Life-Limited Parts: Understanding the new rule

Life-Limited Parts

By Joe Hertzler

Although many of you are aware of the recent addition to the regulations regarding life-limited parts, I would like to discuss the new rule and how it affects both certificated repair station and maintenance organizations using the services of an A&P or an IA for approval for return to service.

The new regulation, issued Jan. 15, 2002, is 14 CFR Part 43.10 titled "Disposition of life-limited aircraft parts." The rule comes as a result of several years work by the FAA in the area of Parts and Suspected Unapproved Parts. A cursory look at the regulation could leave you thinking, "well we are already doing that" or "that rule doesn't really affect me." And both these statements could be true, however, it is important to understand not only the intent of the rule, but the exact meaning of the rule.

Looking at the definitions
Two terms are defined in the rule, "Life-limited Part" and "Life Status."
14CFR Part 43.10 -
Life-limited part means any part for which a mandatory replacement limit is specified in the type design, the Instructions for Continued Airworthiness, or the maintenance manual.
Life status means the accumulated cycles, hours, or any other mandatory replacement limit of a life-limited part.


Most critical is understanding the term "life-limited part." Although the FAA's definition is correct, in my opinion it is not clear enough. A life-limited part is designated as such during the certification process. The key word in the definition is "mandatory." That is, a mandatory replacement limit as opposed to a recommended replacement limit. The FAA's definition works fine for a "limit specified in the type design" or the "Instructions for Continued Airworthiness" because both must be FAA approved. But what we need to understand is that not all parts called out for replacement in the "maintenance manual" are mandatory.

The mandatory replacement times for a part come initially from the type certificate. The type certificate for an aircraft, engine, or propeller either calls out the mandatory replacement limit for parts specifically within the content of the type certificate or it may refer to another document that calls out the limitations.

For example, chapter 5 of the Learjet Model 35 maintenance manual states that the aircraft's mandatory replacement items are contained in an FAA Approved Learjet Report and are identified in the maintenance manual parts replacement schedule by an asterisk (*). What makes those parts mandatory for replacement is not the maintenance manual, but rather the additional reference to the same FAA Approved Learjet Report in the type certificate data sheet for the Learjet Model 35 (Ref. Type Certificate Data Sheet A10CE). What about the parts that are not asterisked? How do we handle them? Well, what is important to understand is that this regulation (43.10) does not affect how those parts are handled. They are not mandatory replacement parts.

Another example is the life-limited parts for an engine, say a Pratt & Whitney PT6A-42, for example, the engine found on the Raytheon B200 King Air. The type certificate for the engine refers you to a service bulletin for replacement times for life-limited parts. Interesting here is that in general service bulletins are not considered mandatory by the FAA unless they have been referenced in an Airworthiness Directive or an Air Carrier's Operation Specification. Here is another instance where the service bulletin is mandatory: when it is referenced in the type certificate for the aircraft, engine, or propeller.

The second term defined in the new rule is "life status." The "life status" is simply where the part is in its life cycle or time line or how much of the limit is used up.

The effect on maintenance
So, now that we know what constitutes a "life-limited part" and its "life cycle," how does the new regulation mandate the handling of life-limited parts and their life cycles?

Who will be complying with this rule? Paragraph (c) of the rule specifically says that "each person who removes a life-limited part from a type-certificated product must ensure that the part is controlled using one of the methods in this paragraph." This points directly at the maintenance person. It doesn't matter if you work for a repair station or you are working in an IA shop. If you remove a life-limited part, the rule now states that you must control that part a particular way.

The only exception is for parts that are removed only temporarily for performing maintenance. If the aircraft, engine, or propeller will not be returned to service until you have reinstalled the same removed part to that article, then you need not comply with the controlling requirements of paragraph (c).

