What is the maximum allowable vapor pressure for aircraft fuel?

The maximum allowable vapor pressure for aircraft fuel is set to ensure safety and proper performance during flight. Vapor pressure is a critical factor for aviation fuel, as it impacts fuel flow and the likelihood of vapor lock in fuel lines, particularly at altitude where pressure changes occur.

Setting a maximum vapor pressure limit, such as 7 PSI in this case, helps to minimize the risks associated with fuel vaporization in the system. If the vapor pressure exceeds this limit, it could lead to the formation of bubbles in the fuel lines, which can disrupt the fuel supply to the engines, potentially leading to engine failure or inefficient operation.

The chosen limit of 7 PSI strikes a balance between safe operation and ensuring the fuel system functions effectively under various operating conditions. It accounts for factors such as temperature fluctuations, altitude changes, and engine demands. This is critical for maintaining the integrity of the aircraft's fuel system and ensuring a safe flight.