Bad vibration on wing strut

[ricky]

Any t craft owner ran across plane with bad vibration on wing strut,an in the cabin, Engine ran great,just bad vibration

[fearofpavement]

Re: Bad vibration on wing strut

please provide more data. Did this just start on a previously vibration free aircraft or has it done it since you owned it? Have you tracked the prop? Looked at your engine mounts? Checked for security of all the airframe parts like empenage wires, etc? Any changes made recently?

[magman]

Re: Bad vibration on wing strut

I flew a Tri-Pacer with a "WingTip Shake".

Turned out to be LOOSE Drag/Anti Drag wires.

[Ragwing nut]

Re: Bad vibration on wing strut

would it be a right strut with a door catch added?

[ricky]

Re: Bad vibration on wing strut

Brought t-craft in09,05 plane flip on it back,wing strut front were bent, wing
spar on left had horizontal crack on top of strut fitting.
Use my other wing to use when other wing are fix, the wing I useing now is
rebuilt on both wing,left has new spar,new hard ware were instal as to t-craft manual,they were freshly cover,inspect before cover started
We ran the original engine with new wooden prop,the other metal guy try to fix,over straighten it, it vibrated strut,insde cabin, it got bad at 1800 to 2000
on flight home,
As I had spare 65 for my other project,switch engine,same thing,cab an
strut vibrate,this 2nd ingine has flange,other engine as taper flange, notice
in fire wall guy install insulation in,between the ffrane an the boot,Rick

[barnstmr]

Re: Bad vibration on wing strut

Ricky,
You must take this very seriously and investigate. Vibrations are BAD. I would NOT fly again until you get to the bottom of this. If it is enough to feel in the seat, the loads must be pretty high. Any loads that severe are traveling through the structure and if you have any part in the load path with a nick or scratch, a crack may form. Vibrations accelerate the growth of fatigue cracks.

It is hard to diagnose with the limited information you have provided. Prop balance/tracking are certainly worth checking. Also look at your engine mount rubbers and security of the attach bolts. Vibrations can present themselves in unusual ways on airplanes. Sometimes the part you notice shaking is nowhere near the source.

If the shake is enough that you can and already say it is the wing strut, what do you mean? Can you see the strut shaking? I am with MAGMAN, it sounds like you could have something wrong with the security of the wing structure. After checking over the prop and engine, I would be cutting out inspection holes in the wing, checking hardware, attach fittings, tie rods, etc. We had a tie rod come loose one time just outboard of the outer wing strut attach points. We didn't even know about it until it was noticed while washing the plane. It was simple enough to fix the problem. The nut on the forward end had just worked its way off.

Anyway... be safe out there and check this out.

[Pearson]

Re: Bad vibration on wing strut

Ricky,

As I understand your last post, you have replaced the engine and BOTH wings. Is that correct??? If that is the situation, I have a couple of suggestions.

See if there is any movement at each wingtip when you apply very LIGHT up and down, and then forward and aft movement. I suspect you have stretched the holes in your wing attach fittings, or the strut attach fittings. Either situation is very very dangerous. Even if you feel NO movement, I would remove the wing root strap and remove the bolts that hold the wing on and inspect the holes in the attach fittings on the wing and the airplane. I would do the same at the strut attach point also. Look for enlarged holes, or bent fittings.

My second area of concern is the adjustment screw on the rear strut. Did you adjust the washout of the wings when you installed them??? Is the adjustment screw still in the end of the rear spar? You didn't by chance put the attach bolt into the slot on the end of the rear strut without an adjustment screw did you?

Terry is right on, DON'T fly until you find and fix whatever is causing this.

[Robert Lees]

Re: Bad vibration on wing strut

Some of you might recall I had a similar problem 8 years ago with my 1941 BC model. This was a fore-and-aft single sinusoidal harmonic vibration of the rear struts, with the node at the jury strut attachment.

We cured it by nipping up the strut attachment points all-over...i.e. at the spar; the fuselage and the jury strut fittings. Perhaps one was too loose.

We could only surmise that it was a harmonic problem at a particular airspeed/engine rpm issue...it only occurred towards the upper airspeed scale.

But it did not return.

Since then, we fitted new struts (as a result of the strut AD), and it has also not reappeared since then.

