pending delivery of

5202-460: The canopy came off at high speed, killing pilot Scott Osler; the aircraft was safely landed by the copilot. The accident resulted in a canopy redesign and the hiring of pilot Tex Johnston as chief test pilot. The second XB-47 (46-066) prototype first flew on 21 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

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5304-416: The city, killing its crew of three. The office of information services at McConnell Air Force Base said the explosion occurred after takeoff, probably at about 2,000 feet altitude. Wreckage was strewn along the countryside for several miles as the wings sheared off and the fuselage tumbled to earth. On 27 July 1956, a B-47 of the 307th Bombardment Wing crashed at RAF Lakenheath killing its crew and causing

5406-751: The competition. As an interim measure, the USAF decided to put the North American bomber into production on a limited basis as the B-45 Tornado. The expectation was that B-45 production would be terminated if either of the remaining two designs in the competition, the Boeing XB-47 and the Martin XB-48, proved superior. It is sometimes claimed that the final production decision was made as a result of Boeing president Bill Allen inviting USAF General K.B. Wolfe, in charge of bomber production, for

5508-437: The compressibility on the aerodynamic characteristics of the airplane are neglected as the flight speed reduces during the flight. For jet aircraft operating in the stratosphere (altitude approximately between 11 and 20 km), the speed of sound is approximately constant, hence flying at a fixed angle of attack and constant Mach number requires the aircraft to climb (as weight decreases due to fuel burn), without changing

5610-576: 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

5712-428: The controls having a fighter-like light touch. The large bubble canopy enhanced the flying crew's vision and gave a fighter-like feel, but also caused internal temperature variations for the crew. The three-man crew consisted of the commander, copilot and a navigator/bombardier or a crew chief. In 1953 the B-47 became operational. It was sluggish on takeoff and too fast on landings, an unpleasant combination. If landed at

5814-529: The controls. It lasted 27 minutes, 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 skeptical about the XB-47, saying that before his first flight he had prayed, "Oh God, please help me through

5916-573: 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, 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;

6018-566: 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. Data radioed back from the dropsondes was logged by the navigator. The RB-47Ks were in service until 1963. The type was succeeded by dedicated reconnaissance aircraft such as the Lockheed U-2 . Over its operating life, 203 B-47s were lost in crashes, with 464 deaths. This represents approximately 10% of

6120-613: 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,

6222-698: The energy characteristics of the fuel with the efficiency of the jet engine. It is often useful to separate these terms. Doing so completes the nondimensionalization of the range equation into fundamental design disciplines of aeronautics . R = Z f a M Z f g c ^ T C L C D ln ⁡ W ^ 1 W ^ 2 {\displaystyle R=Z_{f}{\frac {aM}{Z_{f}g{\widehat {c}}_{T}}}{\frac {C_{L}}{C_{D}}}\ln {\frac {{\widehat {W}}_{1}}{{\widehat {W}}_{2}}}} where giving

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6324-426: The final form of the theoretical range equation (not including operational factors such as wind and routing) R = Z f η eng η aero η struc {\displaystyle R=Z_{f}\eta _{\text{eng}}\eta _{\text{aero}}\eta _{\text{struc}}} The geopotential energy height of the fuel is an intensive property . A physical interpretation

6426-702: 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, Illinois , 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

6528-463: 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, in April 1946, the USAAF ordered two prototypes, to be designated "XB-47". Assembly began in June 1947. The first XB-47 was rolled out on 12 September 1947, a few days before the USAAF became

6630-620: The late 1940s, the bomber was hailed as the fastest of its class in the world. The first prototypes were fitted with General Electric J35 turbojets, the production version of the TG-180, with 3,970 lbf (17.7 kN) 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 1,000 lbf (4.4 kN) of static thrust. Early aircraft had mounts for nine RATO units built into each side of

6732-675: 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 in late 1958: over the Black Sea on 31 October, over the Baltic on 7 November, and over the Sea of Japan on 17 November. On 1 July 1960, a PVO Strany MiG-19 shot down an RB-47H (AF Serial No. 53-4281) in international airspace over

6834-546: The much delayed F-111C aircraft . Three B-47E aircraft flew to Australia for demonstration purposes, but RAAF declined the B-47E as technically outdated and too resource-intensive. During 1963, final phaseout of B-47 bomber wings began; the last were out of SAC service by 1966. The last USAF operational aircraft, WB-47Es assigned to the Air Weather Service , were withdrawn from use in September 1969. Shortly before,

