Note: Operators who are not authorized by OpSpecs to use a reliability program may apply the standards in this AC when proposing adjustments to their time limitations. However, these operators must follow established procedures prior to implementing any adjustments to their time limitations.
1.3 Where You Can Find This AC. You can find this AC on the FAA’s website at http://www.faa.gov/regulations_policies/advisory_circulars.
1.4 What This AC Cancels. AC 120-17A, Maintenance Control by Reliability Methods, dated March 27, 1978, is cancelled.
1.5 Legal Basis.
1.5.1 Title 49 of the United States Code (49 U.S.C.). Title 49 U.S.C. § 44701 is the primary authority for all Federal aviation regulations. Section 44701 instructs the FAA to promote the safe flight of civil aircraft in air commerce by prescribing regulations and standards in the interest of safety.
1.5.2 Title 14 CFR. The 14 CFR regulatory requirements supported by this AC include:
• Part 91, §§ 91.1015(a)(5) and 91.1109(b)(5).
• Part 119, § 119.49(a)(8), (a)(14), (b)(8), and (c)(8).
• Part 121, § 121.135(a)(1) and (b)(18).
• Part 135, §§ 135.23(s) and 135.427(b).
1.5.3 Methods of Compliance.
1.5.3.1 This AC describes processes, techniques, and procedures that will lead to an effective reliability program, and will help to ensure a level of safety appropriate to the type of operations conducted. None of the information in this AC is mandatory or constitutes a regulation. This AC does not impose, reduce, or change regulatory requirements.
1.5.3.2 Each operator is unique, and therefore a single means of compliance for developing, implementing, and maintaining a reliability program applicable to all cannot be provided.
1.5.3.3 By design, this AC is highly dependent upon the assumption that all elements of your CAMP are established, documented, and effective. The standards described in this AC are in no way intended to account for deficiencies in other areas of your CAMP, and as such, can be considered a minimum standard. The FAA’s determination that your proposed reliability program is acceptable may differ from this AC to account for deficiencies in other areas of your CAMP.
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1.6 Definitions. For the purposes of this AC, the following definitions are applicable:
1. Acceptable Level of Reliability. Maintaining operational performance equal to or higher than a value determined by the operator that supports the operator’s operational and economic objectives. Following MSG guidelines, operational failures or a loss of function having a direct effect on safety are never considered acceptable.
2. Airworthiness Limitation (AL). Instructions for mandatory replacement items, inspection intervals, related inspection procedures, and/or configuration control limitations.
3. Certification Maintenance Requirements (CMR), Candidate Certification Maintenance Requirements (CCMR). Refer to AC 25-19, Certification Maintenance Requirements.
4. Data Quality. In a reliability program, data is generally considered high quality if it is fit for its intended uses in operation, analysis, decision making, and planning. Data Quality also includes form, format, and accuracy standards necessary to enable the program’s intended uses.
5. Effective. Capable of achieving the desired result. An indicator of scheduled maintenance effectiveness is the availability of your aircraft for flight or operations.
6. Failure. The inability of an item to perform within previously specified limits.
7. Failure Cause. The fundamental mechanism leading to a failure mode.
8. Failure Condition. The effect on the aircraft and its occupants, both direct and consequential, caused or contributed to by one or more failures, considering relevant adverse operational or environmental conditions.
9. Failure Effect. The result of a functional failure. (See also Failure Condition.)
10. Failure Effect Category (FEC) Code. A scheduled maintenance task classification as defined in the MRBR or equivalent manufacturer’s documents. Refer to Air Transport Association of America (ATA) MSG-3, Operator/Manufacturer Scheduled Maintenance Development, paragraph 2-3-6.
11. Failure Mode. The way in which an item ceases to perform its intended function.
12. Function. The operation of an item in an intended or particular way to achieve a desired state or result.
13. Functional Failure. The inability of an item to perform its intended function within specified limits.
14. Hidden Failure Mode. A failure mode which is not detected through routine flightcrew operations or in-flight monitoring systems.
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15. Hidden Function.
• A function that is active when a system is used but where there is no indication to the operating crew when that function ceases to exist.
• A function that is normally inactive and the state of readiness to perform will not be evident before a demand for use.
16. Inherent Level of Reliability. The theoretical level of reliability established by the design and manufacturing criteria of an item. This is the highest level of reliability that can be expected from a unit, system, or aircraft. Achieving higher levels of reliability generally requires modification or redesign.
(Refer to the ATA MSG-3.)
17. Item. Any level of hardware (e.g., a system, subsystem, module, accessory, component, unit, part, appliance, or structure).
