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Aerial refueling, also called '''in-flight refueling''' ('''IFR''') or '''air-to-air refueling''' ('''AAR'''), is the practice of transferring Fuel from one Aircraft to another during flight. This allows the receiving aircraft to remain airborne longer, and to take off with a greater Payload . Usually, the aircraft providing the fuel is specially designed for the task. The requirement to refuel during a flight is primarily a military requirement, and there are no known regular civilian in-flight refueling operations. HISTORY AND DEVELOPMENT (top right), B-66 Destroyer (top left) and F-100D Super Sabre refuel from a KB-50J tanker. Taken in the early 1960s ]] 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 handheld gas tank on one airplane and placed into the usual fuel filler of the other. It was a very dangerous process until 1935 when brothers Fred And Al Key demonstrated the first spill-free refueling nozzle, designed by A. D. Hunter. 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 around the World in 94 Hours, 1 Min. without stopping. Refuelling was done 3 times during the flight from 4 pairs of KB-29M tankers. The flight started and ended at Fort Worth Texas. Refuelling was done in West Africa , near Guam and in the Pacific between Hawaii and 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. AERIAL REFUELLING SYSTEMS The two most common approaches for making the union between the two aircraft are the ''boom and receptacle'' system and the ''probe and drogue'' system. Much less popular was the ''wing-to-wing'' system, which is no longer used. Boom and receiver approaches a KC-135R]] The ''boom'' is a long, rigid, hollow shaft, usually fitted to the rear of the aircraft. (It almost connects the two lower aircraft in the picture at right.) It usually has a telescoping extension, a Poppet Valve at the end (the boom nozzle) to keep fuel in and permit it to flow, and small Wing s, sometimes known as ''ruddevators'' depending on design particulars (visible in picture below, in the "V" shape), to enable it to be "flown" into the receptacle of the receiver aircraft to be refueled. This ''receptacle'' is fitted onto the top of the aircraft, usually on its centerline and usually either behind or close in front of the Cockpit . The receptacle is a round opening which connects to the fuel tanks, with a valve to keep the fuel in when not being refueled, and dust and debris out. The boom has a nozzle which fits into this opening. During refueling operations, a tanker aircraft will fly in a straight and level altitude at constant speed, while the receiver takes a standard position behind and below the tanker. Modern tankers have lights which illuminate the areas outside this range, so that if the pilot can see them, he is directed to fly back towards the desired spot. Once in position, the receiver pilot flies formation with the tanker, although this can be complicated by Wake Turbulence . The crewman operating the boom, called a ''boomer'' or '' Boom Operator '' (in the USAF , usually an enlisted aircrew member), then unlatches the boom from its stowed position, and directs it towards the receiver by "flying" it with the attached wings. The telescoping section is then Hydraulically extended until the nozzle fits into the receiver's receptacle. When an electrical signal is passed between the boom and receiver, both valves are hydraulically opened, and Pump s operated by the pilot on the tanker drive fuel through the shaft of the boom, and into the receiver. Once the two are mated, additional lights (pilot director lights (PDIs)) on the tanker will be turned on if the receiver flies too far to one side, too low or too high, or too near or too far away, activated by sensing Switch es in the boom. When fueling is complete, the valves are closed and the boom is automatically or manually retracted by the boom operator. In addition to being used by the US Air Force, the boom method is used by the Netherlands (KDC-10), Israel (modified Boeing 707) and Turkey (ex-USAF KC-135R). All the mentioned nations operate US designed aircraft. The primary advantage to this method of refueling is that higher volumes of fuel can be transferred in a shorter amount of time. Although tankers equipped with rigid refueling booms can only service one properly equipped aircraft at a time, the transfer capacity is useful for the US Air Force, which operates many very large aircraft such as Strategic Bomber s. With advancements of the probe and drogue system they are now able to deliver the same amount of fuel flow. 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. Probe and drogue J & Sea Stallion demo at RIAT 2004.]] The Boom to Drogue Adapter (BDA) or ''drogue'' (or ''para-drogue''), sometimes called a ''basket'', is a fitting resembling a plastic Shuttlecock , attached to a flexible hose at its narrow end, with a valve where the two meet. The receiver has a ''probe'', which is a rigid, but sometimes jointed and retractable, arm placed usually on the side of the airplane's nose. Again, the tanker flies straight and level, and the drogue is allowed to trail out behind and below it. The drogue can be flown by the boom operator but the receiver pilot must fly his probe directly into the basket to make contact. The boom operator holds the BDA as motionless as possible. After the receiver states "contact" the boom operator triggers contact which allows the tanker pilot to start the air refueling pumps and offload fuel. 