What temp does Jet A1 freeze

[Fatboyslim]

Anyone??

[EGCC4284]

-47 I THINK OR -45 ????

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A BIT EXTRA FOR MUM.

[CallYouBack]

Freezing temp for Jet A-1 is -47C.
Freezing temp for Jet A is -40C.

[HPSOV]

And you have to maintain the fuel temperature 3 degrees above that or it starts to get a little "thick" (And thats bad).

[mustafagander]

As I understand it, the problem is not that the kero freezes, rather that the wax in the fuel condenses out and blocks the filters etc.

[L J R]

Don't forget that while the fuel will freeze at -45 [ish] the Indicated Outside Air Temperature [IOAT] has to get that cold [ie it may be -45 at 30,000', but when flying at M0.8 at that altitude, the aircraft will be something warmer] - haven't got my whizz wheel or a tricky Rule of Thumb to get the exact number.

It is for this reason that a jet can fly at 40000 without the fuel freezing [if fuel tanks have no warming system]. If the jet slows sufficiently [I mean very slow], fuel freezing may be a problem at the higher altitudes


I'm writing this as I'm trying to read between the lines of your last few questions.

[HPSOV]

Yep thats correct. If the fuel it too cold the wax will tend to become thick and block the fuel lines. The fuel is actually heated before it enters the filters so blocked filters is not normally a problem.
The temperature increase due the the speed of the aircraft is usually around 20-30 degrees. So you have to be flying very high in cold conditions for a long time before the fuel will get to a temperature that would need you to take action. The options are basically to increase speed to increase the temperature rise, or descend to warmer air.

[quid]

LJR-

No need for a whizz wheel if you can remember the following:

Ram rise is 30 at M.80. 1 degree more or less for each .01 M. It's quite accurate.

[AYLGR]

Flew over Siberia a few days ago. OAT at 11,100m was -73 (yes minus seventy three). Fuel temp gradually fell till the warning came on at -37 (set 3 degrees above US spec fuel freeze of -40). We had -47 fuel on board, but when the fuel temp got to -40 we descended to 10,100m and sped up to M0.86. OAT was then -62, TAT -30 but the fuel never warmed back much more than -38C. Bet the stuff was like the Stoly I keep in my freezer!
Bob

[driftdown]

The Freezing point is more a result of how the fuel is produced in the refinery. Where I am -52 is usual

[AYLGR]

Driftdown, aviation fuel is not produced to some arbitary value at the refinery, it is an exact specification. I have only ever seen -40 and -47 jet fuel, but I`m willing to be corrected.

Bob

[CallYouBack]

After almost 30 years of flying 'transport category' aircraft, the Boeing, Douglas and Airbus manuals that I've used all quote the same figures: -47C for Jet A-1, and -40C for Jet A. Not much grey area there.

[SLF3]

SLF from the oil business: the specification you are talking about is 'not higher than'. Different crudes have different wax contents, and different refineries have different blending patterns. Therefore the actual value will be somewhat lower than the upper limit you are all quoting, depending on how they made it and what from. -53 at a specific location is on specifcation and quite possible.

[jetfuel]

That is correct, aviation fuel has to meet minimum specifications which all manuals and SOP’s would base their parameters on. So yes it is possible to have a lower freezing point than 47, unfortunately it is also possible to have the opposite, ie fuel not meeting min specs but this will only really happen in few “backward”, corrupt countries were the local fueler has diluted the product for personal gain.