6936-508: 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

7038-495: 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 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 from Moses Lake AFB to Andrews AFB , averaging 607.8 miles per hour (528.2 kn; 978.2 km/h). During an early test flight,

7140-399: The only major issuing relating to the avionics , typical of the vacuum tube technology used and the placement of equipment outside the pressurized crew compartment. Much work was done to improve avionics reliability, but avionics remained troublesome throughout the B-47's operational life. Starting in 1950, several models of the B-47 included a fuel tank inerting system , in which dry ice

7242-437: The operational efficiency factors may be collected into a single term η ops = η route η wind η temp ⋯ {\displaystyle \eta _{\text{ops}}=\eta _{\text{route}}\eta _{\text{wind}}\eta _{\text{temp}}\cdots } While the peak value of a specific range would provide maximum range operation, long-range cruise operation

7344-500: The outboard engines singly near the wing tip. This arrangement reduced the bending moment at the wing roots, saving structural weight. The engines' mass acted as counter- flutter weights. The wing airfoil was identified by Boeing as the BAC 145, also known as the NACA 64A(.225)12 mod airfoil . Wing flexibility was a concern, flexing as much as 17.5 ft (5.3 m) at the tip; major effort

7446-437: 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 way to get a bomb-bay long enough for an A-bomb was to use a "bicycle landing gear", the two main gear assemblies arranged in a tandem configuration and outrigger struts fitted to

7548-587: The product of individual operational efficiency terms. For example, average wind may be accounted for using the relationship between average GroundSpeed (GS), True AirSpeed (TAS, assumed constant), and average HeadWind (HW) component. η wind = T A S − H W avg T A S = G S avg T A S {\displaystyle \eta _{\text{wind}}={\frac {TAS-HW_{\text{avg}}}{TAS}}={\frac {GS_{\text{avg}}}{TAS}}} Routing efficiency may be defined as

7650-448: The range equation can only be calculated exactly for powered aircraft. It will be derived for both propeller and jet aircraft. If the total mass W {\displaystyle W} of the aircraft at a particular time t {\displaystyle t} is: W = W 0 + W f , {\displaystyle W=W_{0}+W_{f},} where W 0 {\displaystyle W_{0}}

7752-528: The range is obtained from the definite integral below, with t 1 {\displaystyle t_{1}} and t 2 {\displaystyle t_{2}} the start and finish times respectively and W 1 {\displaystyle W_{1}} and W 2 {\displaystyle W_{2}} the initial and final aircraft masses The term V F {\textstyle {\frac {V}{F}}} , where V {\displaystyle V}

7854-698: 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 in (12.7 mm) 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

7956-587: 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. The Army Air Force liked this new configuration, so Boeing's engineers refined it, moving

8058-612: The same mass at takeoff and landing. The logarithmic term with weight ratios is replaced by the direct ratio between W battery / W total {\displaystyle W_{\text{battery}}/W_{\text{total}}} R = E ∗ 1 g η total L D W battery W total {\displaystyle R=E^{*}{\frac {1}{g}}\eta _{\text{total}}{\frac {L}{D}}{\frac {W_{\text{battery}}}{W_{\text{total}}}}} where E ∗ {\displaystyle E^{*}}

8160-546: The so-called 1958 Tybee Island B-47 crash . A B-47 based at Homestead AFB , Florida, 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 7,600 lb (3,400 kg) 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 Air Force Base ,

8262-474: The specific heat capacities of air at constant pressure and constant volume respectively. Or R = a M g c T C L C D ln ⁡ W 1 W 2 {\textstyle R={\frac {aM}{gc_{T}}}{\frac {C_{L}}{C_{D}}}\ln {\frac {W_{1}}{W_{2}}}} , also known as the Breguet range equation after

8364-451: The target before releasing a nuclear weapon. Stress and fatigue incurred in low-altitude operations led to a number of wing failures and crashes, and an extensive refit program was begun 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, in

8466-521: The then Soviet enemy". Three B-47s flew cross country from March Air Force Base to the Philadelphia International Airport as participants in the 1955 Labor Day race . In the 1956 event, three B-47s participated in the G.E. Trophy race for Jet Bombers, flying from Kindley Field , Bermuda, to Oklahoma City . One of these set a course speed record of 601.187 miles per hour (522.417 kn; 967.517 km/h). By 1956,

