[precession]

Hi all. Since I'm not the original builder of my 4, I'm hoping this question isn't too ignorant.

This is a picture looking through the inspection hole at my elevator control horn. Hopefully (assuming I uploaded the photo properly) you can see to the right two black marks on the lower face of the rear spar of the vertical stabilizer. Those marks are from the elevator horn contacting the spar when the control stick is pulled to the full aft position. It's the contact of the horn on the face of the rear spar that limits aft elevator travel. I'm just wondering if this is correct. Seems to me it isn't that healthy to have the control horn impacting the face of the rear VS spar (but what do I know?).

That said, as you might guess, I've never moved the elevator during flight far enough to make contact. It only happens during pre-flight and pre-take off when checking for free and clear elevator travel. But I'm still wondering if this is correct or if something else is supposed to limit elevator travel.

Thanks in advance for any input.

Bill

 

[acroboy]

Not long ago I setup the elevator stops on my build. The plans call for an 1/8th inch stop to be riveted to the bulkhead where your black marks are. The control horn is designed for the back edge to impact just like yours, but onto the stop. In my case I had difficulty getting the desired travel and had to grind down the back of the horn a small amount. Even at that, I had to use a thinner stop to get the required travel. If the wear is light for a decent amount of flight hours I would just leave it. If you are concerned about wear on the bulkhead you will need to reinforce the bulkhead with a plate.

 

[acroboy]

I forgot to mention that if you rivet on a stop plate you need to check that the required elevator motion meet the limits called out in the plans. I don't have the limits in front of me but can provide them if you need them.

 

[fixnflyguy]

Install the stop per plans

Likely, the contact occurs during taxi, and I almost always have mine pulled to the stop when taxiing. In flight, seldom unless serious acro. It doesn't look like the stop was installed on yours during build. You will have to pull the rudder and fairing, but I think that's all to do the stop installation.

 

[precession]

Thanks

Thanks a lot Acroboy and Fixnflyguy for taking the time to reply. Sorry I was away from the computer yesterday and only able to reply now. Also I wanted to look again at the docs I have.

When I acquired the plane I got a copy of the original plans and diagrams, but they were missing pages, so I bought a new set of diagrams (but not plans) from Vans. Before I posted, I had checked the VS diagrams and saw no evidence of a control stop, but based on your posts I went back and this time did find mention of control stops on the newer set of diagrams from Vans dealing with the controls (not the VS). The diagram doesn?t provide any detail at all as to the size or shape of the plate though -- just arrows pointing to where the stops should be -- but I guess I don?t need any detail other than Acroboy?s info that you rivet a 1/8th inch thick piece of aluminum plate to the face of the VS rear spar.

Acroboy, I can?t find any reference in my plans to ?the required motion limits called out in the plans,? so if you have a chance to post those that would be much appreciated.

My aircraft has about 1000 hours on it and the VS spar isn?t cracked where the elevator horn contacts it, so I suppose I could leave it, but either way in the future I will be sure to be gentle when pulling the elevator to the stop because it seems to me (stating the obvious) avoiding the possibility of creating damage or cracks in your VS spar would be wise.

Thanks again for your help guys.

Bill

 

[nauga]

Acroboy, I can’t find any reference in my plans to “the required motion limits called out in the plans,” so if you have a chance to post those that would be much appreciated.

I don't have the plans in front of me but my operating manual lists elevator travel as (min/max) 25/30 deg trailing edge up and 20/25 deg trailing edge down. ISTR this was not on the plans but was in what passed for a manual when I set my travel. I can't for the life of me remember how I built the elevator control stop(s) but I'll check tonight. The fairing's off the tail so I might be able to get a decent picture as well.

 

[precession]

Thanks for the reply, Nauga.

I started searching this forum more for references to elevator travel and came up with one thread (http://www.vansairforce.com/community/showthread.php?t=96304) stating the RV4 plans call for 20-25 degrees down elevator travel, which agrees with your operations manual, and another (http://www.vansairforce.com/community/showthread.php?t=99401) stating the up up elevator travel is to be 25-30 degrees, which also agrees with your manual (although that thread dealt with RV9s).

The first thread above, by David Paule, states "the lack of clearance for the RV-4 elevator horns which are supplied by Van's is well documented", and then has some nice pics depicting how he handled the down elevator stop on his 4 (but doesn't discuss the up elevator stop). So it sounds like Acroboy's experience in having to make some modifications to get sufficient elevator travel is not an isolated instance.

In any event, don't knock yourself out on it because I probably don't need any more detail to fashion a plate as a stop for the up elevator travel.

Thanks again all for your replies!

Bill