From: RicArgente@cs.com
Message-ID: <f3500f8f.247d6eab@cs.com>
Date: Wed, 26 May 1999 11:35:07 EDT
Subject: Aileron Vibration
To: lancair.list@olsusa.com
Mime-Version: 1.0

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I did a couple of web searches at various search engines and found the 
following newsletter article.  The web site address is: 
http://www.canard.com/cp/cp58/cp58-24.html  Looks like a LongEze newsletter 
group.

Before this problem, I have never heard of this phenomena (i.e. aileron 
vibration) but seems to be more  prevalent than I had originally thought.  
What's interesting about this article is that the pilot did not feel any 
vibration on the stick although his solution (adding more leading edge wt) 
was one of the suggestions found here in the Lancair List.

Rick Argente
Still searching for a solution...
N360ZR

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AILERON VIBRATION

Below is an excerpt of a letter received at RAF recently. 

"Thanks for all the good newsletters. Just to clarify, I have had aileron 
flutter (see Ed. note). At 10 hours, I noted a lot of aluminum dust behind 
the aileron hinges. In
flight. I visually could see the tip of both ailerons as a 1/4" blur. I added 
leading edge weight and installed the Teflon hinge pin setup. At this point, 
I had no visible
vibration at 2000 ft at 120 mph, but still had vibration at 8000 ft., 160 
mph. It remained this way for many hours of "hauling rides" but less than 5 
cross country
hours. Note: I never was able to detect any vibration on the stick. 

I recently put more weight on the right aileron which was still vibrating 
slightly at altitude. This extra weight was along the outboard end where I 
had previously not
had any. This finally cured the problem. Now the ailerons hang with the top 
surface level. Note: The problem occurred when the ailerons balanced bottom 
surface
level as per plans. Note: Both ailerons had this problem. The left aileron is 
very accurate dimensionally, the right's trailing edge rises 1/4" in the 
outboard 8" from a
straight line. Also, I have a good surface finish, laminar flow, as evidenced 
by wing drop before the vortilons. 

It is very hard to see the trailing edge of the aileron and difficult to 
decide if it is indeed vibrating 1/4" or if your eye is just not that sharp, 
but having fixed it, I can
verify that it was not an optical illusion. 

I feel that many Long-EZ's probably have this problem and their pilots are 
not aware of it. Again, there is no indication of stick vibration 

Larry Bush

EDITOR'S COMMENT 

We have published Larry's letter as he wrote it because we believe he 
experienced the same phenomena described above: Engine/prop excited "forced
vibration" driving his aileron at the same frequency as the engine/prop. 
"Flutter" is an aerodynamic condition and is normally divergent, i.e., 
expands to
destruction. "Forced vibration" can continue as long as the source 
(engine/prop) is maintained near the same frequency as the natural frequency 
of the
aileron. By overbalancing his ailerons to the top limit as called out in the 
plans, he has (1) changed the mass of his ailerons thereby lowering the 
natural
frequency of the ailerons and, (2) repositioned the CG of the aileron 
relative to the hinge, thus reducing the "forced vibration" input. 

LL your ailerons are vibrating at the trailing edge as Larry's were, you must 
add more leading edge weight. Note: We checked several Long-EZs here at
Mojave and none of them exhibited any visible vibration at the trailing edge, 
however, all of them show some signs of aileron hinge wear (black
aluminum dust on the aileron, particularly after flying through moisture). 

Keep in mind that it may be difficult to spot. Have a passenger in the rear 
seat look at the aileron trailing edges very, very carefully. Spend at least 
30
seconds staring at the ailerons in level flight, in a climb, in a descent, 
and in left and right turns. If any vibration is seen, re-balance the 
ailerons 

The easiest way is to get some lead ribbon from a golf pro shop and stick it 
to the top of the aileron leading edges, full span- until it balances top skin
level. Lay up one ply of BID to permanently secure the lead to the aileron 
leading edge. (see sketch, page 15 [50k gif]) 

We would like to thank Larry Bush for the excellent feedback on this 
situation. This is the kind of information we all need to know about in order 
to keep
the large fleet of EZs flying safely and consistently. 
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