18. Limitation. A binding limit (calendar, hours, or cycles) for scheduled maintenance task intervals.
19. Maintenance Program. Refers to the CAMP as described in AC 120-16, Air Carrier Maintenance Programs.
20. Maintenance Schedule. An element of the CAMP as described in AC 120-16;
also called Time Limitations.
21. Operational Reliability. The reliability of an item calculated from operational data for a specific set of usage conditions, parameters, or element of exposure, such as number of departures, flight-hours, etc.
22. Operational Data. Any data generated as a result of aircraft operations.
Examples of operational data are nonroutine events, Extended Operations (ETOPS) event reports, maintenance log items, delays or cancellations, mechanical interruption summaries, service difficulty reports, repeat items reports, unscheduled parts removals, component “teardown” reports, findings from scheduled maintenance tasks and inspections, etc.
23. Optimization. Substantiated revisions to the maintenance schedule such as a task revision, addition or deletion, or interval adjustment (up or down).
24. Performance Standards. The operational goals or standards developed by an operator to define an acceptable level of operational reliability. A performance standard may be defined within various areas of the operator’s CAMP or business objectives as it relates to fleet performance.
25. Predicted Reliability. The estimated reliability of an item.
26. Reliability. The probability that an item will perform a required function, under specified conditions, without failure, for a specified period of time (calendar, hours, or cycles).
27. Routine Task Findings. Data generated that document failures, defects, or degradation that are identified during the execution of a scheduled maintenance task. This data is usually in the form of nonroutine work cards or 1-4
maintenance findings recorded in the aircraft logbook, and may be used to determine the effectiveness of a routine task or to substantiate an interval adjustment.
28. Scheduled Maintenance. The defined set of maintenance tasks performed at stated intervals which, as a whole, comprises the maintenance schedule element of the operator’s CAMP. Refer to AC 120-16.
29. Scheduled Maintenance Task. An action performed at defined intervals, with the objective of retaining or restoring an item to a serviceable condition, or to discover a hidden failure, or to ensure a function is available.
30. Serviceable Condition. The subject item is capable of supporting or performing its intended function, resulting in continued airworthiness.
31. Task Interval. The specified parameter between consecutive occurrences of a maintenance task expressed in flight-hours, flight cycles, calendar-time, engine/auxiliary power unit (APU) hours/cycles, or defined opportunities where a specific task scope of work is required to be completed.
32. Task Scope. The defined procedures appropriate for satisfying the objective of an effective scheduled maintenance task.
33. Task Type. Standard MSG process classifications for a specific task scope
(e.g., inspection, lube, calibration, detailed visual inspection, or functional check).
34. Task Yield. A measure of the actual interval at which a task is accomplished, relative to the maximum allowed interval as defined in the operator’s maintenance schedule. Yield is expressed as a percentage of the task’s maximum allowable interval since the task was last performed.
1.7 Background.
1.7.1 Part 121 and 135 Operators. Title 14 CFR requires air carriers operating under part 121 and part 135, § 135.411(a)(2) or 135.411(b) to establish and maintain time limitations or standards for determining their time limitations. These time limitations specify the tasks and intervals for scheduled maintenance: the what, how, and when of your scheduled maintenance effort. In the context of the air carrier’s CAMP, this is referred to as the maintenance schedule.
1.7.2 Part 91K Operators. Additionally, 14 CFR also requires part 91K operators who choose to maintain program aircraft under a CAMP to establish and maintain time limitations or standards for determining their time limitations.
1.7.3 Maintenance Schedule. Regardless of the type of operation, the rules are written broadly to allow you to establish and maintain your maintenance schedule by one of two ways:
• You may submit your time limitations to the FAA for review and acceptance, or
• You may develop standards for determining your time limitations and obtain FAA acceptance of those standards.
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Note: After the FAA determines your time limitations or standards for determining time limitations are acceptable, you will be issued the appropriate OpSpec/management specification (MSpec) that authorizes its use.
1.7.4 Maintenance Steering Group - 3rd Task Force (MSG-3). The previous version of this AC integrated the Maintenance Steering Group - 2nd Task Force (MSG-2) maintenance program development process, which focused on individual part failure rates and the maintenance processes designed to control them. This revised AC integrates the MSG-3 process, which focuses on maintaining aircraft system functions, while also considering maintenance cost-effectiveness. In addition, the MSG-3 process identifies the consequences of functional failures, and allows a wider selection of maintenance task types than MSG-2. To the extent possible, this revised AC does not identify any specific Maintenance Steering Group (MSG) process as it relates to the operator’s processes, methods, and standards specified in a reliability program.
