For takeoff, a fuel system icing inhibitor must be used when bulk fuel temperatures are below what temperature?

For takeoff, a fuel system icing inhibitor must be used when bulk fuel temperatures are below -20°C. This requirement is in place to prevent the formation of ice crystals in the fuel system. At lower temperatures, particularly around -20°C and below, the risk of water in the fuel turning into ice increases significantly. Ice can lead to clogs in the fuel lines, filters, and other critical components, which could impede fuel flow and potentially cause engine failure.

In aviation, ensuring a reliable and consistent fuel supply is paramount; thus, using an icing inhibitor at this temperature threshold helps maintain safe and effective operations. These inhibitors work by altering the physical properties of water in the fuel, helping to keep it in a liquid state and preventing the formation of ice that could compromise the aircraft's performance.