While using REX real weather, I fly cruise between 350 and 400. When using default FSX real weather, there aren't very many clouds, sky is always crystal clear at altitude, however the air temps remain nominal so the fuel won't freeze. The MD-11's fuel frrezez at -40C. In REX, the sky are amazingly presented with multiple colorful cloud layers, smog near cities and fog, however the air temps at altitude cause te MD-11s fuel to freeze at about an hour of cruising. Is there a method to keep the fuel from freezing, or is this just an REX anomaly? I know to prevent freezing the pilot must descend to a lower altitude, but that would mean a decent to around 10,000'. I would love to USE REX real weather because it is so immersive and realilistic.

Change fuel type before the flight. This is a FMS entry since we don't actually choose fuel type when loading, see FMS manual page FMS.10.26An explanation of cold fuel recirculation is in the systems manual, pg FUEL.10.18A realistic response is to go to warmer air, usually lower.

Cool thanks for the info. I google jet fuels and it seems jet a and a1 or the most common, however jet b is best for cold weather operations.

See FMS.10.26 PMDG MD-11 manual Flight Management System Preflight.......I have been using JetB JP4 flying in Arctic and although temps will hit 70/80 below at times keep your altitude in the lower levels eg.FL290 and speed up to keep the airframe warmer. Vincent

One thing that you can do or might be done automatically, is to cycle the fuel through the tail so it gets heated up by the No. 2 engine. Atleast that was what my dad said they used to do in the MD11. Or you may need to speed up.Kevin W.