Originally Posted by
CL300
Except that your fuel goes into the nozzles at a constant temperature ( heat exchanger ) negating the "effect" of temperature.
This is why it does not matter much, and everyone is "creating" fuel by the end of cruise.
Now that you've got me started...
The temperature of the fuel at the nozzle is totally irrelevant: the calorific value of a pound of fuel at 100C at the nozzle is exactly the same as it is at -10C in the tank. It is the temperature of the fuel at delivery to the tank that is important.
The volume of a unit mass of fuel changes by about 0.1% per 1C temperature change. A 1,000 litre tank will hold 800kg of 0.80 S.G. fuel at 15C. Because of expansion the same tank would hold only 784kg of fuel if it were delivered at 35C - so a range reduction of 2%. Conversely, 816kg of could be loaded if the delivery temperature was -5C giving an increase in range of 2%.
Now combine this with the discussion in my previous post - a tankfull of 0.79 S.G. fuel delivered at 30C will give 4.5% less range than that tankfull of 0.81 S.G. fuel delivered at 10C.
The 'creation' of fuel in flight is down to inadequacies in the fuel measuring system.
Lastly, be it a Gulfstream or a Falcon, it is a certification requirement that fuel expansion up to 2% (equivalent to heating it by 20C after delivery) will be accommodated by tank design.