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FAA Not Approving T-88 Structural Adhesive Use on Stinson Restoration

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Meighan Chisholm
(@chisholm)
Posts: 12
Active Member
Topic starter
 

Recently found out that the FAA has stopped approving the use of T-88 on certificated aircraft (O.K. for Experimental aircraft). My Stinson 10A restoration is just about ready for cover. After working on it for several years, it may become a museum static display only!!! I guess I didn't need to overhaul that 4AC-199-E3 engine after all. The EAA is trying to help to resolve this. I can provide the reference documents that my local FSDO is referring to if anyone is interested. In the FAA Form 337 I submitted to get the T-88 approved, I attached several previously approved 337s to help (from other FSDOs) but to no avail so far.

Any suggestions appreciated. So far suggestions are to either convert the plane to an Experimental, or redo the project using Resorcinol (like that originally used).

M.K. Chisholm

 
Posted : 12/03/2019 5:10 pm
admin 1
Posts: 37
Eminent Member
 

Please excuse my ignorance, what is T-88?

Is this it? https://www.systemthree.com/products/t-88-structural-epoxy-adhesive

What would you be using it for?

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Thank you.

 
Posted : 13/03/2019 2:01 am
moffetb
Posts: 557
Prominent Member
 

I believe for the wings. In baby Stinsons the wings are wood.

See section 1-4 here: https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_43.13-1B_w-chg1.pdf

1946 Stinson 108-1, Franklin 165, at one time NX8306K

 
Posted : 13/03/2019 4:11 am
lawheelock
Posts: 774
Prominent Member
 

Which and where FSDO not approving? They are not created equal!
This may need to be challenged to higher authority if you have previously approved documentation for certified aircraft.
As an aside, FSDOs get bent out of shape if you ask for approval AFTER you have already done something. If you already had your wings done before asking, that may have offended them!

Larry Wheelock, A&P/IAStinson 108 N584LW 180 LycTexas in Winter; Indiana in Summer

 
Posted : 13/03/2019 5:19 am
Meighan Chisholm
(@chisholm)
Posts: 12
Active Member
Topic starter
 

The T-88 Structural adhesive is the System Three Resins product. In checking with them, they provided more previously approved 337s, but to no avail.
The FSDO is Baltimore. In the past they have been excellent, but recently they have started saying that their "Hands are tied" by constraints placed on them by recent FAA guidance flowed to them from higher up.
It is very true that it is best to discuss any planned alterations from the original Type Data Sheets with the FSDO inspectors prior to making the alterations. They don't like being surprised when the 337s are presented. They have been aware of my restoration project and my plans for three major alterations for some time, but my discussions evidently were not detailed enough until I actually presented the T-88 337. I think that if I had been to the 337 stage and submitted 18 months earlier, there would have been no problem because they were approving T-88 on certificated aircraft then.

The T-88 is used for attaching the spruce spar doublers onto the one-piece spruce spars (they are a 1" thick "plank" for the full length, with doublers "sandwiched" on the sides along the lift strut attachment area). The spars are new. The T-88 is also used to attach saddle gussets at the wooden fuselage former to stringer joints.

The EAA Advocacy representatives are talking with the FAA Small Aircraft Directorate to, hopefully, resolve this so that their policy for wooden certificated aircraft is not different from that of wooden Experimental aircraft.

Thanks for your interest and suggestions

Meighan K. Chisholm Sr.

 
Posted : 13/03/2019 1:31 pm
lawheelock
Posts: 774
Prominent Member
 

Meighan,
Thank you for your reply. Baltimore FSDO? Perhaps they are physically located too close to 800 Independence Ave and perhaps they have some newer, younger inspectors since your first discussion with them. It sounds like CYA prevailed. NO is simpler and safer than YES.

Your comments are interesting as I am repairing (Over a period of several years) a Taylorcraft wing that a mishap had damaged the rear spar. I purchased spar material from Wickes and duplicated the original. I used in accordance with AC 43- 13-1B "Resorcinol is the only known adhesive recommended and approved for use in wooden aircraft structure and fully meets necessary strength and durability requirements. Resorcinol adhesive (resorcinol-formaldehyde resin) is a two-part synthetic resin adhesive consisting of resin and a hardener." I have not yet put the wing back together so I guess I should contact at some point my FSDO in San Antonio to get their blessing on making my spar.

