Hi Swedish Steve,
So where do you put the SG figures to calculate performance?
Performance is based on aircraft mass so we use the Aircraft Fuel Quantity gauges (Kgs) for the fuel on board.
The uplift (litres) is converted to Kgs using actual SG (pocket calculator or mental maths if it's close to 0.8), and compared with the calculated uplift. If the discrepancy (as +/- figures or a % age) is outside FM limits, then we investigate further.