strut attachment AD - failed

[fearofpavement]

Re: strut attachment AD - failed

Visualize your strut as a 10 foot long pry bar.

What you don't want to do is move (or allow to move inadvertently) the unattached (upper) end of the strut fore and aft as you will be using your 10 foot "pry bar" to "spread" or bend the strut attach fitting. Being aware of the issue will likely prevent it from happening but your "helper" also needs to be cautioned as to the importance of fore and aft movement. The fitting is steel and fairly robust but won't stand up to that type of force. I don't think you would damage the fitting by tapping the strut end in or out of the fitting with a mallet. Just keep in mind: force in and out ok, force back and forth NOT OK.

[Buell Powell]

Re: strut attachment AD - failed

Jack,
I think all you need to do is have someone hold the strut in line with the wing fitting and push it strait into the fitting(I put a little grease to make it slide in easier and just used the palm of my hand to tap it in place) and keep it lined up when you raise it to fit in the wing fitting. I have never seen a fitting that was damaged but the post about all the force you could put on it by slightly moving the strut side to side and causing a crack makes sense and I have heard of this happening. I dont think you should have any problem at all if you are careful.
Buell

[hangarb7]

Re: strut attachment AD - failed

OK, gentleman, that makes complete sense. Actually, I guess it really would take ounces of pressure at the end of the long "arm" to damage the strut fitting.

Thanks,

Jack Dernorsek

[Greg Guy]

Re: strut attachment AD - failed

Ten years ago I had one of mine replaced because it had been brazed. I either got an NOS attach bracket from Forrest or a guy in southern Oregon. What say Forrest, was it you? If a member needs one I could give the guy a call.....greg

[Guest]

Re: strut attachment AD - failed

OK, gentleman, that makes complete sense. Actually, I guess it really would take ounces of pressure at the end of the long "arm" to damage the strut fitting.

Thanks,

Jack Dernorsek

Yes, that's the theory and I am very cautious about it.

Here's something that did happen to me though.

The right side set of struts got pushed back 20 degrees and simultaniously swung down nearly to the ground.

The inside end of the struts (those 1/4" tabs that slide into the fitting) were bent about 20 degrees.

Now based on this discussion we might expect to see the fuselage fitting split in two, not so. The fitting looked ok.

Nine years later the plane got flipped on its back in a storm, crushed the upper cabin section and during the repair I found that both fittings were nearly identically cracked.

Go figure.

Did the flip over cause it?, the strut bending? prior strut installations?

once they crack a certain amount do they crack no further even if you bend a strut on them?

I never figured it out

At that time Taylorcraft had fittings but would not sell them for liability reasons.

Dave.

[Buell Powell]

Re: strut attachment AD - failed

Dave,
That is interesting. I wonder how much difference it would make if the struts are made from 4130 or mild steel if the fitting would crack or the strut att. ears would bend first?

[flyguy]

Re: strut attachment AD - failed

My struts came with a fairly thick primer coat (epoxy no doubt, very tough) which created a problem getting them to go into the slots on the attach fitting without applying a lot of pressure (like bang and hammer) and visibly spreading the tabs. Solution, I scraped off the primer on the sides of the strut lower ends and it was then a perfect hand-press snug fit. "Bare" dimensions of strut were perfect. One may take care of the bare metal problem as appropriate.

There is a lot of leverage that could be applied to the fittings by moving the upper end of the strut forward or back, but with a little care the problem is not difficult to prevent. I simply fed my struts down thru a heavy tie wrap that was looped around the bottom of the jury strut. That supported the upper end of the strut in place and allowed me to install the strut without a second person helping. Two people may or may not be better, depending on the second person.

Edit: I jumped in without reading Dave's entry above. That is interesting. Sounds like, when pushed to the limit, the fittings sensitivity to fore and aft movement may be less than the strut end's to being bent. When one considers the flat plate re-inforcement on the fitting under tension versus the bending moment of what is really the end of a tube (with a kink in it) the bend you observed make sense.

Really good to hear of a real life "test" of something we may think that we intuitively understand. Good information. Thanks. Needless to say, it makes one feel better about the strength of the fitting.
Darryl

[Guest]

Re: strut attachment AD - failed

Dave,
That is interesting. I wonder how much difference it would make if the struts are made from 4130 or mild steel if the fitting would crack or the strut att. ears would bend first?

Hey Buell,

I never thought of that but you have a very good point. If that tab was 4130 it would be harder to bend and would cause the most distress to the fitting.

I actually do not know the tab material (yet).

Dave

[Larry Lyons]

Re: strut attachment AD - failed

Is this apples and oranges? If you have the bolt with a nut installed; no one ear of the fitting takes the stress. Larry

[Guest]

Re: strut attachment AD - failed

Is this apples and oranges? If you have the bolt with a nut installed; no one ear of the fitting takes the stress. Larry

Larry,

This is/was with the nuts off and some bolts as this is during assembly or dis-assembly. In may case the bolts were undersized too because it was during dis-assembly.

EDIT- when it flipped over the nuts and proper bolts were installed, maybe that infers that flipping over did not have anything to do with the cracks??

Dave