Aerial refueling

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Aerial refueling, also called Air refueling or in-flight refueling (IFR) or air-to-air refueling (AAR) or (in the UK) tanking. Note that AAR also stands for "After-Action Review" (de-briefing) and in aviation, IFR also stands for "Instrument Flight Rules" (flight by instrument references only such as in cloud ).

Air refueling is the process of transferring fuel from one aircraft (the tanker) to another (the receiver) during flight. This allows the receiving aircraft to remain airborne longer and, more important, to extend its range and therefore those of its weapons or its deployment radius. A series of air refuelings can give range limited only by crew fatigue and engineering factors such as engine oil consumption.

Because the receiver aircraft can be topped up with extra fuel in the air, air refueling can allow a takeoff with a greater weapon payload, less fuel maintaining the allowed maximum takeoff weight. Alternatively a shorter takeoff roll can be achieved because takeoff can be at a lighter weight before refuelling once airborne (as with the US SR-71 Blackbird reconnaissance aicraft).

Usually, the aircraft providing the fuel is specially designed for the task, although refuelling pods can be fitted to existing aircraft designs if the "probe and drogue" system it to be used (see later). The cost of the refueling equipment on both tanker and receiver aircraft and the specialised aircraft handling of the aircraft to be refueled (very close "line astern" formation flying) has resulted in the activity only being used in military operations. There is no known regular civilian in-flight refueling activity. In large-scale military operations, air refueling is extensively used. For instance, in the 1991 conflict with Iraq over its occupation of Kuwait and the 2003 war against Saddam Hussein's Irag, all coalition air sorties were air-refueled except for a few short-range ground attack sorties in the Kuwait area.

Contents 1 History and development 2 Aerial refueling systems 2.1 Boom and receptacle (The Boeing "Flying Boom") 2.2 Probe and drogue 2.3 Probe and Drogue - Receiver Flying Technique 2.4 Hose Drum Units (HDUs) 2.5 Boom Drogue Adapter units 2.6 Multiple refueling systems 2.7 Probe-and-drogue systems in service 2.8 Wing-to-wing refueling 2.9 Grappling systems 3 Strategic and tactical implications 3.1 Strategic uses and considerations 3.2 Tactical uses and considerations 3.2.1 Vietnam War 3.2.2 Falklands War/South Atlantic War 3.2.3 Libya 3.2.4 Persian Gulf War 3.2.5 Kosovo War 3.3 Aerial Rearming 4 Media 5 HIFR (Helicopter In-Flight Refueling) 6 Tanker aircraft by refueling system 6.1 Boom and receiver 6.2 Probe and drogue 7 Popular culture 8 External links 9 See also 10 References

[edit] History and development

Some of the earliest experiments in aerial refueling took place in the 1920s, when it was as simple as two slow-flying aircraft flying 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. A DH-4B biplane remained aloft with mid-air refueling for 37 hours on June 27, 1923.

Development was rapid. In 1929, a group of U. S. Army Air Corps fliers, led by then Major Carl Spaatz, set an endurance record of over 150 hours with the Question Mark over Los Angeles. In 1930, the Hunter brothers set a new record of 553 hours 40 minutes over Chicago. Aerial refuelling remained a very dangerous process until 1935 when brothers Fred and Al Key demonstrated the first 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.^[1]

In the UK, Alan Cobham pioneered research on the probe and drogue method, and gave public demonstrations of the system. In 1934, he founded Flight Refuelling Ltd. (FRL), and by 1938 had used an automatic system to refuel aircraft as large as the Short Empire flying boat Cambria from an Armstrong Whitworth AW.23.^[1] Handley Page Harrows were used to refuel the Empire flying boats for regular transatlantic crossings. FRL still exists as part of Cobham plc.

Nowadays, specialized tanker aircraft have equipment specially designed for the task of offloading fuel to the receiver aircraft, based on Hunter's design, even at the higher speeds modern jet aircraft typically need to remain airborne.

