VC10 Makes a Comeback as Tanker

Like the Victor K Mk2s that they will complement, the VC10 Tankers have three refuelling points – one under each outer wing and one in the underside of the rear fuselage.

The conversion of the VC1O commercial passenger transports to military Tanker aircraft involved two principal requirements – the provision of the three refuelling units and the installation of an additional fuel tank to augment the aircraft’s existing fuel capacity. In the commercial Standard, the basic capacity ie 17,925 Imp Gal (81, 486 litres) in four integral wing tanks and a centre section transfer tank; the Super VC10 carries a total of 19,365 Imp Gal (88,032litres) including the additional integral tank in the fin – a feature also of the RAF’s VC10 C Mk 1 transports. These original capacities have been supplemented in the Tanker configuration by the installation of an additional tank comprising five cylindrical cells in the fuselage of each version.

The increased fuel capacity thus takes the aircraft-laden weight up to the permitted Maximum Take-off Weight. This extra fuel could, of course, be used to provide a substantial, increase in range for emergency operation of the Tanker itself.

Of double-skinned metal construction, with internal flexible bags, the inner skin of these fuselage cells is designed to support the bladder cells and the outer skin is designed to withstand the maximum cabin pressure differential pressure of lb/sq. in. The space between them is then vented to the atmosphere to ensure that fuel vapour does not enter the cabin. Both supply and vent pipes can be rapidly switched between cells or to the main fuel system.

They are mounted on heavy-gauge longitudinal floor-mounted beams. Installing the tanks in the four K Mk3s is simplified by the existence of the forward freight doors, through which the cells are loaded – after which the doors are closed and made inoperative. In the case of the five K Mk 2s, however, a section of the forward fuselage roof was removed to allow the cells to be inserted. Once the cells are in position a heavy ‘A’-frame is installed in front of each one to restrain forward movement in the 9 g crash design case.

The supplementary fuselage tank is refuelled through a riser pipe in the main wheel bay and is interconnected to vent down through the centre wing tank to the wing vent pipe. The fuel feeds by gravity from front to rear – valves at the base of each cell preventing reverse flow – and from the rear cell to the aircraft centre section tank, which retains its function of the primary transfer tank. Two extra pumps are fitted in this central tank, and there are four new ones in the wing tanks to meet the requirement to feed fuel outwards to the underwing refuelling pods – using the previously installed fuel jettison line in modified form – and to the rear fuselage Hose Drum Unit (HDU).

Of the three refuelling points fitted, the rear fuselage installation requires the largest modification of the airframe, involving cutting into the pressurised structure aft of the main wheel-well and ahead of the carry-through structure for the rear engine mountings, and the Hose Drum Unit is located in the same position relative to the rear of both types of aircraft. This installation, featuring a Flight Refuelling Mk 178 HDU capable of a refuelling rate of 500 Imp Gal per minute, actually occupies much of the original rear underfloor freight hold. New pressure bulkheads are provided fore and aft of the cut-out, with a pressure floor over the top and new sidewalls. The HDU is remotely controlled from the flight deck and includes 81 ft (24. 7 m) of trading.

New structure is provided between the spars to carry the wing refuelling pods and the pylons are permanently attached to the underside of the wing – although the aircraft can be flown with the pods removed. These wing pylons located in order to be clear of the extensive trailing edge flaps. The installation is designed to accept the newer and lighter Flight Refuelling Mk 32/2800 HOU, which introduces digital electronic control and a ram air turbine to drive the fuel pump which also powers the HDU and needing no hydraulic system. Each of these wing pods trails 50 ft (15. 26 m) of hose.

Using the system previously developed for the VC10 C Mk 1 aircraft, the VC10 Tankers also have their own in-flight refuelling receiving provision. This system uses a 9 ft long nose-mounted probe Oust above the radome). For night use, this probe is floodlit by two lights positioned on either side of the mounting. The probe feeds the aircraft’s main fuel system via a supply line running along the left-hand lower fuselage and feeding the refuel/de-fuel gallery line which supplies all four main wing tanks. The in-flight refuelling rate via this probe is 500 Imp Gal per minute and the operation is controlled from the flight engineer’s station with indicator lights for the pilots on the dashboard panels.

The total system in the Tankers thus allows for the transfer to receiver aircraft of all but sufficient fuel for the Tanker’s own mission requirement or to take on board a similar recharge volume via the nose-mounted probe.

As with the transport version, the VC10Tankers have a primary flight crew of four – comprising two pilots, a flight engineer and a navigator. The flight engineer’s station on the right-hand side of the flight deck is modified to include the AAA Tanker operating facilities including the cathode ray tube display for the CCTV equipment. The navigator’s station is aft-facing on the left side of the flight deck. Both engineer and navigator have swivelling seats so that they can face forwards when required and between them is a forward-facing supernumerary seat. The crew toilet, galley and miscellaneous storage units are located immediately aft of the flight deck. At the front end of the cabin, ahead of the fuel tanks, seats are being retained for the use of essential ground personnel who need to be carried for overseas deployments away from the home base. Standard RAF triple seat units are used, but as the Standard and Super VC10s have different cabin door positions, these seating compartments differ between the two Tanker versions – with six triples and five triples plus a double seat (18 and 17 places) respectively.

The avionics fit in the Tankers is based upon that of the VC1O C Mk 1 – with a dual Smiths SFS6 flight director system and dual Sperry GM9 compass system; dual HF and VHF/UHF communications; single ADF navigation and OMEGA for long-range navigation; with TACAN as the primary aid to air-to-air refuelling contacts. A nose-mounted weather radar is standard.

Access to the flight deck and passenger compartment is through the right-hand service door in the front fuselage, the left front door having been modified to permit the crew to leave by parachute in case of emergency. The other two existing fuselage doors are being made inoperative and around half of the cabin windows (approximately every second unit) are being blanked off. However, the windows of the small passenger compartment at the front end are retained. The overhead racks are removed from the remainder of the cabin.

The forward underfloor freight hold is unchanged from the commercial airliner and allows the underwing pods to be carried internally if required during ferry flying; alternatively, the hold may be used to transport spares. Spare drogues are carried at the forward end of the fuselage tank compartment and one 10-man and one 26-man dinghy are located in the passenger compartment ceiling.

As Britain’s air power relies more than ever before on its strategic global mobility and its versatility of response and combat readiness, the VC10 air-to-air refuelling Tanker fleet now forming represents a major step forward in the strategic deployment of Britain’s air combat power and complement to its long-range air transport and surveillance force – which capabilities are so central and vital to all concepts of modern defensive warfare.

Joining the Royal Air Force’s existing fleet of VC1O Mk 1 multimission transports in worldwide service from the Brize Norton base, the new VC10 Tanker fleet thus signifies a reassuring step in the development and strengthening of the UK national and international defence capability.