Ater my retirement from a legacy carrier on 747 aircraft equiped with RB211-524 engines, I operated a 747-100F with JT9D engines which had engine de-icing systems providing controlled heating of the fuel when manually activated if the fuel temperature indicator showed fuel temperature at the engine to be 0c or below, or when the fuel icing light illuminated. Heating was limited to a one minute heater operation or two minutes if No.1 tank temeperature was below -40c, for every 30 minute cycle. Kept the flight engineer pretty busy. The fuel heater was situated between the boost and high pressure stages of the engine driven fuel pump and heating was provided by 15th stage bleed air. As far as I know, fuel heating is automatic on all modern high performance powerplants but the problem of fuel icing is old hat and well known.