The fuel system in the VC10 is a conventional four-tank system with the centre section used as a long range transfer tank and (only on the Super VC10 and C Mk.1) additional fuel in the fin. Integral tankage is used, otherwise known as a 'wet-wing' in which the inside of the wing structure is sealed to use the maximum available space for fuel storage. The system is designed for use with either kerosene (JP-1) or wide-cut gasoline (JP-4).
The following description applies to the Super VC10 but the only main change from the Standard is the addition of the fin tank.
A simplified schematic showing the fuel system layout for the Standard VC10
The fuel is stored in four integral wing tanks, a centre transfer tank and a fin tank. All the wing tanks are contained by the wing torsion box and the outer tanks are subdivided into two. The centre transfer tank is also integral and is contained in the centre torsion box. Small surge-vent tanks are located at the outboard ends of each wing to collect the fuel surging into the venting system during manoeuvres. Anti-surge valves are fitted within the wing tanks. These arrangements allow for the control of the centre of gravity by the flight engineer, and also prevent any sudden change in c.g. position caused by the movements of the fuel within the tanks. The fuel in the fin tank is transferred by gravity to the centre section tank via shut-off valves controlled by float switches in the centre section tank. Failure of one valve will not prevent the transfer of fuel. The shut-off valves are selected by switches at the flight engineer's panel on the Flight Deck. In an emergency a third valve can be opened but this valve will not close automatically when the float switches close and is also not flow restricted so the c.g. must be carefully monitored in this case.
The centre wing tank structure, I once thought about crawling around in there when I did a survey of A4O-AB, but didn't when it turned out that there was still a small amount of fuel in the tank
The total usable fuel capacity is 19,340 Imperial gallons contained in the tanks as follows:
Refuelling and Defuelling
The two refuelling points, one located by each main landing gear leg, are of
the standard 2.5 inch self-sealing type; either or both may be used. The
refuelling / defuelling operation may be carried out without the aid of steps or
other staging. Adjacent to the starboard point is a control panel and from this
panel the entire refuelling operation may be controlled and carried out by one
of two alternative methods. The panel has fuel contents gauges for each tank and
an operator can select manually which tank to fill and stop filling the tank at
the desired level. However the second method is simpler; the quantity of fuel
required in each tank is selected on the appropriate gauge and the control set
to auto. The tanks are filled until the required level is reached and then the
valve controlling the admission of fuel into that tank is automatically closed.
If the amount of fuel which is selected is less than that already in the tank no
more fuel will be passed into that tank. If the maximum amount of fuel is
required the cut-out will operate so that sufficient expansion space remains.
During refuelling the cross-feed valve must remain closed if two bowsers are
used. The fin tank is fuelled from the main refuelling points on the wings.
Jettisoning of fuel from this tank is by gravity via a master valve and a
corona-protected outlet at the rear of the fuselage tailcone. Jettison of fuel
from all other tanks is via wing trailing edge outlets similarly protected. The
maximum refuelling rate is 1,150 Imp. gall/min. at 50 lb./sq. in.
A more detailed schematic of the Super VC10 fuel system.
The fuel contents can be determined from the capacitance type contents gauging system that transmits information to individual contents gauges on the flight engineer's panel or from the under-wing magnetic fuel level indicators. For the second system be sure to park the aircraft on a level surface and bring a screwdriver and pen and paper.
The main change to the fuel system for the K2 and K3 tankers that are (were) in service with the RAF is the addition of five cylindrical fuel cells mounted in the cabin and holding 3,500 Imp. gallons. Extra pumps were installed in the wing and centre tanks and the new fuel cells were connected to feed into the centre wing tank.