Dihedral angle is the upward angle from horizontal of the wings or tailplane of a fixed-wing aircraft . "Anhedral angle" is the name given to negative dihedral angle, that is, when there is a downward angle from horizontal of the wings or tailplane of a fixed-wing aircraft.
149-589: The Boeing KC-135 Stratotanker is an American military aerial refueling tanker aircraft that was developed from the Boeing 367-80 prototype, alongside the Boeing 707 airliner. It has a narrower fuselage and is shorter than the 707. Boeing gave the aircraft the internal designation of Model 717 (number later assigned to a different Boeing aircraft ). The KC-135 was the United States Air Force (USAF)'s first jet-powered refueling tanker and replaced
298-399: A V-tail configuration, are used to move the boom by creating aerodynamic forces. They are actuated hydraulically and controlled by the boom operator using a control stick. The boom operator also telescopes the boom to make the connection with the receiver's receptacle. To complete an aerial refueling, the tanker and receiver aircraft rendezvous, flying in formation. The receiver moves to
447-520: A carrier air wing ) to extend the range of its strike aircraft. In other cases, using the buddy store method allows a carrier -based aircraft to take-off with a heavier than usual load less fuel than might be necessary for its tasking. The aircraft would then topped-up with fuel from an HDU-equipped "buddy" tanker, a method previously used by the Royal Navy in operating its Supermarine Scimitar , de Havilland Sea Vixen , and Blackburn Buccaneers ; in
596-597: A piston-engined aircraft. In the 1980s, the first modification program retrofitted 157 Air Force Reserve (AFRES) and Air National Guard (ANG) tankers with the Pratt & Whitney TF33-PW-102 turbofan engines from 707 airliners retired in the late 1970s and early 1980s. The modified tanker, designated the KC-135E, was 14% more fuel-efficient than the KC-135A and could offload 20% more fuel on long-duration flights. Only
745-401: A stability derivative called C l β {\displaystyle \beta } meaning the change in rolling moment coefficient (the " C l ") per degree (or radian) of change in sideslip angle (the " β {\displaystyle \beta } "). The purpose of dihedral effect is to contribute to stability in the roll axis. It is an important factor in
894-451: A 100% increase compared to the original J57 engine. The modified tanker, designated KC-135R (modified KC-135A or E) or KC-135T (modified KC-135Q), can offload up to 50% more fuel (on a long-duration sortie), is 25% more fuel-efficient, and costs 25% less to operate than with the previous engines. It is also significantly quieter than the KC-135A, with noise levels at takeoff reduced from 126 to 99 decibels . This 27 dB noise reduction results in
1043-474: A Boeing or LTV receiver system and a secure voice SATCOM radio. Three of the aircraft (60-0356, -0357, and -0362) were converted to tankers from RC-135Ds, from which they retained their added equipment. KC-135Q re-engined with CFM56 engines, 54 modified. A new-built variant for France as dual-role tanker/cargo and troop carrier aircraft. 12 were built for the French Air Force with the addition of
1192-634: A Boeing-developed flying boom and extra kerosene (jet fuel) tanks feeding the boom. The Stratocruiser airliner itself was developed from the Boeing B-29 Superfortress bomber after World War II . In the KC-97, the mixed gasoline/kerosene fuel system was clearly not desirable and it was obvious that a jet-powered tanker aircraft would be the next development, having a single type of fuel for both its own engines and for passing to receiver aircraft. The 230 mph (370 km/h) cruise speed of
1341-455: A Hose Drum Unit (HDU). When not in use, the hose/drogue is reeled completely into the HDU. The receiver has a probe , which is a rigid, protruding or pivoted retractable arm placed on the aircraft's nose or fuselage to make the connection. Most modern versions of the probe are usually designed to be retractable, and are retracted when not in use, particularly on high-speed aircraft. At the end of
1490-587: A Return-To-Launch-Site abort capability if necessary. At its most efficient altitude and speed, the Blackbird was capable of flying for many hours without refueling. The SR-71 used a special fuel, JP-7 , with a very high flash point to withstand the extreme skin temperatures generated during Mach 3+ cruise flight. While JP-7 could be used by other aircraft, its burn characteristics posed problems in certain situations (such as high-altitude, emergency engine starts) that made it less than optimal for aircraft other than
1639-540: A boom system followed quickly in the autumn of 1948. The first use of aerial refueling in combat took place during the Korean War, involving F-84 fighter-bombers flying missions from Japanese airfields, due to Chinese-North Korean forces overrunning many of the bases for jet aircraft in South Korea, refueling from converted B-29s using the drogue-and-probe in-flight refueling system with the probe located in one of
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#17327806110881788-714: A drogue adapter on the refueling boom. Given Boeing model numbers 717-164 and 717-165. 11 surviving C-135Fs upgraded with CFM International F108 turbofans between 1985 and 1988. Later modified with MPRS wing pods. An airborne command post modified in 1984 to support CINCCENT . Aircraft 55-3125 was the only EC-135Y. Unlike its sister EC-135N, it was a true tanker that could also receive in-flight refueling. Pratt & Whitney TF33-PW-102. Retired to 309th AMARG at Davis-Monthan AFB, AZ. Note Italy has been reported in some sources as operating several KC-135s, however these are Boeing 707-300s converted to tanker configuration. As of 2020, 52 Stratotankers have been lost to accidents during
1937-580: A feat made possible by four aerial refuelings from four pairs of KB-29M tankers of the 43d ARS. Before the mission, crews of the 43rd had experienced only a single operational air refueling contact. The flight started and ended at Carswell Air Force Base in Fort Worth, Texas with the refuelings accomplished over the Azores , Saudi Arabia , the Pacific Ocean near Guam , and between Hawaii and
2086-403: A flexible hose that trails from the tanker aircraft. The drogue (or para-drogue ), sometimes called a basket , is a fitting resembling a shuttlecock , attached at its narrow end (like the "cork" nose of a shuttlecock) with a valve to a flexible hose. The drogue stabilizes the hose in flight and provides a funnel to aid insertion of the receiver aircraft probe into the hose. The hose connects to
2235-404: A four-aircraft strike package. USAF KC-135 and French Air Force KC-135FR refueling-boom equipped tankers can be field-converted to a probe-and-drogue system using a special adapter unit. In this configuration, the tanker retains its articulated boom, but has a hose/drogue at the end of it instead of the usual nozzle. The tanker boom operator holds the boom still while the receiver aircraft flies
2384-493: A hose-and-drogue system, dubbed UPAZ, and thus later Russian aircraft may be equipped with probe and drogue. The Chinese PLAF has a fleet of Xian H-6 bombers modified for aerial refueling, and plans to add Russian Ilyushin Il-78 aerial refueling tankers. Tankers can be equipped with multipoint hose-and-drogue systems, allowing them to refuel two (or more) aircraft simultaneously, reducing time spent refueling by as much as 75% for
2533-440: A low-wing configuration. A side effect of too much dihedral effect, caused by excessive dihedral angle among other things, can be yaw-roll coupling (a tendency for an aircraft to Dutch roll ). This can be unpleasant to experience, or in extreme conditions it can lead to loss of control or can overstress an aircraft. Military fighter aircraft often have near zero or even anhedral angle reducing dihedral effect and hence reducing
2682-416: A much smaller position-keeping tolerance, staying properly connected to a KC-135 adapter unit is considerably more difficult than staying in a traditional hose/drogue configuration. When fueling is complete, the receiver carefully backs off until the probe refueling valve disconnects from the valve in the basket. Off center disengagements, like engagements, can cause the drogue to "prang" the probe and/or strike
2831-526: A new build airframe based on the Boeing 707-320B. All KC-135s were originally equipped with Pratt & Whitney J57-P-59W turbojet engines, which produced 10,000 lbf (44 kN) of thrust dry, and approximately 13,000 lbf (58 kN) of thrust wet . Wet thrust is achieved through the use of water injection on takeoff, as opposed to "wet thrust" when used to describe an afterburning engine . 670 US gallons (2,500 L) of water are injected into
