REFLECTOR: Uncommanded pitch trim up

[Michael Watson via Reflector]

John,

Are you using a MAC trim system?  If yes, I have had the down SW stick down
a couple of times.
I had to use my finger nails to pop it back up. I repositioned the SW
slightly and it never happened again.

Call me If you need more info on the MAC system.

Mike W.


On Fri, Aug 1, 2014 at 12:22 PM, John Dibble via Reflector <
reflector at tvbf.org> wrote:

> 2 1/2 years ago I reported experiencing uncommanded pitch trim up. I
> suspected that the solid state relay was the source of the problem as I had
> other problems with it in the past.  I wired the trim buttons direct to the
> trim motor and had no problems for 200 hours. Today the problem happened
> again, so it looks like the problem is either in the stick (where the trim
> buttons are) or the trim motor. Here are the details.
>
> It only happens when I'm in the pattern.  IIRC it begins when I'm abeam
> the numbers where I do my GUMP. I have a thermistor on the IVO prop and I
> hold the toggle to fine pitch until I see the current increase to 15 amps,
> indicating it's at the end of the travel.  The problem usually goes away
> after I turn to final.  Having learned from car window control battles with
> my kids, I know that if both the up and down buttons are pushed at the same
> time, that nothing happens.  So I held the trim down button to stop it from
> further trimming up.  Once the stick began moving forward, I knew the
> problem was gone.  Any ideas what the problem is?
>
> John
>
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