Originally Posted by
CL300
The indication is weight, but through the engines nozzles goes volume. Therefore as long as the tanks are full ( volume) irrespective of the weight being shown, you will get the range.
Now, everyone is "happier" when the weight is "higher" on cold fuel, leading to the view of higher range, alas...there is no such thing, like GF wrote above, at the end of the day after 10 hours at minus 50 ( to -70) you will get your fuel "back".
Some probes are compensated for temperatures some are not, i would believe that the 8X and 5X are, not on the F2TH or GLEX early generations
AFAIK
CL300, I hope you don't fly a long range aircraft. Or at least never had to top up your tanks. If you do, I recommend you some reading...
What you mentioned above is for TEMPERATURE variations only! DENSITY (determined by the quality of the crude used to produce the fuel and the refining process) plays a much more important role.
Jet-A fuel density limits are established by the American Society for Testing and Materials (ASTM) Specification D1655. At 60°F the density limits are from 6.46 to 6.99 lbs/gallon.
If I may recommend a starting point for your reading, what about that study by Gulfstream?
GV/G500/G550 (ATA 28): Fuel Density Variations
A GV flight crew reported experiencing the inability to fully fuel their aircraft during a
fueling stop. During fueling, the Fuel Quantity Monitoring System (FQMS) indicated a
maximum fuel load of 39,900 lb. The flight crew also indicated that the ambient and wing fuel
tank temperatures were low.
The crew further attempted to fill the wing by pulling the left- and right-fueling shutoff
circuit breakers, parking the aircraft nose down, shaking the wing, and eventually over wing
fueling. The over wing fueling resulted in only an additional 15 gallons of fuel.
The maximum volumetric fuel capacity of the GV aircraft is nominally 6,100 U.S. gallons
(USG). Based on a fuel temperature of 60°F and a typical fuel density of 6.767 lb./USG, the
maximum fuel weight is 41,300 lb. (Note: The aircraft range is determined by fuel weight, not
volume.)
Variations in fuel density and expansion at elevated temperatures, especially when fuel is
stored above ground in hot climates, will result in an inability to obtain the nominal maximum
fuel weight of 41,300 lb. at 6,100 USG.
Per specifications as listed in the AFM, Section 1, “Engine Fuel Grades,” manufactured fuel
density at a constant temperature can vary to the acceptable lower limits of 6.47 lb./USG at
60°F. The GV FQMS includes a densitometer and will automatically compensate for density
effects and correctly display the actual fuel weight. At the lower limit of 6.47 lb./USG at 60°F,
the FQMS would indicate a full fuel reading of approximately 39,400 lb. at 6,100 USG.
Fuel temperatures greater than 60°F also limit the nominal maximum fuel weight due to
thermal expansion of the fuel. For each additional 10 degrees in fuel temperature, the
maximum fuel weight is reduced by approximately 200 lb. at 6,100 USG.
The following table, generated by the Gulfstream ECS Power Plant group, illustrates fuel
density variations as affected by temperature and the acceptable upper and lower limits at
constant temperature. The source data used in the table is compiled from the Coordinated
Research Counsel (CRC) Report 530 – Aviation Fuel Properties, and the American Society for
Testing & Materials ASTM D1655 – Standard Specification for Aviation Turbine Fuels. CRC
Report 530 contributors include participation from the major petroleum companies, and
sustaining members include the American Petroleum Institute (API) and the Society of
Automotive Engineers (SAE).