REFLECTOR: Pitch Trim Mystery

John Dibble aminetech at bluefrog.com
Wed Feb 15 11:28:10 CST 2006


Well, that sounds like a good guess.  For the entire flight either the autopilot or
myself was adding a little extra pressure to maintain level flight.  After I got out
of the plane I pushed down on the elevator a little.  Maybe that is what made it work
again.  I'll check it out.  But wouldn't pulling back on the stick also do the same
thing?  Or am I not understanding this right?

Scott - It took a lot of force and of course the farther I pulled back, the stronger
the force.  It felt like I might break something.  I suppose you could trim your
elevator all the way up and feel the force to pull the stick back to neutral.

John

Alex Balic wrote:

> The pitch trim jack screw has an internal "switch" that turns it off in the
> particular direction of travel that would bottom it out- possibly this is
> just slightly out or the contact is burned, hard to tell- not sure if you
> could even open it up to check that - you might want to do some
> experimenting- see if you run it all of the way to the bottom and you force
> it if it might move just a bit more and loose contact internally, after
> relieving pressure, apply pressure in the opposite direction-  might move
> back just a tiny bit to regain contact again- just a guess......
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of John Dibble
> Sent: Wednesday, February 15, 2006 10:46 AM
> To: Velocity Aircraft Owners and Builders list
> Subject: REFLECTOR: Pitch Trim Mystery
>
> Seems like when the Reflector has a what-if discussion, soon after someone
> has to go
> out and experience it.  I guess the pitch trim failure had my name on it.
> Last night
> I flew 1.7 hrs at 180 kn with the pitch trim pegged at down trim.  I cut
> power just
> enough to descend at 500 fpm and kept the trim pegged.  At 5 miles out I
> slowed to get
> set up for landing and noticed the pitch up trim wasn't working.
> Fortunately I've
> flown at night enough, so that that didn't add much to the problem.  I had a
> 5000 ft
> runway and a direct 10kn headwind which was a good thing.  Didn't know how
> long my arm
> would hold out so I took the fastest way in and kept my speed up to 90kn.
> Wasn't sure
> if I could hold it off at 70.  The landing was a little rough, but I've done
> worse.
> Today I checked it out and the trim is working fine.  Can anyone tell me
> what
> happened?  I have fuses and no CBs so it wasn't that.
>
> John
>
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