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stratfordman10

Autopilot Issue PMDG 737 NGX

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I have been flying the above aircraft for a year now with no issues whatsoever until today.

 

When I have taken off I action LNAV and VNAV and then the CMD(autopilot).

 

However,when I action the Autopilot it does not kick in and after repeated tries it will light up but then the VNAV disengages itself and when I re engage it the CMD goes out,all very strange.

 

Could anyone possibily throw any light as to what may be causing this problem.

 

Many thanks in anticipation.

 

Michael

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I'm not sure, it's been a while since I've used a Boeing in the sim, but isn't the Boeing AP designed to be engaged only at or above 1000ft? Could that possibly be the problem?

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Thanks for your replies.

 

Yes FD is turned on and I only engage A/P above 1,000 feet.

 

Any other thoughts would be appreciated.

 

Many thanks.

 

Michael

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Any other thoughts would be appreciated.

 

If the first waypoint is more than @ 5 degrees off of the runway heading or 3 nm away, LNAV won't engage (NGX FCTM pdf page 131).  Could this be the problem?

 

Mike

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Did you try other modes than simply LNAV/VNAV?

 

If you can replicate, it's best to record a videoclip and post it here.

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If the first waypoint is more than @ 5 degrees off of the runway heading or 3 nm away, LNAV won't engage (NGX FCTM pdf page 131).  Could this be the problem?

 

Mike

 

That right there actually made flying this plane more fun once I realized what was happening. Hand flying this plane to the first way point when that situation applies is actually more fun than just enabling LNAV right away for me at least. 

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That right there actually made flying this plane more fun once I realized what was happening. Hand flying this plane to the first way point when that situation applies is actually more fun than just enabling LNAV right away for me at least.

 

Hi, Michael,

 

You could also use heading select to direct the plane to the first waypoint.  Also the manual says 737-600 - 900ER you can engage autopilot at 400 ft AGL.  However certainly is good practice to hand fly!

 

Mike

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Thanks again for your replies.

 

I have done loads of flights in this aircraft with no issues at all and cannot understand why the autopilot will not respond.

 

I have just gone into my aircraft config file which states under the autopilot section the following;

 

autopilot_available =0

 

Am I right in thinking that this is incorrect-I have not touched the config file at all since purchase.

 

The other thing that I will mention is that yesterday I  installed by CD Orbyx FTX USA CANADA Pacific North West scenery and I am wondering if this is just conincidental.

 

Further comments would be appreciated.

 

Michael

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Michael do you have Realistic autopilot engagement turn on or off in the NGX FMC options menu? Having it set to realistic can cause the autopilot not to engage if certain conditions are not met.

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HI Jim,

 

Thanks for your reply.

 

I just turned my Realistic Autopilot to Off in the options menu,it was set to On before.I then loaded up a flight etc,took off LNAV then VNAV engaged and Autopilot also engaged and I thought we had cracked it.Then after about 20 seconds or so VNAV disengaged itself,I then re engaged it then the autopilot disengaged again and therefore I am back to square one.

 

The mystery is that having had this for 12 months trouble free I cannot understand what could have caused this now.

 

Further feedback/observations would be appreciated.

 

Michael

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Sorry Michael, thought that might have been it.

 

The only other thing I can think of is a key combo assigned somewhere for autopilot connect that is in conflict with something else. Or a key that is set to repeat via FSUIPC or the FSX controls and is making autopilot turn off.

 

If thats not it just open a support ticket with PMDG before you uninstall and reinstall or spend too much time wracking your brain.

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I arm LNAV and VNAV at the gate. They almost always turn green.

When I start running in the RWY to take off and hit TOGA, their green light comes off

Then, few secods after lift-off they become green again and at that point I engage the autopitlot lever switch.

This is what I learnt with the PMDG learning flights ( Amsterdam and Insbruck)

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Again,thanks for your replies.

 

I am unable to record a video clip,sorry.

 

One thing that I have been able to execute is before take off or at the gate I can light up the LNAV button but not VNAV-could this be a part of my problem.

 

I am wondering why I am unable to initiate VNAV whilst on the ground.

 

Also could my recent install of ORBYX scenery be an issue with this problem.

 

Further comments would be appreciated.

 

MIchael


Again,thanks for your replies.

 

I am unable to record a video clip,sorry.

 

One thing that I have been able to execute is before take off or at the gate I can light up the LNAV button but not VNAV-could this be a part of my problem.

 

I am wondering why I am unable to initiate VNAV whilst on the ground.

 

Also could my recent install of ORBYX scenery be an issue with this problem.

 

Further comments would be appreciated.

 

MIchael

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One thing  that hasnt been mentioned  have you filled out your  fmc  out correctly?

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Yes,the FMC is filled out properly.

 

The problem seems to centre around VNAV and the CMD-when one lights up the other goes out.

 

Really strange behaviour which has never happened before and really do not know what is causing it.

 

Further observations would be welcome.

 

Michael

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It's a known problem with many joysticks. The joystick shuts down CMD after you engage it after takeoff. It can disengage AP during a flight too if the weather is heavy. When I take off, I enable LNAV/VNAV first, take my hand off the joystick then enable the CMD/AP. In rough weather it can sometimes be a chore to get the CMD to engage and I have to manually takeover until the weather gets smoother. It will also not engage until I am pointed at the first waypoint (or any waypoint in the flight plan).

 

Best regards,

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Michael,

 

Have you checked your joystick, or controller calibration?  Suggesting this only because the apparent behavior matches what happens when on the jet is on autopilot and the pilot manually moves the yoke.  

 

Regards

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