In 1949 from February 26 to March 3 an American B-50 Superfortress "Lucky Lady II" flew non-stop around the World in 94 hours, 1 min., a feat made possible by 3 aerial refuelings from 4 pairs of KB-29M tankers. The flight started and ended at Carswell Air Force Base in Fort Worth, Texas with the refuelings accomplished over West Africa, the Pacific ocean near Guam and between Hawaii and the West Coast. This first nonstop circumnavigation of the globe proved that vast distances and geographical barriers were no longer an obstacle to military air power, thanks to aerial refueling.

[edit] Aerial refueling systems

The two most common approaches for making the union between the two aircraft are the boom and receptacle system (sometimes called flying boom) and the probe and drogue system. Much less popular was the wing-to-wing system, which is no longer used.

[edit] Boom and receptacle (The Boeing "Flying Boom")

In 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. Boeing engineers came up with the concept of the “Flying Boom,” system that is described in more detail below.

The B-29 was the first to employ the flying boom system, and between 1950 and 1951, 116 original B-29s, designated KB-29Ps, were converted at the Boeing plant at Renton, Washington State.

Boeing went on to develop the world’s first production aerial tanker, the KC-97 Stratotanker, 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 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. It was no surprise that, after the KC-97, Boeing receiving contracts from the USAF to build Jet Tankers based on the Boeing 707 airframe. This modified B707 became the KC135 Stratotanker and 732 were built. Modern air refueling as we now know it, was born.

The Boeing "flying boom" is a long, rigid, hollow shaft fitted to the rear of the aircraft, in which is tube that can pass fuel. The end of the fuel tube can be exended rather like a telescope. The telescoping fuel tube has a valve at the end that mates to the "receptacle" in the receiver aircraft. The poppet valve prevents fuel from exiting the tube until "contact" is properly made between the tanker's boom valve and the receiver's receptacle. Mounted on the hollow shaft surrounding the fuel tube are small wings, or ruddevators (visible in the picture, in a "V" shape). This enables the boom operator to "fly" the boom into alignment between the end of the boom and the receptacle. Once aligned, the fuel tube is hydraulically extended to effect "contact". Toggles in the receptacle engage the valve assembly, holding it locked during fuel transfer. The receiver's receptacle is fitted on the top of the aircraft, usually on its centerline behind the pilot.

During refueling operations the tanker aircraft will fly at a constant altitude and speed with the boom unlatched and flying in the "trail" position (see the photo). From an initial rendezvous point (the "RV"), the receiver aircraft manoeuvers into the "pre-contact position", a standard position behind and below the tanker. This is to enable a closer approach to the tanker, enabling "contact" with the boom within its movement and extension limits.

Receiver positioning is aided with either voice or visual commands from the crewmember operating the boom, called a "boom operator" or "boomer". In the USAF, the boomer is usually an enlisted aircrew member. The boom operator faces toward the rear (i.e., toward the receiver aircraft) during refueling, lying prone in the KC-135 or sitting in a rear-facing seat in the KC-10. For radio-silent operations, visual commands are through pilot director indicators (PDIs) on the bottom of the tanker. The boomer illuminates these, directing the receiver pilot to move fore/aft and up/down into the correct position. Once in position, the receiver pilot holds this position with resect to the tanker. This is made more difficult by turbulence or poor tanker flying. Normally, the tanker autopilot is engaged for refueling, but may be disengaged if malfunctioning or for training. Once the receiver is in the contact position, the boomer flies the nozzle into alignment with the receptacle by positioning the ruddevators with a control stick. At the same time, the boomer extends the nozzle at the end of the fuel tube into contact with the conical receptacle using the extension control lever. Pumps operated by the pilot on the tanker drive fuel through the fuel tube into the receiver.

While in contact, the PDIs show the boom's position to the receiver pilot so that he can fly close line astern formation to remain within the air refueling envelope. In addition, the inner extensible tube of the boom has color-coded stripes to aid the receiver pilot in keeping it extended to a proper length. The air refueling envelope is different for each receiver; it is based either on the boom's mechanical limits, or to prevent the receiver from moving into a position where any portion of the boom might contact the receiver outside the receptacle while in contact. When fueling is complete, either aircraft (typically the boomer) can effect a disconnect by sending an electrical signal through the boom, disengaging the toggles in the receptacle. An automatic pressure disconnect can also trigger this disengagement when the receiver's fuel system has been filled to capacity. The boomer retracts the fuel tube from the receptacle and "flies" the boom clear of the receiver. While not in use, the boom is "flown" up to the bottom of the tanker to minimise drag, and latched in position.

