What type of fuel does the C-5 APU use?

The C-5 APU uses Jet A or Jet A-1 fuel due to its specific thermal and operational properties that align with the requirements of jet engines and auxiliary power units. Jet A and Jet A-1 are types of kerosene-based aviation fuels that provide excellent performance in cold temperatures, have a high flash point, and offer good stability during storage, making them suitable for the demanding conditions of military aircraft like the C-5.

Jet A is the fuel commonly used in commercial aviation, while Jet A-1 is a similar grade with a lower freezing point, making it suitable for operations in a wider range of climates, particularly where temperatures may be an issue. This compatibility allows the C-5 APU to operate efficiently and reliably during various mission scenarios.

The other fuel options listed are not appropriate for the C-5 APU. Aviation gasoline is typically used in smaller general aviation aircraft and is not suited for turbojet engines like those in the C-5. Diesel fuel, while used in many ground vehicles and some types of engines, does not meet the requirements for aircraft propulsion systems.