Aerial Tanker Refueling Aircraft
The usefulness of air refueling became apparent to the military almost as soon as they started using aircraft. The main advantage of air refueling is obvious: it enables aircraft to stay airborne longer. Since most aircraft are incapable of taking off with maximum fuel and full payload, without in-flight refueling there is always a balance to be struck between range, payload, and fuel. Air refueling is more than just a range stretcher: it allows one to carry out missions with a smaller number of sorties, or alternatively, fewer aircraft. The Soviets seemingly lost interest in the technology until the early 1960s. Even then, they never became as enthusiastic about aerial refueling as the US Air Force, preferring to operate smaller aircraft closer to their bases.
- Several variants of the Tu-4 were made. An experimental tanker was developed in 1952. Three Soviet Tupolev Tu-4 bombers (a virtual copy of the American B-29 Superfortress) were equipped as tankers and three were equipped as receivers.
- To increase range, the TU-16 subsequently received an air refueling system. Some TU-16 were converted into tanker aircraft, which were first tested in 1955 and received the designation TU-16E [some Western sources suggest the designation was Tu-16Z]. However, they could still be used as bombers. This initial inflight refuelling tanker version used a novel "wingtip-to-wingtip" method, with a hose trailed from the right wingtip and snagged by grapnel trailed by receiver, then winched into fitting in receiver's port wingtip. Later such a system was installed on Tu-16 bombers, but it was slightly changed. Now the recipient aircraft was releasing a fuel hose with a stabilizing parachute, and the tanker aircraft had to hook with a hook on the wing tip and pull it to the fueling unit. The use of the wing-wing system ceased in the 1960s, giving way to a more convenient "hose-cone".
- From 1963 on the TU-16 was converted into TU-16N tanker aircraft. This tanker version featured a 'Probe and drogue' system with a Yakovlev-built centerline fueling unit in the bomb bay and ARK-5 beacon. It was mainly used to support probe-equipped Tu-22 and Tu-22M Blinder bomber regiments.
- The Myasishchev M-4 Bison today serves primarily as a tanker. The 3MS2 tanker aircraft included refueling equipment in the bomb bay. The tanker variant used the "drogue and probe" aerial refueling technique.
- The Il-78 'Midas' is an air-to-air refuelling development of the Il-76, built to replace Myasishchev 'Bison' tankers. Service entry was in 1987
- An aerial tanker version of the MiG-29K was developed. large internal fuel capacity, two drop tanks and the UPAZ unified refueling pod are good prerequisites for a MiG-29 tanker version;
Common refueling aircraft have a plurality of wing fuel tanks and a central wing tank. Auxiliary fuel tanks can also be provided within or proximate to a fuselage of the aircraft. Fuel is commonly transferred to the boom or hose via a single wall header which is isolable by one or more shut-off valves. Common refueling systems include pumps to pressurize the fuel for transfer from one or more of the tanks, and valves which are controlled between an open and closed condition by simple on-off switches normally positioned on a refueling system panel and manually selected by a trained refueling operator.
Several systems are used by aircraft in order to aerially refuel other aircraft. The advent of nuclear weapons forced governments around the world, particularly the Soviet Union and the United States, to think about ways to increase the radius of their strategic and tactical aircraft operations. Research into in-flight refueling methods received official status. In the Soviet Union, work was conducted on various sizes of aircraft. Test pilots Igor Shelest and Victor Vasyatin developed their own wing-to-wing system of in-air refueling. Their invention was subsequently adopted by the Soviet Air Force and used through the late-1990s. The wing-to-wing system was only in the USSR, and then only with the Tu-4 and Tu-16 airplanes. No other country utilized this method, believing it to be too risky.
another type of refueling system is the so-called "boom deploy" system. In this type of system, a boom extends from the tanker or fuel-source aircraft to the fuel-receiving aircraft, whereby fuel is conveyed from the former to the latter aircraft. The boom is generally pivotally mounted beneath the tail of the fuel-source aircraft and must be deployed (i.e., extended) downwardly from the fuel-source aircraft to a fuel-receiving aircraft positioned behind and beneath the fuel-source aircraft.
The other approach to in-flight refueling is the hose-and-drogue system, in which a drogue attached to a fuel hose is extended from the refueling aircraft's belly or wings. The receiver aircraft is equipped with a fixed or retractable probe and the receiving aircraft's pilot flies the probe into the drogue. The advantages of the hose-and-drogue system are the following: (a) up to three receivers can take fuel simultaneously; (b) if one hose/drogue unit (HDU) becomes unserviceable, the tanker still can offload its fuel; (c) the HDU is inherently safer than the heavy, rigid boom, which is restricted in its movements; (d) it is easier to install on non-purpose-built aircraft; and (e) it is compatible with most receivers, e.g., fixed wings, as well as rotorcraft. There were, however, two disadvantages to early hose and drogue system: it has lower fuel transfer rates than the boom system, and the drogue is uncontrollable and is susceptible to winds and gusts. In bad weather conditions and particularly in low level refueling situations the hookup process was very difficult and demanded excessive receiving aircraft pilot maneuvers.
The only enterprise in Russia currently working on in-air refueling systems is Zvezda, which is developing fuel receiver heads that are mounted on the booms of refueling aircraft, as well as several modified uniform suspended refueling units for tanker planes. They feature a hose 26-28 meters long with a flowing capacity of 1,600-2,900 liters per minute. The average time for in-air refueling lasts six minutes for helicopters, twenty minutes for bombers, and forty-five minutes for tankers.
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