Martin wire

[Garry Crookham]

Re: Martin wire

Letter from Denver ACO

[flylo]

Re: Martin wire

Problem with stitching is it is NOT approved for stamped rib wings. Even though I tend to roll my eyes at many things the Feds say is "not approved" this one is a good one. The stamped ribs do NOT have the edge of the rib rolled under far enough to clear the stitching cord. The cords will rub on the sharp edge and can be cut by the edge of the ribs. If you are going to rib stitch a stamped rib you need to either roll the edge in far enough ON EVERY RIB that the cord does NOT touch the sharp edge or you need to put something over the edge to protect the cord. Doing this "SHOULD" require some kind of official approval since it modifies the rib and or the covering procedure specified in the Type Certificate. If it isn't shown in the log book you are probably NOT LEGAL and probably NOT SAFE!!!!! That was the safety of flight part of the rant.

The LEGAL part of the rant is that Taylorcraft NEVER approved of rib stitching on stamped ribs. The letter floating around from Dorthy Ferris is for a PRE WAR ribbed wing with stick ribs. Those planes WERE rib stitched. You can use stitches on ANY stick rib wing, even if it is on a post war plane. You CAN NOT use stitching on a POST WAR WING even if it is on a PRE WAR plane! If you stitch a stamped rib wing you are putting your life and your mechanics certificate at risk. If you HAVE a stitched wing wing stamped rib you really should open up the inspection covers and take a CAREFUL look inside for dangling stitching cords. They DO get cut! Remember that Taylorcraft DID allow the substitution of one type rib for another on ANY WING so many aircraft have a mix of ribs. You CAN NOT use wires on stick ribs and you SHOULD NOT use stitching on a stamped rib. There are lots of planes with a mix of ribs, and YES, that means there SHOULD BE wings with some ribs stitched and some with wires.

Hank

I am NOT addressing all of the wings that have STCs or other approvals for screws or rivets. That is a whole different "Kettle of Fish".

Hank, not doubting your word Sir but I've seen it done & done it & never saw any cut cords & what else to do if the wire isn't available & I believe it can be done right & legal. Do you have something from the FAA saying it's not legal? Glad the 160 HP is experimental home built.

[Robert Lees]

Re: Martin wire

Letter from Denver ACO

That refers to an F19, and does not show the "memo dated October 15, 2009"

For a BC12D, good luck in FAA land.

Rob

[Hank Jarrett]

Re: Martin wire

Not going to argue this point, it has been talked to many times before. Many say it is OK because they have never seen a stitch cut by a rib. I have. The fact that you haven't is irrelevant to me. If a stitch rubs on a raw edge of a rib it CAN be cut. Might not, but might. I won't use it.

There is the safety side and the legal side. I ALWAYS follow the safety side no matter what the FAA says when my limit is more strict than theirs. No FAA rep can order me to fly. If they did, I would laugh and walk away. If I say it isn't safe I don't care what the FAA says from their comfortable desk in an office building. I'm not going to do it.

From the LEGAL side if the FAA says I can't do it and I know perfectly well it is safe, well, different story. I STILL can't do it. Get the difference? I can default to SAFER than the FAA says, but can not default to potentially LESS safe. Everyone else can set their safety rules however they want, but that is MY rule.

The letter Dorthy sent (the only piece of paper anyone has ever shown me saying stitching is OK on a post war Taylorcraft) was NOT clear as a blanket OK to deviate from the factory configuration. She told many people it was OK to substitute stamped ribs for stick ribs and stick ribs for stamped ribs. No problem, but I haven't seen ANYTHING that says you can use the stamped rib wires on stick ribs or the rib stitching on stamped ribs. If you have it, POST IT! Like I said, I have seen cords cut by the edge of the rib and I WILL NOT FLY with a stamped rib with rib stitching. If you have stamped ribs with stitching I would strongly suggest you inspect through the inspection holes for dangling, cut cords. IF you find them I would STRONGLY suggest you NOT fly with them, but that is just me. Up to you. The looking doesn't cost you a thing. If I'm right it could save you an unpleasant arrival. If I am wrong, it still didn't cost you a thing.

As I said at the front of this post, I will not argue the point. To me it is like arguing with someone telling me my hand won't get burned if it put it in the fire. I have no intention of being the proof that he is right or wrong. Do you feel like putting your hand in the fire?

Hank

[Garry Crookham]

Re: Martin wire

For a BC12D, good luck in FAA land.