1.7.5 Continuing Analysis and Surveillance System (CASS). A properly designed and effective reliability program is a part of your CASS, and can fulfill a portion of your CASS requirements regarding operational data collection, analysis, and corrective action.
As is the case for CASS, your reliability program is not intended to duplicate your 14 CFR part 5 Safety Management System (SMS) Safety Assurance (SA) requirements.
Rather, all these systems should be designed to naturally interface and complement each other, resulting in little or no duplication of effort or responsibilities.
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CHAPTER 2. RELIABILITY PROGRAM EVALUATION AND REVIEW
2.1 Program Creation and Revisions.
2.1.1 Main Parts of an Operator’s Reliability Program. The elements of an operator’s reliability program are typically:
• A data collection system,
• A performance standards system,
• Analysis and recommendation,
• Internal approval and implementation, and
• A reporting and display format.
Note: Figure 2-1, Reliability Program Management and Administration, is a closed-loop, process-oriented flow diagram of the reliability process described in this AC.
2.1.2 Documentation Within the Operator’s Manual. You should ensure your standards for determining time limitations contain the following:
1. A general description of the reliability program, including definitions of (or reference to) significant terms used in the reliability program.
Note: You may not use your reliability program as a means to change the meaning or intent of regulatory-based definitions, restrictions, limitations, or reporting requirements. When defining terms, you should be as specific as possible and when applicable, provide qualifying criteria to avoid ambiguity and confusion when executing program requirements.
2. The application of the reliability program by aircraft fleet type and model.
3. Procedures and standards for data collection and ensuring applicability/data quality.
4. The organizational responsibilities, training, and experience requirements.
5. Duties and responsibilities for personnel who perform program requirements.
This includes personnel such as those who monitor performance standards or alert/event levels, analyze operational data, and board members or personnel who perform decision-making functions.
6. The procedures for monitoring and revising the performance standards.
7. Data analysis methods.
8. The corrective action recommendation process, including approval and implementation.
9. Reports used or generated, and the frequency.
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10. Standards and procedures for adjusting time limitations.
11. Description or references to forms unique to the reliability program.
12. Management and administration procedures, including reliability program revision process.
13. Requirements or references to self-audits and other monitoring procedures for the performance and effectiveness of the reliability program.
14. Description or organizational chart of reliability program organizational authority and delegation. The administration of a reliability program generally requires a board or other organizational body within an operator’s maintenance organization. This board should be comprised of experienced and competent personnel with decision-making authority to approve changes to the operator’s maintenance schedule.
2.1.3 Identifying Participants. You should identify in your manual those participants who have authority and responsibility for your reliability program, including:
1. The Director of Maintenance (DOM) or equivalent who has overall authority and responsibility for the entire program.
2. The person who has direct authority and responsibility for the reliability program process.
3. The individual positions in the operator’s organization and their role within the reliability program, including responsibilities and authority.
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Figure 2-1. Reliability Program Management and Administration Reliability Review and Regulatory Continuous Chapter Program Creation Acceptance, Evaluation 2 and Revision OpSpec Data Collection System Performance Standards System Analysis and Identify Alert Level Goals Recommendations Data Trend Monitoring Sources Variation Identify Event Level Goals from Variation from Identify Performance Composite Performance Performance Performance Data Standards Index Standard Standard Chapter Types Scheduled Maintenance Analysis Findings Index Chapter Other Performance Data Standards System Quality Scheduled Non-Performance Standard Chapter Task Driven Request Effectiveness Analysis Correction/Action - Internal Approval and Implementation Internal Recommendation Implementation Approved Change Approval Process Chapter Chapter Continue to Monitor Chapter Reporting and Display Format 2-3
2.1.4 Reliability Personnel Training/Technical Competency.
2.1.4.1 You should determine your own specialized technical standards and training documentation requirements for persons whose role is to collect, analyze, and compile reliability data or reports. The desired competency and capability standards should be defined and be based on the level of complexity of the operational and scheduled maintenance data you collect (see Table 2-1, Competency Training).
2.1.4.2 You may adjust the content, frequency, and method of training provided to individuals depending on an evaluation of the individual’s roles and responsibilities, previous training, hands-on maintenance experience, and/or demonstration of aptitude, and the results being achieved.
2.1.4.3 The FAA expects reliability program participants with approval authority to fully understand their roles and responsibilities relative to the reliability program.
