Composite Joint Allowables

[edmeister]

What a wonderful profession !
Involved with construction of Cabin VIP interior monuments (Galleys; Wardrobes; Lavs ..)
Recently learned that Joint (Pin & Insert as well) allowable values are not readily available & each STC endeavor requires another set of Coupons to be sent out for testing.
- It would be nice if a few coupons of geometry would suffice - but alas .. in this one case im dealing with 500+ Test coupons for 5 different panel combinations..
The cost of the testing will exceed the material cost of the panels! A Short & long beam bending of each panel type 'may be available' by the vendor - but the joints & insert allowable have to be tested .. argument that panel build; adhesive batch; construction process is always a variable - and cannot be assumed to be consistent.
Initially I presumed that when the data was obtained for 1 aircraft STC - it could be used for another project .. Again Foiled!
Test Data & Test Report pertains to a unique ODA project number - thus non transferable ..
Fortunately the customer has deep pockets .. because i sure do not!
Any thoughts about obtaining data without signing off the kids college fund!

 

[rb1957]

if it is your STC (so you have all teh data) then I'd've thought it was reusable. If it's someone else's STC then it is not transferrable (since you don't have the data).

I'd've thought that you could do some standard joint designs, instead of doing a different joint for each design.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[SWComposites]

If your company owns an STC, and the material/process/design are the same for a new STC project, data for the previous STC can be used for the new STC project. Just like any other internal company cert program.

Now if the previous STC is tied to a customer project number, and you now have a new customer, then you are probably screwed.

Provide more details and perhaps we can help.

 

[Sparweb]

How likely are the margins to be close to zero?
If your interior is over-designed, then you can live with A-basis values with an enormous knock-down to get to the 95% confidence - read: allowables much lower than average value because you used a small batch of coupons. Saves time and money if you don't need to spend it.

I don't get why you aren't re-using test data. I do this all the time. Maybe what you're doing is stepping so far away from the scope of what was done previously that the relationship doesn't exist. If I intend to re-use test data from the past, then I DON'T swap aluminum for fiberglass facings, DON'T swap Fastweld for EC1357, DON'T swap NAS inserts for Shur-loks, and I tell my designers to stick to the stuff that was tested already.

Assuming you are referring to 1 (one) STC certification program that was completed in the past and currently working on 1 (one) STC certification program in the present, AND in BOTH cases:
- aircraft certification basis is the same
- types of interior structures are same or similar
- materials used in assembly are same or similar
- process standards for fabrication & bonding are same or similar
...Then for each of these comparisons that are not true, it gets harder to re-use the data from the previous test program.

 

[edmeister]

Im associated with a Canadian MRO - but spend majority of our Engineering with FAA DERs & ODAs. Apologize in advance if i drag simple concepts to excessive details ..

At this time we require to send our coupon to a US Testing facility. They require an ODA Project number for their Test Report. Our desire is to have this data transferable to other projects for other customers without having the requirement for retest. We also would like to design this test program so our data could not be used by others organizations as well.
Acknowledge that Panel build & supplier is a 'Constant'; Adhesive also 'Constant' - only variable here is our in-house process for constructing the coupons -
Retaining this process (not allowing others to duplicate the assembly instructions) to will prevent other from using this data.
- Yesterday I was informed the testing facility could issue an 8130-3 for the test results without a tie-in with an ongoing STC project ..
itemizing panel PN, adhesive, our in house construction process & their test equipment & facilities only..
.. any comment on this ?

 

[SWComposites]

ed -

so the test house has a DER that will issue an 8130-3? Seems like a good way to go without tying to a specific STC project. And even if it was tied to a specific STC, if nothing changes there should be no reason why you can't reference the test report for another STC project.

 

[edmeister]

This is fun part of this business ..
Test House did not admit it can issue a 8110-3 without ODA project #.
- Outside DER believed it could be done ...
considering amount of $$ we paying .. why would the Test house shoot themselves in the foot ..

 

[SWComposites]

ok, but I still don't see what is stopping you from using a test report with an project number on the 8110-3 on another project. The test data is "FAA approved/acceptable" with the form. As long as the material/process/design does not change, should be ok to use on another project.

 

[rb1957]

isn't the project cert plan creating the need for the test, and so the test is tied to this plan/approval ?

But why wouldn't the lab issue a report saying we tested to this standard (whatever you've specified) and it passed ?

Oh, I know ... "more than my job's worth"

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[edmeister]

This is why im attempting to glean the fine details here ..
In my Master Drawing Document List for Job B .. can I can attach the Allowables Test Report previously done for Job A ??
.. noting that the original test report specifically lists the ODA project # for Job A ..
& the customer for Job B is not the same customer as for Job A ?? (nor is ODA/A same as ODA/B)
- only similarity between Job A & Job B is we are fabricating monuments from the same materials & processes ..
- Would this be accepted as a "kosher" method of 're-applying' existing data ?

 

[SWComposites]

so is the job A ODA number from the customer or from your own company (internal ODA)? if the former, you are likely SOL; if the latter then you can just reference it on job B.

 

[edmeister]

In the Canadian system the DAO (ODA) or DAR (DER) opens up a NAPA# which ties in the project to a Federal Transport Canada Registry. I was under the assumption that this ODA file number is a registry to the a FAA system. Any internal ODA reference# is of limited use & only useful dealing with that particular Engineering facility.

 

[Sparweb]

In Canada the NAPA number is a file number, nothing more. It does not connote approval. It's like the project number on your drawing, no more meaning than that.

If you have "approved data" in your hands, then you use it in all the ways that approved data can be used. The nature of the approved data may make it applicable to one aircraft, one product, one material, one fastener, etc. The CARs don't tell you that those uses are confined to just one project. Approved data is defined in the CARS in such a way that allows you to use it as long as it's applicable. The process of generating approved data is also defined by the CARs.

Cross-reference to Part 21 to get the FAA's take on this.

 

[rb1957]

unless the lab limited the test report by contract or maybe an NDA ?

I don't think the FAA has something similar to TC's NAPA ... but they must (have some way of filing projects) ??

They could use the approval number ... I mean projects lead to some approval (so why create some other number ?)

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[edmeister]

I understood that he NAPA # does not constitute an approval.

So general consensus is that Test Data approved under a 8110-3 or STC is 'approved data' irrelevant of the ODA# or originating ODA/DER. It can be used to any project given same material /adhesive and specified process is being used .. Have i flogged the horse dead by now ?

 

[rb1957]

sure, until you come a across a DER with a different opinion !

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[Sparweb]

Yes, consider it completely whipped


And just make sure the data is fully applicable, too.