The primary advantage of the boom method is a high fuel flow rate(up to 1000 US gallons per minute for the KC-135 tanker). This is because the diameter of the fuel pipe in the flying boom was greater than could be achieved by the rival "probe and droge" system (see below) at the time. High fuel transfer rate was considered vital for the Strategic Air Command bomber fleet when this system was selected because pilot fatigue during the refueling operation was a concern. Receiver pilots need high concentration to fly close linbe-astern formation throughout the procedure. Another feature of the boom system is the cost of the "boomer". In addition to US Air Force, the boom system is in use by the Netherlands (KDC-10), Israel (modified Boeing 707) and Turkey (ex-USAF KC-135R). Iran is also understood to operate a boom-equipped Boeing 747 tanker - possibly the largest tanker aircraft.

The European EADS group has developed a boom refueling system using "fly-by-wire" controls that is compatible with other boom systems. This is offered on modified European Airbus type aircraft that are to function as tankers.

The simpler and cheaper probe-and-drogue system is used by many other military organizations including the US Navy and Marine Corps and many non-US forces. The lower flow rates then available from the lower pressure and limited diameter of the hose used in the probe-and-drogue system result in longer refueling times compared to the Flying Boom system. However, lighter aircraft are refueled quicker because their fuel capacity is smaller.

[1] [2] [3]

[edit] Probe and drogue

The drogue (or para-drogue), sometimes called a basket, is a fitting resembling a plastic shuttlecock, attached, at its narrow end, with a valve, to a flexible hose, running from the hose drum unit (HDU) or boom to drogue adapter (BDA). The receiver has a probe, which is a rigid arm placed on the aircraft's nose or, in some aircraft, to the side of the nose. At the end of the probe is a valve that is closed until it mates with the drogue, 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. This standardisation of refuelling valves makes the probe and drogue system worldwide. Drogue-equipped tanker aircraft from many nations can refuel probe-equipped aircraft from others. The NATO standard probe system incorporates shear rivets that attach the refueling valve to the end of the probe. This is so that, if a large side-load or up-and-down load develops while in contact with the drogue, the rivets shear and the fuel valve breaks off rather than the probe itself being structurally damaged. Since the probe has a strong structural attachment to the aircraft fuselage, this also prevents the possibility of damage to the fuselage of the receiver aircraft itself. 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.

[edit] Probe and Drogue - Receiver Flying Technique

The tanker aircraft flies straight and level (S&L), and the drogue attached to its hose (flexible fuel pipe) is allowed to trail out behind and below the tanker under normal aerodynamic forces. The pilot of the receiver aircraft must then use his normal flight controls to "fly" his refueling probe directly into the basket so that the basket and probe refuel valves lock together so that fuel can flow from one to the other. This requires a closure rate of at least two knots or so, less gives a so-called "soft contact" in which the valves are not properly locked and fuel can spill out, for instance over the receiver aircraft's windscreen. Too high a contact speed is dangerous and can lead to a bow developing in the hose that can cause a side-load on the valve at the end of the probe, severing its mounting on the probe, ending the refueling and maybe leading to a diversion to another airfield. The optimal approach to the drogue is from behind and below (not level with it) along the line of the hang of the drogue below its Hose Drum Unit (HDU). A good rule for the receiver pilot is, when formating behind and below the tanker, the receiver is positioned so that the drogue is visually in line with the Hose Drum Unit on the tanker. This juxtaposition of drogue and HDU as a slow approach to the drogue is made ensures that, after initial contact, the velocity vector of the receiver aircraft is in the right direction to slowly push the drogue towards the tanker at the correct angle without further flight path adjustments, allowing the hose to reel a short distance on to the HDU drum, thereby opening the main fuel valve of the tanker and allowing refueling to start. Because of the significant inertia of large aircraft when approaching the drogue, the above technique is normally followed. However, with lighter and more manouevrable fighter aircraft there is the temptation to "rush" at the drogue from the same level. This sometimes leads to a so-called "broken probe" in which the shear rivets that attach the short refuelling valve to the probe itself, break. Note that if that if this happens, the probe itself should not be damaged, just the fuel valve at the end. Sometimes the valve is retained in the tanker drogue and prevents further refueling from that drogue until removed ready for the next sortie. With proper training of receiver pilots, this sort of event should be minimised.