Table 2-1. Competency Training Subject Training Reliability Personnel Knowledge Standards 14 CFR part 121/135 operation specifications (OpSpecs); part 91K management specifications (MSpecs) Familiarization and awareness Systems analysis training General training in quality standards and statistical analysis methods Reliability data training Experience or training in conducting and reporting analysis results for operational data and other scheduled maintenance findings Maintenance Steering Group (MSG):
current or applicable Understanding of applicable MSG methodology used in developing the maintenance schedule Risk assessment training The ability to assess risk as it relates to a situation, failure, or hazard Root cause analysis training, including human factors Method of problem solving that identifies the root causes of faults, failures, deficiencies, or hazards.
Failure Mode and Effects Analysis (FMEA) training Method of analysis that identifies the failure modes and failure effects related to specific faults or failures Technical training Aircraft-specific (make, model, and series (M/M/S)) 2-4
2.2 Regulatory Requirements. There is no regulatory requirement that an operator must have or maintain a reliability program. However, if an operator elects to use a reliability program, certain regulations, OpSpecs, and requirements must be taken into consideration.
2.2.1 OpSpecs/MSpecs.
• D072, Aircraft Maintenance—Continuous Airworthiness Maintenance Program (CAMP) Authorization.
• D074, Reliability Program Authorization: Entire Aircraft.
• D075, Reliability Program Authorization: Airframe, Powerplant, Systems or Selected Items.
• D079, Reliability Program Contractual Arrangement Authorization.
• D088, Maintenance Time Limitations Authorization.
2.2.2 Reliability Program Submission. Your initial reliability program submission and subsequent revisions do not require FAA approval. However, prior to use, you must submit your initial reliability program and each subsequent revision to the FAA office with oversight responsibility. You may use your program after the principal maintenance inspector (PMI) has notified you that the program is acceptable and has issued the appropriate OpSpec/MSpec authorizing its use.
2.3 Continuous Evaluation. As part of an effective Continuing Analysis and Surveillance System (CASS), you continually monitor the performance and effectiveness of your reliability program, and make revisions as necessary. You should also conduct periodic, documented reviews to determine that your performance standards are realistic and are effective in identifying deficiencies.
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CHAPTER 3. DATA COLLECTION SYSTEM
3.1 Identification of Data Sources. An operator should identify data sources from all of these four general categories of an operator’s fleet:
• Systems,
• Components/line replaceable units (LRU),
• Structures, and
• Engines/APUs.
3.2 Identification of Data Types. The data collection system should include the identification of data types. Table 3-1, Data Types lists typical types of operational data;
however, all of these data types do not need to be included in the reliability program, nor does this list prohibit the use of other types of information.
Table 3-1. Data Types Data Type In-Service Data Routine Task Findings Aircraft maintenance log (mechanical irregularities) X X Engine in-flight shut down (IFSD) X Operational interruptions (delays, cancellations, diversions, etc.) X Unscheduled component removals X Component maintenance findings X X Sampling inspections X X Special inspections X X Maintenance deferred with minimum equipment list (MEL) X X Chronic systems X X Unscheduled maintenance X Integrated Vehicle Health Monitoring
a) Aircraft health monitoring
b) Engine health monitoring X X Materials usage X X 3-1
Data Type In-Service Data Routine Task Findings Extended Operations (ETOPS) Event Reports, Reduced Vertical Separation Minimum (RVSM), Category II/III (CAT II/III) X Scheduled maintenance findings X X Accidents or incidents X X Unconfirmed components or part removal X Unscheduled engine removal X X Service Difficulty Reports (SDR) X X Mechanical Interruption Summary Report (MISR) X Flight logs X
3.3 Data Quality.
3.3.1 General. Data sources and associated data types form the foundation of any reliability program. Data can be considered of sufficient quality when it is accurate, free from substantive recording errors, and comprehensive enough in both scope and detail to facilitate its intended function in operations, analysis, and decision making.
3.3.2 Ensuring Validity and Accuracy of Data. You should develop a process to validate the accuracy of the data used in support of your reliability program. A typical data accuracy/data quality process includes:
• Adopting comprehensive data and maintenance recording standards and instructions;
• Forms and instructions designed to achieve compliance with the data standards;
• Performing and documenting data audits to detect deficiencies and correct data irregularities;
• Establishing a documented method for providing feedback to organizational elements demonstrating deviations from the data standards; and
• A common coding convention or system used to correlate mechanical irregularities in aircraft systems with defects found during routine maintenance tasks, shop teardown reports and other relevant data.
Note: While an electronic means of collecting, storing, retrieving, and analyzing data is not required by rule, limitations in these areas may restrict or preclude you from exercising the requisite responsibilities necessary to implement and maintain an effective reliability program.
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