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Section 2  Common Areas of Confusion in Maintenance

3-606    OBJECTIVE. This section discusses frequent areas of confusion or misinterpretation in aircraft maintenance.

3-607    TYPE CERTIFICATE DATA SHEET (TCDS) NOTES. Federal Aviation Administration (FAA) legal interpretations state that TCDS notes containing overhaul limits are not mandatory under current regulations. TCDS notes define the design of the aircraft and how that design meets its certification basis, not how it is maintained. Some manufacturers have attempted to put information into a TCDS that defines requirements for continuing maintenance of their aircraft; however, such information is not regulatory and is outside the purpose of the TCDS notes. Information not specifically referencing the design and configuration of an aircraft, such as ongoing maintenance requirements, is inappropriate and not binding on the owner/operator in a regulatory sense. The Aircraft Certification Service (AIR) has published FAA Order 8110.121, Type Certificate Data Sheet (TCDS) Notes, that explains the intent and design of TCDS notes in greater detail, including descriptions of appropriate content.

3-608    COMPLIANCE WITH MANUFACTURERS SERVICE BULLETINS (SB). Manufacturers publish many forms of maintenance-related information using varying names, such as SBs, service instructions (SI), etc. We will refer to them hereafter as SBs for simplicity. These documents typically contain information that supplements a manufacturer’s published maintenance manual or instructions for continued airworthiness (ICA). A manufacturer must meet applicable certification standards regarding the content of their ICA, as well as having an ICA program to identify how ICAs are revised. Typically, a manufacturer will identify in their principal ICA document what documents (by name) are considered part of the complete set of ICAs required by Title 14 of the Code of Federal Regulations (14 CFR) part 21, § 21.50(b), and what documents are not considered ICA. For example, SBs can be issued by one manufacturer as a method to revise their ICAs, whereas another manufacturer issues SBs for critical continued airworthiness information. Other documents may be in the form of Service Letters (SL) to announce product improvements or other technical issues that would not be considered ICA. It is important the end user understands the manufacturer’s ICA program to know what are considered ICAs and what are not when determining the applicability of a published service document with respect to the continued airworthiness of a product. When determining whether a manufacturer’s SB is mandatory or not, further explanation needs to be considered before answering. There are two parts to this issue: the timeframe that is sometimes prescribed, and the instructions themselves.

A.    Title 14 CFR Part 91 (excluding part 91 subpart K (part 91K)). With some exceptions (described in the following paragraphs), compliance with manufacturer SBs is not required to be accomplished on any specific timetable for part 91 operators. However, once the operator chooses to perform an SB, they must follow the methods, techniques, and practices prescribed within, unless they are using some other methods, techniques, and practices acceptable to the FAA. SBs often provide supplemental maintenance information, a topic addressed by 14 CFR part 43, § 43.13, which requires that each person performing maintenance, alterations, or preventive maintenance use the methods, techniques, and practices prescribed in the current manufacturer’s maintenance manual or ICAs prepared by its manufacturer. Persons performing maintenance, alterations, or preventative maintenance can also use other methods, techniques, and practices acceptable to the Administrator. However, note that § 43.13 states the “methods, techniques, and practices” must be followed, not the specific timeframes or schedules defined by the manufacturer. Also, the rule specifically addresses people who are “performing” maintenance, so the rule applies only once a maintenance activity has been initiated; the rule does not require a certain maintenance activity to be “scheduled.” Therefore, once a maintenance action is initiated, maintenance personnel must follow the manufacturer’s instructions (or some other instructions acceptable to the FAA); but part 91 operators can choose not to perform the SB at their discretion unless it has been mandated by an Airworthiness Directive (AD) or other rule.

B.    Title 14 CFR Part 121, 125, and 135 Certificate Holders. When dealing with certificate holders, determining whether a manufacturer’s SB is mandatory or not gets more complicated. For example, part 135, § 135.421 requires operators to comply with the manufacturer’s recommended maintenance programs, or a program approved by the Administrator. Operators who are required to comply with a maintenance program of some type are also required to comply with SBs that are explicitly defined as part of that program. Likewise, operators with a Continuous Airworthiness Maintenance Program (CAMP) must have a program that covers maintenance, preventive maintenance, and alterations. However, with a CAMP, the certificate holder can customize the program to include what they must accomplish in that program, as long as what they propose is acceptable to the FAA. As a result, some SBs require compliance at defined intervals, while some do not; it depends on the purpose of the SB and whether it is referenced as part of the required maintenance program. The important distinction is that a maintenance program is required; unlike under part 91, where only an inspection program is required.

