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flightsimuser1962

strange things with the autopilot 737/800 NGX from PMDG

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Hi friends, I have a problem with my 737/800 NGX from PMDG.

As soon as I engage the autopilot, it is not possible to change the flightdirection without switching the heading button from the autopliot and turning the headingselection knob.

 

For example:

Assumed heading direction is 300. Assumed speed is 250 knots and Altitude is 9000 feet. Now I engage the Autopilot with a chosen speed from 250 knots and an Altitude 9000 feet, both set by the Altitude and Speed knobs. Also the Autothrottle is switched on and the green LEDs are glowing. The plane flies now the 250 knots and holds the Altitude perfect as chosen.

 

But I can not control the plane to change the heading, by only using the yoke, even if I did not engage the Button for holding the headingdirection.

 

To operate a headingdirection change, I have to engage the "Holding Heading" and I have to use the heading selector knob to change the direction by turning it into the wished direction.

 

If I do not so, I can move the yoke full right or left, but the plane moves only unruly a few degrees in the chosen direction, and after putting it back to the middle position, the plane returns to the last headingcourse before engaging the autopilot.

It seems to me, that there is anywhere a kind or courseprogramming taking place, that brings the plane to the last flown course, even if the heading selector of the autopilot is switched off.

After disengaging the autopilot at all, I can control the plane normal by using the yoke.

 

I have no idea, how to fix this problem.

 

Does anybody has a solution for this strange behaviour of the plane?

Thanks a lot.

Robert Hammer

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What you are describing is correct behaviour. The autopilot defaults to engaging in heading hold mode. It will always try and maintain the heading it had when AP was engaged. You have to use Heading Select (the SEL button in the centre of the heading knob) and turn the heading knob to control heading in command mode.

 

The autopilot has two modes of engagement:

 

Command (CMD) which follows the inputs from the autopilot mode control panel (and the FMC).

Control Wheel Steering (CWS) which follows the inputs from the yoke.

 

So if you want to use the yoke to control pitch and roll angle you can engage the AP in CWS mode (the CWS button is below the CMD button). However it's more useful to use command mode and let the autopilot do it's job.

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Does anybody has a solution for this strange behaviour of the plane?

If you have not flown Tutorial #1, I believe you need to try it. There is a lot if information in both Tutorial #1 and #2 that can help you and answer your questions in situation that you have described. Have a good time flying.

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Thanks for help. Unfortunately my english is quite bad, that I do not understand everything in the tutorial and it is very very strange to translate everything by dictionary.

Thats whay I often ask questions, which seems to be stupid for you.

I apologize.

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As mentioned, you need to engage CWS if you want to handfly either roll mode or pitch mode with AP on.

 

Given that you recently had your AP broken because you applied too much force, it does not want to get broken again ! LOL ! Just kidding.

 

Apply gentle force on the yoke while on CMD A or B, the AP should trip over to CWS R or CWS P depending on whether you applied roll force or pitch force. Just as in real aircraft if you were recovering from an unusual attitude, try not to apply both at the same time and if you apply too much you will break the AP again. CWS will hold the roll or pitch input on the yoke for you. Pregty neat eh ?

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Thats whay I often ask questions, which seems to be stupid for you.

I apologize.

No need to apologize and there are no stupid questions

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@picubine: Thank you for your understanding.

 

@Alf1: your suggestion to apply gentle force on the yoke while on CMD A or B, the AP does not help anyway.  
The machine does not trip over to CWS R or CWS P.

And even if I switch manualy to the CWS modes, nothing happens. The machine always is ruly then and goes back to the former course.

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Hmm, and you are sure that there are no failures (check in the CDU)

 

That is very odd. Let me look in mine and come back.

 

And dont forget to edit your signature.

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And even if I switch manualy to the CWS modes, nothing happens.

 

That just plain doesn't make sense, if you switch to CWS mode there should be an indication on the PFD that CWS mode is active.  That is not nothing, it is something.  I'm not sure what you are doing, or even trying to do.

 

Include the FMA indications in your problem description, it is always telling you what modes for thrust,  pitch and roll the aircraft is in.

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I will make some screenshots today, so that can see you, what is going on there. Probably I can make a little video. I will come back as soon I made it.

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Check if you activated the realistic AP engagement or not in the pmdg options. I could have something to do with that option. It needs to be ON.

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Ok, I got it, I solved the problem. It was nothing, we were thinking about.

The problem was FSUIPC.

I usually control the whole plain by setting it up over FSUIPC and to prevent conflicts, I had switched off the controllers from the P3D software. So also the yoke axes, of course.

I don`t know why, it was just a feelling to do this, but I disconnected the axes control for the yoke from FSUIPC and set it up by P3D settings. 

And what can I say: It works now like cutting a knife through soft butter.In other words: I can control the heading again by using the yoke during engaged AP with HLD and SPD in a smooth and proper way.

Don`t ask me why FSUIPC did make those troubles. May be there are two settings, which produced conflicts with the controls.

may be it will help others, if they will get the same prblems as me.
Dear fellows, thank you all for your help again.

  • Upvote 1

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