stec 55x elevator or trim servo question

[Browncbr1]

Hey guys, I have a question for you stec elevator or trim servo owners.  This isn't in the mooney, but in the baron I fly regularly.  

Recently, I've noticed when I disconnect the AP from the yoke button, the ailerons go limp like they should, but the elevator is still stiff.  When I apply pull or push the yoke with a little more pressure, it seems to break free from the servo.  Of course, from the extra pressure, it makes it feel like a sudden jerk on the elevator when the servo lets go.   i'm not sure if this is an elevator or trim servo sticking... I think it is elevator servo because I haven't received any trim annunciations on the aspen like you would if the trim servo switch is turned off.

 

Has anyone experienced this?  any advice?

thanks!  Craig

[neilpilot]

Craig,

I the C I used to fly, if you disconnect the 60-2 but the trim is still switched on, the trim switch is still active and the elevator will naturally be stiff.  Obviously not the same installation as yours, but I'm wondering if you also need to switch off your trim?

[Browncbr1]

3 minutes ago, neilpilot said:

Craig,

I the C I used to fly, if you disconnect the 60-2 but the trim is still switched on, the trim switch is still active and the elevator will naturally be stiff.  Obviously not the same installation as yours, but I'm wondering if you also need to switch off your trim?

I have always left the trim switch on, but don't recall this stiffness (and resulting jerk when it pops loose) before the last two or three flights.  

I was in approach mode on short final each time when I disconnected the AP and experienced this.  So, the trim servo was definitely working a lot in the time leading up to disconnect, and the electric trim continued to work as normal down to landing.  The elevator is stiff like the AP is still on, but after it pops loose, it is light again like in all other phases of flight when AP is not coupled.  I've always left the electric trim switch on.. 

[Danb]

I also have the 55X and don’t experience that situation, in all likelihood it is hanging up like you expressed, but just a guess.

[Marauder]

I have always left the trim switch on, but don't recall this stiffness (and resulting jerk when it pops loose) before the last two or three flights.  
I was in approach mode on short final each time when I disconnected the AP and experienced this.  So, the trim servo was definitely working a lot in the time leading up to disconnect, and the electric trim continued to work as normal down to landing.  The elevator is stiff like the AP is still on, but after it pops loose, it is light again like in all other phases of flight when AP is not coupled.  I've always left the electric trim switch on.. 

I have an STEC 60-2 with autotrim. When I disconnect I don’t find the elevator sticks. I suspect that either your trim/pitch servo is sticking.


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[Browncbr1]

I spoke with Gensys and they say it sounds like a pitch servo solenoid is sticking.   

[Andy95W]

54 minutes ago, Browncbr1 said:

I spoke with Gensys and they say it sounds like a pitch servo solenoid is sticking.   

This is my guess as well.  I have a 20 year old STEC-50 and occasionally it will do exactly what you described.  I do not have electric trim.

[Mooney in Oz]

22 hours ago, Browncbr1 said:

Has anyone experienced this?  any advice?

I have a STEC 55x with auto trim and also do not experience what you describe plus the Auto Trim switch always remains on.  I cannot remember the last time I needed to switch it off.

[Browncbr1]

It’s definitely the pitch servo..  yesterday, I turned off the electric trim and just trimmed manually for the whole flight.  After disconnecting, it did it again.  

[carusoam]

See if you can get the system disabled properly, before something gets jammed... faulty clutch or electromagnetic device...

Thoughts of faulty MCAS systems still in my head...

Except in this case, you have turned the system off, and it is still physically connected...!  Meaning that you have to overpower the servo drive to operate the elevator...

PP thoughts only, not an electronics tech...

Best regards,

-a-

[Browncbr1]

10 hours ago, carusoam said:

See if you can get the system disabled properly, before something gets jammed... faulty clutch or electromagnetic device...

Thoughts of faulty MCAS systems still in my head...

Except in this case, you have turned the system off, and it is still physically connected...!  Meaning that you have to overpower the servo drive to operate the elevator...

PP thoughts only, not an electronics tech...

Best regards,

-a-

I did not turn the autopilot power off at the switch.   I only hit the disconnect button on the yoke, which does not kill power to the AP system.  So, I’ll see if it still sticks even when turning the AP power switch off.