Tweet
Re: Bc12d info
We do need to understand that there is more than one failure mode. In a cross wind landing where the gear is pulled away from the fuselage by tire drag a corroded brace tube would be exposed to TENSION failure. If the tire load was TOWARDS the fuselage the compression would tend top cause buckling of the brace tube. A hard landing will cause the gear to spread and again, put the tube in tension.
The big problem is corrosion will cause a stress concentration that makes the failure initiation point really hard to predict. ANY dent or kink in the tubes is cause for real concern because it will weaken the tube. What we need is a way to be sure a tube isn't corroded inside. We can do a visual for external damage. I have never been a fan of drain holes. Kind of like leaning into an inside pitch to me....or drilling a hole in the bottom of your boat to let the water out. One of the things Piper did right was to make the struts fully OPEN on both ends so water drains out and you can inspect inside the strut. Sealing a tube only works as long as it stays sealed and you can verify it.
If I was doing the design today I would make the gear brace removable from BOTH ends so it could be removed and proof tested. If you put a cable in while you test it the test would be cheap and effective. You could even do it on each annual and KNOW your gear was safe.
Hank
If I was designing new wing struts today I would do the same and probably use aluminum for the strut material. It would be easy to design a strut that was no heavier, only slightly larger and much longer lasting than our steel struts, plus it would be MUCH more resistant to dent damage. Too bad we missed out on buying the TC for our planes. Mexico sure isn't going to make the design change.
We do need to understand that there is more than one failure mode. In a cross wind landing where the gear is pulled away from the fuselage by tire drag a corroded brace tube would be exposed to TENSION failure. If the tire load was TOWARDS the fuselage the compression would tend top cause buckling of the brace tube. A hard landing will cause the gear to spread and again, put the tube in tension.
The big problem is corrosion will cause a stress concentration that makes the failure initiation point really hard to predict. ANY dent or kink in the tubes is cause for real concern because it will weaken the tube. What we need is a way to be sure a tube isn't corroded inside. We can do a visual for external damage. I have never been a fan of drain holes. Kind of like leaning into an inside pitch to me....or drilling a hole in the bottom of your boat to let the water out. One of the things Piper did right was to make the struts fully OPEN on both ends so water drains out and you can inspect inside the strut. Sealing a tube only works as long as it stays sealed and you can verify it.
If I was doing the design today I would make the gear brace removable from BOTH ends so it could be removed and proof tested. If you put a cable in while you test it the test would be cheap and effective. You could even do it on each annual and KNOW your gear was safe.
Hank
If I was designing new wing struts today I would do the same and probably use aluminum for the strut material. It would be easy to design a strut that was no heavier, only slightly larger and much longer lasting than our steel struts, plus it would be MUCH more resistant to dent damage. Too bad we missed out on buying the TC for our planes. Mexico sure isn't going to make the design change.
Comment