2980-444: A new jet endurance record. FRL still exists as part of Cobham plc . Modern specialized tanker aircraft have equipment specially designed for the task of offloading fuel to the receiver aircraft, based on drogue and probe, even at the higher speeds modern jet aircraft typically need to remain airborne. In January 1948, General Carl Spaatz, then the first Chief of Staff of the new United States Air Force , made aerial refueling
3129-484: A pioneer of long-distance aviation. During the 1920s, he made long-distance flights to places as far afield as Africa and Australia and he began experimenting with the possibilities of in-flight refueling to extend the range of flight. Cobham was one of the founding directors of Airspeed Limited , an aircraft manufacturing company that went on to produce a specially-adapted Airspeed Courier that Cobham used for his early experiments with in-flight refueling. This craft
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#17327806110883278-407: A position behind the tanker, within safe limits of travel for the boom, aided by director lights or directions radioed by the boom operator. Once in position, the operator extends the boom to make contact with the receiver aircraft. Once in contact, fuel is pumped through the boom into the receiver aircraft. While in contact, the receiver pilot must continue to fly within the "air refueling envelope",
3427-462: A similar but lesser effect. The center of mass , usually called the center of gravity or "CG", is the balance point of an aircraft. If suspended at this point and allowed to rotate, a body (aircraft) will be balanced. The front-to-back location of the CG is of primary importance for the general stability of the aircraft, but the vertical location has important effects as well. The vertical location of
3576-584: A similar dropped line from the receiver, allowing the refueling to commence. In 1935, Cobham sold off the airline Cobham Air Routes Ltd to Olley Air Service and turned to the development of inflight refueling, founding the company Flight Refuelling Ltd . Atcherly's system was bought up by Cobham's company, and with some refinement and continuous improvement through the late '30s, it became the first practical refueling system. Sir Alan Cobham 's grappled-line looped-hose air-to-air refueling system borrowed from techniques patented by David Nicolson and John Lord, and
3725-417: A single mission, without landing to install an adapter. Other tankers are equipped with hose-and-drogue attachments that do not interfere with the operation of the centerline boom: many KC-135s are equipped with dual under-wing attachments known as Multi-point Refueling System (MPRSs), while some KC-10s and A330 MRTTs have similar under-wing refueling pods (referred to as Wing Air Refueling Pods or WARPs on
3874-509: A small number of FRL looped-hose units and fitted a number of B-29s as tankers to refuel specially equipped B-29s and later B-50s. The USAF made only one major change in the system used by the RAF. The USAF version had auto-coupling of the refueling nozzle, where the leader line with the refueling hose is pulled to the receiver aircraft and a refueling receptacle on the belly of the aircraft, allowing high-altitude air-to-air refueling and doing away with
4023-657: A sound pressure level of about 5% of the original level. The KC-135R's operational range is 60% greater than the KC-135E for comparable fuel offloads, providing a wider range of basing options. Upgrading the remaining KC-135Es into KC-135Rs is no longer in consideration; this would have cost approximately US$ 3 billion, $ 24 million per aircraft. According to USAF data, the KC-135 fleet had a total operation and support cost in fiscal year 2001 of about $ 2.2 billion (~$ 3.62 billion in 2023). The older E model aircraft averaged total costs of about $ 4.6 million per aircraft, while
4172-575: A squadron of Javelin air defense aircraft was refueled in stages from the UK to India and back (exercise "Shiksha"). After the retirement of the Valiant in 1965, the Handley Page Victor took over the UK refueling role and had three hoses (HDUs). These were a fuselage-mounted HDU and a refueling pod on each wing. The center hose could refuel any probe-equipped aircraft, the wing pods could refuel
4321-465: A strong influence on dihedral effect. Some of these important factors are: wing sweep , vertical center of gravity , and the height and size of anything on an aircraft that changes its sidewards force as sideslip changes. Dihedral angle on an aircraft almost always implies the angle between two paired surfaces, one on each side of the aircraft . Even then, it is almost always between the left and right wings . However, mathematically dihedral means
4470-600: A top priority of the service. In March 1948, the USAF purchased two sets of FRL's looped-hose in-flight refueling equipment, which had been in practical use with British Overseas Airways Corporation (BOAC) since 1946, and manufacturing rights to the system. FRL also provided a year of technical assistance. The sets were immediately installed in two Boeing B-29 Superfortresses , with plans to equip 80 B-29s. Flight testing began in May 1948 at Wright-Patterson Air Force Base , Ohio , and
4619-495: Is currently flying double its planned yearly flying hour program to meet airborne refueling requirements, and has resulted in higher than forecast usage and sustainment costs. In March 2009, the Air Force indicated that KC-135s would require additional skin replacement to allow their continued use beyond 2018. The USAF decided to replace the KC-135 fleet. However, the fleet is large and will need to be replaced gradually. Initially
Boeing KC-135 Stratotanker - Misplaced Pages Continue
4768-431: Is not roll stability in and of itself. Roll stability is less-ambiguously termed "spiral mode stability" and dihedral effect is a contributing factor to it. The dihedral angle contributes to the total dihedral effect of the aircraft. In turn, the dihedral effect contributes to stability of the spiral mode . A stable spiral mode will cause the aircraft to eventually return to a nominally "wings level" bank angle when
4917-573: Is not caused by yaw rate , nor by the rate of sideslip change . Since dihedral effect is noticed by pilots when "rudder is applied", many pilots and other near-experts explain that the rolling moment is caused by one wing moving more quickly through the air and one wing less quickly. Indeed, these are actual effects, but they are not the dihedral effect, which is caused by being at a sideslip angle, not by getting to one. These other effects are called "rolling moment due to yaw rate" and "rolling moment due to sideslip rate" respectively. Dihedral effect
5066-472: Is not compatible with flying boom equipment, creating a problem for military planners where mixed forces are involved. Incompatibility can also complicate the procurement of new systems. The Royal Canadian Air Force currently wish to purchase the F-35A , which can only refuel via the flying boom, but only possess probe-and-drogue refuelers . The potential cost of converting F-35As to probe-and-drogue refueling (as
5215-419: Is not the whole picture however. At the same time that angle of sideslip is building up, the vertical fin is trying to turn the nose back into the wind, much like a weathervane, minimizing the amount of sideslip that can be present. If there is no sideslip, there can be no restoring rolling moment. If there is less sideslip, there is less restoring rolling moment. Yaw stability created by the vertical fin opposes
5364-429: Is online with the first 45 upgraded aircraft delivered by January 2017. Block 45 adds a new glass cockpit digital display, radio altimeter, digital autopilot, digital flight director and computer updates. The original, no longer procurable, analog instruments, including all engine gauges, were replaced. Rockwell Collins again supplied the major avionic modules, with modification done at Tinker AFB . The KC-135Q variant
5513-447: Is relatively light (typically soft canvas webbing) and subject to aerodynamic forces, it can be pushed around by the bow wave of approaching aircraft, exacerbating engagement even in smooth air. After initial contact, the hose and drogue is pushed forward by the receiver a certain distance (typically, a few feet), and the hose is reeled slowly back onto its drum in the HDU. This opens the tanker's main refueling valve allowing fuel to flow to