Rob

Guess I must be lucky, had no problem using the letter. In spite off all the bad press the FAA receives they have many talented people and have been very helpful. During my 50 year involvement I've run into a few less than pleasant FAA employees but most have been easy to work with.

[Garry Crookham]

Re: Martin wire

From the LEGAL side if the FAA says I can't do it and I know perfectly well it is safe, well, different story. I STILL can't do it. Get the difference? I can default to SAFER than the FAA says, but can not default to potentially LESS safe. Everyone else can set their safety rules however they want, but that is MY rule.
Hank

And this is from the guy who said an IA can easily do half a dozen Annuals in a day.

[Hank Jarrett]

Re: Martin wire

And this is from the guy who said an IA can easily do half a dozen Annuals in a day.

That was a special case where we wanted to do several of the same make and model planes at the same time with a group of owners doing the assists. The IAs time was used in a day. The total man hours were more than just his time. There can be huge efficiencies when you batch load work.

Again, not going to argue the point. If you don't think it can be done safely I would suggest you shouldn't try it or even think about it.

Hank

[waltermrich]

Re: Martin wire

The Taylorcraft wire not being available I used rivets with DER approval, works wonderfully

[Edwin Otha]

Re: Martin wire

I look at this on a case by case method. The wing needs some kind of fabric attachment device and procedure. Any way, with in reason, is acceptable as a minor alteration. The problems come in when the method of attachment becomes damaged. At that point the installation is not airworthy and needs to be repaired. The owner/operator needs to know this information before they deviate from any installation or STC.
The same would hold true if the wire was in a damaged condition. It will require repair prior to returning to service.
EO

[Jim Adams]

Re: Martin wire

Havent figured this out yet but getting close

[Scott]

Re: Martin wire

Yes, useful to pour some water instead of gasoline on this fire.

Here is the one and only rib stitch I found damaged after fifty years,thirty in service :

http://1.bp.blogspot.com/-_pF3YBcveuE/VJumohxJPdI/AAAAAAAABEk/RrqmJN1GFHw/s1600/DSCN2680.JPG

Even though it was not polyester lacing, it had a long way to go before failure, and a single failure is not going to cause any problems. I did a little experimenting with the flat polyester lacing I used, trying to cut it on the flange of a wing rib. Basically as long as the rib had been properly deburred, it's not going to hurt the lacing. Worth remembering that by the time all the coats of dope, poly, or Stewart are applied along with tapes, there just isn't going to be any movement. The fabric is effectively glued to the ribs. I added the anti-chafe tape for good measure.

From a risk perspective, has there ever been a fatal or even none-fatal accident caused by chafed rib stitching? Even in the linen days? I'm sure this doesn't even make the top 100 risk factors for GA.

Univair produces replacement ribs for various aircraft... stamped ribs to replace truss ribs. Their only stipulation for rib stitching is to stitch the whole flange ie don't go through the holes drilled for other fasteners.

There are a few things to be concerned about from a risk perspective, with these old birds, fabric fastening is not one of them. As can be clearly seen at the beginning of this thread, it can be messed up considerably and the only problems are how the next guy is going to fix it.

[Scott]

Re: Martin wire

That refers to an F19, and does not show the "memo dated October 15, 2009"

For a BC12D, good luck in FAA land.

Rob

This is from the 337. Pretty straightforward really. The F19 is an evolution of the type, has for all intents and purposes the same wing and the aircraft has a VNE 10MPH higher than the BC12D.

The 337, the FAA Memo, the Polyfiber Manual, AC43.13-1a, to which they both refer, other 337's that are out there, constitute "acceptable data" in my view. More than enough to support the modification and whatever certification is required.

Note that one of the reasons for the modification is to "eliminate damage to the wing ribs during removal and installation of the wire." I would be interested to hear from anyone who has found undamaged ribs. Most of the holes in my ribs were keyholed, meaning that even new wire would be compromised had I used it.

[Scott]

Re: Martin wire

Havent figured this out yet but getting close

You got a ways to go yet!! Nice job so far

[Ray36048]

Re: Martin wire

I still don't know why someone does not take ownership of the old STC to use screws.

[3Dreaming]

Re: Martin wire

My take on this is that it would take multiple stich failures on multiple ribs for there to ever be an issue. For an airplane to get to that point someone would have to be negligent in performing annual inspections. And I do know that ballooning fabric can cause an accident.

As a side note I know of someone with a Cub, who years ago in the days of cotton fabric, took it in for a annual inspection. Most of the rib stitching had been chewed by mice. The IA showed the owner how to tie a rib lacing knot and sent him home with the airplane and a roll of rib lacing cord.