What is the minimum engine fuel temperature prior to takeoff, and the minimum bulk fuel temperature depending on fuel type?

• A. 5 C; -30 C or -40 C
• B. -5 C; -25 C or -35 C
• C. 0 C; -20 C or -30 C
• D. 10 C; -15 C or -25 C

Answer: (A)

Fuel temperature limits are set to keep the fuel in a safe, pumpable state and to prevent problems in the fuel system at takeoff. The engine fuel temperature must be at least 5 C before takeoff. This minimum helps ensure reliable fuel pump operation and metering, and reduces the risk of fuel-line icing or other issues as the engine starts and transitions to takeoff power.

The bulk fuel temperature minimum depends on the fuel type because different jet fuels have different wax content and cloud/freeze points. Some fuels require the bulk fuel not to be colder than -30 C, while others specify -40 C. This reflects the properties of the particular fuel formulation and its behavior at very low temperatures; setting the threshold helps prevent wax formation or gelation and ensures consistent fuel flow from storage tanks to the aircraft.

Other choices don’t align with these safety and specification-driven limits, where a higher engine temperature requirement and a fuel-type–dependent bulk temperature are used to balance reliability and cold-weather performance.