Autopilot Problems - V8.60


X-Plane 8.60 introduced a number of subtle but important changes in how the autopilot works. For revised details on how to use the autopilot, see the V8.60 autopilot FAQ page.

Trying to use the 8.60+ autopilot with assumptions based on earlier X-Plane versions will be an exercise in frustration and lead you to believe that the autopilot is broken. So the general FAQ for this page is...

The Autopilot Doesn't Work!!

In particular...

I've engaged the autopilot and it's not controlling the plane

Turn on the flight director by setting the Flight Director control switch to AUTO. X-Plane tends to turn the flight director off anytime you manually place the plane (for example, with Location->ILS Final). If your plane has no flight director switch the autopilot should turn on whenever you engage any mode.

Altitude hold is always armed

That's the way it works now. This is how the autopilots on the Boeing heavies and some other units work. The behavior of other units, where altitude arming can be selectively enabled, cannot be modeled. The autopilot will always lock onto the set altitude if you climb or descend through it. To avoid having the autopilot lock onto some altitude as you fly through it, set the altitude to something you won't fly to, like zero.

When I press ALT HOLD the autopilot holds my current altitude

That's the way it works now (and that's the way it works in all real autopilots).

I'm flying in ALT HOLD and can't climb or descend with VS or FLCH

You must select a new target altitude first, or you will remain locked onto your current set altitude.

The S-TEC 55 won't switch to VS mode from ALT HOLD

This is a special case of the above problem. Only the S-TEC 55 doesn't have a target altitude dial, so there's no way for you to change it. To go back to VS mode in the S-TEC 55, you must disengage the autopilot with the "!" key (or with an assigned joystick button), manually fly a couple hundred feet away from your current altitude, and then re-engage VS.

When I engage FLCH engine power goes to maximum or idle

This happens when you engage FLCH with ATHR engaged. Again, it works this way because the Boeings work this way (kind of). The real Boeing autopilot is a little more sophisticated about it; X-Plane's behavior can be rather abrupt. To avoid this behavior, use SPD instead or switch off ATHR before engaging FLCH.

I can't shut off the autopilot; for example...

When I disengage VS or FLCH mode the autopilot switches to PTCH

Another that's the way it works now. Almost all real autopilots revert to pitch hold mode when you toggle off the current vertical mode. To stop the autopilot from controlling the plane, disconnect it with the "!" key, an assigned joystick button, or by setting the Flight Director switch to OFF.

When I disengage HDG or LOC mode the autopilot switches to WLV

Another that's the way it works now. Almost all real autopilots revert to wing leveler mode when you toggle off the current lateral mode. To stop the autopilot from controlling the plane, disconnect it with the "!" key, an assigned joystick button, or by setting the Flight Director switch to OFF.

When I engage VS (or FLCH or SPD or ALT) the autopilot engages WLV
When I engage HDG (or LOC) the autopilot engages PTCH

The pitch and roll modes cannot be separately engaged. Engaging the autopilot in any mode automatically engages at least attitude hold mode for the other axis. This is how most civilian autopilots work.

WLV doesn't hold the wings level

Also matches real world behavior of many autopilots. It's not really wings level but attitude hold - i.e., it holds your current roll angle.

I engage LOC mode to intercept a VOR radial and the plane doesn't turn toward an intercept course

This is another change from previous autopilot behavior. You must turn the plane to an intercept course by flying it manually or selecting an appropriate heading in HDG mode. LOC mode is armed when you engage it (like it always worked for a localizer) but it does not become active until you approach the VOR radial and the CDI starts to come off maximum deflection.

I program a GPS leg or an FMS course and the plane does not fly the course when I engage LOC mode

Same problem as above. You must initially fly a course to intercept the GPS leg or initial FMS course to let the autopilot lock on.


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