A320 outer tank temperatures
 

I notice always on ground and before take off a slight difference in the outer tank temperatur. On the left outer tank for example 7 deegres celcius and on the right outer tank 10 or 11 deegres. It makes a difference of about 3 to 4 deegres.
After departure and about 15 to 20 minutes flight the temperatures on both outer tanks stabilize at the same values.
Can someone explain to me why this happens?
I thank you all in advance for your replies.

Need more details to take a guess :rolleyes:

- Always the same aircraft?
- Is the fueling done from the left or from the right side?
- CFM56 or V2500?

Here's a guess. The IDG cooling system dumps the hot fuel from the fuel cooled oil coolers into the outer tanks. If you start the right hand engine first (sops with most airlines) the RH IDG oil temp will reach it's dump temp before the LH and thus increase the temp of the fuel in the right outer tank. Sounds good techno waffle to me and i'm sure i'd convince most pilots that I know what i'm talking about. :O

idg cooling / fuel heating normal operation ... also check out the procedure for fuel temp advisory (QRH 2.40):

Fuel temp greater than 45 degrees C in inner cell or 55 degrees C in outer cell = GALLEY p/b OFF