Method and apparatus for cooling fuel in an aircraft fuel tank

A method of reducing fuel flammability in a fuselage fuel tank of an airborne aircraft, the airborne aircraft having one or more external surfaces defining at least one of a fuselage and a fixed wing, wherein the method comprises the following steps:

• providing a cooling region located to the exterior of the fuselage fuel tank and directly adjacent to a tank wall;
• causing air to flow (i) from the exterior of the aircraft, (ii) via a ram air intake disposed on said one or more external surfaces, (iii) to said cooling region at which the air cools said fuselage fuel tank, and
• then exhausting the air.

A method of reducing fuel flammability in a fuselage fuel tank of an airborne aircraft, comprising:

• causing air to flow from the exterior of the aircraft via an external surface of the aircraft in which there is provided a ram air intake, through an air supply passage extending from the ram air intake to a cooling region, said cooling region being located to the exterior of the fuel tank, and from said cooling region to a region located downstream of, and remote from, said cooling region, and
• cooling the fuel in the fuselage tank by thermal conduction of heat from the fuel in the fuselage fuel tank to the air in the cooling region via the fuselage tank itself, and
• wherein the method is performed such that air is caused to flow from the exterior of the aircraft via said external surface primarily by means of at least one of (a) the inherent energy of the air to the exterior of the aircraft resulting from the relative motion between the whole aircraft and the atmosphere and (b) the pressure difference created as a result of the relative motion between the whole aircraft and the atmosphere.