Tomas J

Tomas J

Active Member
The elevator trim on my RV4 is a little bit loose. Not the hinge, but the wire to the lever in the cockpit allows the trailing edge of the trim to move about 1/4", depending on a play in the wire for about 1/16". Is that normal and okay? I'm a bit worry about flutter...
I have not been flying yet, but will in just a couple of weeks.

wire_1.jpg

wire_2.jpg
 
Make it tight...

Hi Tomas,
Several years ago I was descending from 11,500 feet skirting my way around Thunderstorms in my RV4. During the high TAS transition going through 10,000' I felt a very strong high frequency vibration in the stick that got my attention. Having never experienced flutter (and being a spoiled F16 Pilot with no real airspeed limits) I contacted Van himself and discussed the matter at length. I wrote up the incident for the former RV newsletter The RVAtor. I posted a link below, reference page 2 of the PDF.

Post flight inspection revealed no damage or anything that would lead me to believe there was a problem. I did however find my manual elevator trim tab with nearly 1/4" free play. I removed it, tightened up the slack and never had another problem.

Later, I owned a Harmon Rocket that cruised at 200 Knots TAS at 11,500' and could easily descend at 220 Knots from high altitudes. It's 3 axis electric trim and tabs have very tight tolerances, no play. Lesson learned. As Van told me in his email, "The trim tab at high airspeeds has considerable influence on control surface movement". Now on RV inspections I pay very close attention to trim tab free play, it can make a difference.

Smokey

www.vansaircraft.com/pdf/hp_limts.pdf
 
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smokyray said:
Hi Tomas,
I did however find my manual elevator trim tab with nearly 1/4" free play. I removed it, tightened up the slack and never had another problem.
Click to expand...
How does one tighten up "free play" in the green trim cables? This issue has been discussed in the forums before and I've never seen a response that didn't indicate this is just the way these cables are. http://www.vansairforce.com/community/showthread.php?t=71068&highlight=trim+tab+flutter&page=4

FWIW, Mike Seager's manual trim RV-7 has the same 1/4" free play on the tab. And every post I've seen where Van's has been contacted, the free play is described as normal.

Still, if someone knows how to take slack out of the green manual cable, please let me know.
 
Me 2...

Hi Steve,
I too faced the same dilemma, how to remove the "normal" slack. I removed my empennage fairing and installed 2 cable anchors in the form of adell clamps at positions which stabilized it better. I then fabricated a .040 elevator exit bracket and used screws to attach it where it holds the cable. This helped immensely. I also fabricated a .032 attach bracket doubler, redrilled it and installed a small bushing. (I have since seen steel brackets on several RV4's I have performed pre-buy inspections on.) I also tightened my trim tab knob friction in the cockpit. All this reduced my trim tab play to almost nil.

Your mileage may vary...:)

Smokey
 
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Retrofited an electric trim control?

Has anybody retrofitted an RC Allen trim motor in in the cockpit?

It looks like a major project to open up the elevator and install the trim motor, and this of course would be the most functional/desirable. But has anybody installed the trim motor in the cockpit utilizing the existing cable set up or would that be out of the question? Too much free play in that type set up? Electric servo not strong enough?

Just a thought.... Thanx
 
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