[fearofpavement]

Re: Bad vibration on wing strut

I would follow some of the suggestions posted and make sure nothing is loose before you fly. However, a problem like this may not be able to be resolved without additional flights. If you don't find a cause on the ground, one thing you can do when you are up flying is determine if the vibration is coming from the airframe or the engine/propeller combination. If you are at cruise speed and seeing or feeling the vibration and change the engine rpm (ie, reduce power) the vibration will change frequency if it is is engine or prop related. To confirm this, descend enough to maintain the same airspeed. If you increase the power, the vibration should then again change and return to what it was at cruise. (again, adjust pitch to maintain the same airspeed.) If the vibration does NOT change with engine rpm, try flying the plane at different speeds and see what happens. If the variations in airspeed cause the vibration frequency or amplitude to change then there is something on the airframe that is inducing the vibration. My guess, is that if it an airframe induced vibration, it is something in the tail area, less likely to be the wings. There are LOTS of things that can cause vibration in an aircraft just like in a car so narrowing it down is important to zero in on it.

[mike lutz]

Re: Bad vibration on wing strut

If your t-craft is a pre-war with the little flipper trim tabs under the tail,be sure to check that the mounting holes are NOT enlongated.I know from experiance that this can cause a very noticable vibration.If it was the tab on the elevator you would feel it in the controls.The little flipper trim tabs will flutter if the holes enlongate,and wont be felt in the controls.Also,you might try a different prop.Sometimes removing prop and reinstalling it 180 degrees from where it was will help also.

[Hank Jarrett]

Re: Bad vibration on wing strut

Herman (fearofpavement),
Sorry but I have to STRONGLY disagree. What you are talking about is isolating the vibration through flight test which is some of the most DANGEROUS flying possible. Flutter is a killer and the strut vibration could be the indicator of the big failure just around the corner.
I would go closer to Bob Lees suggestions and keep looking for a cause (ON THE GROUND). Move the strut up and down gently and look for something loose. A jury strut with play in it would be a prime candidate. Oversize or elongated holes at the spar or strut attach is another (and a potential KILLER). Check the hinges and pushrods in the ailerons for play. Are the ailerons out of rig? Cables tensioned right? How about the jury strut fittings where they thread into the wing compression tubes? If those threads are not solid the struts can vibrate. How about cracks in the spar? Any indication the wings have ever been hit at the tip (even TINY damage! That is a LOOOONG moment arm).
There is SOMETHING wrong. The first step is to find something causing it, NOT to fly and watch it happen some more. Keep looking until you are sure you have found something the could be the cause.
Test pilots get paid a LOT of money, because some of them DIE, SUDDENLY. This is the time to be as conservative as you can. DON'T fly it till you find the problem!
Hank

[ricky]

Re: Bad vibration on wing strut

Thank guy's. both engine have low time,one perpellar was bent,anthe new wood prop was install,both has vibration, but the trac on both prop was true.
Metal prop went to prop shop

The both wing were rebuilt,my ame spent lot of time in checking my work,
makeing sure that bolt were all tieten up,the bolt threw the front an back
fitting by root in has no play at all,when I move it up an down,while ame was at the root fitting.

The drag wire were tiehten up,an put black tape in middle of drag wire,an the stop nut,

where going to use an nother prop,that my ame use in one flight in his luscome have no vibration at all,metal prop,foe 65 continnital.

I'll keep you all posted this weekend see what happen,than guy for your input on this matter.
Rick

[ricky]

Re: Bad vibration on wing strut

Hank,there was no crack in the spar,two new one install,pre cut drill at the
talorcraft le grange shop,the two that replace,that the other ame put filler by the front wing root bracket, decided to replace both, before wing were install,
we did run up with out the wing,the vibration was there,.

Could any you guy tell me,the other owner put insulation in the cabin,
the insulation is between the frame of fusledge an the boot cowel,is that ok to have,that leave tight space beteen frame an boot. it not a space,but insulation is quash agaist the boot

[ricky]

Re: Bad vibration on wing strut

fearof pavement,when the engine is at idle,no vibration,as I did run up ,instilly the vibration start,that was with or with the wing on.

[barnstmr]

Re: Bad vibration on wing strut

I am not sure I understand exactly what you are trying to explain about the insulation between the boot cowl and the frame. But you must have a solid metal-to-metal contact between the engine mount and the fuselage frame.