Repair Evaluation – Revision Data

When an aircraft is damaged; this damage is evaluated and will either need a repair or could remain “as is” when assessed IAW (in accordance with) the SRM (structural Repair Manual).

We will consider SRM (structural Repair Manual) repairable damage for this example.

While many factors are very important, one piece of information is pivotal in your evaluation. This is the “Revision Status” of the documentation used.

The revision status on documentation for a repair carried out 5 years ago would be different to that the repair that we would carry out today.

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Modifications Status Review

Once the returning airline has provided a certified list of the Modification Status you are then able to look at the major and the minor modifications embodied as per the Modification Report.

The “Dirty Finger Print” (DFP) review of the technical records and in particular for any modification classed as Major will need to demonstrate details of an STC “Supplemental Type Certificate” along with all the data, manuals and very importantly a letter confirming that the modification has a “right to use” confirmation letter.

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Engine Life Limited Part Considerations

Last week we noted landing gear LLP (Life Limited Part) and some considerations, while a similar concept to landing gear, an engine LLP have some additional factors to be aware of.

An engine can operate at multiple different thrust levels, for example, the CFM56-7 on the Boeing 737 NG series where one engine can be used on different variants and the thrust changed accordingly. Often the LLP life is based on a thrust setting – the higher the thrust rating the lower the life.

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Service Bulletins

Service Bulletins commonly referred to as “SB’s” are airworthiness documents that originate from the original equipment manufacturer (OEM).
The purpose of these documents is a work instruction that may be anything from an inspection right through to a change of parts or the actual design.

The purpose of the Service Bulletin (SB) can vary and they aim to achieve many purposes including:
* Improve reliability
* Improve safety by reducing the risk
* Change a configuration – example thrust rating for an engine.
* Address an issue found to affect airworthiness – enforced by an AD (Airworthiness Directive)
* Change a process or maintenance task.

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