Fix PMDG 737 autothrottle problems in FS2004 by checking MCP/FMA modes, throttle-axis conflicts, FSUIPC calibration and panel state.
To fix PMDG 737 autothrottle problems in FS2004, first confirm the A/T ARM switch is armed and an active thrust mode appears on the PFD flight-mode annunciator. If the mode is valid but the levers still fight or disconnect, remove duplicate throttle assignments, calibrate the axes, and test without FSUIPC or hardware inputs.
Match the symptom to the likely cause
| Symptom | Likely cause | What to check |
|---|---|---|
ARM is displayed but thrust does not change | The autothrottle is armed but has no active thrust command | Select a valid mode and confirm the FMA changes to N1, MCP SPD, FMC SPD or another expected mode |
N1 is active but speed changes | The system is commanding a thrust limit rather than holding speed directly | Check whether aircraft pitch is supposed to control speed in the selected vertical mode |
| Levers twitch, jump or fight the autothrottle | A noisy or duplicated throttle-axis input is overriding PMDG | Disable the hardware axes and test again |
| Only one engine responds correctly | Separate engine axes are misassigned or calibrated differently | Inspect the throttle 1 and throttle 2 assignments and ranges |
| The fault appears only in a saved flight | The saved situation contains incompatible panel or autopilot variables | Restart FS2004 and load a fresh PMDG 737 flight |
How to troubleshoot the PMDG 737 autothrottle
- Begin with a fresh flight. Exit and restart FS2004, then load the PMDG 737 without using an old situation created with another aircraft or panel. Clear any deliberately enabled PMDG system failures.
- Test manual thrust first. With the autothrottle disengaged, move both throttles through their normal range. Both engines should respond smoothly and independently. If they do not, the underlying problem is an axis assignment, calibration or engine configuration fault rather than the autothrottle.
- Set up a valid mode. Move the
A/T ARMswitch to ARM, select a sensible MCP speed and engage the thrust mode appropriate to the phase of flight. For take-off, use the normal flight-director, MCP and TO/GA sequence described in our Boeing 737 take-off setup procedure. - Read the FMA rather than the switch. The ARM switch only makes the system available. The thrust-mode column on the PFD tells you what it is actually doing. Our explanation of 737 autothrottle modes, MCP targets and FMA indications covers the distinction between modes such as
N1,MCP SPDandFMC SPD. - Isolate the controllers. Temporarily remove every throttle-axis assignment from FS2004 and FSUIPC, then repeat the test. If the virtual levers now move correctly under autothrottle control, restore one input route at a time until the conflict returns.
- Remove duplicate commands. Do not route the same throttle through both FS2004 and FSUIPC. Also check for duplicated autothrottle-disconnect, throttle-decrease and reverse-thrust bindings. Review FS2004's default throttle key commands if an F1–F4 key or controller button may be repeating.
- Calibrate the chosen input path. Check that each axis reaches idle and full thrust cleanly, does not enter reverse unintentionally and remains stable when untouched. A worn potentiometer can send continual small changes even when the physical lever appears stationary.
Why does A/T show ARM but not move the throttles?
ARM means the system is ready; it does not mean that an active thrust mode has been selected. The PMDG 737 will not move the levers merely because the MCP switch is armed.
Look for a green thrust-mode annunciation on the PFD. On take-off this normally follows TO/GA engagement. In flight, the displayed mode depends on the selected pitch and navigation modes. If the A/T switch will not remain armed at all, check for a repeating disconnect command, an enabled system failure or an incompletely powered aircraft.
Why does the autothrottle hold the wrong speed?
The first check is whether the PMDG 737 is controlling speed with thrust or with pitch. In MCP SPD or FMC SPD, thrust normally changes to maintain the commanded speed. In an N1 climb, thrust is set near the calculated limit while pitch controls speed; during some descents, thrust remains at idle while pitch again controls speed.
Also inspect the MCP target, FMC restrictions, thrust-limit selection and aircraft configuration. An autothrottle cannot maintain speed if the landing gear or speedbrakes create excessive drag, the selected thrust limit is insufficient, or the commanded speed is unsuitable for the flap configuration.
Why do the PMDG throttles hunt or disconnect?
Repeated lever movement with a valid speed mode usually points to hardware input noise, duplicate assignments or unstable flight conditions. Test in calm weather at a steady altitude before changing PMDG files.
Unlike the motorised levers in the real aircraft, most desktop throttle quadrants remain where the pilot left them. Moving that physical lever while the PMDG autothrottle is active can send a manual command that overrides or fights the virtual lever. After disconnecting the autothrottle, match the hardware position to the virtual thrust setting before taking manual control; otherwise the engines may jump abruptly.
If FSUIPC is part of the control setup, assign and calibrate the axes either there or through FS2004—not both. When the module itself reports an error, use our FS2004 FSUIPC error checks before relying on it for throttle control.
Is idle thrust during descent or landing a fault?
Idle thrust can be normal when the selected descent mode uses pitch to maintain speed. The autothrottle may remain armed while the levers sit at idle, then become active again if additional thrust is required.
Retarding the levers during the flare is also expected behaviour. Diagnose a fault only if the FMA shows an inappropriate mode, the thrust does not respond when required, or the system disconnects well before the expected landing sequence.
When should the PMDG aircraft be reinstalled?
Reinstall only after a fresh-flight test and a controller-free test both fail. First restore any modified PMDG panel, gauge and aircraft configuration files, and make sure files from an FSX or newer PMDG 737 have not been mixed into the FS2004 installation.
If the problem persists, reinstall from the original FS2004 package and apply only the matching update intended for that exact PMDG edition. A repaint alone rarely causes an autothrottle fault, but a replacement panel, edited gauge set or incompatible saved panel state can.