Winglet and aileron vibrations

[mikelongez]

Hello, glad to be here!!! I have bought an used Long ez, It flies quiet well but I have to do some work on it. One of my concerns is a vibration on the winglets and the ailerons, mainly on the right side. First of all I balanced the propeller, Second I did a dynamical balance and now I'm thinking to change the engine mounts. The vibration happens in flights and being on land with full power. I will greatle appreciates any idea. Thanks. Michael

[go ez]

I'd check the 3 wing mounting bolts each side (and particularly the starboard) are snug ( first wiggle the wing tip to see if there is any play). I'd also check the aileron max weight and mass balancing of the ailerons are according to the plans/CP notes.

When removed and are suspended on wires from their hinges, check whether they float nose down within Rutan's prescribed angle limits - ie at an angle which is between the top aileron surface being level and the bottom aileron surface being level.

Regards
Steve

[Rodney]

Make sure there is no contact between the engine and the cowling.

[A. Bruce Hughes]

Hi Mike

You committed the sin so common on this website; You did not say where you live.
Give us that information and we probably can get some help to you.   If you just
give the state, the CSA probably has a state representative for you.   You DO
belong to CSA don't you?   It is the best $30 you will spend on aviation.   You will
get a directory of 736 members (and some have joined since the directory went
to press) .   And you get 4 newsletters/year.

Good luck on finding the problem.

Bruce Hughes   

[go ez]

From CP 52 page 5

We recently heard from a Cozy builder who had been chasing a minor but
annoying vibration in his aircraft for some time.  He finally traced it
to the fact that his wing attach bolts were slightly loose allowing his
wings to move a little in flight.  After he tightened the three 1/2"
bolts in each wing (the Cozy uses the Long-EZ wing and wing attach
system) the vibration went away.  He checked several Long-EZs in his
area and found a couple of them with the same problem.  We had not had
anything like this reported to us before and we checked the two Long-
EZs we have here at RAF, both were solid.

The way to check for this problem is to have someone put their hands on
the joint between the centersection spar and the wing to feel for
excess movement while you lift at the wing tip.  A small amount of
movement, less than 1/16" at the wing root leading edge, is normal.  If
excessive movement is detected, you must remove the wing bolt covers
and torque the bolts.  It is difficult to use a torque wrench in this
area.  We simply used two ratchet wrenches, each 6" long, and pulled
about as hard as we could.  It takes two people to do it right.

Since a person can pull with about 75lbs of force with one hand, we can
calculate the torque - 75x5=375in/lbs or 31ft/lbs.  Using this method,
we have never had one of these bolts work loose.  A 1/2-20 aircraft
bolt can handle 600in/lbs (50ft/lbs) of torque.  However, with the
glass plies in between the aluminum hard points, we would recommend no
more than 400in/lbs (33ft/lbs) of torque on these bolts.

Regards
Steve

[mikelongez]

Thanks for all of your answers.
Steve I have already checked the 3 mounting bolts and they are perfectly, I still have to check the max weight and balance of the ailerons, but I think that the problem should be somewhere else because the winglets are vibrating too. 
Rodney, I have run the engine with and without the cowlings and the vibration is still there, but thanks too.
Bruce, I live in South America, and we are only two of this marvelous machines flying around here.

Any other suggestions are welcome, and again thanks for all your help and concern.

Mike

[Bill James]

With the engine off, check the 4 extrusions going into the firewall for movement; they may be broken inside the firewall where the crack wouldn't be visible. Get a good view and check for movement of each extrusion as the engine is pushed left and right, up and down. Check the extrusion bolt holes on top of, and underneath the spar if you can.
Also with the engine off, check the prop track using a chair or other stationary object to match the tip arc.

With the engine running, visually check the track when standing by the winglet, at idle, and with some power.

Checking these items on a new plane, with all the noise and commotion and whirring things, one is in an extremely vulnerable position to become distracted by potential faulty items and such, and forgetting to be exactly deliberate when moving around the prop. I suggest having the same initial step to any and every entry into the proximity of the prop area whether the engine is running or not -  Stop and repeat out loud, "Yes the engine is off, Yes i do intend to walk up and stand right there, Yes the prop stationary."  Extreme deliberateness each time. In a former life one of our best crew chiefs swung under the tail boom and stood up into the tail rotor. He had done it dozens of times with the rotor stopped. Sorry for the downer. And for likely suggesting something you probably already do. I am reminding myself again.
Good flying-

[rglos]

Here is a couple of more suggestions

Use the thicker washers under the head and nut on the bolts on the ailerons. This is to insure the nut is not bottoming out on the threads. This can be misleading. A bolt that is bottoming out on the threads will "feel" tight.

Remove the prop completely and run the engine. It will not hurt to do this. Don't go to MAX RPM however.
If the vibration disappears you can then narrow down your search.