What is the maximum vapor pressure allowable for aircraft fuel?

The maximum vapor pressure allowable for aircraft fuel is set to ensure that the fuel system operates safely and efficiently under various temperature and pressure conditions. Vapor pressure refers to the tendency of a liquid to evaporate and form vapor; higher vapor pressures can lead to issues such as fuel vapor lock, which can impede the flow of fuel to the engine, particularly during changes in altitude or temperature.

In the context of aviation fuels, maintaining an upper limit on vapor pressure helps to prevent these safety and performance issues. The correct maximum vapor pressure for most aviation fuels is 7 PSI, as this level provides a balance between performance and safety, ensuring that the fuel remains in a liquid state under typical operating conditions.

Understanding the significance of vapor pressure is crucial for aircraft safety, as excess vapor can disrupt the fuel system, especially during operations that involve rapid changes in temperature or altitude. Therefore, the specification of 7 PSI as the maximum vapor pressure underscores its importance in engineering safe and reliable aviation fuel systems.