Repair qualification, beyond SRM limits 3

[CoffinsCorner]

Hello

I have a question regarding repairs of structural damage beyond SRM limits.

What qualification will an engineer achieve when taking the following BOEING courses:

"Structural Repair for Engineers - Part I/II/III"

(These courses teaches the engineer to design, and analyze a metallic repair for damage beyond the limits in the SRM)

Will the engineer be "allowed/qualified" to design, on his own, an adequate repair in such a case?

In other words, will it relieve an airline from sending a service request to the OEM (BOEING)?

I hope that some of you could help me get some clarification on this matter.

- Thank you

 

[rerig]

The SRM is Approved Data and if you exceed the SRM limits you must get the repair FAA Approved.

The course will help you to undertand how to substantiate a repair you design. But the Repair must still be Approved by the FAA. Either through an FAA DER or OEM Eng. Dept. with their DER Approval.

Unless you become a DER you can't Approve your own repair.

 

[rb1957]

the boeing courses will "only" give you some information, possibly some understanding of what the limits mean, why they are there, what is causing them. knowing this you should be in a better position to design a repair.

designing a repair using the SRM is only an easy way out, 'cause the SRM is approved. if you can't apply the SRM, you can still design a repair, only now you can't use the SRM as a means of approving it ... you'll need to analyze it (including DT) and have your design approved (most likely with an RDA).

 

[CoffinsCorner]

Thank you guys for the enlightenment!

 

[Sparweb]

...That said, I am told that the Boeing courses are an excellent training experience in airframe repair, and that those who take them can see the issues more clearly. You're lucky to have the opportunity to take these (expensive) classes.


Steven Fahey, CET

 

[Fatstress]

Hello Coffin,

I don't think so. If you intend to design your own repair beyond the SRM limit you will still be required to contact the OEM to get an approval for your design. In other words, you will always be dependent and the SRM is the most they can give you to do things on your own. The repair courses that you will be attending is meant mainly for you to have an adequate background to perform a repair or to interpretate an allowable damage limit acording to the SRM. I have seen a few SRMs, Boeing, Airbus, de Havilland, C-130, etc. Quite different from one another, even from one aircraft type to another from the same aircraft manufacturer. But what is similar, you have to contact them when your repair or your damage are beyond their SRM limits. Anyway, I would suggest you to contact them for confirmation ? I hope it helps.

 

[Kwan]

You can obtain DER approval for your repair. The OEM is not the only option. The stress courses helps you substantiate the repair such that the DER is willing to give an approval. (or OEM depending on which course you will take for the approval).

 

[debodine]

rerig had it right from the very first post. Repairs outside the SRM require FAA approval. An FAA engineer may provide the approval (from their Aircraft Certification Office, usually referred to as the ACO) or an appropriately rated FAA/DER may provide the approval. The OEM is typically one source of an appropriately rated FAA/DER approval, albeit the OEM usually has all the original design data on hand if exotic number crunching is required to substantiate an approval.

Star for rerig...

 

[CoffinsCorner]

Thank you guys for the contributions to this thread.

If we (my company) have a repair outside the SRM limits, then we would make an initial repair proposal, send it to the OEM, upon approval we would carry out the repair, and request the OEM to issue an FAA form 8100-9.

If you have a DER working in your company, can this DER approve the repair by signing an FAA form 8110-3, and then the a/c be released to service?

If this latter method of repair approval can be used, then I guess you would be able to save considerable AOG time?

I work under EASA rules (in Europe), so I do not know how it works in the US.

 

[debodine]

CoffinsCorner:

To clarify and enhance this question you asked:

"If you have a DER working in your company, can this DER approve the repair by signing an FAA form 8110-3, and then the a/c be released to service?"

Let me take this question a bit further and turn it into a statement. Keep in mind that under all circumstances (Part 43, Part 145, Part 21, etc) an FAA/DER only approves the engineering data. An FAA/DER signature is never the approval authority for the actual implementation of the repair/alteration or the final signature to return an aircraft to service. (Keep in mind the function, not the person. There are persons in the industry with both an FAA/DER and the other authority necessary to return an aircraft to service such as an FAA/DAR or part 145 repair station FAA Form 337 authority or under Part 43, an A&P mechanic...but when that person returns an aircraft to service they are NOT doing it under their FAA/DER authority).