5662-448: Is significantly more unforgiving of pilot error in the receiving aircraft than conventional trailing hose arrangements; an aircraft so fitted is also incapable of refueling by the normal flying boom method until the attachment is removed. A cargo deck above the refueling system can hold a mixed load of passengers and cargo. Depending on fuel storage configuration, the KC-135 can carry up to 83,000 pounds (38,000 kg) of cargo. The KC-135
5811-413: Is simpler to adapt to existing aircraft and the flying boom , which offers faster fuel transfer, but requires a dedicated boom operator station. The procedure allows the receiving aircraft to remain airborne longer, extending its range or loiter time. A series of air refuelings can give range limited only by crew fatigue /physical needs and engineering factors such as engine oil consumption. Because
5960-484: Is used by itself it is usually intended to mean "dihedral angle ". However, context may otherwise indicate that "dihedral effect " is the intended meaning. Dihedral angle is the upward angle from horizontal of the wings of a fixed-wing aircraft , or of any paired nominally-horizontal surfaces on any aircraft . The term can also apply to the wings of a bird . Dihedral angle is also used in some types of kites such as box kites. Wings with more than one angle change along
6109-479: Is used on US Navy & Marine Corps F-35Bs and F-35Cs ) added to the early-2010s political controversy which surrounded F-35 procurement within the RCAF. These concerns can be addressed by drogue adapters (see section "Boom drogue adapter units" above) that allow drogue aircraft to refuel from boom-equipped aircraft, and by refuelers that are equipped with both drogue and boom units and can thus refuel both types in
Boeing KC-135 Stratotanker - Misplaced Pages Continue
6258-417: Is usually a relatively simple way to adjust the overall dihedral effect. This is to compensate for other design elements' influence on the dihedral effect. These other elements (such as wing sweep, vertical mount point of the wing, etc.) may be more difficult to change than the dihedral angle. As a result, differing amounts of dihedral angle can be found on different types of fixed-wing aircraft. For example,
6407-455: Is visible in Figure 2. As greater angle of attack produces more lift (in the usual case, when the wing is not near stalling), the forward wing will have more lift and the rearward wing will have less lift. This difference in lift between the wings is a rolling moment, and it is caused by the sideslip. It is a contribution to the total dihedral effect of the aircraft. The rolling moment created by
6556-670: The Air Education and Training Command (AETC). All AFRC KC-135s and most of the ANG KC-135 fleet became operationally-gained by AMC, while Alaska Air National Guard and Hawaii Air National Guard KC-135s became operationally-gained by PACAF. AMC managed 396 Stratotankers, of which the AFRC and ANG flew 243 in support of AMC's mission as of May 2018. The KC-135 is one of a few military aircraft types with over 50 years of continuous service with its original operator as of 2009. Israel
6705-643: The Aéro-Club de France and the 34th Aviation Regiment of the French Air Force were able to demonstrate passing fuel between machines at the annual aviation fete at Vincennes in 1928. The UK's Royal Aircraft Establishment was also running mid-air refueling trials, with the aim to use this technique to extend the range of the long-distance flying boats that serviced the British Empire . By 1931 they had demonstrated refueling between two Vickers Virginias , with fuel flow controlled by an automatic valve on
6854-576: The Beriev Be-12 were designed with gull wings bent near the root. Others, such as the Vought F4U Corsair , used an inverted gull wing design, which allowed for shorter landing struts and extra ground clearance for large propellers and external payloads, such as external fuel tanks or bombs. Modern polyhedral wing designs generally bend upwards near the wingtips (also known as tip dihedral ), increasing dihedral effect without increasing
7003-577: The KC-97 Stratofreighter . The KC-135 was initially tasked with refueling strategic bombers, but it was used extensively in the Vietnam War and later conflicts such as Operation Desert Storm to extend the range and endurance of US tactical fighters and bombers. The KC-135 entered service with the USAF in 1957; it is one of nine military fixed-wing aircraft with over 60 years of continuous service with its original operator. The KC-135
7152-730: The KC-X program with a request for proposal (RFP). KC-X was the first phase of three acquisition programs meant to replace the KC-135 fleet. On 29 February 2008, the US Defense Department announced that it had selected the EADS / Northrop Grumman "KC-30" (to be designated the KC-45A ) over the Boeing KC-767. Boeing protested the award on 11 March 2008, citing irregularities in the competition and bid evaluation. On 18 June 2008,
7301-595: The Langley Research Center , were tested at Armstrong, using an NKC-135A tanker loaned to NASA by the Air Force. Winglets are small, nearly vertical fins installed on an aircraft's wing tips. The results of the research showed that drag was reduced and range could be increased by as much as 7 percent at cruise speeds. Winglets are now being incorporated into most new commercial and military transport/passenger jets, as well as business aviation jets. NASA also has operated several KC-135 aircraft (without
7450-618: The Short Empire flying boat Cambria from an Armstrong Whitworth AW.23 . Handley Page Harrows were used in the 1939 trials to perform aerial refueling of the Empire flying boats for regular transatlantic crossings. From 5 August to 1 October 1939, sixteen crossings of the Atlantic were made by Empire flying boats, with fifteen crossings using FRL's aerial refueling system. After the sixteen crossings further trials were suspended due to
7599-695: The Tu-134 and Tu-154 . In any case, wing sweepback can also occur with a dihedral configuration. For instance, two small biplanes produced from the 1930s to 1945 by Bücker Flugzeugbau in Germany, the Bücker Jungmann two-seat trainer and the Bücker Jungmeister aerobatic competition biplane, were designed with sweepbacks of approximately 11 degrees, which provided significant dihedral effect – in addition to their small dihedral angles having
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#17327806110887748-476: The West Coast . Cobham's company FRL soon realized that their looped-hose system left much to be desired and began work on an improved system that is now commonly called the probe-and-drogue air-to-air refueling system and today is one of the two systems chosen by air forces for air-to-air refueling, the other being the flying-boom system. In post-war trials the RAF used a modified Lancaster tanker employing
7897-422: The keel effect ) and so additional dihedral angle is often not required. Such designs can have excessive dihedral effect and so be excessively stable in the spiral mode, so anhedral angle on the wing is added to cancel out some of the dihedral effect so that the aircraft can be more easily maneuvered. Most aircraft have been designed with planar wings with simple dihedral (or anhedral). Some older aircraft such as
8046-465: The pendulum effect . An extreme example of the effect of vertical CG on dihedral effect is a paraglider . The dihedral effect created by the very low vertical CG more than compensates for the negative dihedral effect created by the strong anhedral of the necessarily strongly downward curving wing. The wing location on a fixed-wing aircraft will also influence its dihedral effect. A high-wing configuration provides about 5° of effective dihedral over
8195-415: The roll axis. Longitudinal dihedral is a comparatively obscure term related to the pitch axis of an airplane. It is the angle between the zero-lift axis of the wing and the zero-lift axis of the horizontal tail. Longitudinal dihedral can influence the nature of controllability about the pitch axis and the nature of an aircraft's phugoid -mode oscillation. When the term "dihedral" (of an aircraft)
8344-433: The "receptacle" in the receiver aircraft during fuel transfer. A poppet valve in the end of the nozzle prevents fuel from exiting the tube until the nozzle properly mates with the receiver's refueling receptacle. Once properly mated, toggles in the receptacle engage the nozzle, holding it locked during fuel transfer. The "flying" boom is so named because flight control surfaces , small movable airfoils that are often in
