Learn how to check fuel quantity and fuel remaining in any flight simulator, confirm the units and fix mismatched cockpit readings.
To check fuel quantity in an aviation or real-world flying simulator, power the aircraft’s electrical system, read each tank indication and the total fuel figure, then confirm the units. Cross-check that cockpit value against the simulator’s fuel-and-payload screen and use fuel flow plus elapsed time to detect an incorrect gauge.
Where is fuel remaining shown?
Fuel remaining is normally displayed on a cockpit gauge, engine-monitoring display or dedicated fuel system page. The exact location and format depend on the aircraft.
| Aircraft or system | Where to look | Typical indication |
|---|---|---|
| Light piston aircraft | Analogue gauges or an engine-monitoring display | Left and right tanks in US gallons, litres or fractions of full |
| Business jets and airliners | Fuel, systems, EICAS or ECAM display | Individual tanks and total fuel in kilograms or pounds |
| FMS-equipped aircraft | Progress or performance page | Fuel on board and predicted fuel at the destination |
| Simulator interface or aircraft tablet | Fuel-and-payload panel or loading page | Loaded quantity by tank, total mass or percentage |
Analogue needles may move only after the battery or electrical master is switched on. Some aircraft also require the correct display page or a tank-selector switch. Our explanation of how tank gauges sense and display fuel covers their limitations in more detail.
How do I check fuel quantity correctly?
The reliable method is to read every tank, confirm the measurement unit and compare the total with an independent source.
- Supply electrical power. Turn on the battery or appropriate electrical buses and allow electronic displays to complete their self-test.
- Find every tank indication. Check the left, right, centre and auxiliary tanks fitted to that aircraft. A single wing-tank gauge is not necessarily the total.
- Confirm the units. Look for labels such as
US GAL,L,LB,KGor%. Do not compare two figures until their units match. - Calculate the total. Use the displayed total if available; otherwise add the individual tank quantities. Check whether the aircraft reports total or usable fuel, since usable fuel excludes fuel that cannot be supplied to the engines.
- Cross-check the loaded amount. Open the simulator or add-on loading interface without changing its values. If the tanks were never loaded correctly, follow our guidance for setting fuel and payload before departure.
- Monitor consumption. Record the quantity after engine start and compare later readings with total fuel flow and elapsed time.
Be careful when opening a fuel-loading panel during flight: many simulators let you edit the amount immediately, which can accidentally refuel or empty the aircraft.
What do the fuel units mean?
Fuel quantity may be expressed as volume, mass or percentage, and those figures are not directly interchangeable without tank capacity and fuel density.
- US gallons and litres measure volume. One US gallon is approximately 3.785 litres.
- Imperial gallons are larger than US gallons, so never assume that an unlabelled gallon value is interchangeable.
- Pounds and kilograms measure mass. One kilogram is approximately 2.205 pounds.
- Percentage shows the proportion of the modelled tank capacity. Confirm whether that capacity represents total or usable fuel.
Converting gallons to pounds or kilograms requires the density of the loaded fuel. Avgas and jet fuel have different densities, and density can vary with temperature, so use the aircraft’s loading system or approved planning data rather than a water-based conversion.
Why do the cockpit and loading screen disagree?
Mismatched fuel readings usually come from different units, unpowered instruments, prediction versus actual quantity, or an add-on using its own fuel-loading system.
| Symptom | Likely cause | What to check |
|---|---|---|
| Cockpit gauges show zero but the loading screen has fuel | No electrical power, wrong systems page or an active failure | Battery, buses, circuit breakers, display page and failure settings |
| FMS destination fuel is lower than the cockpit total | The FMS is predicting fuel at arrival | Compare present fuel on board, not estimated fuel at destination |
| Figures differ by a large, consistent ratio | Kilograms versus pounds, or gallons versus litres | Unit labels on both displays |
| Fuel returns to an earlier value | A high-fidelity add-on is overwriting the simulator’s loading panel | Use the aircraft’s tablet or loader consistently |
| Fuel never decreases | Unlimited-fuel assistance, automatic refuelling or incomplete fuel-system modelling | Assistance options, add-on settings and engine fuel flow |
| One tank empties much faster | Tank selection, pumps, crossfeed configuration or an actual imbalance | Fuel selector, pump switches and the aircraft’s fuel synoptic |
How can I verify fuel burn during flight?
You can estimate remaining fuel by subtracting fuel consumed from the usable quantity recorded at engine start.
Remaining fuel = starting usable fuel − average total fuel flow × elapsed time
Use the combined flow of all operating engines and keep every figure in the same unit. For example, starting with 40 US gallons and averaging 10 US gallons per hour for 1.5 hours gives an estimated 25 US gallons remaining. Allow for taxi burn, auxiliary equipment and changes in power setting.
In an FMS aircraft, distinguish fuel on board from estimated fuel at destination. The first represents the aircraft’s present fuel figure; the second is a prediction based on the programmed route, winds, altitude and consumption model.
Which fuel reading should I trust?
During normal flight, use the powered cockpit quantity indication as the operational reference and use the simulator’s loading screen as a diagnostic cross-check.
For a complex add-on, its own tablet or loading utility may initialise and control the tanks, so editing the simulator’s general fuel panel afterwards can cause a conflict. A fuel-flow calculation is the best tie-breaker when two indications disagree.
How much fuel should remain before landing?
You need enough fuel for the rest of the flight plus the reserve appropriate to the aircraft, route and operating rules; merely showing a quantity above zero is not sufficient.
Compare predicted arrival fuel with the reserve you planned before departure. Our simulator reserve-fuel guidance explains practical margins and why legal real-world requirements vary by flight type and jurisdiction.