Fix PMDG 737/777 autothrottle disconnects in MSFS by checking FMA modes, throttle-axis noise, duplicate bindings, override settings and failures.
The PMDG 737/777 autothrottle can disconnect in Microsoft Flight Simulator because a mapped disconnect command, noisy or moved throttle hardware, duplicate bindings, reverse-thrust input or a simulated failure overrides it. First distinguish a true disconnect from normal modes such as THR HLD, HOLD, ARM, IDLE or RETARD by reading the flight mode annunciator.
Confirm whether the autothrottle really disconnected
A true disconnect removes autothrottle control and produces the aircraft's disconnect indication. Depending on the model and cause, this may include the A/T ARM switch going OFF, a flashing A/T warning in the 737, an EICAS message in the 777, or the expected thrust mode disappearing from the flight mode annunciator.
The A/T ARM switch by itself does not mean the system is actively controlling speed or thrust. Read the thrust-mode column on the primary flight display as soon as the problem occurs.
| FMA indication | What it means | Is it a disconnect? |
|---|---|---|
| THR HLD in the 737 or HOLD in the 777 | Automatic lever movement is temporarily released; manual lever movement is possible. | No |
| ARM | The system is armed but waiting for an active thrust or speed mode. | No |
| IDLE or RETARD | The autothrottle is commanding reduced or idle thrust during the relevant descent or landing phase. | No |
| N1, THR REF, THR, MCP SPD, FMC SPD or SPD | An active thrust or speed-control mode is engaged, subject to thrust limits and aircraft energy. | No |
If an active speed mode remains displayed but the aircraft does not maintain speed, use our diagnosis for an engaged autothrottle that will not hold speed. That is a different fault from a genuine A/T disconnect.
What causes repeated PMDG autothrottle disconnects?
Most repeated disconnections come from controller inputs rather than the PMDG system itself. PMDG aircraft use their own Boeing systems logic, but MSFS throttle-axis and button events still reach the aircraft.
- Noisy throttle axes: A worn potentiometer can send small movements continuously. The virtual thrust levers then twitch, split or override the autothrottle even though the physical quadrant appears stationary.
- Non-motorised throttle mismatch: The autothrottle moves the virtual levers while the physical levers remain elsewhere. Touching the hardware can send an abrupt new position and take control away from the automation.
- Duplicate bindings: A second quadrant, gamepad, joystick or keyboard profile may also control the throttles or issue an autothrottle command.
- Incorrect button assignments: Autothrottle disconnect, A/T arm, throttle cut and reverse-thrust commands are sometimes assigned to the same button or switch position.
- PMDG throttle-override settings: The 737 and 777 can provide options governing when hardware is allowed to override automatic thrust. An unsuitable setting can make ordinary axis movement look like a manual takeover.
- Failures or external commands: A configured aircraft failure, lost electrical source, AI assistance or external control software can change the A/T state.
How do I stop the PMDG autothrottle disconnecting?
The quickest fix is to isolate controller input first, then verify the aircraft's mode logic.
- Record the exact indication. Note the FMA thrust mode, A/T ARM switch position, warning message and flight phase before resetting anything. This separates an actual disconnect from HOLD, THR HLD, ARM or IDLE.
- Test without the throttle quadrant. Repeat the event using a clean controller profile or with the suspect device disconnected. If the fault stops, follow these controller-axis checks for a creeping throttle.
- Remove duplicate assignments. Search every connected MSFS device for throttle, autothrottle, disconnect and reverse-thrust commands. Each throttle lever should have one intended axis, and an A/T disconnect command should exist only where you deliberately assigned it. Binding names can differ between MSFS 2020 and MSFS 2024.
- Calibrate the axes. Check that each lever travels smoothly from idle to full thrust, then add a small dead zone if the input flickers while untouched. Dual throttles should reach matching positions.
- Review PMDG override behaviour. For diagnosis, select the aircraft option that prevents an inactive hardware axis from overriding automatic thrust. The available wording and choices differ between the 737 and 777, so do not assume both packages use the same setting.
- Verify proper engagement. Arm the autothrottle, configure the flight directors and select the appropriate TO/GA or speed mode while watching the FMA. Our explanation of how the 737 TO/GA switch changes thrust modes covers the expected take-off sequence.
- Eliminate simulated faults. Load a known PMDG panel state, disable configured failures and temporarily stop external control software or AI piloting assistance. Reintroduce each item individually once the autothrottle works normally.
After a genuine disconnect, remove the bad input and synchronise the physical throttles with the virtual levers before re-arming A/T. Otherwise, the same position jump can disconnect or override it again immediately.
Why does it disconnect during take-off or landing?
Many apparent take-off and landing disconnects are normal Boeing mode transitions rather than failures. During take-off, THR HLD in the 737 or HOLD in the 777 releases automatic lever movement temporarily; it does not mean the autothrottle has failed.
If the A/T warning appears or the system drops out exactly when TO/GA is pressed, inspect the TO/GA, A/T disconnect and throttle-axis bindings. Do not substitute a generic autothrottle toggle command for the aircraft's correct TO/GA operation.
During landing, RETARD or IDLE commands the thrust levers towards idle, and an automatic disconnect after touchdown is expected as the landing and reverse-thrust sequence begins. A genuine disconnect on final approach before the normal flare sequence is not expected unless it was commanded, caused by hardware input or triggered by a simulated fault.
Why do the autopilot and autothrottle disconnect together?
The autopilot and autothrottle are separate systems, so manually disconnecting the autopilot should not normally disconnect A/T. If both drop out simultaneously, check for a button mapped to both commands, a controller or USB interruption, an electrical failure, or external software sending multiple events.
If the autopilot disconnects but an active A/T mode remains on the FMA, the autothrottle is still engaged. Speed may nevertheless change because the pilot now controls pitch, and automatic thrust cannot instantly correct a large pitch or drag change. Our PMDG 737 autopilot mode setup explains how the flight directors, MCP modes and FMA should agree.