8493-999: The 309th AMARG at Davis-Monthan AFB by September 2009 and replaced with R models. Test-configured KC-135E. 55-3132 NKC-135E "Big Crow I" & 63-8050 NKC-135B "Big Crow II" used as airborne targets for the Boeing YAL-1 Airborne Laser carrier. KC-135As modified to carry JP-7 fuel necessary for the SR-71 Blackbird, 56 modified, survivors to KC-135T. 4 JC/KC-135As converted to Rivet Stand (Later Rivet Quick ) configuration for reconnaissance and evaluation of above ground nuclear test (55-3121, 59–1465, 59–1514, 58–0126; 58-0126 replaced 59-1465 after it crashed in 1967). These aircraft were powered by Pratt & Whitney J57 engines and were based at Offutt AFB , Nebraska . KC-135As and some KC-135Es re-engined with CFM56 engines, more than 417 converted Receiver-capable KC-135R Stratotanker; eight modified with either
8642-459: The 707, but has a narrower fuselage and is shorter than the 707. The KC-135 predates the 707, and is structurally quite different from the civilian airliner. Boeing gave the future KC-135 tanker the initial designation Model 717. In 1954 USAF's Strategic Air Command (SAC) held a competition for a jet-powered aerial refueling tanker. Lockheed Corporation 's tanker version of the proposed Lockheed L-193 airliner with rear fuselage-mounted engines
8791-462: The Air Force, only a few KC-135s would reach these limits by 2040, when some aircraft would be about 80 years old. A later 2005 Air Force study estimated that KC-135Es upgraded to the R standard could remain in use until 2030. In 2006, the KC-135E fleet was flying an annual average of 350 hours per aircraft and the KC-135R fleet was flying an annual average of 710 hours per aircraft. The KC-135 fleet
8940-572: The Blackbird constantly leaked fuel before heating expanded the airframe enough to seal its fuel tanks. Following the supersonic dash the SR-71 would then rendezvous with a tanker to fill its now nearly empty tanks before proceeding on its mission. This was referred to as the LTTR (for "Launch To Tanker Rendezvous") profile. LTTR had the added advantage of providing an operational test of the Blackbird's refueling capability within minutes after takeoff, enabling
9089-457: The Boeing plant at Renton, Washington . Boeing went on to develop the world's first production aerial tanker, the KC-97 Stratofreighter , a piston-engined Boeing Stratocruiser (USAF designation C-97 Stratofreighter ) with a Boeing-developed flying boom and extra kerosene (jet fuel) tanks feeding the boom. The Stratocruiser airliner itself was developed from the B-29 bomber after World War II . In
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#17327806110889238-509: The Buccaneer's case using a bomb-bay-mounted tank and HDU. The tanker aircraft flies straight and level and extends the hose/drogue, which is allowed to trail out behind and below the tanker under normal aerodynamic forces. The pilot of the receiver aircraft extends the probe (if required) and uses normal flight controls to "fly" the refueling probe directly into the basket. This requires a closure rate of about two knots (walking speed) to push
9387-400: The CG changes the amount of dihedral effect. As the "vertical CG" moves lower, dihedral effect increases. This is caused by the center of lift and drag being further above the CG and having a longer moment arm. So, the same forces that change as sideslip changes (primarily sideforce, but also lift and drag) produce a larger moment about the CG of the aircraft. This is sometimes referred to as
9536-452: The F-84's wing-tip fuel tanks. The flying boom is a rigid, telescoping tube with movable flight control surfaces that a boom operator on the tanker aircraft extends and inserts into a receptacle on the receiving aircraft. All boom-equipped tankers (e.g. KC-135 Stratotanker , KC-10 Extender , KC-46 Pegasus ) have a single boom and can refuel one aircraft at a time with this mechanism. In
9685-405: The HDU. If the hose is pushed in too far or not far enough, a cutoff switch will inhibit fuel flow, which is typically accompanied by an amber light. Disengagement is commanded by the tanker pilot with a red light. The US Navy , Marine Corps , and some Army aircraft refuel using the "hose-and-drogue" system, as do most aircraft flown by western European militaries. The Soviet Union also used
9834-457: The KC-10). A small number of Soviet Tu-4s and Tu-16s (the tanker variant was Tu-16Z). used a wing-to-wing method. Similar to the probe-and-drogue method but more complicated, the tanker aircraft released a flexible hose from its wingtip. An aircraft flying alongside had to catch the hose with a special lock under its wingtip. After the hose was locked and the connection was established, the fuel
9983-625: The KC-135 Stratotanker in service with Regular Air Force SAC units from 1957 through 1992 and with SAC-gained ANG and AFRES units from 1975 through 1992. Following a major USAF reorganization that resulted in the inactivation of SAC in 1992, most KC-135s were reassigned to the newly created AMC. While AMC gained the preponderance of the aerial refueling mission, a small number of KC-135s were also assigned directly to United States Air Forces in Europe (USAFE), Pacific Air Forces (PACAF) and
10132-412: The KC-135's wings. The pods allow refueling of U.S. Navy, U.S. Marine Corps and most NATO tactical jet aircraft while keeping the tail-mounted refueling boom. The pods themselves are Flight Refueling Limited MK.32B model pods, and refuel via the probe and drogue method common to Navy/Marine Corps tactical jets, rather than the primary " flying boom " method used by Air Force fixed-wing aircraft. This allows
10281-906: The KC-135E aircraft were equipped with thrust reversers for aborted takeoffs and shorter landing roll-outs. The KC-135E fleet has since either been retrofitted as the R-model configuration or placed into long-term storage ("XJ"), as Congress has prevented the USAF from formally retiring them. The final KC-135E, tail number 56-3630 , was delivered by the 101st Air Refueling Wing to the 309th Aerospace Maintenance and Regeneration Group (AMARG) at Davis–Monthan Air Force Base in September 2009. The second modification program retrofitted 500 aircraft with new CFM International CFM56 (military designation: F108) high-bypass turbofan engines produced by General Electric and Safran . The CFM56 engine produces approximately 22,500 lbf (100 kN) of thrust, nearly
10430-400: The KC-97, the mixed gasoline/kerosene fuel system was clearly not desirable and it was obvious that a jet-powered tanker aircraft would be the next development, having a single type of fuel for both its own engines and for passing to receiver aircraft. The 230 mph (370 km/h) cruise speed of the slower, piston-engined KC-97 was also a serious issue, as using it as an aerial tanker forced
10579-460: The R models averaged about $ 3.7 million per aircraft. Those costs include personnel, fuel, maintenance, modifications, and spare parts. In order to expand the KC-135's capabilities and improve its reliability, the aircraft has undergone a number of avionics upgrades. Among these was the Pacer-CRAG program (compass, radar and GPS) which ran from 1999 to 2002 and modified all the aircraft in
10728-466: The RC-135As on-board photo-mapping systems. Later re-engined with Pratt & Whitney TF33 engines and a cockpit update to KC-135E standards in 1990 and were retired to the 309th AMARG at Davis-Monthan AFB , AZ in 2007. Air National Guard and Air Force Reserve KC-135As re-engined with Pratt & Whitney TF33-PW-102 engines from retired 707 airliners (161 modified). All E model aircraft were retired to
10877-445: The SR-71. Dihedral (aircraft) Dihedral angle has a strong influence on dihedral effect , which is named after it. Dihedral effect is the amount of roll moment produced in proportion to the amount of sideslip . Dihedral effect is a critical factor in the stability of an aircraft about the roll axis (the spiral mode ). It is also pertinent to the nature of an aircraft's Dutch roll oscillation and to maneuverability about
11026-755: The US Government Accountability Office sustained Boeing's protest of the selection of the Northrop Grumman/EADS's tanker. In February 2010, the US Air Force restarted the KC-X competition with the release of a revised request for proposal (RFP). After evaluating bids, the USAF selected Boeing's 767-based tanker design, with the military designation KC-46 , as a replacement in February 2011. The first KC-46A Pegasus