[edit] Hose Drum Units (HDUs)

Here, a long hose (flexible fuel pipe) connects the drogue to the unit in the tanker aircraft that is to supply the fuel, the Hose Drum Unit, HDU or "Hoodoo". The hose and drogue can be either reeled in completely to the HDU for transit flight, or "trailed" to the full length of the hose so that the receiver aircraft can approach to make a refueling "contact". After initial contact, when the hose and drogue is pushed forward by the receiver by a certain distance (typically, a few feet), the hose is reeled slowly back onto its drum in the HDU and the tanker's main refuelling valve opens to allow fuel to flow to the drogue under the appropriate pressure for air refueling. The hose is aerodynamically "balanced" so as to make it easier (even, possible) for the receiver aircraft. If the natural aerodynamic drag on the drogue was, for instance, 1000 units, unless something is done, the receiver aircraft would have to push forward on the drogue with this large force, the flexible hose would bend rather than reel in and the side-load would cause the refuelling valve at the end of the probe to break off. To avoid this, a motor in the HDU provides a balacing force to the aerodynamic drag of the drogue. If the drag force is 1000, the HDU balacing force might be 950, resulting in only a small forward force being needed from the probe after initial contact to reel in the hose and open the tanker's main refueling valve. In this situation, after initial contact, the velocity vector of the receiver carries it further towards the tanker, the hose slowly reels in to the HDU, the fuel valve opens and the receiver throttles so as not to get too close to the tanker.

[edit] Boom Drogue Adapter units

Here a short hose is attached to a flying boom system and has a drogue on the end. In this system, the tanker boom operator (the "boomer") "flies" the boom into a position which experience has shown is optimal for the receiver aircraft. After the receiver pilot calls "contact" the boom operator starts the refueling. The receiver maintains his position during refueling, keeping an eye on the hose to make sure he remains in a suitable position. When fueling is complete, he slowly backs off until the probe refueling valve disconnects from the valve in the basket.

[edit] Multiple refueling systems

Some boom-carrying tankers have special hoses which can be attached before flight to the end of the boom to allow them to also refuel probe-equipped aircraft. Others boom-carrying tankers may have both a boom and one or more hose-and-drogue assemblies attached to the wing tips known as the Multi-Point Refueling System or MPRS.

[edit] Probe-and-drogue systems in service

The U.S. Navy, Marine Corps, and other NATO nations use the probe and drogue system rather than the boom. Unlike the boom system, multiple aircraft can be refuelled simultaneously if more than one drogue unit is fitted to the tanker aircraft, typically by pods fitted under each wing. A centre-line HDU is also available and allows more fuel flow than wing pods. Drogue-equipped tankers can have up to three refueling points, centre-line and two on the wings.

The probe-and-drogue method allows aircraft not originally designed as tankers to be converted by attaching a refueling pod. The pod contains a drogue and hose reel. Where similar types of fighter ground-attack aircraft are pod-equipped (compared to large tansport aircraft) this is known as "buddy tanking" or "buddy-buddy" refueling.

This system was first used on late models of the KB-29M Superfortress. Its first use in combat occurred on May 29, 1952 when twelve F-84s were refueled during a mission from Itazuke, Japan to Sariwon, North Korea.

The incompatibility of probe-and drogue and flying boom refueling is a problem for military planners. This problem was experienced during the Gulf War of 1991, leading to consideration by the USAF of converting boom systems to probe-and-drogue. Advancements of the probe and drogue system now allow a fuel flow comparable to the boom method. In some cases, such as the KC-135FR in service with the French Air Force, refueling-boom equipped tankers can be converted to an all probe-and-drogue system. The KC-135FR retains its articulated boom, but has a hose at the end of it instead of the usual nozzle.

