Maintenance Records: What Constitutes a Complete Set?

Nov. 4, 2005
Avtrak Inc., Federal Aviation Administration Info: 14 CFR Part 91.417 is the regulation that spells out the required maintenance records for an aircraft. Author Joe Hertzler describes each paragraph to help fully understand the requirements.

In this issue we will outline what aircraft maintenance records are required for an aircraft owner/operator. 14 CFR Part 91.417 is the regulation that spells out the required maintenance records for an aircraft. We will dig deep into the details of each paragraph in 14 CFR Part 91.417 (a) (1) and (2) and in the end fully understand the requirements.

The logbooks — Is That All There Is?

The “logbooks” for an aircraft come in many different packages. One aircraft’s set of logbooks may have one airframe logbook, and a logbook for each engine and each propeller supplemented by a dozen or so maintenance release documents (yellow tags or 8130s), while an identical aircraft with the same amount of time could easily have six 4-inch three-ring binders full of documents, (each including individual signature for the maintenance described on the card) and three other 4-inch binders filled with work orders and maintenance release documents, all in addition to the original airframe, engine, and propeller logbooks provided with the aircraft when it was new.

But regardless of the format or quantity of logbooks and maintenance records for an aircraft, the question at hand is “what content is required by regulation?”

14 CFR Part 91.417 spells out what maintenance records are required and how long those records must be kept by the owner/operator. To simplify the discussion lets divide the maintenance records called out in this rule into two different categories. Category A (permanent records) and Category B (expiring records).

Permanent Records — Category A

“Category A” records are those maintenance records that must be kept and maintained for the aircraft indefinitely. Category A records reflect the current “status” of the aircraft with respect to issues such as inspections, life-limited parts, major changes to type design, and AD compliance. Looking at 14 CFR Part 91.417 (a)(2) we see the list of records that must be “retained and transferred with the aircraft at the time the aircraft is sold” (Ref 14 CFR Part 91.417(b)(2)). As we step through this list of record types let’s discuss each type of record specifically addressed.

Total Time in Service
14 CFR Part 91.417 (a)(2(i)

Having a record of the total time in service of the airframe, each engine, each propeller, and each rotor is simply a matter of keeping track of time accumulation. In order to do that effectively we need to first know the definition of “time in service”.That definition is found in 14 CFR Part 1 and basically defines “Time in Service” as being from the time the tires on the landing gear leave the ground during take off to the time the tires touch back down at the point of landing. In a normal situation this would be very simple. Most aircraft are equipped with an hour meter that is tied to a landing gear squat switch and begins counting time when the aircraft leave the ground and then stops when it touches back down, thus keeping accurate and correct time. When it gets tricky is when the hour meter breaks or is replaced, or when engines, propellers, and rotors are replaced with new or time continued components. In such a case you have to be sure to carry over the correct times prior to the beginning of each flight. With an airframe, two engines, and two propellers it is possible to have five different total times to keep track of and tally up each day or week.

There are some challenges to keeping up with total times. Like in the case of rebuilt engines, propellers with unknown total time, and engines whose time is tracked independently on individual modules. Each of these cases is addressed in FAA Advisory Circular 43-9C “Maintenance Records” (see paragraph 5. (g)(1)(a), (b), and (c); and Paragraph 12).

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.

Life-Limited Parts
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:

  • Which parts on my aircraft are life-limited?

  • What are their life-limits? (This can change periodically.)

  • What are their serial numbers?

  • How much of the life-limit is used up or how much of the life-limit remains?
  • 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:

  • Which components on the aircraft have a recommended overhaul period?

  • What are their serial numbers?

  • How much total time has accumulated since the last overhaul?
  • Look for more from Joe Hertzler on Maintenance Records in the next issue of Aircraft Maintenance Technology.

    About the Author

    Joe Hertzler