Hello Folks,

 

need to know if something wrong or not;

FL 350 with a TAT -20°c and my fuel temp was +10°c !

any of you guys have the same temp fuel with this kind of OAT ?

Thanks in advance.

Cheers.

Fuel needs time to cool down or heat up. Just wait and it'll become cooler.

 

Just a little note: OAT is not the same thing as TAT.

Not sure how it works in a 737, but in the 717 the fuel / wings are kept warm by heat exchange (and cooling of) engine oil. This in turn reduces the risk of wing surface ice... If I recall correctly from being in the cockpit of a 717 flight, the fuel was at +16C with the TAT being shown at around -30C in cruise at FL360. I asked the same question and the captain explained how the systems are integrated to make use of the heat!

 

Geoff

Same on 737 and many other planes.

 

Fuel keeps oil cool and oil keeps fuel warm.

True. Oil and hydraulic liquids are cooled down with fuel.

But it's very possible that fuel will have minus temperature even on a three-hour flight. Limitations for fuel temperatures are written in FCOM, QRH got recommendations how to deal with overcooled fuel.

You can also check photos on A.net for this.

thanks for your replies, sounds good to me and logical.

Cheers.

Cold fuel in flight is rarely a problem for the NG. It's more of a problem on the ground with Cold Soaked Fuel Frost.

+10 isn't a problem. +50 is See the limitations section in FCOM1.

 

As Spin737, CSFF (cold soaked fuel frost) is an issue with the 73 NG. Usually seeing fuel temps of -20 after a couple of hours in the high FL380 or thereabouts. That means, especially when tankering fuel, that even when the airport is +20 there is ice on the wing that won't go away unless we transfer the fuel to the centre tank and fill with the wings with warm fresh gas.

 

For more info see FCOM1, Supplementary Procedures, Section 2 - Anti-ice and Rain.