[edit] Wing-to-wing refueling

In this method, similar to the probe and drogue method but more complicated, the tanker aircraft released a flexible hose from its wingtip. An aircraft, flying beside it, had to catch the hose with a special lock under its wingtip. After the hose was locked, and the connection was established, the fuel was pumped. It was used on a small number of Soviet Tu-4 and Tu-16 only (the tanker variant was Tu-16Z).

[edit] Grappling systems

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, and also the first ever non-stop around-the-world flight by Strategic Air Command's B-50 nuclear-capable bomber nicknamed the Lucky Lady II in 1949.

[edit] Strategic and tactical implications

[edit] Strategic uses and considerations

The development of the KC-97 and 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 Mutually Assured Destruction, or to bomb the U.S.S.R. first had it been ordered to do so by the President. 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 the bombers' airfields could not obliterate the U.S.'s ability to retaliate by bomber. A noted example of refueling used in this manner in the movies can be seen in the opening credits of Dr. Strangelove (a fictional movie, but the refueling scenes are from actual B-52s refueling from KC-135s).

In the UK, Valiant tankers were operational from 1958 and had one HDU mounted in the bomb-bay. Valiant tankers 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 involved Valiant tankers and Javelin and Lightning fighters. For instance, in 1962 a squadron of Javelin air defence 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 refuelling pod on each wing. The centre hose could refuel any probe-equipped aircraft, the wing pods could refuel the more manoeuverable flighter/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 the transoceanic distances without aerial refueling, even with intermediate bases in Hawaii and 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. Its home base was at Beale AFB in central California, but to make actual reconnaissance missions over enemy territory, it was necessary to deploy the craft to forward bases in Okinawa or in Europe. Hence, there were lots of trans-Pacific and trans-Atlantic flights. Also, for safe takeoff performance, it was necessary for the SR-71 to take off with less-than-full fuel tanks. The SR-71 would the rendezvous with a specially modified KC-135 to top up its tanks. Then the SR-71 was capable of flying for many hours on its own. This tanker variant was necessary because the SR-71 used a special fuel, JP-7, with a very high flash point (needed to withstand the high skin temperatures of Mach 3+ cruising flight) which could not be used in other aircraft engines and the KC-135Q was equipped with a separate internal bladder system to carry and deliver this non-standard fuel.

[edit] Tactical uses and considerations

The capability of refueling after takeoff conveys two considerable tactical advantages to those forces with access to tankers. It allows attack aircraft, fighters, and bombers to reach distances they could not without refueling, and patrol aircraft to remain airborne longer. Additionally, since an aircraft's maximum takeoff weight is generally less than the maximum weight with which it can stay airborne, this allows an aircraft to take off with only a partial fuel load, and carry additional payload weight instead. Then, after reaching altitude, the aircraft's tanks can be topped up by a tanker, bringing it up to its maximum flight weight.

[edit] Vietnam War

It was common for USAF fighter-bombers flying from Thailand to North Vietnam to refuel from KC-135s en-route to their target. Besides extending their range, this enabled the F-105s and F-4 Phantoms to carry more bombs and rockets. Tankers were also available for refueling on the way back if necessary. In addition to ferrying aircraft across the Pacific Ocean, aerial refueling made it possible for battle damaged fighters, with heavily leaking fuel tanks, to hook up to the tankers and let the tanker feed its engine(s) until the point where they could glide to the base and land. This saved numerous aircraft.

The US Navy frequently used carrier-based aerial tankers like the KA-3 Skywarrior to refuel Navy and Marine aircraft such as the F-4, A-4, A-6, and A-7. This was particularly useful when a pilot returning from an airstrike was having difficulty landing and was running low on jet fuel. This gave him fuel for more attempts at landing for a successful "trap" on an aircraft carrier. The KA-3 could also refuel fighters on extended Combat Air Patrol and E-2 Hawkeye Airborne Electronic Warning aircraft on extended patrol. USMC jets based in South Vietnam and Thailand also used USMC KC-130 Hercules transports for air-to-air refueling on missions.

