When can you us Chapter 51.

[Jetman021]

Consulting with follow outside engineer's, we have a customer that said they were being advised by a Boeing rep that we could not use 757 SRM 51-70-10 to perform a repair unless directed by another SRM or CMM. The damage we repaired was not covered in the CMM or the applicable chapter 54. Has anyone else ran into this situation?

 

[SWComposites]

Boeing is correct. Chapter 51 is just repair procedures. Other chapters in the SRM for structural components must call out a specific Ch 51 repair as applicable to repair of that component, on the defined locations on the component, and within the defined repair size limits.

If you repaired damage not covered by the SRM, then you MUST get a DER to approve the repair, and he/she will have to have FAA approved data to in turn approve the repair.

 

[Sparweb]

This situation is common. For any repair that is not directly addressed by the SRM/CMM, then you need specific instructions that are approved. I believe Boeing can provide you with an approved repair (if you are willing to wait) but the DER is probably faster, possibly cheaper. Not all DERs will want to support your repair because they won't necessarily have access to structural data needed to design and substantiate it.

 

[DominicLee]

Thanks for this interesting solution!

 

[WKTaylor]

Notes from experience of Wil Taylor..

As a long-time liaison engineer, field service engineer and depot engineer, I learned the hard way that 'I had to be the one to design' a high quality [detailed] repair... for strength and fatigue durability... with materials, parts and processes suitable-for/common-to the aircraft/operational environment and the locale/environment/tools and maintainers, etc. IF needed I also had to define the tools and steps to accomplish the work.

I then called the [OEM or Depot] cognizant engineer to discuss details for repair 'as discussed'... especially IF the design was complex or 'risky'. With my eyes-on every detail, I usually had a VERY comprehensive repair in-mind that was do-able: easy to understand the problem, see the repair in full technical detail and see all the other routine... but important details were also includes such as, Tech Data references, materials, finishes, fasteners, sealants, part-sizing/manufacturing, cautions, warnings, etc... in-depth... typical Taylor-repair.

At this POINT, I then wrote/drew-up the repair in full depth/gory-details, IE: written procedure, photos/sketches, my field-stress analysis notes/comments/summary, etc... then faxed/emailed the repair to the cognizant engineer for go-ahead approval 'with' or 'without' any necessary revisions from the CE..

In most cases I received little/no push-back [negative comments] and usually had amazingly fast turn-around approval/concur to 'go-ahead as written'... or... 'begin and expect any changes or final approval'... by xxx date... fully in time to incorporate changes into the final phase of repair... so we could 'get-moving'... IE: tear-down, prep repair parts, gather materials, fasteners, etc.

LESSON LEARNED: getting up-to-speed with [and ahead of] the Cognizant Engineer in every aspect eliminates doubts, inconsistencies and irregularities... and paves the way for the rapid analysis/approval/go-ahead. NEVER expect someone that has a long-distance view to understand details like YOU... the engineer on-site... to design that repair. It is amazing how long it will take for a confused/ill-defined repair-response from the 'main office' that will drive everyone nuts. It is a lot easier to receive a confirming answer [blessing] from a CE reviewer, when they are provided quality documentation on a well-thought-out process!!!

CAUTION. I have rarely encountered a CE that refuses to make a decision, any decision, on a complex problem... but it happens. I worked with a CE composites engineer on a specific MIL aircraft that was obviously competent... but drove me crazy. He would NEVER provide a 'straight arrow' advice or answer or affirmation during a conversation... or follow-up. I finally had to state unambiguously: "Here is the repair procedure X as discussed [attached]. Please provide Your response with recommendations within 72-hours; otherwise we will assume You concur and 'proceed'."


Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov