Citabria right strut vibrates

Rickster51

Rickster51

Member
Joined
Mar 23, 2020
Messages
24
how normal is it for the right rear strut to vibrate in flight it is moving 1/2inch or so up and down rather fast. every thing is secure no cracks, braces or tight and the inboard fabric on both sides vibrate so bat im loosing inspection pnls
 
Doesn't sound good. Fabric in the slip stream takes a beating, and you may need a PK screw in inboard inspection plates, but that srut would worry me. Check for a twist - something that would vary the angle of attack of that streamline tube from one end to the other. And check the jury strut where it bolts to the spar.
 
Just watched your video on the fabric when was this covered? I am no expert or even say I have good knowledge but a few questions, how long has it done this? if it just started then I would have someone with great knowledge look at the structure and see what changed. It would appear to me it looks like it wasn't shrunk completely when covered or did this just start? how does the other wing look? When on the ground does it seem loose to you compared to the other side? Keep us informed on what you find.
 
I just got this plane have flown it 3 times now got 3 and one half hrs in it , ok so i took the vented inspection plates off that where under fuel tanks replaced them with dome pop plates and the fabric has stoped vibrating, i also got a door post and installed it and it stoped the rear strut from vibrating
 
that little post on the strut stopped it? that's probably good but I don't think it should have been vibrating in the first place.

If you go out to the wing tip and gently push up or down is there much play? weird noises? If you gently push and pull the rear strut is there any play? any weird noises?

That rear strut has a single bolt through the top of the strut that then goes through the rear spar. I'd take a look at that to make sure it's all tight and that there's no play. Like Bob said, look for twist in the strut also.

Maybe it's nothing but it definitely deserves a good going over.
 
I was staying out of this but I don't think the op has a serious problem.

A couple of years ago I was on a cross country in my plane and took some pictures of mount Stuart out my left window. And a few more out the right.

Looking at the images later I couldn't help but notice that my left front strut was blurry. Over the next few flights I studied it carefully and there is all almost imperceptible vibration on the section between the fuselage and the jury strut. Had I not caught it on "film" [cough], I would be sitting dumb.
Well I might be sitting and dumb, but I've read about these conditions before and many times they are extinguished with a strip of grip tape on the strut. So the door catch doing the same isn't so crazy.

As a guitar player and guy who drives over the Tacoma Narrows bridge (aka galloping gurty) I'm going to say it's a harmonic resonance thing.
 
Harmonic resonance is not a good thing for an airplane. You might have been looking at propwash vibration.
 
I think, in general, a persistent vibration in a structural member is undesirable. Not knowing what is normal for the entire fleet of these aircraft though, it's hard to say what's bad and what's acceptable.
 
lt was a Harmonic resonance and yes it is the down wash side, the door post disturb the the harmonics so yes its better my naboar took his door post off and at 2400 rpm his started to vibrate door post on it 2 stoped
 
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