How do I check fuel quantity in a flight simulator?
Check fuel quantity and fuel remaining, fix FUEL QTY MISCOMPARE alerts, verify units, and identify Avien, EA and Simmonds fuel hardware.
To check fuel quantity in an Aviation & Real-World Flying simulator, power the aircraft, open its fuel indication, read every tank and the total, and confirm whether the units are gallons, litres, pounds or kilograms. Cross-check the figure against the fuel-and-payload screen, then monitor fuel flow to catch a faulty or mismatched indication.
Where is fuel remaining shown?
Fuel remaining is normally displayed on analogue gauges, an engine monitor, a fuel-system page or the aircraft’s primary systems display.
| Aircraft or system | Where to look | What it normally shows |
|---|---|---|
| Light piston aircraft | Individual fuel gauges or engine monitor | Left and right tanks in gallons, litres or fractions of full |
| Turboprops and business jets | Fuel panel, systems page or engine display | Tank quantities and total fuel by mass |
| Airliners | ECAM, EICAS or dedicated fuel synoptic | Left, centre, right and auxiliary tank quantities, plus total fuel |
| FMS-equipped aircraft | Progress or performance page | Present fuel on board and predicted fuel at the destination |
| Simulator interface or aircraft tablet | Fuel-and-payload or loading page | Loaded fuel by tank, total mass or percentage |
Analogue needles may remain at zero until the battery or relevant electrical bus is powered. Some cockpits use one gauge with a selector for several tanks, while glass-cockpit aircraft may hide the detail on a separate systems page. Our explanation of how aircraft fuel gauges obtain and display their readings covers the difference between float, capacitance and computed indications.
Do not confuse fuel on board with predicted destination fuel. A flight management system may show both, but only the first is an indication of the fuel remaining at that moment.
How do I check fuel quantity correctly?
The dependable method is to inspect every tank, confirm the units and compare the cockpit total with an independent value.
- Apply electrical power. Switch on the battery or appropriate buses and let electronic displays complete their self-test. A dark or unpowered gauge is not evidence of an empty tank.
- Find every fitted tank. Check left, right, centre, auxiliary and tip tanks as applicable. Reading one wing gauge does not give the aircraft total.
- Check selectors and system configuration. If one gauge serves several tanks, select each tank in turn. On complex aircraft, check that the correct fuel page is displayed.
- Confirm the units. Look for labels such as
US GAL,IMP GAL,L,LB,KGor%. Never compare unconverted volume and mass figures. - Add the quantities. Use the displayed total when available; otherwise add all individual tank indications. Establish whether the aircraft reports total or usable fuel, because unusable fuel is not available to the engines.
- Cross-check the loaded fuel. Open the simulator’s loading interface without moving its controls. If the amount was not set before departure, use the aircraft’s own loader or follow our guidance on setting fuel and payload without upsetting the balance.
- Record a starting value. Note the quantity after engine start and compare later indications with fuel used, total fuel flow and elapsed time.
A mistake we see constantly is opening a fuel panel during flight and accidentally moving a slider. In many simulators that edits the tanks immediately, effectively adding or removing fuel rather than merely inspecting it.
What do fuel quantity units mean?
Fuel quantity may be expressed as volume, mass or percentage, and those values are not directly interchangeable without knowing 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. Treat an unlabelled gallon figure as ambiguous until the aircraft documentation or loading page identifies it.
- Pounds and kilograms measure mass. One kilogram is approximately 2.205 pounds.
- Percentage represents a proportion of the modelled tank capacity. It may be shown per tank rather than for the aircraft as a whole.
Converting volume to mass requires the density of the fuel loaded. Avgas and jet fuel have different densities, and temperature also changes density, so a fixed gallons-to-pounds shortcut can introduce a noticeable error.
Quantity is not the same as endurance. For example, 30 gallons remaining does not reveal the flying time available until total fuel flow, unusable fuel and the required reserve are considered.
Why do the cockpit gauge and loading screen disagree?
Most disagreements come from mismatched units, unpowered instruments, add-on loading logic or confusion between present and predicted fuel.
| Symptom | Likely cause | What to check |
|---|---|---|
| Gauge shows zero while the loading screen contains fuel | No electrical power, wrong display page or a simulated failure | Battery, buses, display selection, circuit breakers and failure settings |
| Values differ by a ratio near 2.205 | Kilograms compared with pounds | Unit labels and aircraft display settings |
| Values differ by a ratio near 3.785 | Litres compared with US gallons | Loading-screen and cockpit volume units |
| FMS destination fuel is lower than the gauge total | The FMS is predicting arrival fuel | Compare the gauge with present fuel on board, not estimated arrival fuel |
| Fuel returns to an earlier value | The add-on’s tablet or loader is overwriting the simulator panel | Use one loading method consistently and allow it to finish initialising |
| Fuel never decreases or rises in flight | Unlimited-fuel assistance, automatic refuelling or a bound refuel command | Assistance settings, controller assignments and add-on options |
| One tank drains much faster | Fuel selector, pump, crossfeed or engine-feed configuration | Tank selectors, pumps, crossfeed valves and the fuel synoptic |
High-fidelity add-ons often maintain their own fuel state. Their tablet or loader may be authoritative during initialisation, while the simulator’s general loading panel is only a secondary view. Editing both can create repeated jumps or synchronisation loops.