C.    Other Situations. The following describe situations when compliance with the prescribed intervals of a SB would be mandatory:

1)    All or a portion of an SB is incorporated as part of an AD.
2)    The SB is incorporated directly or by reference into an FAA-approved inspection program, such as an approved inspection program (AIP), Approved Aircraft Inspection Program (AAIP), or a CAMP.
3)    The SB is listed as an additional maintenance requirement in the certificate holder’s operations specifications (OpSpecs).
4)    The SB is part of the FAA-approved Airworthiness Limitation Section (ALS) of the manufacturer’s manual or the type certificate (TC). However, compliance with a new or revised ALS issued by a design approval holder (DAH) or other entity as a type design change, is not mandatory for in-service aircraft operating per part 91, unless it is mandated by one of the other situations above. Operators can always elect to comply with the new or revised limits voluntarily.

D.    SB Version. To add to the complexity of this issue, we must consider which version of the SB is the relevant one. If it is determined that an SB is required to be complied with, the next thing is to determine which version is required to be complied with. This varies depending on what is driving the requirement.

1)    For an AD, you have to comply with whatever version the AD references. To properly comply with the AD, you must comply with the version of the SB referenced in the AD, even if the manufacturer has published a new version. To be able to comply with a later version of the SB, either the AD would have to be revised by the FAA to include the latest version, or the operator could request an alternative method of compliance (AMOC). In the case of the latter, it would be up to the operator to present the case that compliance with the latest version of the SB still accomplishes the intent of the AD. However, this is almost always the case, and becomes mostly a paperwork exercise and a formality. Although it may seem like a pointless exercise, it is still a necessary step because ADs are an extension of the regulations, and any deviation from the rule needs to be properly authorized.
2)    For maintenance programs, the operator would only be required to comply with the SB version that was current at the time the program was initially selected by the operator. Furthermore, making minor subsequent revisions to that program does not reset the clock and require compliance to a more recent version of the program. The reason for this is the FAA legal position on the use of the word “current” as it applies to the regulations. FAA legal has issued several interpretations that state that an operator is only obligated to follow the manufacturer’s maintenance instructions that were current at the time the operator adopted them, unless otherwise mandated by the FAA (such as by rule or AD).

3-609    INSPECTION PROGRAMS VERSUS MAINTENANCE PROGRAMS. An inspection program should not be confused with a maintenance program. An inspection program will capture a list of scheduled inspections which are completed at designated intervals. A maintenance program should encompass all the elements of maintenance, to include inspections, overhaul requirements, repair schemes, Corrosion Prevention and Control Programs (CPCPs), and the scheduled replacement of parts. Scheduled replacements of parts (e.g., filters and seals) are maintenance, not inspection. Part replacements are a part of the overall maintenance program and should not be included in an inspection program. However, if an inspection of an item is destructive in nature and mandates the replacement of the part after the inspection (such as an oil filter), it could still be appropriate to include these items in an inspection program. Some operations under the regulations (such as operations strictly under part 91, excluding part 91K) require compliance only with an inspection program and have no requirements for compliance with a maintenance program. This is discussed in greater detail below.

NOTE:  Certain part replacements (e.g., life-limited parts and parts affected by ADs) remain mandatory for aircraft operated under part 91 due to other regulatory requirements, even though they are not part of the inspection program.

A.    Inspection Program Content. Not all tasks classified or described as “inspections” are part of an inspection program. Inspection programs refer to a list of scheduled inspection items accomplished at defined intervals, whose main purpose is to determine the condition of the aircraft and its components (e.g., airframe, engines, propellers, rotors, appliances, survival equipment, and emergency equipment) to ensure continued serviceability. Inspections look for issues which have not yet been discovered, as known issues must be addressed as soon as they are discovered. They can also include scheduled items that are event-driven and not a set number of hours/cycles/days, such as a hard landing or prop strike. However, inspections that are part of a larger maintenance process, such as inspections performed during an overhaul, are classified as a maintenance action and are not a part of an inspection program for the reasons stated above.

NOTE:  While scheduled items of maintenance (other than inspections) are not required to be included in the inspection program, they become mandatory if the operator chooses to include them in an AIP, such as one developed under part 91, § 91.409(f)(4). However, items of scheduled maintenance that are not inspection tasks and which the manufacturer has inserted in its inspection programs, are not mandatory to operators utilizing a program under § 91.409(f)(3).