There are six methods for part control described in paragraph (c) that are intended to "deter" the installation of a life-limited part that has exceeded its limit. The first is "record keeping system." This method requires that each time a part is removed from an aircraft the life status must be recorded or updated in the record keeping system. The system may be computer or paper based and must include the part number, serial number, and current life status of the part. The challenge to using this method alone is that the part is not physically tied to the record keeping system. It will indicate the status of the life-limited parts and identify them by part number and serial number, but the record keeping system is not a tag tied to the part.

The most common is the method frequently used by certificated repair stations to tag removed parts, "tag or record attached to part". In order to become a Certificated Repair Station, a maintenance entity must present a manual to the FAA that describes the inspection system for that repair station. The inspection system commonly includes a tagging system for parts within the repair station. Likely a system within that repair station will need little modification in order to comply with this new rule. Frequently when a part is removed, information such as time or cycles in service is not included on the tag. For parts that do not have a mandatory life limit this information is not required and knowing what parts have a mandatory life limit is sometimes a challenge. Some manufacturers provide a series of life-limited parts cards within the maintenance records. The life-limited parts cards also meet the controlling requirements of this method as long as they are completed properly by the person removing the part. They contain and maintain an installation record and running total of the life status of the part.

Two of the other methods outlined in the rule are "permanent marking" and "non-permanent marking." These methods require marking the part itself in a way that shows the life status information. If using the non-permanent method, the marking cannot be removed unless another method to identify the life status of the part is used. One caveat to this method is that "The mark must be accomplished in accordance with the instructions under ยง45.16 of this chapter in order to maintain the integrity of the part." What 14 CFR Part 45.16 basically says is that in order to mark the part, either permanently or non-permanently, you must ask the manufacturer how to mark the part safely (i.e. electronic etch, chemical etch, marker) and the manufacturer must provide a safe way to mark the part. If the manufacturer cannot provide a safe way, then a different method must be used. Many life-limited engine components are marked using this method.

The next method listed is segregation. Life-limited parts can be removed and segregated from all other parts as long as a system is in place to record the part number, serial numbers, and life status of the part, and the parts are stored in a physical location unmistakably separate from parts that are eligible for installation on an aircraft, engine, or propeller.

The last method listed is mutilation. This is best stated in the rule itself, "the mutilation must render the part beyond repair and incapable of being reworked to appear to be airworthy." Obviously, if a part is mutilated as defined in this rule, record of its life status and even serial number is irrelevant. However, we recommend that as a maintenance organization, if you practice part mutilation, keep a record of the part number, serial number, and life status at the time of mutilation.

The FAA also leaves the opportunity open to create your own method and submit that method for approval by your local authorities.

So the problem presents itself, how do I know what parts are life-limited? Well, unless you spend a lot of time with a particular aircraft make/model it is difficult to remember which parts have a mandatory life limit and which ones don't. The owner of the aircraft is required to maintain records of life-limited parts and their life status (ref. CFR Part 91.417(a)(2)(i)). Such records are usually in the form of raw maintenance records. Therefore, the maintenance records for the aircraft will be the place to look to find life status information for mandatory life-limited parts. But unless you know which parts are limited and which parts are not you are at risk of non-compliance. Learn how to find the life-limited parts list quickly. Life-limited parts are generally serialized, but not always. I can think of several examples of non-serialized life-limited parts. For example, the wing bolts on a Raytheon King Air B200 are limited to 15 years but they are not serialized or marked in any special way.

Create a system for your organization that fits well into the current work flow process and includes a combination of the methods listed within the new rule. If you do not mutilate the parts, place them in a quarantine area segregated from normal inventory and keep good records of parts removed. Use the tagging system you already have in place and modify it if needed to meet these new requirements. Make sure you fill out the tags completely. If the part comes with a life-limited part card keep it with the part in a plastic bag for protection.



Joe Hertzler is the president of AVTRAK, Inc., an Aurora, CO-based company. Joe is an Airframe and Powerplant Mechanic with Inspection Authorization and also a Private Pilot.

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