Perhaps you should take a vacation and travel west of the Mississippi river. It seems that western FSDOs are usually much more co-operative (reads knowledgable and realistic)than many eastern ones. I sure would not give up on the airplane being a legal, certified aircraft.

Next question: are you an A&P and or an IA? They seem to much more like to talk with certified mechanics than to "common folks".

Good luck.

Larry Wheelock, A&P/IAStinson 108 N584LW 180 LycTexas in Winter; Indiana in Summer

 
Posted : 13/03/2019 7:55 pm
Meighan Chisholm
(@chisholm)
Posts: 12
Active Member
Topic starter
 

Excellent Suggestions Larry!
My next nearest FSDO is Philadelphia, but I certainly understand a preference for West of the Mississippi 😉
I am a A-P, I.A. and as I am "Arm Wrestling" with the FSDO, they have my I.A. card for renewal!
The FSDO has no problem with my new spars (Spruce ordered from Aircraft Spruce... over $1K but the wood is beautiful...no knots at all, which surpasses the Mil-Spec) because I fabricated them along side the originals and the measurements match spot on. I did not choose resorcinol because it is difficult to work with as far as clamping pressures, temperature and both wood and ambient moisture measurements, as well as it has no gap filling capability. Your decision to go with resorcinol will probably turn out to be a sound one, but please make sure you have adequate respiratory protection while working with it.

I think there are three formulas for resorcinol, but didn't this all begin with the Dehaviland (sp.) Mosquito? I would think the right epoxies would have more advanced chemistry by now. They no longer send old horses to the "Glue Factory" 😉

I'll let you know how this turns out.

Meighan

 
Posted : 13/03/2019 11:06 pm
orange4sky
Posts: 93
Trusted Member
 

I wonder if the change has to do with the collective skills of the applicators rather than the product itself. Epoxy is not forgiving of under mixing. I have seen non structural pieces rendered useless after being laid up by professionals with under mixed west system epoxy. Resorcinol is much easier to mix properly.

Marcus Sabathil: Owner of Skookumchuck Voyageur 108

 
Posted : 14/03/2019 2:58 pm
Alistair
Posts: 113
Estimable Member
 

FYI - do not go anywhere near the PHL FSDO... I have a contact in Harrisburg and can put out some feelers for you if you want...

Al

Al Corden
N97555 - Sid
1946 108

 
Posted : 15/03/2019 8:08 pm
Meighan Chisholm
(@chisholm)
Posts: 12
Active Member
Topic starter
 

Thank you Al.
I will try to attach my FAA 337 if I can figure out how. If you don't get it. You could let me know the e-mail address that I should send it to.

Best Regards

Meighan K. Chisholm Sr.

 
Posted : 15/03/2019 8:51 pm
Alistair
Posts: 113
Estimable Member
 

Let me test the water first... I'll let you know.

Al

Al Corden
N97555 - Sid
1946 108

 
Posted : 17/03/2019 5:31 pm
Meighan Chisholm
(@chisholm)
Posts: 12
Active Member
Topic starter
 

Thank you very much Al !

Meighan

 
Posted : 17/03/2019 6:15 pm
lawheelock
Posts: 774
Prominent Member
 

Meighan,
If you can, send me a copy, too. If for no other reason, for my reference. If Al can't help, possibly I can. I got help on another matter through a person in the Alaska FSDO calling mine here in SAT.

My email is: lawheelock@earthlink.net

By the way, I got my IA card renewed at an IA seminar in SAT on March 6.

Larry Wheelock, A&P/IAStinson 108 N584LW 180 LycTexas in Winter; Indiana in Summer

 
Posted : 18/03/2019 5:13 am
Meighan Chisholm
(@chisholm)
Posts: 12
Active Member
Topic starter
 

Thank You Larry!
I am sending the 337 now.
Meighan

 
Posted : 18/03/2019 11:36 am
Alistair
Posts: 113
Estimable Member
 

Well, that was a dead end I'm afraid, hopefully Larry can help...

Al

Al Corden
N97555 - Sid
1946 108

 
Posted : 19/03/2019 12:40 pm
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