In all cases, it is the responsibility of the owner/operator of the aircraft to know and provide the aircraft total time to the FAA and to maintenance personnel when requested/required. Maintenance record entries only require total time references when an inspection is accomplished (Ref 14 CFR 43.11) but we highly recommend recording all applicable total times and cycles in every maintenance record entry whenever possible.
14 CFR Part 91.417 (a)(2)(ii)
Life-limited parts are those parts that have received a specific life-limit from an approved FAA document for that aircraft or its components. Some examples of FAA approved documents are the Type Certificate Data Sheets (TCDS), Approved Airplane Flight Manual, the FAA Approved Airworthiness Limitations Section of the aircraft maintenance manual, and Airworthiness Directives.
With the exception of life-limited parts called out by Airworthiness Directives, life-limits generally begin with the type certificate. The type certificate will contain either specific reference to parts numbers that are required to be replaced at a specific time or refer us to a document that contains such information. A good example is turbine engines. Turbine engine life-limited parts are usually called out in a service bulletin. Service bulletins are not mandatory by regulation in nature but the life-limited parts called out in a service bulletin generally are. Why? Because the Type Certificate Data Sheet for the engine references the service bulletin as the source for the life-limited parts listing making the replacement times contained in the service bulletin mandatory. To determine what parts are life-limited for your aircraft it is best to start at the Type Certificate Data Sheet and follow the road signs from there. The regulation refers to the “current status” of life-limited parts. To know the current status of life-limited parts we need to know the answers to the following questions:
Operation of an aircraft with expired life-limited parts is against regulations (Ref 14 CFR Part 91.403 (c) and 91.409(e)). Therefore, 91.417 requires our records include the status of each life-limited part to be sure we aren’t out of compliance.
Some life-limited parts must be replaced based not upon total time in service but rather upon total cycles in service. This can be a trap to owner/operators. You see the regulation referring to keeping the current total time (91.417((a)(2)(ii)) does not refer to the cycle count or landing count. Therefore, keeping track of the cycles and landings on your aircraft becomes a requirement by default. When the life-limited parts replacement requirement calls out replacement of a part at a total cycle count of XYZ, and we don’t know the total cycle count, we cannot demonstrate that the part is not past the limit. The situation then mandates tracking of landings and cycles in order to demonstrate compliance.
Time Since Last Overhaul
14 CFR Part 91.417 (a)(2)(iii)
Overhaul frequencies for items are generally called out in maintenance manuals and service information. The maintenance manual will usually contain a section in Chapter 5 that specifically refers to overhaul requirements. This section will list the items that the manufacturer requires be overhauled. The rule requires that we be able to show the time since last overhaul for those items.
Incidentally, this rule does not mandate the overhaul of such items, just the recording of the time since last overhaul. For operations conducted under 14 CFR Part 91, overhaul is not a mandatory requirement as long as the item continues to pass required inspection criteria. It has been our experience, however, that overhauls performed at the recommended intervals are far more desirable for cost-effective maintenance. Often very expensive component parts will pass overhaul inspection criteria when inspected at the recommended interval but will be worn just below minimums if the overhaul is postponed too far, resulting in a much greater expense to the owner.
The regulation refers to the “time since last overhaul” of parts requiring overhaul. To demonstrate knowledge of the time since overhaul of these parts we need to know the answer to the following questions:
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