Fix the PMDG FMC “INSUFFICIENT FUEL” warning by checking reserve units, route data, cruise inputs and actual tank fuel.
The PMDG FMC shows INSUFFICIENT FUEL when its predicted fuel at the destination is below the reserve entered on PERF INIT. Verify the reserve units, route, cruise altitude, zero-fuel weight and actual tank quantity; then add fuel or correct the bad entry. Pressing CLR only acknowledges the warning.
This general logic applies across PMDG Boeing add-ons in Microsoft Flight Simulator, Prepar3D and FSX, although the loading interface and exact CDU labels vary. It is a forecast from the FMC, not a direct low-tank or fuel-pump warning.
What triggers the PMDG INSUFFICIENT FUEL warning?
The warning appears when the FMC’s calculated arrival fuel falls below the value in the RESERVES field. It does not necessarily mean that the aircraft cannot reach the destination; it means the predicted landing fuel will breach the reserve threshold you entered.
The calculation uses actual or calculated fuel aboard, aircraft weight, active-route distance, cruise altitude, cost index and available wind data. A route loop, wrong weight or unrealistic reserve entry can therefore produce the warning even when the tank gauges appear healthy.
PMDG Boeing fuel values are normally shown in thousands of the selected unit. A value of 3.0 represents 3,000 kg in KG mode or 3,000 lb in LB mode. Read the CDU’s unit indication rather than copying the same number between kilogram and pound configurations.
How do I correct the warning before departure?
Correct the inputs first, then add fuel only if the FMC’s prediction reflects a genuine shortfall.
- Read the destination prediction. Open the
PROGRESSpage and note the estimated fuel at the destination. Compare it withRESERVESusing the same mass unit. - Check the reserve entry. Enter the planned minimum fuel required at destination under your chosen operating policy. Do not enter total block fuel in the reserves field, and do not reduce a valid reserve merely to suppress the message.
- Verify physical fuel in the tanks. A fuel figure copied into PERF INIT or written on a flight plan does not load the aircraft. Use the PMDG-supported aircraft loading interface and confirm that the cockpit tank indications match the planned block fuel. Our block-fuel and refuelling guide explains taxi, trip, alternate and reserve quantities.
- Inspect the active route. Check the origin, destination, total distance and every page of
LEGS. Remove accidental loops or duplicate waypoints, resolve discontinuities appropriately and confirm that the selected SID, STAR and runway belong to the intended flight. Use our route-entry and FMC verification steps if the route distance looks wrong. - Correct PERF INIT. Zero-fuel weight excludes usable fuel; do not substitute gross or ramp weight. Enter a realistic cruise altitude, the intended cost index and wind or temperature information supported by that PMDG model.
- Execute the changes. Route and performance modifications must become active before the prediction is meaningful. Confirm that no unexecuted modification remains, revisit
PROGRESS, and then useCLRto acknowledge the old message. - Resolve a real deficit. If the corrected arrival prediction is still below reserves, load more fuel before departure or revise the route, cruise plan or destination. The warning is then doing its job.
Can I clear the PMDG INSUFFICIENT FUEL message?
The CLR key removes the displayed advisory, but the message will return if predicted destination fuel remains below reserves. Use the symptom to identify what the FMC is still seeing.
| What you see | Likely cause | What to check |
|---|---|---|
| Warning appears immediately after entering reserves | Wrong unit, scale or reserve amount | Check KG versus LB and the CDU’s thousands format |
| Warning appears after selecting an arrival | Long arrival, route loop or duplicate leg | Inspect route distance and every active LEGS page |
| You added fuel but the tank gauges did not change | Only a planned or manual FMC value was changed | Load physical fuel through the PMDG-supported interface |
| Tank gauges changed but the prediction did not | Loading has not finished or active performance data remain stale | Complete the loading process, then recheck PERF INIT and PROGRESS |
| Arrival fuel is now above reserves but the message remains displayed | The old advisory has not been acknowledged | Press CLR; investigate further if it returns |
Changing fuel-pump or crossfeed settings is not a direct cure for this prediction. On the PMDG 737, the crossfeed valve connects the engine feed manifolds; it does not move fuel from one tank to another. If centre-tank or wing-tank behaviour is causing confusion, check how 737 pumps, tank priority and crossfeed work.
What should I do if the warning appears in flight?
An in-flight warning should be treated as a forecast that the entered reserve will be breached, not dismissed as a nuisance message.
- Confirm the prediction. Compare the destination fuel on
PROGRESSwith both the reserve entry and the planned fuel remaining at your present waypoint. - Check for a route error. Look for an unintended leg, extended vector, changed destination or arrival modification. Correct and execute only entries that are genuinely wrong.
- Assess the fuel trend. Stronger headwinds, prolonged low-level flight, holding, extra track miles or unusually high engine fuel flow can turn a valid departure plan into a reserve shortfall.
- Reduce avoidable burn. Request a direct routing or a more efficient altitude when aircraft performance and the flight situation permit. A more economical cruise setting may help, but it cannot recover fuel already burned.
- Choose a nearer landing option early. If the prediction remains below the required reserve, diverting is the realistic correction. Lowering
RESERVESchanges only the warning threshold; it does not put fuel back in the tanks.
If fuel is disappearing much faster than the FMC model predicts, inspect individual tank quantities, engine fuel flow and enabled failure settings. A simulated leak or engine fault requires fault management rather than another PERF INIT entry.