HiI`m in need of a 747 expert. My Questions are:-When does one use the `Probe Heaters`??When do you use the `Fuel Boost Pumps`?When do you use the `Fuel Heat`??Would greatly appreciate the answers guys??Yours John

>Hi >>I`m in need of a 747 expert. My Questions are:- >>When does one use the `Probe Heaters`?? >Probe heat is your pitotheat. Heats the pitottube/probe to prevent it from getting blocked with ice (which would mean you no longer can determine your altitude).>When do you use the `Fuel Boost Pumps`? >To pump fuel into the engines. >When do you use the `Fuel Heat`?? >Preheating fuel. Very cold fuel doesn't burn as well (less efficient and you need higher temperatures in the surrounding area to get it to burn).Fuel heaters are required when the fueltanktemperature sinks below a certain level. I don't know what that temperature is.

Good answer. To be a little more specific, the fuel pumps pressurize the manifold which actually feeds the engines. Usually a forward and an aft pump for each tank.Fuel Heat is normally used in any sort of altitude situation for the reasons given and usually shut down on final approach.Ed Green, KCLThttp://www.panelshop.com/images/ELAL-350.jpg