What does FUEL QTY MISCOMPARE mean?
A FUEL QTY MISCOMPARE message means that two fuel values expected to agree have remained outside the aircraft system’s permitted tolerance.
Depending on the aircraft, the comparison may involve duplicate sensing channels, an indicated total versus the sum of individual tanks, or sensed quantity versus a calculated value. The permitted difference and delay are aircraft-specific, so the message cannot be diagnosed from its wording alone.
- Read the individual tanks. Add them and compare the result with the displayed total.
- Compare like units. Check that the loader, cockpit and FMS are not mixing kilograms, pounds, gallons or litres.
- Check power and failures. A failed probe, channel, bus or circuit breaker can leave one value invalid or frozen.
- Inspect the loading source. Confirm that a custom add-on loader is not fighting the simulator’s general fuel panel.
- Use the aircraft checklist. In a procedural simulator or real aircraft, do not clear the message by cycling equipment unless the applicable checklist directs it.
How can I calculate fuel remaining from fuel burn?
Estimate fuel remaining by subtracting fuel consumed from the usable quantity recorded at engine start.
Estimated remaining fuel = starting usable fuel − average total fuel flow × elapsed time
Use the combined flow of every operating engine and keep all figures in the same unit. 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 fuel, auxiliary power unit consumption and changes in power setting. If the aircraft displays fuel used, subtract that value from the starting usable fuel instead, but check whether the fuel-used counter was reset before engine start.
This calculation is a diagnostic cross-check, not an exact replacement for a serviceable quantity system. It is especially useful when a simulator gauge is frozen, an add-on has a known indication fault or two displays disagree.
Which fuel reading should I trust?
Use the powered cockpit fuel indication as the operational reference, while treating the loading screen and fuel-burn calculation as independent checks.
For a complex add-on, use its own tablet or loading utility to initialise the tanks. For a default or simpler aircraft, the simulator’s general fuel-and-payload page will usually represent the loaded state directly. If the cockpit total disagrees with both the tank sum and the burn calculation, suspect an instrument, electrical or add-on-state problem.
Minor needle movement can be normal in aircraft that model attitude effects or fuel slosh. A persistent large difference, a frozen indication or fuel increasing without refuelling is not normal behaviour.
Are Avien 1616 fuel qty ind. simulators flight-simulation add-ons?
Avien units described as fuel qty ind. simulators are physical maintenance test instruments, not PC flight-simulation software.
The word “simulator” here means that the test set supplies a known electrical input in place of an aircraft tank-sensing circuit so a fuel quantity indicator or system can be checked. Avien 1616-05-68, Avien 1616-022-100, Avien 1616-04-67 and 1616-04-113 are distinct identifiers; similar cases or controls do not make their connections, ranges or aircraft applications interchangeable.
Before using or acquiring one, verify the complete model and dash number, applicable test-set manual, required leads or adaptors, output range and calibration status. A sales description such as “fuel qty ind. simulator” does not establish that the unit is serviceable, in calibration or compatible with a particular indicator.
What are EA18B-692, EA1612-18R-9715, EA584-786 and EA-16 fuel quantity tank units?
These EA identifiers are part or model references associated in listings and data plates with fuel quantity tank units; they are not measurements of tank capacity or fuel remaining.
A tank unit is the in-tank sensing component that sends quantity information to an indicator, amplifier or totaliser. Aircraft systems may use floats, resistance-based senders or capacitance probes, but the identifiers EA18B-692, EA1612-18R-9715, EA584-786 and EA-16 do not by themselves prove which sensing principle, aircraft or electrical specification applies.
Compatibility must be established from approved parts and maintenance data using the complete part number, manufacturer, modification status and connector or installation details. Do not substitute units because the main number looks similar, and do not improvise electrical tests on equipment installed in or removed from a fuel tank.
What is a Simmonds 393081-111 fuel quantity totalizer?
A Simmonds 393081-111 fuel quantity totalizer is identified by a hardware part number rather than a simulator setting.
A fuel-quantity totaliser generally combines tank-unit information to present total fuel remaining. It should not be confused with a fuel-used totaliser, which integrates fuel flow over time. The exact display units, power requirements, connector pinout and approved aircraft application must be confirmed from the component’s data plate and applicable maintenance documentation.
How much fuel should remain before landing?
The aircraft needs enough fuel for the remaining flight plus the planned reserve; a gauge reading above zero is not an adequate landing criterion.
Compare predicted arrival fuel with the reserve established before departure, using the same mass or volume unit throughout. Our practical guide to simulator reserve fuel explains the difference between contingency, alternate and final reserve fuel without assuming one rule fits every aircraft or operation.