‘Flying gas stations’
Modern strategists talk about force multipliers, and for air operations, air-to-air refuelling is without doubt the greatest force multiplier of all. In-flight refuelling has enabled the longest bombing missions in history and also persistence in air defence, reach in transport and flexibility in ground-attack tasks.
Originally developed for transatlantic passenger flights, the ‘flying gas stations’ such as the Boeing KC-135 and Handley Page Victor became critical to USAF and RAF Cold War operations.
As explained by Chris Gibson in his book Air-to-Air Refuelling Aircraft, as was the case with USAF and RAF, the Soviet Dal’naya Aviatsiya Vozdushnikh Syl (Long-Range Aviation of Air Forces) required aircraft to carry nuclear weapons deep into ‘enemy’ territory.
Tupolev wing-to-wing in-flight Refueling System
Two refueling systems evolved in the Soviet Union: probe-and-drogue (as per the Western system) and wing tip-to-wing tip. The latter, a variation on the looped-hose method, was the forte of the Tupolev design bureau and used on the Tu-16 ‘Badger,’ with the tanker designated Tu-16Z. This specialist variant carried a hose drum in the fuselage. The hose was fed to a fairing at the starboard wing tip from which the equipment was trailed, stabilised by a small drogue parachute.
The Tupolev refuelling technique was reminiscent of ships undergoing replenishment at sea and involved a shot line, complete with drogue chute, attached to the coupling at the end of the hose. The hose drum (HDU) in the bomb bay fed the hose out along the starboard wing to the hose guide on the wing tip.
The drogue chute stabilised the hose as it was streamed behind the tanker on the 40m (130f) shot line, similar to a cable used to haul hoses between ships underway. The receiver drew up alongside the end of the hose and, guided by the tail gunner, the pilot positioned the port wing tip over the hose. Under the receiver’s wing tip, a device with a latch captured the receiver’s end of the hose and coupled it to the refuelling receptacle. The shot line was hauled in by the tanker, and the other end of the hose coupled to the fuel feed on the tanker.
Complex and dangerous
The Tupolev refuelling system was complex and even dangerous, but once the ends of the hose were connected, the spectacle took on a rather graceful appearance.
The system was installed on two operational types, the Tu-4 Bull (a reverse-engineered Boeing B-29 Superfortress) and the Tu-16 Badger. The procedure required very skillful flying on the receiver’s part as the process took place approximately 52ft (15.8m) to port and 59f (18m) aft of the receiver’s cockpit. The tanker was required to conduct a number of separate stages to prepare for a fuel transfer.
The Tu-16Z had, by 1963, been replaced by the Tu-16N, which featured a probe-and-drogue system with an HDU in the bomb bay and operated by Soviet Naval Aviation (Aviatsiya voyenno-morskogo flota) in support of maritime operations by Tupolev Tu-22 ‘Blinder’ and Tu-22M ‘Backfire’ missile carriers. One of the reasons (aside from its complexity) the Tupolev wing tip system failed to prosper was wing flex, particularly on larger aircraft like the Tu-95 ‘Bear` due to its high aspect ratio wings flexing too much at the tip.
