I have never seen any overhaul-able item with a documented limit on the number of times it can be overhauled. In all cases it was subject to analysis and predicated on it passing certain tests. Has anyone else heard of such a limit?

If so, what examples of aircraft components with such limits and what kind of aircraft can it be found on?


Yes, but its a fairly new change from the FAA. The FAA recently regulated part Life Limits, a limit in place at certification time (or through a later AD etc.). The IATA also outlines guidance for life limited parts. This is a fairly new reg and many of the older aircraft out there may not be subject to it since they were certified prior to it. This AC also outlines some info relating to it.

However for any mechanical part there, in theory, is a limit to the amount of times it can be overhauled if that work requires reductive machining. Something like a crank case, cylinder head or piston sleeve can only be machined so many times before there is not enough material left for a proper overhaul.

The definitions of overhaul vs rebuild are important. A rebuild may reset a parts life, you can read more on that in this question.

Any life limited part should be listed in the documentation for the specific airframe/model in question. For example here is the list of the Robinson R-22 helicopter. More notably the Cirrus SR-22 has an airframe life limit of 12,000 hours as part of its certification.

The certification requirements of 14 CFR 23.573 require that the composite airframe structure, cabin, wing, empennage their carry thru, and attaching structure whose failure would be catastrophic must be designed to damage tolerant criteria. Damage tolerant certification for the selected airframe life of 12,000 flight hours has been established for all of the affected parts with no special structural limitations or inspections.

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    $\begingroup$ Hourly life limits on components is fairly common ... what I haven't seen personally is the concept of a documented max number of overhauls allowed. The example given where there is reductive machining makes sense, but that would be an example of an on-condition ... in my question I was wondering if there were any aircraft manuals that have a documented number of times a crank case can be overhauled (e.g. 5 times) or, as I would expect, is likely worded "can be overhauled as many times as the material of the crank case will allow". $\endgroup$
    – Aeyrium
    Sep 12 '18 at 22:55
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    $\begingroup$ @Aeyrium technically that could be stipulated (i dont know of any cases) but it does not make much sense from a mechanical/engineering standpoint. Wear and tear does not always occur at a linear rate and TBO times are really just suggestions so its most important to routinely watch components and base your overhaul decisions on condition. $\endgroup$
    – Dave
    Sep 14 '18 at 14:37

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