calculated vs totalizer on fms

[thinkingpilot]

B777 FMS maybe others too.... what are the possible causes of totalizer fuel being less (or even more) than the calculated on progg page 2 . no leak of course .
thanks in advance

[ggofpac]

If i remember correctly, it has to do with temperature changes. I think on the 767 sometimes u can see more than a 1- 1.5 tonnes of difference. They then come back together after. sometimes it takes few hours.
I think what the guys usually do was to set the the fuel to the lesser of the 2 on the fms. then clear the entry once they are almost even.
I don't fly the 777 but it shud be more or less the same sort of thing i, guessing.

[thomas8]

The totalizer on FMS is from FQI, it shows the fuel computer measures the total fuel QTY in fuel tanks, the caculated on FMS is from the total fuel which you key in FMS subtract (fuel flow * Time) !
NOTE : Fuel flow data may come from HMU

[rudderrudderrat]

Hi thinkingpilot,

thomas8 is correct. Belt & braces in case your tank guages fail to indicate the correct amount (grossly over read).