AP - manual trim strange behavior

Luigi.Seccia

I love flying!
Joined
Dec 1, 2016
Messages
3
Hi, 
here a strange problem I can't understand...

On feb 2017 I've installed D10A, AP74 and 2 servos SV32 all updated to last software available (version 5.6.1).

All works fine till a plane maintenance 2 weeks ago.
During this maintenance the CT official maintainer decide to check also the stabilator and trim positions and equilibration.
Now, after that maintenance, an AP strange behavior  appears.
And I can’ understand it and/or recover a good & safe AP performance.

Assume:
1) I’ve done, after the above maintenance, successfully from the begin, all servos setups required (Servo Test + Servo Calibration)
2) In a normal flight, I'm going to trim the plane for strait and level hands off (the plane behavior looks normal as per before maintenance)
3) At this time, if I engage AP, for a while all goes fine (correct pitch & roll, heading, altitude)
4) But, after some seconds, appears the yellow trim flash requesting to trim forward
5) At this time, If I disengage AP the plane is still strait and level as before
6) If I engage AP, again within some seconds, AP is asking to trim forward
7) If I execute the requests going to erase the flash all goes fine, the AP maintains correctly the altitude
8) But, at this time, if I disengage the AP the plane goes in a very deep dive that needs a quick stick recovery
9) After the stick recovery, I’ve to trim newly the plane – the trim position requested by AP wasn’t correct (and of course the stick position)

Any idea?
Many thanks for the help

Luigi
 

dlloyd

Member
Joined
Oct 12, 2011
Messages
139
Location
Locust, NC
Luigi,
I had the same problem except for up trim being needed. After some back an forth with Dynon, the pitch servo was returned and replaced under warranty.
 

Luigi.Seccia

I love flying!
Joined
Dec 1, 2016
Messages
3
Thanks Dlloyy for the answer.

Just a couple of questions.

1) did you tried reload the software to pitch servo?

2) The first step in Servo Calib requests to set the stick in center position. Did you tried to set it a bit off center (even if the stabilator isn't)?

I'm convinced this means nothing.
I'm convinced when AP is engaged the software on servo processor act as we do. Just to neutralize the force applied on stick (and this is relative to air conditions).

But just to know what do you think after many test I suspsect you have done.

thanks again

Luigi
 

dlloyd

Member
Joined
Oct 12, 2011
Messages
139
Location
Locust, NC
1)no
2)no

Worked properly for 100 hours or so. Then the trim up message would happen a little at a time. Dynon confirmed it seemed to be a servo problem.
 

Luigi.Seccia

I love flying!
Joined
Dec 1, 2016
Messages
3
Thanks agn Dlloyd.

I've sent a direct message to Dynon support.
Let see their opinions.

have nice xmast time there!

Luigi
 
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