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alexzar14

AP doesn't engage below 28,000 ft.

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Bizarre  problem, but it exists and it is irritatish. AP doesn't engage after take off. Everything (electrics, generators, hydraulic pumps etc) is ON, IRS aligned, LNAV and VNAV do engage and AT works, but Autopilot does not engage. This started happening after I upgraded to P3D v3.3 and back to 3.2 (it was ok with 3.3) - that's all that I did in the sim. First flight in downgraded 3.2, AP could not engage until 30,000 ft. Now second flight, again, was able to engage at 28,000 ft. Please see how to get out of it.

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if  the autopilot  doesn't  work    must be  some  conflict  since   it  needs  to be  in a level  flight  before it  engages

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I am sure you meant aircraft in proper trim and alignment with the Flight Director and not level flight. OP, recycle your flight directors and make sure the airplane is properly trimmed, and that you have selected a roll and pitch mode in the MCP.

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I did cycle the FD, I tried engaging AP with LNAV/VNAV - on, off, and with VS/HDG modes on, it did not engage until high altitudes. Will try a third flight, if the AP doesn't engage on 3rd flight I think I will have to reinstall.

2 years flying this plane with no problems, well understanding the AP, CDU functions, FD bars etc.

 

Tonight will fly a 777 for the first time since I went back to 3.2 and see how that one does, may be the same thing...

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2 years flying this plane with no problems, well understanding the AP, CDU functions, FD bars etc.

 

This usually points to a change in your personal workflow (usually exacerbated by flying other aircraft).

 

My bet would be an out-of-trim situation. Trim up, or turn off the realistic AP engagement option.

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I set trim per value calculated by CDU, usually it needs a lot of trim but within green sector. Take off and manual climbs are nice and smooth. But I will paly with trim per suggestion if the AP doesn't engage. Yesterday I flew a 777 and it did ok. Tonight will fly the NGX.

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I set trim per value calculated by CDU, usually it needs a lot of trim but within green sector.

 

Takeoff trim and in flight trim are separate animals. Takeoff trim is meant to keep you in trim for a good rotation. In flight, you're continuously adjusting it to keep forces off of the yoke. If you're out of trim, the AP will not take over. This is noted in the Intro Manual.

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Yes, I do retrim downwards after takeoff, as I accelerate the takeoff trim is too much and needs to be trimmed down (especially on MD-80 both Coolsky and Rotate for XP need a lot of retrimming work in manual flight), that we understand. 

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Alexander,

 

Are you using a Flight Controller or just the Arrow keys on the keyboard for your Column Inputs?

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I use CH yoke, pedals and throttle, I'm not saving on my hobbies and good time ; )

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ok, this time it worked, although I went back to 3.3.5, that may have fixed it. Also with two previous flights I manually inputted the route inputting airways, and today I imported the Routefinder plan straight (sids stars transitions added afterwards). Next time I'll have to try inputting the route manually again and see if that works too.

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although I went back to 3.3.5

 

My money is on this being the fix.

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My money is on this being the fix.

 

It works so far, but the VAS usage increased in 3.3.5 - effected PMDG planes only. NGX flights still have VAS reserve at the end but the 777 is.... disaster. Having to restart 2 times to complete a flight.

Haven't tried iFly 747, if that performs as it was in 3.2, then the problem confirms to PMDG. 

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