[edit] Falklands War/South Atlantic War

Aerial refueling played a vital role in all of the Argentine successful attacks against the Royal Navy. The Argentine Air Force had only 2 KC-130H Hercules available and they were used to refuel both Air Force and Navy A-4 Skyhawks and Navy Super Etendards in their Exocet strikes, with the two models achieving almost all of the British ships sunk. The Hercules on several occasions approached the islands (where the Sea Harriers were in patrol) to search and guide the A-4s in their returning flights. On one of those flights (callsign Jaguar) one of the KC-130s went to rescue a damaged A-4 and delivered 39,000 lb of fuel while carrying it to its airfield at San Julian. On the other hand, the Mirage IIIs and Daggers lack of air refuelling capability prevented them from achieving better results. The Mirages were unable to reach the islands with a strike payload, and the Daggers could do so only for a 5 minute strike flight.

On the British side, air refueling was carried out by the Handley Page Victor K.2 and after the Argentine surrender by modified C-130 Hercules tankers. These aircraft aided deployments from the UK to the Ascension Island staging post in the Atlantic and further deployments south of bomber, transport and maritime patrol aircraft. The most famous refueling missions were the "Operation Black Buck" sorties which involved 14 Victor tankers refueling single Avro Vulcan bombers to attack the Argentine-captured airfield at Port Stanley on the Falkland Islands. They attempted to knock out the Port Stanley runway, blocking the Argentine C-130 Hercules re-inforcement operations. The raids were the longest-range bombing raids in history until surpassed by the B-52 in the 1991 Gulf War and later B-2 flights.

The Victor tankers, retired in 1993, were replaced in RAF service by Lockheed L-1011 and Vickers VC10 transports which were bought second-hand and fitted as tankers. The L-1011s, converted by Marshall Aerospace, and VC10s, converted by British Aerospace, can refuel any aircraft fitted with the NATO standard probe system.

[edit] Libya

During Operation El Dorado Canyon, several F-111 Aardvark fighter-bombers stationed in the United Kingdom utilized aerial refuelling to enable them to operate non-stop against targets in Libya. Since the aircraft were allowed to cross neither French nor Spanish airspace, they should make a detour around the Iberian Peninsula and stay above International waters during all transit.

[edit] Persian Gulf War

During the time of Operation Desert Shield, the military build up to the Persian Gulf War, US Air Force KC-135s, McDonnell Douglas KC-10As, and USMC KC-130 Hercules aircraft were deployed to forward air bases in England, Diego Garcia, and Saudia Arabia. Aircraft stationed in Saudi Arabia normally maintained an orbit in the Iraq-Saudi Arabia neutral zone, informally known as "Frisbee", and refueled Coalition Aircraft whenever necessary. Two side by side tracks over central Saudi Arabia called "Prune" and "Raisin" featured 2-4 basket equipped KC-135 tankers each and were used by Navy aircraft from the Red Sea Battle Force. Large Navy strike groups from the Red Sea would send A-6 tankers to the Prune and Raisin tracks ahead of the strike aircraft arriving to top off and take up station to the right of the tankers thereby providing an additional tanking point. RAF VC-10 tankers were also used to refuel coalition aircraft and were popular for their docile basket behavior and having three point refuelling stations. An additional track was maintained close to the northwest border for the EA-3 ELINT aircraft and any Navy aircraft needing emergency fuel. These 24-hour air-refueling zone helped make the intense air campaign during Operation Desert Storm possible. An additional 24/7 tanker presence was maintained over the Red Sea itself to refuel Navy F-14 Tomcats maintaining Combat Air Patrol tracks. During the last week of the conflict, KC-10 tankers moved inside Iraq to support barrier CAP missions set up to block Iraqi fighters from escaping to Iran.

On January 16-17 1991, the first combat sortie of Desert Storm, and the longest combat sortie in history, at that time, was launched from Barksdale AFB, Louisiana. Seven B-52Gs flew a thirty-five hour mission to the Persian Gulf region, and back, to launch Boeing Air Launched Cruise Missiles (ALCMs) with the surprise use of conventional warheads. All of this was made possible by in-flight refueling, and by the secret switch away from nuclear warheads on the ALCMs.