8568-543: The top of the B-47's envelope, about 35,000 feet (11,000 m), it was in " coffin corner ". That means that at this level, which produced the most range at most weights due to fuel consumption, there was an envelope of 5 kn (9.3 km/h) 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

8670-651: The total number produced. On 8 February 1954, a B-47 of the 22nd Bomber Wing, March AFB, California, crashed in Stoke Wood, a mile and a half short of the runway at RAF Upper Heyford, England, while on a training run. All three crew were killed. On 28 February 1955, a crippled B-47 crashed into a trailer park in Lake Charles, Louisiana , killing the three crewmen and two people on the ground. On 10 March 1956, four B-47s left MacDill Air Force Base in Florida for

8772-580: The training for this imposes repeated high stress on the aircraft, the airframe lifetime would have been severely limited by metal fatigue , and this maneuver was eliminated. 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, having only three crew members to operate it. Boeing's B-52 Stratofortress , in contrast, generally had six crewmen, five officers and one enlisted, with more internal cabin space. An XB-47

8874-481: The transport of aircraft without any passengers or cargo. Combat radius is a related measure based on the maximum distance a warplane can travel from its base of operations, accomplish some objective, and return to its original airfield with minimal reserves. For most unpowered aircraft, the maximum flight time is variable, limited by available daylight hours, aircraft design (performance), weather conditions, aircraft potential energy, and pilot endurance. Therefore,

8976-629: The value of the local speed of sound. In this case: V = a M {\displaystyle V=aM} where M {\displaystyle M} is the cruise Mach number and a {\displaystyle a} the speed of sound . W is the weight. The range equation reduces to: R = a M g c T C L C D ∫ W 2 W 1 d W W {\displaystyle R={\frac {aM}{gc_{T}}}{\frac {C_{L}}{C_{D}}}\int _{W_{2}}^{W_{1}}{\frac {dW}{W}}} where

9078-454: 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 pressurized forward compartment: a pilot and copilot, in tandem , in a long fighter-style bubble canopy , and a navigator / bombardier in a compartment in the nose. The copilot doubled as tail gunner (using

9180-399: 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. The B-47 was regarded as a maintenance "hog". General reliability was good,

9282-484: Was Chanute AFB where it was used as a maintenance and familiarization aircraft. The second prototype was equipped with more powerful General Electric J47-GE-3 turbojets with 5,200  lbf (23 kN) 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

9384-424: Was sublimed into carbon dioxide vapor while the fuel pumps operated or while the in-flight refueling 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

9486-520: 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

9588-467: 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 aerial photography equipment, K-17 and K-38 cameras,

9690-447: 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 425  kn (787  km/h ) 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

9792-403: Was flown in the 1951 Operation Greenhouse nuclear weapons test . This was followed by a B-47B being flown in the 1952 test, Operation Ivy and the 1954 test, Operation Castle . A B-47E was then flown in the 1956 test, Operation Redwing . "Reflex" missions proved the long-endurance (eighteen hours) and long range capability of the B-47 and aircrews. These were "simulated strike missions against

9894-574: Was killed in the crash; Pinecastle AFB was later renamed McCoy AFB in his honor. Range (aeronautics) Some aircraft can gain energy while airborne through the environment (e.g. collecting solar energy or through rising air currents from mechanical or thermal lifting) or from in-flight refueling. These aircraft could theoretically have an infinite range. Ferry range means the maximum range that an aircraft engaged in ferry flying can achieve. This usually means maximum fuel load, optionally with extra fuel tanks and minimum equipment. It refers to

9996-476: 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 . During

10098-576: Was 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. 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. Crews were trained in "pop-up" attacks, coming in at low level at 425 knots (787 km/h) and then climbing abruptly near

10200-528: 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 . 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 R. T. Jones at Langley, but seeing German models of swept-wing aircraft and extensive supersonic wind-tunnel data,

10302-417: Was to be 25,000 lb (11 t). 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 at higher altitudes, where the pure turbojet engines could produce good fuel economy, the wing was very compromised. At

10404-491: 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 17 April 1955, when it was intercepted by Soviet MiG-15s in international airspace before disappearing. Between 21 March and 10 May 1956, 16 RB-47Es and five RB-47Hs operating from Thule performed overflights

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