11175-510: The USAF to build jet tankers based on the Boeing 367-80 (Dash-80) airframe. The result was the Boeing KC-135 Stratotanker , of which 732 were built. The flying boom is attached to the rear of the tanker aircraft. The attachment is gimballed , allowing the boom to move with the receiver aircraft. The boom contains a rigid pipe to transfer fuel. The fuel pipe ends in a nozzle with a flexible ball joint. The nozzle mates to
11324-522: The USSR first had it been ordered to do so. The bombers would fly orbits around their assigned positions from which they were to enter Soviet airspace if they received the order, and the tankers would refill the bombers' fuel tanks so that they could keep a force in the air 24 hours a day, and still have enough fuel to reach their targets in the Soviet Union. This also ensured that a first strike against
11473-501: The aircraft having to fly to a lower altitude to be depressurized so a crew member could manually do the coupling. This air-to-air refueling system was used by the B-50 Superfortress Lucky Lady II of the 43rd Bomb Wing to make its famous first non-stop around-the-world flight in 1949. From 26 February to 3 March 1949, Lucky Lady II flew non-stop around the world in 94 hours and 1 minute,
11622-483: The aircraft made its mission impossible without aerial refueling. Based at Beale AFB in central California , SR-71s had to be forward-deployed to Europe and Japan prior to flying actual reconnaissance missions. These trans-Pacific and trans-Atlantic flights during deployment were impossible without aerial refueling. The SR-71's designers traded takeoff performance for better high-speed, high-altitude performance, necessitating takeoff with less-than-full fuel tanks from even
11771-408: The aircraft to be refueled (very close "line astern" formation flying) has resulted in the activity only being used in military operations ; there are no regular civilian in-flight refueling activities. Originally trialed shortly before World War II on a limited scale to extend the range of British civilian transatlantic flying boats , and then employed after World War II on a large scale to extend
11920-449: The aircraft's fuselage and causing damage. The other major difference with this system is that when contacted, the hose does not "retract" into an HDU. Instead, the hose bends depending on how far it is pushed toward the boom. If it is pushed too far, it can loop around the probe or nose of the aircraft, damage the windscreen, or cause contact with the rigid boom. If not pushed far enough, the probe will disengage, halting fueling. Because of
12069-409: The aircraft's fuselage. Some tankers have both a boom and one or more complete hose-and-drogue systems. The USAF KC-10 has both a flying boom and a separate hose-and-drogue system manufactured by Cobham . Both are on the aircraft centerline at the tail of the aircraft, so only one can be used at once. However, such a system allows all types of probe- and receptacle-equipped aircraft to be refueled in
12218-408: The angle between any two planes. So, in aeronautics, in one case, the term "dihedral" is applied to mean the difference in angles between two front-to-back surfaces: Longitudinal dihedral is the difference between the angle of incidence of the wing root chord and angle of incidence of the horizontal tail root chord. Longitudinal dihedral can also mean the angle between the zero-lift axis of
12367-404: The angle of the wings is disturbed to become off-level. If a disturbance causes an aircraft to roll away from its normal wings-level position as in Figure 1, the aircraft will begin to move somewhat sideways toward the lower wing. In Figure 2, the airplane's flight path has started to move toward its left while the nose of the airplane is still pointing in the original direction. This means that
12516-412: The angle the wings meet at the root, which may be restricted to meet other design criteria. Polyhedral is seen on gliders and some other aircraft. The McDonnell Douglas F-4 Phantom II is one such example, unique among jet fighters for having dihedral wingtips. This was added after flight testing of the flat winged prototype showed the need to correct some unanticipated spiral mode instability – angling
12665-416: The area in which contact with the boom is safe. Moving outside of this envelope can damage the boom or lead to mid-air collision, for example the 1966 Palomares B-52 crash . If the receiving aircraft approaches the outer limits of the envelope, the boom operator will command the receiver pilot to correct their position and disconnect the boom if necessary. When the desired amount of fuel has been transferred,
12814-542: The body tanks and wing tanks separately. Eight KC-135R aircraft are receiver-capable tankers, commonly referred to as KC-135R(RT). All eight aircraft were with the 22d Air Refueling Wing at McConnell AFB , Kansas, in 1994. They are primarily used for force extension and Special Operations missions, and are crewed by highly qualified receiver capable crews. If not used for the receiver mission, these aircraft can be flown just like any other KC-135R. The Multi-point Refueling Systems (MPRS) modification adds refueling pods to
12963-574: The bombers' airfields could not obliterate the US's ability to retaliate by bomber. In 1958, Valiant tankers in the UK were developed with one HDU mounted in the bomb-bay. Valiant tankers of 214 Squadron were used to demonstrate radius of action by refueling a Valiant bomber non-stop from UK to Singapore in 1960 and a Vulcan bomber to Australia in 1961. Other UK exercises involving refueling aircraft from Valiant tankers included Javelin and Lightning fighters, also Vulcan and Victor bombers. For instance, in 1962
13112-528: The brothers John, Kenneth, Albert, and Walter Hunter set a new record of 553 hours 40 minutes over Chicago using two Stinson SM-1 Detroiters as refueler and receiver. Aerial refueling remained a very dangerous process until 1935, when brothers Fred and Al Key demonstrated a spill-free refueling nozzle, designed by A. D. Hunter . They exceeded the Hunters' record by nearly 100 hours in a Curtiss Robin monoplane, staying aloft for more than 27 days. The US
13261-568: The commercial Boeing 707 and 720 aircraft, although it is a different aircraft. Reconnaissance and command post variants of the aircraft, including the RC-135 Rivet Joint and EC-135 Looking Glass aircraft were operated by SAC from 1963 through 1992, when they were reassigned to the Air Combat Command (ACC). The USAF EC-135 Looking Glass was subsequently replaced in its role by the U.S. Navy E-6 Mercury aircraft,
13410-585: The development of Alexander P. de Seversky , between two planes occurred on 25 June 1923, between two Airco DH-4B biplanes of the United States Army Air Service . An endurance record was set by three DH-4Bs (a receiver and two tankers) on 27–28 August 1923, in which the receiver airplane remained aloft for more than 37 hours using nine mid-air refueling to transfer 687 US gallons (2,600 L) of aviation gasoline and 38 US gallons (140 L) of engine oil. The same crews demonstrated
13559-563: The dihedral angle is usually greater on low-wing aircraft than on otherwise-similar high-wing aircraft. This is because "highness" of a wing (or "lowness" of vertical center of gravity compared to the wing) naturally creates more dihedral effect itself. This makes it so less dihedral angle is needed to get the amount of dihedral effect needed. Dihedral effect is defined simply to be the rolling moment caused by sideslip and nothing else. Rolling moments caused by other things that may be related to sideslip have different names. Dihedral effect
13708-402: The drogue under the appropriate pressure (assuming the tanker crew has energized the pump). Tension on the hose is aerodynamically 'balanced' by a motor in the HDU so that as the receiver aircraft moves fore and aft, the hose retracts and extends, thus preventing bends in the hose that would cause undue side loads on the probe. Fuel flow is typically indicated by illumination of a green light near
13857-430: The early 1950s, the basic airframe is characterized by 35-degree aft swept wings and tail , four underwing-mounted engine pods, a horizontal stabilizer mounted on the fuselage near the bottom of the vertical stabilizer with positive dihedral on the two horizontal planes and a hi-frequency radio antenna which protrudes forward from the top of the vertical fin or stabilizer. These basic features make it strongly resemble