An extremely useful aerial tanker in Desert Storm was the USAF KC-10A Extender. Besides being larger than the other tankers, the KC-10A is equipped with the USAF "boom" refueling and also the "probe-and-drogue" system. This makes it possible for the KC-10A to refuel USAF aircraft, and also USMC and US Navy jets that use the "probe-and-drogue" system, and also allied aircraft, such as those from the UK and Saudi Arabia. KC-135's may be equipped with a drogue depending on the mission profile.

The KC-10A was originally designed for the support of NATO in Europe by the USAF. In the case of armed conflict, with a full jet fuel load, the KC-10A is capable of flying from a base on the east coast of the US or Canada, flying nonstop to Europe, transferring a considerable amount of fuel in air-to-air refueling, and then returning to its home base, all without landing anywhere. This could have been very useful in the case when numerous European bases become disabled by Warsaw Pact strikes in Germany, Holland, France, and Great Britain.

[edit] Kosovo War

The USAF provided nearly 90 percent of the NATO tanker force, 112 active and 63 Reserve-component KC-135 and KC-10 tankers.[4] Tankers were also provided from Britain’s RAF (Tristars and VC-10s), French Air Force and Turkish Air Force KC-135s, Spanish Air Force KC-130 Hercules and Royal Netherlands Air Force KDC-10s. Although some European nations provided air-refuelling aircraft, the conflict highlighted the problem Europe has with a lack of such aircraft and dependence on the United States for tanker support during a major operation. Some European nations sought to address this lack of capability, such as the Italian Air Force purchase of the Boeing KC-767, but there is still a huge difference in air-refuelling capability between the US and Europe.

[edit] Aerial Rearming

In 2003 the U.S. Air Force and Far Technologies applied secretly for patents on mid-air rearming of aircraft. The technique proposed is similar in many respects to airborne refueling, with a number of notable modifications. The air borne rearming system is comprised of a rearming plane with an internal bomb storage area and loading device consisting of a large aft door and a modified remote-driven robotic arm (boom) equipped with a day-night camera as well as sensors. On the attack aircraft, a special pylon to receive the arms from the boom. At present financial and technological problems stand in the way of aerial rearming; mainly the need for an automatic system to perform the rearm currently under development for aerial refueling [5].

[edit] Media

[edit] HIFR (Helicopter In-Flight Refueling)

A variation of aerial refueling is when a naval helicopter approaches a warship (not necessarily suited for landing operations) and receives fuel through the cabin while hovering.

Note: Alternatively, some helicopters equipped with a probe extending out the front can be refueled from a drogue-equipped tanker aircraft in a similar manner to fixed-wing aircraft by matching a high forward speed for a helicopter to a slow speed for the fixed-wing tanker. Therefore a less ambiguous meaning for the abbreviation HIFR would be HOVER In-Flight Refueling.

Note also: The transfer of cargo while an aircraft is hovering is known within the US Navy and the United States Coast Guard as Vertical Replenishment (VERTREP).

[edit] Tanker aircraft by refueling system

[edit] Boom and receiver

• KB-29P (No longer in service)
  • adapted from the B-29 Superfortress bomber
• KC-97 Stratotanker (No longer in service)
  • derived from the C-97 Stratofreighter
• KC-135 Stratotanker
  • related to the Boeing 707 airliner
  • also used by the French Air Force, Republic of Singapore Air Force and Turkish Air Force
  • boom can be fitted preflight with a drogue adapter. French Air Force KC-135 Stratotankers use the probe and drogue system
  • MPRS models will have two drogue hose reels (pods) at the wingtips
  • Modified Boeing 707 tankers users, past and present, include the Royal Australian Air Force, Brazilian Air Force, Israeli Air Force, Italian Air Force and South African Air Force
• KC-10 Extender
  • adapted from the McDonnell Douglas DC-10 airliner
  • also has a retractable hose and drogue that can be selected in-flight
  • The Royal Netherlands Air Force operates two KDC-10s - former civil aircraft modified to a similar standard to the KC-10
• KC-767
  • adapted from the Boeing 767 airliner (Not yet in service - In developmental flight test as of Oct06)
  • to be used by the Italian Air Force and Japan Air Self Defense Force
  • All US models, if ordered, will have fitting for MPRS
• Airbus A330 MRTT
  • development of Airbus A330-200 airliner. Australian aircraft will be equipped with both a flying boom and probe-and-drogue units to accommodate both RAAF F-111s as well as F/A-18s and will be known as KC-30B. UK aircraft will be probe-and-drogue only.

