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Manual Trim Issue

Bubblehead

Well Known Member
Yesterday when approaching to land I pulled power back and started running my manual trim nose up to trim for approach speed but I never got the speed change I expected. I ran it all the way out and had to hold back pressure for the landing. I was ready to do a go around if needed but the landing worked out fine. I wish I had left the trim tab where it was so I could look at it after landing but I did not.

After parking the plane I got a little help from a local mechanic and we cycled the trim full up to full down and then did it with a little pressure on the tab and everything worked fine.

The mechanic mentioned that some manual trim systems include a clutch in them that can slip so that the pilot thinks he is moving the trim tab but is just turning the knob. He does not know RVs.

Hence my posting to the forum. Has anyone else had a similar experience?

BTW I am in Talkeetna, AK today. Am doing my bucket list flying vacation from Texas through Alberta, BC, the Yukon and into Alaska. Very interesting, tremendously beautiful, but with challenging weather. Definitely not Texas "severe clear" flying.
 
More info - I was the only person in the plane, I had about 30 lbs in the front baggage compartment and nothing in the back. ForeFlight wt and bal showed I was still in the envelope but on the nose-heavy side. Maybe I just don't have enough trim authority at fwd cgs and need to move stuff behind the back seat.
 
no clutch on the RV manual trim system.
you probably just ran out of trim. Not uncommon with forward CG 8's.
 
Thanks Mike. The more I think about it the more I think you are right. I rarely fly without traveling bags and stuff in the back, or a passenger, and on this trip I have extra tie-down material in the front baggage compartment. I am within the cg envelope but ran out of trim.

BTW I now have 998.8 hrs flying this RV and tomorrow will go over the 1000 hours mark. The plane has more - I am the 4th owner and have had it for 11 years.
 
Look at the base of your trim control knob. There is a nut on the cable housing that screws to the base of the trim control knob. Make sure it?s tight. Before I converted from manual trim to electric trim I had that cable nut become loose and then off the trim control knob (twice). If it happens in flight you?ve got your hands full of aircraft, but it?s still controllable. However, it?s feels strange to release stick pressures to land.

Had that happen which is one of the reasons I converted to electric trim. I love my electric trim system!
 
Solo I always put my tiedowns, oil, tools and any luggage in the back for better CG. In your configuration I would run out of trim but my knob will stop turning.
 
You will get better fuel economy with the G of G aft, rather than forward. The only reason to have weight forward is if you are getting too close to the aft C of G.
 
I gave this a lot of thought and I am sure the problem is that I had nothing in the back and more than normal stuff (tie down, oil, some tools) in the front. I appreciate all the information. It is very rare for me to be solo in the plane without luggage etc. in the back that I guess I never had the cg that far forward!.

TankerPilot 75 - I will check that nut too.
 
The only reason to have weight forward is if you are getting too close to the aft C of G.
The other only reason is convenience. Tiedowns and gust locks are quick and easy to access at a stop.

Another only reason is for a small oxygen bottle if one doesn't have room inside the cockpit.
 
TankerPilot 75 - I will check that nut too.

One more thought. Take off the panel on the bottom of your horizontal stabilizer that your manual trim cable passes through to your elevator trim tab. The trim cable housing should have a secure attachment point (nut) that hold the trim cable tight so you can adjust the trim tab connection for proper operation. There should also be a jam nut to lock the connector. Ensure everything is correctly adjusted, secure and the jam nut is tight.

If you?re running out of trim authority it could be something has slipped.
 
One more thought. Take off the panel on the bottom of your horizontal stabilizer that your manual trim cable passes through to your elevator trim tab. The trim cable housing should have a secure attachment point (nut) that hold the trim cable tight so you can adjust the trim tab connection for proper operation. There should also be a jam nut to lock the connector. Ensure everything is correctly adjusted, secure and the jam nut is tight.

If you?re running out of trim authority it could be something has slipped.

And related to the above is the old SB on the manual trim "mount" nut:
https://www.vansaircraft.com/service-information-and-revisions/sb-06-9-20/
 
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