Fuel freezes at altitude

[davidzill 8]

I have set the FMS to JetB, which has a freeze temp of -50c. I just flew from KLAX and made it have way to boston in real weather. outside air temp at 30,000 was -73C. Fuel froze and each engine flamed out. is it typical for an md-11 to descend and cruise a route at 10,000' to keep the fuel from freezing? I know it should take fuel about 5 hours to cool to the outside air temp but the md-11's fuel freezes in just an hour and a half. any input?

[michal 44]

There were numerous posts on the subject of fuel freeze. Your -73 C is very, very cold. Before each flight check expected temperatures and loadfuel with the freezing point (configurable through FMC) best suited for the trip. Yes, if all fails you may need to descend lower. Also it may take5 hours to cool to the outside temp. but fuel freezing point is often higher than the outside temperature. The rate of heat transfer is proportionalto temperature difference and this seems to be correctly replicated in this sim. Again, search the forum for more details.

[theace6 0]

Well to keep this from happening you can either descend, speed up, or in the real plane you can cycle fuel thru the tail. How slow were you flying to have the TAT be -73C. And are you using a WX addons in the game or the default weather because when I look at the real world temps at FL300 they are usually around -55C. And even descending to FL240 should raise the temp around 12C with standard temperature change.Kevin W.

[davidzill 8]

I was using REX real weather, I think this had something to do with it, because when I use default fsx real weather, i never have this problem. even when flying in tropical climates in summer the fuel will still freeze. i had my fms set to a cost index of 150, so the md-11 was pretty much redlining it. fuel recirculation activated but did not solve the problem. I guess i am going to switch to fsx real weather for now on

[theace6 0]

That seems weird because I also use REX2.0 with real world weather and have never had a fuel freezing problem. Are you sure it's not possibly happening because of engine icing, but I have also never seen temps as low as -75C. Kevin W.

[Turbine777 13]

That is a little cold I'd say, especially from KLAX-KBOS. I do that trip a lot and about FL310-370 and never seen it that cold. You could have a corrupt saved flight that's holding onto some bogus wx data. I have alleviated many strange issues by not using saved defaults anymore. Just a thought.You could also try to clear all weather with FSUIPC, then just have REX's Wasys reinject it.

[davidzill 8]

Problem solved: Don't use REX real weather when flying, FSX real weather actually gives more updated, acuarate weather with no ecentrically cold temps at altitude. Cruised at -33C instead of -73C, and the cloud sets on fsx real weather where more immersive than what rex was presenting. fsx real weather does use the rex cloud textures,

[Turbine777 13]

Problem solved: Don't use REX real weather when flying, FSX real weather actually gives more updated, acuarate weather with no ecentrically cold temps at altitude. Cruised at -33C instead of -73C, and the cloud sets on fsx real weather where more immersive than what rex was presenting. fsx real weather does use the rex cloud textures,

It's funny but your right David. I have mentioned a few times before that FSX seems to have a better choice of the textures than both REX and ASA. I wouldn't fly without my Rex textures of course, but I have tested this countless times and FSX skies are always more accurately depicted. Unfortunately, the default wx has it's bugs that make using it all the time more of headache that it's proprer depiction is worth. I mostly use ASA, but if I am showing the sim to a friend, I will let fsx choose the textures. I look forward to Rex's next weather engine.