14006-451: The engines over the course of three minutes. The water is injected into the inlet and the diffuser case in front of the combustion case. The water cools the air in the engine to increase its density; it also reduces the turbine gas temperature, which is a primary limitation on many jet engines. This allows the use of more fuel for proper combustion and creates more thrust for short periods of time, similar in concept to " War Emergency Power " in
14155-565: The first batch of replacement planes was to be an air tanker version of the Boeing 767 , leased from Boeing . In 2003, this was changed to contract where the Air Force would purchase 80 KC-767 aircraft and lease 20 more. In December 2003, the Pentagon froze the contract and in January 2006, the KC-767 contract was canceled. This move followed public revelations of corruption in how the contract
14304-501: The flying boom system, along with Australia (KC-30A), the Netherlands (KDC-10), Israel (modified Boeing 707), Japan (KC-767), Turkey (KC-135Rs), and Iran (Boeing 707 and 747). The system allows higher fuel flow rates (up to 1,000 US gallons (3,800 L) / 6,500 pounds (2,900 kg) per minute for the KC-135, but does require a boom operator, and can only refuel one aircraft at a time. The probe-and-drogue refueling method employs
14453-422: The full span are said to be polyhedral . Dihedral angle has important stabilizing effects on flying bodies because it has a strong influence on the dihedral effect. Dihedral effect of an aircraft is a rolling moment resulting from the vehicle having a non-zero angle of sideslip . Increasing the dihedral angle of an aircraft increases the dihedral effect on it. However, many other aircraft parameters also have
14602-399: The hose several feet into the HDU and solidly couple the probe and drogue. Too little closure will cause an incomplete connection and no fuel flow (or occasionally leaking fuel). Too much closure is dangerous because it can trigger a strong transverse oscillation in the hose, severing the probe tip. The optimal approach is from behind and below (not level with) the drogue. Because the drogue
14751-458: The hose was connected, the tanker climbed sufficiently above the receiver aircraft to allow the fuel to flow under gravity. When Cobham was developing his system, he saw the need as purely for long-range transoceanic commercial aircraft flights, but modern aerial refueling is used exclusively by military aircraft. In 1934, Cobham had founded Flight Refuelling Ltd (FRL) and by 1938 had used its looped-hose system to refuel aircraft as large as
14900-460: The hose which would cut off if contact was lost. Royal Air Force officer Richard Atcherley had observed the dangerous aerial-refueling techniques in use at barnstorming events in the US and determined to create a workable system. While posted to the Middle East he developed and patented his 'crossover' system in 1934, in which the tanker trailed a large hooked line that would reel in
15049-689: The inventory to eliminate the Navigator position from the flight crew. The fuel management system was also replaced. The program development was done by Rockwell Collins in Iowa and installation was performed by BAE Systems at the Mojave Airport in California. Block 40.6 allows the KC-135 to comply with global air-traffic management . The latest block upgrade to the KC-135, the Block 45 program,
15198-478: The late 1940s, General Curtis LeMay , commander of the Strategic Air Command (SAC), asked Boeing to develop a refueling system that could transfer fuel at a higher rate than had been possible with earlier systems using flexible hoses, resulting in the flying boom system. The B-29 was the first to employ the boom, and between 1950 and 1951, 116 original B-29s, designated KB-29Ps, were converted at
15347-432: The longest runways. Once airborne, the Blackbird would accelerate to supersonic speed using afterburners to facilitate structural heating and expansion. The magnitude of temperature changes experienced by the SR-71, from parked to its maximum speed, resulted in significant expansion of its structural parts in cruise flight. To allow for the expansion, the Blackbird's parts had to fit loosely when cold, so loosely, in fact, that
15496-507: The market with a family of airliners based on the 707. In 1954, the USAF placed an initial order for 29 KC-135As, the first of an eventual 820 of all variants of the basic C-135 family. The first aircraft flew in August 1956 and the initial production Stratotanker was delivered to Castle Air Force Base , California , in June 1957. The last KC-135 was delivered to the USAF in 1965. Developed in
15645-554: The mission, the Navy and Marine Corps not having fitted their aircraft with flying boom receptacles since the USAF boom system was impractical for aircraft carrier operations. Crews also helped to bring in damaged aircraft which could sometimes fly while being fed by fuel to a landing site or to ditch over the water (specifically those with punctured fuel tanks). KC-135s continued their tactical support role in later conflicts such as Operation Desert Storm and current aerial strategy. SAC had
15794-594: The model number 717-166. All four RC-135As ( Pacer Swan ) were modified to partial KC-135A configuration in 1979. The four aircraft (serial numbers 63-8058, 63-8059, 63-8060 and 63-8061 ) were given a unique designation KC-135D as they differed from the KC-135A in that they were built with a flight engineer's position on the flight deck. The flight engineer's position was removed when the aircraft were modified to KC-135 standards but they retained their electrically powered wing flap secondary (emergency) drive mechanism and second air conditioning pack which had been used to cool
15943-416: The more maneuverable fighter/ground attack types. A byproduct of this development effort and the building of large numbers of tankers was that these tankers were also available to refuel cargo aircraft , fighter aircraft , and ground attack aircraft , in addition to bombers, for ferrying to distant theaters of operations. This was much used during the Vietnam War , when many aircraft could not have covered
16092-527: The much improved probe-and-drogue system, with a modified Gloster Meteor F.3 jet fighter, serial EE397 , fitted with a nose-mounted probe. On 7 August 1949, the Meteor flown by FRL test pilot Pat Hornidge took off from Tarrant Rushton and remained airborne for 12 hours and 3 minutes, receiving 2,352 imperial gallons (10,690 L) of fuel in ten refuelings from a Lancaster tanker. Hornidge flew an overall distance of 3,600 mi (5,800 km), achieving
16241-404: The newer jet-powered military aircraft to slow down to mate with the tanker's boom, a highly serious issue with the newer supersonic aircraft coming into service at that time, which could force such receiving aircraft in some situations to slow down enough to approach their stall speed during the approach to the tanker. It was no surprise that, after the KC-97, Boeing began receiving contracts from
16390-407: The oncoming air is arriving somewhat from the left of the nose. The airplane now has sideslip angle in addition to the bank angle. Figure 2 shows the airplane as it presents itself to the oncoming air. In Figure 2, the sideslip conditions produce greater angle of attack on the forward-yawed wing and smaller angle of attack on the rearward-yawed wing. This alteration of angle of attack by sideslip
16539-506: The outbreak of World War II. During the closing months of World War II, it had been intended that Tiger Force 's Lancaster and Lincoln bombers would be in-flight refueled by converted Halifax tanker aircraft, fitted with the FRL's looped-hose units, in operations against the Japanese homelands , but the war ended before the aircraft could be deployed. After the war ended, the USAF bought
16688-558: The over sixty years of service, involving 385 fatalities. Data from USAF Fact Sheet, Boeing.com : KC-135 General characteristics Aerial refueling Aerial refueling ( en-us ), or aerial refuelling ( en-gb ), also referred to as air refueling , in-flight refueling ( IFR ), air-to-air refueling ( AAR ), and tanking , is the process of transferring aviation fuel from one aircraft (the tanker ) to another (the receiver) while both aircraft are in flight. The two main refueling systems are probe-and-drogue , which
16837-445: The probe into the basket. Unlike the soft canvas basket used in most drogue systems, the adapter units use a steel basket, grimly known as the "iron maiden" by naval aviators because of its unforgiving nature. Soft drogues can be contacted slightly off center, wherein the probe is guided into the hose receptacle by the canvas drogue. The metal drogue, when contacted even slightly off center, will pivot out of place, potentially "slapping"