For the repair scenario you describe, your statement could be modified as follows to be more accurate:

If you have an appropriately ratedFAA/DER working in your company, this DER can approve the repair engineering data (note the approval of the engineering data only) by signing an FAA form 8110-3, and then the A&P mechanic fills out and signs an FAA Form 337 (under Part 43); or the repair station (under Part 145) has their internally designated return-to-service person fill out and sign an FAA Form 337. The A/C is then released to service on the authority of the FAA Form 337 signature. Essentially the FAA Form 337 signature is certifying that the actual repair on the aircraft was accomplished in accordance with the previously approved engineering data, and that the aircraft now meets all the requirements for airworthiness, allowing return to service.

I hope this helps. If you ever get involved in the STC process and prototyping or major alterations, those are different worlds and I won't discuss those paths here because it will cause confusion. Suffice it to say the modified statement above is intended to provide guidance only for repairs outside the SRM as noted in your original post.

debodine

 

[CoffinsCorner]

debodine:

Nice clarification, thank you.

 

[kontiki99]

debodine,

I'm curious to better understand the role of the DER here.

If your repair goes beyond the scope of the OEM's SRM, the repair is no longer approved by the administrator under the OEM's TC.

So the DER's approval of the data in your description is actually exercising approval authority for the repair defined by the paperwork, on that one aircraft, on behalf of the administrator?

I just never fully understood what "approving the data" meant.

 

[SWComposites]

The DER approves the engineering data that demonstrates that the specific repair for the specific aircraft meets all of the applicable FAR requirements. "Engineering data" includes material properties and allowables, methods of analysis, loads, the static strength analysis of the repair, the damage tolerance analysis of the repair, etc. The "problem" is that a non-OEM DER may have difficulty obtaining some or all of this "data" without assistance from the OEM. In some cases, a very knowledgable person can reverse engineer the original structure to a sufficient degree to develop acceptable engineering data.

 

[debodine]

kontiki99:

Your two statements are correct. A repair outside the SRM is not covered under the aircraft type certificate. And an appropriately rated DER is designated by the FAA to act on behalf of the administrator to approve the repair defined by the data for that one aircraft.

Also, SWComposites explanation about what the DER is actually approving is right on target, and a much better explanation than my original answer where I said, "...albeit the OEM usually has all the original design data on hand if exotic number crunching is required to substantiate an approval."

Its the age old conflict between theory and practice, which is sometimes referred more as a fact than a jest that this conflict is exactly why engineers exist!

In theory, any appropriately rated FAA/DER has the authority to approve the repair because they have demonstrated the knowledge, skill and experience to the FAA. Also in theory the OEM DER has demonstrated the same, BUT in practice the OEM DER has access to all the original OEM design data including the original OEM research. Therefore SWComposites is right on target to indicate that in practice, the OEM DER may have an advantage.

I work for a non-OEM DAS engineering firm, and one of the very first tasks we have when working with a customer (we service commercial airlines and obtain our STC's under Part 25) is to have the customer obtain the data noted by SWComposites from the OEM for our DER team and substantiation engineers to review.

Some customers such as major international airlines and first tier leasing companies have plenty of influence with the OEM and can get what we request.

Other customers such as smaller airlines (i.e., buy fewer aircraft from the OEM) and other non-first tier operators often cannot get us what we request. Then, as indicated by SWComposites, our knowledgeable and experienced DER staff uses reverse engineering coupled with generously conservative estimations to develop engineering data to substantiate the design.

debodine

 

[debodine]

Because I detest being inaccurate, please allow me one minor correction to my last post. I said:

"...we service commercial airlines and obtain our STC's under Part 25..."

I should have said:

"...we service commercial airlines and obtain our STC's under Part 21..."

The aircraft for which we obtain STC's are certified under Part 25.

debodine