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How Aircraft Avoid Fuel Pressure Issues In The Atmosphere

When managing volatile and flammable gases and liquids under intense pressure, properly calibrated relief valves are a vitally important part of these systems, designed to reduce the risk of damage to the tank and the potential dangers such materials under pressure would pose.

However, one unusual situation requires somewhat unusual and complex solutions. Most fuel tanks are either stored on a single site or if they are in motion are not prone to sudden shifts in elevation.

Most tankers that are even driving to places of varying altitudes are reducing in altitude at a low enough rate that a relief valve can work normally to equalise the pressure or to avoid a fuel vacuum when increasing in altitude.

One exceptionally notable exception to this is an aircraft fuel tank system, which consists of several fuel tanks that pump fuel to the engines through a series of suction pumps via a control valve or selector.

Most larger aircraft use their wings as large storage tanks, which helps not only with maintaining a better weight distribution but also reduces the stresses on the wings.

One unique aspect of an aircraft is that throughout most of the flight, the fuel is kept at a slight positive pressure, but this is to counteract the reduced atmospheric pressure caused by being at a higher altitude, which in turn reduces the fuel’s boiling point.

Without this, a common problem is fuel evaporation and reduced fuel pressure, which can lead to decreased performance and even a potential vapour lock, where a vacuum forms in the tanks and causes a blockage in one of the fuel pumps.

This is avoided through the use of multiple tank pumps, which draw fuel into a more centralised engine-driven fuel pump which pressurises the fuel and pumps it through a heat exchanger to increase its temperature by lowering the temperature of engine oil.