16986-585: The probe is a valve that is closed until it mates with the drogue's forward internal receptacle, after which it opens and allows fuel to pass from tanker to receiver. The valves in the probe and drogue that are most commonly used are to a NATO standard and were originally developed by the company Flight Refuelling Limited in the UK and deployed in the late 1940s and 1950s. This standardization enables drogue-equipped tanker aircraft from many nations to refuel probe-equipped aircraft from other nations. The NATO-standard probe system incorporates shear rivets that attach
17135-414: The range of strategic bombers , aerial refueling since the Vietnam War has been extensively used in large-scale military operations. Some of the earliest experiments in aerial refueling took place in the 1920s; two slow-flying aircraft flew in formation, with a hose run down from a hand-held fuel tank on one aircraft and placed into the usual fuel filler of the other. The first mid-air refueling, based on
17284-420: The range of 35–40% have been estimated for long-haul flights (including the fuel used during the tanker missions). Usually, the aircraft providing the fuel is specially designed for the task, although refueling pods may be fitted to existing aircraft designs in the case of "probe-and-drogue" systems. The cost of the refueling equipment on both tanker and receiver aircraft and the specialized aircraft handling of
17433-462: The receiver aircraft is topped-off with extra fuel in the air, air refueling can allow a takeoff with a greater payload which could be weapons, cargo, or personnel: the maximum takeoff weight is maintained by carrying less fuel and topping up once airborne. Aerial refueling has also been considered as a means to reduce fuel consumption on long-distance flights greater than 3,000 nautical miles (5,600 km; 3,500 mi). Potential fuel savings in
17582-430: The refueling valve to the end of the probe. This is so that if a large side or vertical load develops while in contact with the drogue, the rivets shear and the fuel valve breaks off, rather than the probe or receiver aircraft suffering structural damage. A so-called "broken probe" (actually a broken fuel valve, as described above) may happen if poor flying technique is used by the receiver pilot, or in turbulence. Sometimes
17731-456: The runway on rotation/touchdown. In military aircraft dihedral angle space may be used for mounting materiel and drop-tanks on wing hard points, especially in aircraft with low wings. The increased dihedral effect caused by this design choice may need to be compensated for, perhaps by decreasing the dihedral angle on the horizontal tail. During design of a fixed-wing aircraft (or any aircraft with horizontal surfaces), changing dihedral angle
17880-655: The same flight, such as the KC-10, MPRS KC-135, or Airbus A330 MRTT. The development of the KC-97 and Boeing KC-135 Stratotankers was pushed by the Cold War requirement of the United States to be able to keep fleets of nuclear -armed B-47 Stratojet and B-52 Stratofortress strategic bombers airborne around-the-clock either to threaten retaliation against a Soviet strike for mutual assured destruction , or to bomb
18029-541: The same year, but these early experiments were not yet regarded as a practical proposition, and were generally dismissed as stunts. As the 1920s progressed, greater numbers of aviation enthusiasts vied to set new aerial long-distance records, using inflight air refueling. One such enthusiast, who would revolutionize aerial refueling was Sir Alan Cobham , member of the Royal Flying Corps in World War I , and
18178-412: The sideslip (labeled as "P") tends to roll the aircraft back to wings level. More dihedral effect tries to roll the wings in the "leveling" direction more strongly, and less dihedral effect tries to roll the wings in the "leveling" direction less strongly. Dihedral effect helps stabilize the spiral mode by tending to roll the wings toward level in proportion to the amount of sideslip that builds up. It
18327-421: The slower, piston-engined KC-97 was also a serious issue, as using it as an aerial tanker forced the newer jet-powered military aircraft to slow down to mate with the tanker's boom. Like its sibling, the commercial Boeing 707 jet airliner , the KC-135 was derived from the Boeing 367-80 jet transport "proof of concept" demonstrator, which was commonly called the "Dash-80". The KC-135 is similar in appearance to
18476-475: The stability of the spiral mode which is sometimes called "roll stability". The dihedral effect does not contribute directly to the restoring of "wings level", but it indirectly helps restore "wings level" through its effect on the spiral mode of motion described below. Aircraft designers may increase dihedral angle to provide greater clearance between the wing tips and the runway. This is of particular concern with swept-wing aircraft, whose wingtips could hit
18625-535: The stability of the spiral mode, although there are other factors that affect it less strongly. Factors of design other than dihedral angle also contribute to dihedral effect. Each increases or decreases total aircraft dihedral effect to a greater or lesser degree. Wing sweepback also increases the dihedral effect, for roughly 1° of effective dihedral with every 10° of sweepback. This is one reason for anhedral configuration on aircraft with high sweep angle, as well as on some airliners, even on low-wing aircraft such as
18774-422: The stability of the spiral mode. This increases maneuverability which is desirable in fighter-type aircraft. Anhedral angles are also seen on aircraft with a high mounted wing, such as the very large Antonov An-124 and Lockheed C-5 Galaxy cargo aircraft. In such designs, the high mounted wing is above the aircraft's center of gravity which confers extra dihedral effect due to the pendulum effect (also called
18923-956: The tanker equipment installed) as their famed Vomit Comet zero-gravity simulator aircraft. The longest-serving (1973 to 1995) version was KC-135A, AF Ser. No. 59-1481 , named Weightless Wonder IV and registered as N930NA. Between 1993 and 2003, the amount of KC-135 depot maintenance work doubled, and the overhaul cost per aircraft tripled. In 1996, it cost $ 8,400 per flight hour for the KC-135, and in 2002 this had grown to $ 11,000. The Air Force's 15-year estimates project further significant cost growth through fiscal year 2017. KC-135 fleet operations and support costs were estimated to grow from about $ 2.2 billion in fiscal year 2003 to $ 5.1 billion (2003 dollars) in fiscal year 2017, an increase of over 130 percent, which represented an annual operating cost growth rate of about 6.2 percent. The USAF projected that E and R models have lifetime flying hour limits of 36,000 and 39,000 hours, respectively. According to
19072-623: The tanker to refuel two receivers at the same time, which increases throughput compared to the boom drogue adapter. A number of KC-135A and KC-135B aircraft have been modified to EC-135, RC-135 and OC-135 configurations for use in several different roles (although these could also be considered variants of the C-135 Stratolifter family). The KC-135R has four turbofan engines, mounted under 35-degree swept wings, which power it to takeoffs at gross weights up to 322,500 pounds (146,300 kg). Nearly all internal fuel can be pumped through
19221-455: The tanker's flying boom , the KC-135's primary fuel transfer method. A boom operator stationed in the rear of the aircraft controls the boom while lying prone, viewing through a window at the bottom of the tail. Both the flying boom and operator's station are similar to those of the previous KC-97. A special shuttlecock-shaped drogue, attached to and trailing behind the flying boom, may be used to refuel aircraft fitted with probes. This apparatus
19370-412: The tendency for dihedral effect to roll the wings back level by limiting sideslip. The spiral mode is the tendency to slowly diverge from, or the tendency to slowly return to wings level. If the spiral mode is stable, the aircraft will slowly return to wings-level, if it is unstable, the aircraft will slowly diverge from wings-level. Dihedral effect and yaw stability are the two primary factors that affect