B.    Differences Between Operating Rules. Although part 91 aircraft have been the focus, it is prudent to mention that many other operating rules require compliance with some form of a maintenance program (beyond the inspection program requirements). Parts 121 and 135 both require compliance with some form of scheduled maintenance. Refer to part 121, §§ 121.135, 121.367, and 121.369; and §§ 135.411 and 135.421 through 135.443. The only form of scheduled maintenance required under part 125 is compliance with the manufacturer’s recommended overhaul period (refer to part 125, § 125.247). Part 91K operators are only required to comply with scheduled maintenance items if they elect to develop their own CAMP under § 91.1411 (refer to §§ 91.1411 through 91.1443). Likewise, part 91K operators are only required to comply with overhaul limits if included in their CAMP developed per § 91.1411.

C.    Manufacturer’s Inspection Programs. Recently, there have been questions surrounding what is specifically required under § 91.409(f)(3) and what constitutes a program recommended by the manufacturer. A manufacturer, as part of the certification process, is required to provide an ICA. All certification rules have appendices with nearly identical wording in regards to ICAs, which specifies the ICA must be in the form of a manual or manuals that provide for a practical arrangement. For example, 14 CFR parts 23 and 25 specify requirements for ICAs prepared by the aircraft manufacturer. Similarly, 14 CFR parts 33 and 35 prescribe similar requirements for engine and propeller manufacturers respectively. ICAs must contain the following information (an example from part 23 appendix G, § G2.3(b)): “(b) Maintenance instructions. (1) Scheduling information for each part of the airplane and its engines, auxiliary power units, propellers, accessories, instruments, and equipment that provides the recommended periods at which they should be cleaned, inspected, adjusted, tested, and lubricated, and the degree of inspection, the applicable wear tolerances, and work recommended at these periods. However, the applicant may refer to an accessory, instrument, or equipment manufacturer as the source of this information if the applicant shows that the item has an exceptionally high degree of complexity requiring specialized maintenance techniques, test equipment, or expertise. The recommended overhaul periods and necessary cross reference to the Airworthiness Limitations section of the manual must also be included. In addition [to what is listed above], the applicant must include an inspection program that includes the frequency and extent of the inspections necessary to provide for the continued airworthiness of the airplane.”

1)    Being a program created by the manufacturers of the TC’d products, an owner or operator does not need to research every appliance and equipment manual for potential inspection items. Proper compliance with a manufacturer’s inspection program would therefore include the programs from the airframe, engine, and propeller manufacturers. Note that sometimes the aircraft manufacturer includes the inspection items from the engine and propeller manufacturers in their program, making for a one-stop place to find the inspection requirements. Additionally, modifying the aircraft, such as through a Supplemental Type Certificate (STC) or field approval, does not necessarily make a manufacturer’s inspection program inappropriate. In such cases, the owner/operator must comply with the inspection program recommended by the manufacturer as well as any additional inspection program items from the ICA of aftermarket equipment and/or modifications. This is no different than compliance with additional inspections called out in applicable ADs. Items removed from the aircraft with extensive modifications, such as for passenger-to-cargo conversions, should be deleted from the manufacturer’s program as the inspections no longer apply. Extensive modifications may make another kind of program, such as one under § 91.409(f)(4), more appropriate.
2)    Manufacturer’s maintenance programs must contain instructions or procedures for performing inspections, or a reference to where they can be found in the manufacturer’s manuals. Without at least a reference to the instructions on how to perform the inspections, the inspection program is not adequate. This is why a manufacturer’s Maintenance Planning Document (MPD) or Maintenance Review Board Report (MRBR) is not considered a complete manufacturer’s inspection program. These types of documents typically only provide a starting point for operators to develop their own programs.

NOTE:  Items of scheduled maintenance that are not inspection tasks and which the manufacturer has inserted in its inspection programs are not mandatory (by regulation) to operators utilizing a program under § 91.409(f)(3).

D.    AIPs. There are several rules requiring aircraft to have an AIP, but the programs are basically identical in structure and required content. For example, an inspection approved under § 135.419 is referred to as an AAIP, while an inspection program approved under § 91.409(f)(4) is referred to as an AIP. While the terminology may vary, the intent and design are the same. The same can be said for §§ 91.1109 and 125.247. If the rule requires the inspection program to be approved, it can be generically referred to as the AIP for that aircraft. Note, though, some operating rules also require operators to comply with a maintenance program, which are either the manufacturer’s recommended items or something developed by the operator (depending on the rule). This is in addition to the inspection program requirements. Finally, there are rules that allow, or require, a CAMP. These are all-inclusive programs that have even more requirements than the basic maintenance and inspection program requirements required elsewhere.

NOTE:  While scheduled items of maintenance (other than inspections) are not required to be included in the inspection program, they become mandatory if the operator chooses to include them in an AIP, such as one developed under § 91.409(f)(4). However, the FAA should not require or advocate that these items be added.

RESERVED. Paragraphs 3-610 through 3-615.