Aircraft weight limitations (call it "mass" if you use nerds and geeks vocabulary)...
They are based on kilos or pounds, depending on what units you use.
There are
no aircraft limitations which use "liters" or "gallons" for certification.
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Aviation gasoline specific gravity is .69...
Meaning a liter of gasoline weighs 690 grams per liter.
Air Force "wide cut" JP-4 specific gravity is .78...
Which is 780 grams per liter. That is the fuel generally used by USAF.
Excellent for low temperature concerns... if you are in Alaska in winter.
Jet-A fuel has .812 gravity.
So 812 grams per liter.
And Jet-A1 has .813 gravity. US Navy calls it JP-5 -
Bla bla bla - 813 grams per liter. Most airlines have that fuel in tanks.
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Specific gravities above are based on 15ºC temperature.
On a hot day, in Jeddah (Holy be thy name) Jet-A1 might be only .79 SG...
And on a cold winter day in Khabarovsk, Jet-A might be .835 SG.
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Your tanks are
volume, meaning - if you "fill-up" volumewise...
Full tanks in a given 747, you might be 5 tons over limitations on cold days.
And on hot days, your tank "weight capacity" might be only 5 tons less.
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Definitely brings a CG question about the tail tanks in a 747-400...
You might end with a CG outside of the "aft limit" on a cold day.
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Be aware that your tanks gage readings are compensated for temperature.
They measure weight...
NOT volume.
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Happy contrails
P.S.
In this day and age, of expensive car gasoline (petrol for my UK friends) -
Your pump delivers gallons/liters... you pay by
volume.
Remember: your best buy is
cold gasoline/petrol.
Because your engine uses
weight for energy, not volume.
Best time to buy - early morning, or in... winter.