19519-624: The transoceanic distances without aerial refueling, even with intermediate bases such as Hickam Air Force Base , Hawaii and Kadena Air Base , Okinawa. In addition to allowing the transport of the aircraft themselves, the cargo aircraft could also carry matériel , supplies, and personnel to Vietnam without landing to refuel. KC-135s were also frequently used for refueling of air combat missions from air bases in Thailand. The USAF SR-71 Blackbird strategic reconnaissance aircraft made frequent use of air-to-air refueling. Indeed, design considerations of
19668-522: The two aircraft disconnect and the receiver aircraft departs the formation. When not in use, the boom is stored flush with the bottom of the tanker's fuselage to minimize drag. In the KC-97 and KC-135 the boom operator lies prone, while the operator is seated in the KC-10 , all viewing operations through a window at the tail. The KC-46 seats two operators at the front of the aircraft viewing camera video on 3D screens. The US Air Force fixed-wing aircraft use
19817-406: The usage " di hedral" evolved to mean the positive, up angle between the left and right wings, while usage with the prefix "an-" (as in " an hedral") evolved to mean the negative, down angle between the wings. The aerodynamic stabilizing qualities of a dihedral angle were described in an influential 1810 article by Sir George Cayley . In analysis of aircraft stability, the dihedral effect is also
19966-775: The utility of the technique on 25 October 1923, when a DH-4 flew from Sumas, Washington , on the Canada–United States border , to Tijuana, Mexico , landing in San Diego , using mid-air refuelings at Eugene, Oregon , and Sacramento, California . Similar trial demonstrations of mid-air refueling technique took place at the Royal Aircraft Establishment in England and by the Armée de l'Air in France in
20115-465: The valve is retained in the tanker drogue and prevents further refueling from that drogue until removed during ground maintenance. A "buddy store" or "buddy pod" is an external pod loaded on an aircraft hardpoint that contains a hose and drogue system (HDU). Buddy stores allow fighter / bomber aircraft to be reconfigured for "buddy tanking" other aircraft. This allows an air combat force without dedicated/specialized tanker support (for instance,
20264-457: The wing and the zero-lift axis of the horizontal tail instead of between the root chords of the two surfaces. This is the more meaningful usage because the directions of zero-lift are pertinent to trim and stability while the directions of the root chords are not. This measurement is also often referred to as decalage . In geometry, dihedral angle is the angle between two planes. Aviation usage differs slightly from usage in geometry. In aviation,
20413-459: Was awarded, as well as controversy regarding the original leasing rather than outright purchase agreement. The then Secretary of Defense Rumsfeld stated that that move would in no way impair the Air Force's ability to deliver the mission of the KC-767, which would be accomplished by implementing continuing upgrades to the KC-135 and KC-10 Extender fleet. In January 2007, the U.S. Air Force launched
20562-457: Was capable of separating the main body tanks from the wing tanks where the KC-135 draws its engine fuel. The only external difference between a KC-135R and a KC-135T is the presence of a clear window on the underside of the empennage of the KC-135T where a remote controlled searchlight is mounted. It also has two ground refueling ports, located in each rear wheel well so ground crews can fuel both
20711-480: Was declared the winner in 1955. Since Boeing's proposal was already flying, the KC-135 could be delivered two years earlier and Air Force Secretary Harold E. Talbott ordered 250 KC-135 tankers until Lockheed's design could be manufactured. In the end, orders for the Lockheed tanker were dropped rather than supporting two tanker designs. Lockheed never produced its jet airliner, while Boeing would eventually dominate
20860-681: Was delivered to the U.S. Air Force on 10 January 2019. Two export users of the KC-135, the French Air and Space Force and the Republic of Singapore Air Force took deliveries of Airbus A330 MRTTs as replacements for their Stratotankers. Original production version powered by four Pratt & Whitney J57s , 732 built. Given the Boeing model numbers 717-100A, 717-146 and 717-148. Test-configured KC-135A. Airborne command post version equipped with turbofan engines, 17 built. Provided with in-flight refueling capability and redesignated EC-135C. Given
21009-470: Was eventually modified by Airspeed to Cobham's specification, for a non-stop flight from London to India , using in-flight refueling to extend the plane's flight duration. Meanwhile, in 1929, a group of US Army Air Corps fliers, led by then Major Carl Spaatz , set an endurance record of over 150 hours with a Fokker C-2A named the Question Mark over Los Angeles. Between 11 June and 4 July 1930,
21158-675: Was initially purchased to support SAC bombers, but by the late 1960s, in the Southeast Asia theater, the KC-135 Stratotanker's ability as a force multiplier came to the fore. Midair refueling of F-105 and F-4 fighter-bombers as well as B-52 bombers brought far-flung bombing targets within reach, and allowed fighter missions to spend hours at the front, rather than a few minutes, which was usual due to their limited fuel reserves and high fuel consumption. KC-135 crews refueled both USAF and Navy/ Marine Corps aircraft; though they would have to change to probe and drogue adapters depending upon
21307-417: Was mainly concerned about transatlantic flights for faster postal service between Europe and America. In 1931 W. Irving Glover, the second assistant postmaster, wrote an extensive article for Popular Mechanics concerning the challenges and the need for such a regular service. In his article he even mentioned the use of aerial refueling after takeoff as a possible solution. At Le Bourget Airport near Paris,
21456-640: Was modified to carry JP-7 fuel necessary for the Lockheed SR-71 Blackbird by separating the JP-7 from the KC-135's own fuel supply (the body tanks carrying JP-7, and the wing tanks carrying JP-4 or JP-8 ). The tanker also had special fuel systems for moving the different fuels between different tanks. When the KC-135Q model received the CFM56 engines, it was redesignated the KC-135T model, which
21605-669: Was offered KC-135s again in 2013, after turning down the aging aircraft twice due to expense of keeping them flying. The IAF again rejected the offered KC-135Es, but said that it would consider up to a dozen of the newer KC-135Rs. Besides its primary role as an inflight aircraft refueler, the KC-135, designated NKC-135, has assisted in several research projects at the NASA Armstrong Flight Research Center at Edwards Air Force Base , California. One such project occurred between 1979 and 1980 when special wingtip " winglets ", developed by Richard Whitcomb of
21754-416: Was publicly demonstrated for the first time in 1935. In the system the receiver aircraft, at one time an Airspeed Courier , trailed a steel cable which was then grappled by a line shot from the tanker, a Handley Page Type W10 . The line was then drawn back into the tanker where the receiver's cable was connected to the refueling hose. The receiver could then haul back in its cable bringing the hose to it. Once
21903-495: Was pumped. Some historic systems used for pioneering aerial refueling used the grappling method, where the tanker aircraft unreeled the fuel hose and the receiver aircraft would grapple the hose midair, reel it in and connect it so that fuel can be transferred either with the assistance of pumps or simply by gravity feed . This was the method used on the Question Mark endurance flight in 1929. The probe-and-drogue system
22052-422: Was so successful that in June orders went out to equip all new B-50s and subsequent bombers with receiving equipment. Two dedicated air refueling units were formed on 30 June 1948: the 43d Air Refueling Squadron at Davis-Monthan Air Force Base , Arizona , and the 509th Air Refueling Squadron at Walker Air Force Base , New Mexico . The first ARS aircraft used FRL's looped-hose refueling system, but testing with
22201-637: Was supplemented by the larger McDonnell Douglas KC-10 Extender . Studies have concluded that many of the aircraft could be flown until 2030, although maintenance costs have greatly increased. The KC-135 is to be partially replaced by the Boeing KC-46 Pegasus . Starting in 1950 the USAF operated the world's first production aerial tanker, the Boeing KC-97 Stratofreighter , a gasoline fueled piston-engined Boeing Stratocruiser (USAF designation C-97 Stratofreighter ) with
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