Fuel tank selection & switching
Multiple selectable tanks: check the Aircraft Flight Manual. Some tanks may be barred from takeoff or landing use (TP 1102).
| Tank type | Use |
|---|---|
| Auxiliary (generally) | May be barred from takeoff/landing |
| Main | Cleared for takeoff and landing |
Tank use by phase (TP 1102):
| Phase | Tank | Rule |
|---|---|---|
| Start/taxi | Auxiliary, then main | Start and warm up on auxiliary to check system. Select main before run-up and takeoff |
| Climb/cruise | Auxiliary | Not until cruising altitude, level flight |
| Descent/landing | Main | Select well before landing, commonly at start of descent. Recheck on pre-landing check |
- Lateral trim: use fuel alternately from each side, not one side down first (TP 1102).
Run a tank dry only if fuel shortage forces it. Risks:
- Sediment or water drawn into carburettor or injection system
- Air lock
- Vapour lock (completely dry tank): engine hard to restart
If forced: run dry at altitude, level flight, cruise speed.
Manage by time, not gauge:
- Calculate consumption, time each tank. Gauges monitor only.
- Certification requires gauge accuracy only at "empty" (PHAK ch.7).
- Check levels visually on preflight.
If it goes wrong:
| Symptom | Action |
|---|---|
| Warning light flickers | Select new tank, boost pump on. Do not select an empty tank position (TP 1102) |
| Engine falters (fuel starvation) | Select new tank, then ease throttle to half-way between idle and cruise until smooth |
Trap: timing tanks by gauge instead of calculated consumption; gauge certified accurate only at empty.
References
- TP 1102 Aeroplane Flight Training Manual, Type Conversion: Fuel Systems
- FAA-H-8083-25 PHAK ch.7 (fuel gauges, fuel selectors)