Hi
This is part question, part possibly a bug. I’m trying to get the total fuel for an aircraft for a bush-flying VA, and there seems to be inconsistencies with how the unusable fuel is accounted for.
We’ve been using FUEL TOTAL QUANTITY to know whether the total amount in the aircraft matches the prior state of the aircraft, however there appears to be inconsistencies in how this handles unavailable fuel.
In the TBM (old fuel system - FUELSYSTEM TANK CAPACITY:1 shows 0), if you select 150 gal fuel in the UI, the simvar shows 150 gal, with the in-flight Garmin showing 70+71 gal usable (reflecting the 9 gal unusable - the simvar is inclusive of unusable).
In the Longitude (new fuel system - FUELSYSTEM simvars populated), if you select 7244 lbs (1082 gal), the Garmin shows 7140 lbs “fuel qty” (about 1066 gal) which is what the simvar says (reflecting 12.4gal unusable - the simvar is exclusive of unusable).
Is it expected there to be this discrepancy? If so, we also noticed the NEW FUEL SYSTEM simvar isn’t working for us in 2024 (works in 2020), so we would need to test the first FUELSYSTEM tank instead if we need handle this on our side. With most of the fleet having minimal unusable fuel or the old fuel system in 2020, we didn’t notice this variation, however in 2024 many of the smaller aircraft have been updated and causing us issues.
I assume the FUEL TOTAL QUANTITY variable is a ‘legacy’ variable, but the alternative is enumerating an unknown number of fuel tanks. I can’t work out how to ascertain how many exist, nor their name (given the docs imply not to rely on the index number being consistent should we ever want to set fuel). Is there some other way we should be doing this?
Thanks in advance 