<P> To avoid water condensation or the fuel itself solidifying at low temperatures (- 55 ° C), fuel tanks have thermometers and heating systems . Many are pressurized with engine bleed air to keep moist air out and ensure positive pressure feed to the pumps . In larger aircraft, fuel tanks also are in the fuselage and their load affects the center of gravity of the aircraft . This imposes limitations on the amount of fuel carried and the order in which fuel must be used . Turbine engines burn fuel faster than reciprocating engines do . Because fuel needs to be injected in to a combustor, the injection system of a turbine aircraft must provide fuel at higher pressure and flow compared to that for a piston engine aircraft . </P> <P> The refueling system of larger aircraft includes a single positive pressure refueling point from which all tanks can be fueled . How much and to which tanks fuel is fed during refueling operations is determined by the controls in the refueling panel, usually installed nearby and accessible to ground crews . </P> <P> External tanks are used to extend the range of an aircraft . Drop tanks are used by combat aircraft that need to discard them after use for performance reasons . To transfer fuel from the tip tank to the main tank on each side, there must be a fuel pump in the tip tank . </P>

Where is the engine fuel shut off valve usually located