Fix a FlightGear throttle that will not respond: test keyboard input, remove duplicate axis bindings, calibrate hardware and check aircraft state.
A FlightGear throttle usually stops responding because the hardware axis is unassigned, mapped twice, reversed or not detected; keyboard focus and aircraft state can also be responsible. Test Page Up first, then verify the controller outside FlightGear, remove conflicting bindings, calibrate the axis and confirm that the engine is actually running.
How do I diagnose the FlightGear throttle problem?
The result of one keyboard test usually separates a FlightGear binding fault from an aircraft-system problem. Disconnect or disable external controllers, load a stock aircraft with its engine running, click inside the simulator window and press Page Up and Page Down.
| What happens | Likely cause | Next action |
|---|---|---|
| Keyboard works, but the hardware lever does not | Missing, incorrect or conflicting axis binding | Clear and reassign the throttle axis |
| The input flickers or snaps back | Two devices are commanding throttle, or the axis is noisy | Remove duplicate bindings and test the hardware |
| The cockpit lever moves but engine speed does not rise | Engine, fuel, mixture or autothrottle state | Check the aircraft systems |
| Engine speed rises but the aircraft remains stationary | Parking brake, toe brakes, chocks or pause | Check ground restraints and brake axes |
| Only one engine responds | Throttle assigned to one engine rather than all engines | Correct the per-engine assignments |
How do I fix the joystick or throttle axis?
Fix the axis by confirming hardware movement first, then creating one clean continuous throttle assignment in FlightGear.
- Connect the controller before launching FlightGear. Close the simulator, attach the throttle directly to the computer if possible and restart. Hot-plug detection varies, and identical devices can exchange controller numbers when their USB order changes.
- Test a stock aircraft. Use an unmodified aircraft and a start state that explicitly loads the engine running. This prevents a custom aircraft or cold-and-dark procedure from disguising an input problem.
- Check the keyboard commands. Click the 3D view so a search box or dialogue is not capturing the keys, then use
Page UpandPage Down. Laptop keyboards may require anFnmodifier. Our reference for FlightGear's standard key commands covers the other default bindings. - Verify the physical axis outside the simulator. The indicated axis should travel smoothly from one end to the other without jumping. Windows users can follow our controller-axis detection and calibration checks; on other systems, use the operating system's controller utility.
- Remove conflicting assignments. Open the joystick or controller configuration available in your FlightGear build. Clear every unintended throttle assignment, especially axes from a second joystick, gamepad or quadrant. A connected axis can repeatedly overwrite keyboard input.
- Assign the continuous throttle axis. Move the physical lever to identify it, then bind it to the normal throttle control rather than a throttle-increase button command. For a single lever, choose the all-engines control where available; multi-lever quadrants should use the matching per-engine controls.
- Calibrate the range and direction. Move the lever through its full travel, apply reversal only if idle and full power are exchanged, and use a small dead zone only when the axis jitters. A throttle is not a centred control, so a large centre dead zone can produce an apparent half-travel fault.
- Save and verify the control value. If your build exposes the property browser, watch
/controls/engines/engine[0]/throttle. A conventional throttle should move between approximately 0 at idle and 1 at full power. Custom aircraft may process the control through additional systems, but this property remains a useful first check.
Why does the throttle move but the aircraft stay still?
If the cockpit throttle moves correctly, the binding itself is probably working. Watch engine RPM in a piston aircraft or the appropriate turbine power indication rather than judging the throttle solely by ground movement.
- Piston aircraft: check that the engine is running, the fuel selector is open, the mixture is not at cut-off and the ignition controls are set correctly.
- Turbine aircraft: check the engine master, fuel or condition levers and the completed start sequence. Advancing a throttle cannot create thrust from an unlit engine.
- All aircraft: release the parking brake, check that toe-brake axes are not reversed and remove wheel chocks if the aircraft models them. Also make sure the simulation is not paused.
- Automated aircraft: disconnect autothrottle or automatic thrust control while testing. Some systems immediately replace a manual axis command with their commanded power setting.
A reversed toe-brake axis is a mistake we see constantly: engine power rises normally, yet the aircraft remains pinned to the ground. The practical first-flight checks in our FlightGear overview cover brakes, engine state and duplicate controls together.
Why does only one engine respond?
Only one engine responds when a single physical lever is bound to an engine-specific throttle instead of the all-engines command. On a twin, inspect both /controls/engines/engine[0]/throttle and /controls/engines/engine[1]/throttle; either map one lever to all engines or assign separate quadrant levers to each engine.
Sophisticated aircraft may deliberately keep their throttles separate or apply custom FADEC logic. If the same hardware controls every engine in a stock multi-engine aircraft, the remaining fault belongs to that aircraft's systems or control implementation rather than the global joystick profile.
Why is the FlightGear throttle reversed or stuck at half travel?
A reversed or half-range throttle is usually a calibration or range-conversion fault. Confirm that the operating system reports full physical travel, then reverse the axis once in FlightGear rather than reversing it in several layers.
Some hardware reports an axis from -1 to +1 while FlightGear's normal throttle control expects 0 to 1. The built-in assignment interface should perform that conversion; a manually created controller definition with the wrong offset or scale may not. Throttles with an idle detent or reverse section may also require a separate reverse-thrust command, depending on the aircraft, rather than mapping the entire physical range as forward throttle.
What if the keyboard throttle also does not work?
If keyboard throttle fails in a stock aircraft with external controllers disconnected, check input focus and user settings before reinstalling FlightGear. Close open dialogues, click the simulator view and repeat the test with an engine-running start state.
Next, create a fresh user profile or use the reset-user-settings function offered by your FlightGear build, backing up the existing profile first. If a stock aircraft works under the clean profile but an add-on does not, its custom systems or local files are responsible. If neither keyboard input nor a clean profile works, repair or reinstall FlightGear without restoring the old input configuration until the default controls have been tested.