Whats an average temperature for fuel in the NGX? I am down by Brisbane Austrailia and at Cruise at FL360 and my Fuel Temp gauge says 12 ºC which is 53.6 ºF While the outside Temperature is -27C = -16.6 ºF ? Is that normal? I remember the MD-11x temps being way lower when it was -27c outside.

In general, JetA cools at a rate of 3-to-5 degrees C per hour, so if you departed from an airport in a warm location, where the fuel might have been (initially) at a temperature of 20 degrees C when pumped into the aircraft - it will take quite a long time at altitude before the fuel cools down to a temperature anywhere close to actual TAT. The NGX is the first add-on I have ever seen which appears to model actual fuel cooling rates. In all other add-ons, (including earlier PMDG models), the fuel temperature falls to match TAT almost immediately.

In general, JetA cools at a rate of 3-to-5 degrees C per hour, so if you departed from an airport in a warm location, where the fuel might have been (initially) at a temperature of 20 degrees C when pumped into the aircraft - it will take quite a long time at altitude before the fuel cools down to a temperature anywhere close to actual TAT. The NGX is the first add-on I have ever seen which appears to model actual fuel cooling rates. In all other add-ons, (including earlier PMDG models), the fuel temperature falls to match TAT almost immediately.

I've a question ; Am I required to know this to persue my pilot career? :|

Further to what Jim has said, fuel temperature will drop down to the Total Air Temperature, not the Outside Ambient Air Temperature. The difference is that as you are rushing through that atmosphere at 450KTAS, all of those air molecules you are hitting cause the fuselage to heat up. This means that the temperature of the aircraft's skin will be warmer than the outside air temperature. As the fuel tanks are not far from the outer skin, the fuel will not cool much below the TAT. Newton's Law of Cooling is good fun for calculus students too :(

Also remember that the NG wing is smaller than an MD11 wing, I don't know abot the MD11, but inside the NG wings are stored hydraulic heat excanger that warm fuel. If MD11 uses a similar way, the difference is in the amount of fuel that must be warmed by probably a similar (in dimensions) heat exchanger.

As Andrea said. Hydraulic fluid heat-exchangers in the left and right tanks keep things nice a toasty in there. Nice cool hydraulic fuel - nice warm fuel. Everbody's happy :) Make sure you have a bit of fuel in each tank (I think it's around 1500 pounds total) or you'll get some hydraulic overheats.

I've a question ; Am I required to know this to persue my pilot career? :|

I don't know for sure, but I would have it in my head the freezing point of the fuel you are carrying. It would be bad if you found yourself with a block of frozen fuel in your tanks.

I don't know for sure, but I would have it in my head the freezing point of the fuel you are carrying. It would be bad if you found yourself with a block of frozen fuel in your tanks.

Fuel Freeze +3C or -43C. I've only seen it come close on Anchorage-Chicago in the winter. Yep - keep it in your head, but not necessarily on top.

As Andrea said. Hydraulic fluid heat-exchangers in the left and right tanks keep things nice a toasty in there. Nice cool hydraulic fuel - nice warm fuel. Everbody's happy :) Make sure you have a bit of fuel in each tank (I think it's around 1500 pounds total) or you'll get some hydraulic overheats.

Yes, 760kgs in kilograms in each wing.They cool only the case drain of the pumps, not te whole hydraulic fluid.