[edit] Probe and drogue

• Airbus A330
  • RAF Future Strategic Tanker Aircraft, due in service around 2008.
• Airbus A310 MRTT
  • 4 for Luftwaffe
  • 2 for Canadian Forces (as CC-150 Polaris)
• Avro Lancaster (retired)
  • Refueled Gloster Meteors in 1940's
• Avro Lincoln^[2] (retired)
  • Refueled Gloster Meteors in 1940's
• Avro Vulcan (No longer in service)
  • specially modified for operations during the Falklands War
• Blackburn Buccaneer (No longer in service)
  • Equipped for buddy tanking
• Boeing 707
  • Used by the Brazilian Air Force, Royal Australian Air Force, South African Air Force and others
  • French Air Force KC-135 Stratotankers use the probe and drogue system.
• KB-29M (No longer in service)
  • adapted from the B-29 Superfortress; earlier versions used a "grappling hose" system; later models used a true probe-and-drogue.
• KB-50 (No longer in service)
  • adapted from the B-50 Superfortress, an improved model of the B-29 Superfortress.
• HC-130 Hercules and KC-130 Hercules, especially in United States Marine Corps service as well as KC-130s in Argentine Air Force, Brazilian Air Force, Israel Air Force, Republic of Singapore Air Force and Spanish Air Force service.
  • variants of the C-130 Hercules
• Lockheed L-1011 Tristar
  • K1 and KC1 variants deployed by the Royal Air Force
• Vickers Valiant (No longer in service)
• Vickers VC-10
• Handley Page Victor (No longer in service)
• KA-3 (No longer in service)
• A-4 Skyhawk
  • Equipped for buddy tanking with several nations - in US use known as the KA-4.
• KA-6 (No longer in service)
  • normal A-6 also equipped for buddy tanking
• KA-7 (No longer in service)
  • equipped for buddy tanking
• S-3 Viking
  • The current primary carrier-based tanker, equipped for buddy tanking
• F/A-18E/F
  • equipped for buddy refueling as "Strike tankers"
• Il-78 Midas
  • Standard Russian tanker, adapted from Il-76
  • the MKI variants currently deployed by the Indian Air Force (IAF)
• Myasishchev M-4-2
  • adapted from the M-4 bomber
• Myasishchev 3MS-2
  • adapted from the 3M bomber
• Tu-16N (and Tu-16Z with wing-to-wing system)
• Su-24M
  • equipped for buddy refueling with the UPAZ container as "Strike tankers"
• Su-33
  • equipped for buddy refueling

[edit] Popular culture

• The film The Starfighters has a great deal of footage of F-104 Starfighter jet fighters refueling. This was extensively mocked when The Starfighters showed up on Mystery Science Theater 3000 as episode #612.
• The movie Dr. Strangelove from 1964 has genuine footage of a "boom and receptacle" operation between USAF KC-135 Stratotanker and B-52 Stratofortress in turbulent air.
• The movie The Final Countdown from 1980 has genuine footage of a "probe and drogue" operation between US Navy KA-6 Intruder and F-14 Tomcats from USS Nimitz.
• The OVA series Macross Zero shows a VF-0 variable fighter refueling from a KS-3 tanker aircraft.
• In the film Air Force One, a US Air Force KC-10 Extender refuels the hijacked Presidential aircraft, "Air Force One", a specially converted Boeing 747.

[edit] External links

• Photo aerial tanking 1929
• Aerial tanking history
• Airborne rearming - A comprehensive article including a video.
• Aerial Refuelling on APA
• Official KC-30 Tanker website

[edit] See also

Regarding spacecraft: see Docking maneuver.

[edit] References

1. ^ ^{a b} History of Aviation, Part 19, 1938
2. ^ https://www.airforcehistory.hq.af.mil/Publications/fulltext/75yrs_inflight_refueling.pdf