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 decelerates hard enough to yank the probe out of the basket. Some boom-carrying tankers have special hoses which can be attached to the nozzle of the boom to allow them to also refuel probe-equipped aircraft. Others 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. The U.S. Navy, Marine Corps, and other NATO nations use this system, rather than the boom system. Unlike the boom-and-receiver system, multiple aircraft can be refuelled simultaneously with the probe-and-drogue system. 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 . Wing-to-wing In this method, 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). STRATEGIC AND TACTICAL IMPLICATIONS disengages from a KC-10 Extender ]] from Travis Air Force Base , California, refuels an F/A-22 Raptor ]] Strategic uses and considerations The early development of the '' (a fictional movie, but the air-ballet of refueling scenes are from actual B-52s refueling from KC-135s). 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 airplane 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 potential enemies, it was necessary to fly the craft to forward bases on Okinawa or in Europe. Hence, there were lots of trans-Pacific and trans-Atlantic flights. Also, for best performance, it was necessary for the SR-71 to take off with less-than-full jet-fuel tanks. Next, the SR-71 would immediately rendezvous with a specially modified KC-135 to top off its tanks for full extended-range. Then, the SR-71 was capable of flying for many hours on its own. This KC-135Q variant was necessary because the SR-71's fuel, JP-7, was different from the fuel that was standard for other USAF aircraft. Tactical uses and considerations The capability of refueling after takeoff conveys two considerable tactical advantages to those with tankers. Most obviously, it allows attack aircraft, fighters, and bombers to reach distances they couldn't otherwise, 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 off by a tanker, bringing it up to its maximum flight weight. 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 damaged fighters to hook up to the tankers and be towed to the point where they could glide to the base and land. This saved numerous airplanes. 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 was 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. Falklands/Malvinas War Aerial refueling played a vital role in all of the Argentine successful attacks against the Royal Navy . The Argentine Air Force had 2 KC-130H Hercules available and were used to refuel both Air Force and Navy A-4 Skyhawk s and the Navy Super Etendard s in their Exocet s strikes, with the two models achieving almost all of the British ships sunks. The Hercules in several occasions they approached to the islands (where the Sea Harrier s 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-130 went to rescue a damaged A-4 and delivered 39.000 LB of fuel while carry him to its airfield at San Julian . On the other hand, the Mirage III s and Dagger s lack of air refuelling capability stop them to achieve better results. In spite of this, as the Daggers had more fuel capability they managed to reach the islands for a 5 minutes strike flight. For the British side, Aerial refueling was carried out almost exclusively by the Handley Page Victor . These aircraft aided deployments from the UK to the Ascension Island staging post in the South Atlantic, and further deployments south of attack, transport, and maritime patrol aircraft. The most famous refueling missions were the " Operation Black Buck " sorties which involved Victor tankers refueling Avro Vulcan bombers to attack the Argentine-captured airbase at Port Stanley on the Falkland Islands . Despite only one direct hit, the raids were the longest ranged bombing raids in history until surpassed by the B-2 Spirit in the 1991 Gulf War . The Victor tankers were shortly afterwards retired from service, and they were replaced for RAF service by Lockheed L-1011 transports which were bought economically on the second-hand airliner market. These L-1011s, converted by Marshall Aerospace , have the capability of refueling jets from the RAF, the Royal Navy, and NATO aircraft. The 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. This 24-hour air-refueling zone helped make the intense air campaign during Operation Desert Storm possible. On January 16/17th, 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 U.K. 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. Kosovo War MEDIA
TANKER AIRCRAFT BY REFUELING SYSTEM Boom and receiver prepares to refuel from a KC-135R]]
Probe and drogue
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