U.S. Department of Transportation Federal Aviation Administration Advisory Circular Subject: Developing and Implementing an Air Carrier Continuing Analysis and Surveillance System Date: 9/7/10 Initiated by: AFS-300 AC No: 120-79A Change:
FOREWORD This advisory circular (AC) provides information on methods of developing and implementing a Continuing Analysis and Surveillance System (CASS) required for commercial operators and air carriers certificated under Title 14 of the Code of Federal Regulations (14 CFR) part 119 and conducting operations under either 14 CFR part 121 or 135. A CASS is a system that air carriers and commercial operators use to monitor, analyze, and optimize the performance and effectiveness of their air carrier maintenance programs.
The regulations in part 121, § 121.373 and part 135, § 135.431 that define CASS are written in a performance-based format. Performance-based regulation is a regulatory approach that focuses on measurable outcomes, rather than prescriptive processes, techniques, or procedures.
Performance-based regulation leads to defined results without a specific direction or specific instruction in the regulation regarding how to obtain those results.
This AC describes methods of compliance with the performance-based CASS regulatory requirements that the Federal Aviation Administration (FAA) has found to be acceptable. This AC describes processes, techniques, and procedures that will lead to the defined results in the CASS regulation. The information in this AC is not mandatory and does not constitute a regulation. This AC does not include any material that imposes, reduces, or changes a regulatory burden on anyone. Because using the method of compliance presented in this AC is not mandatory, the term “should” used herein applies only if you choose to follow these particular methods. A CASS should be tailored to each particular and specific operation; therefore, this AC cannot provide a single means of compliance that applies to all certificate holders required to develop and implement a CASS.
When “must” or “will” are used in this AC, such use reflects actual regulatory requirements.
When “you” or “your” is used in this AC, it refers to an air carrier or commercial operator.
for John M. Allen Director, Flight Standards Service
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TABLE OF CONTENTS Paragraph Page CHAPTER 1. INTRODUCTION
1-1. Purpose1
1-2. Applicability1
CHAPTER 2. BACKGROUND ON CASS
2-1. History of the CASS3
2-2. Relevant Regulations3
2-3. Standard Definitions Used in CASS4
2-4. Purpose of a CASS6
2-5. Structure of a CASS7
CHAPTER 3. USING THIS AC TO DESIGN A CASS
3-1. Types of Operators This AC Helps11
3-2. Approach of This AC11
CHAPTER 4. CASS IN YOUR ORGANIZATION
4-1. CASS Documentation13
4-2. Written Policy and Procedures13
CHAPTER 5. MAJOR CASS ACTIVITIES
5-1. Summary of a CASS15
Figure 5-1. The Four Basic CASS Activities: Surveillance, Analysis, Corrective Action,
Followup15
5-2. Verifying Performance of your Maintenance Program16
Figure 5-2. Risk Management Process16
5-3. Verifying the Effectiveness of your Maintenance Program26
5-4. Final RCA and Corrective Action29
5-5. Followup35
CHAPTER 6. PERSONNEL WHO PERFORM CASS FUNCTIONS
6-1. Personnel Managing CASS Functions37
6-2. CASS Personnel Training and Experience37
Table 6-1. Subject Training39
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CONTENTS (CONTINUED) Paragraph Page CHAPTER 7. COMMUNICATIONS BETWEEN YOUR CASS PERSONNEL AND OTHER
DEPARTMENTS
7-1. Communicating Specific CASS Results and Actions41
7-2. Educating Personnel on CASS41
7-3. Communications with Personnel Outside the CASS42
CHAPTER 8. HOW YOUR CASS DIFFERS FROM AND RELATES TO OTHER
PROGRAMS
8-1. Summary of Other Programs45
8-2. Discussion of Individual Programs45
CHAPTER 9. HOW TO DETERMINE IF YOUR CASS IS WORKING PROPERLY
9-1. Why You Should Evaluate Your CASS49
9-2. Steps to Evaluate your CASS49
CHAPTER 10. THE ROLE OF THE FAA IN RELATION YOUR CASS
10-1. The FAA’s Role, in General53
10-2. The FAA PI’s Role53
CHAPTER 11. ADMINISTRATIVE INFORMATION
11-1. How to Obtain This and Other FAA Publications55
APPENDIX 1. SAMPLE CASS FOR A LARGE CERTIFICATE HOLDER (8 pages)1
APPENDIX 2. SAMPLE CASS FOR A MEDIUM CERTIFICATE HOLDER (6 pages)1
APPENDIX 3. SAMPLE CASS FOR A SMALL CERTIFICATE HOLDER (6 pages)1
APPENDIX 4. CASS MANUAL/DOCUMENT SAMPLE CONTENTS (2 pages)1
APPENDIX 5. PUBLICATIONS USED TO DEVELOP THIS AC (2 pages)1
Par 1-1 Page 1 CHAPTER 1. INTRODUCTION
1-1. PURPOSE.
a. Applicability. This advisory circular (AC) provides information for developing and implementing a Continuing Analysis and Surveillance System (CASS). This AC applies to you if you are a Title 14 of the Code of Federal Regulations (14 CFR) part 119 certificate holder conducting operations under 14 CFR part 121 or 135. For part 135 operations, this AC applies if you conduct your maintenance operations under part 135, § 135.411(a)(2). This AC also applies to each person employed or used by you as a part 119 certificate holder for any maintenance, preventive maintenance, and alteration of your aircraft. Title 14 CFR part 1, § 1.1 defines “person” as “an individual, firm, partnership, corporation, company, association, joint-stock association, or governmental entity. It includes a trustee, receiver, assignee, or similar representative of any of them.”
b. Method of Compliance. This AC is a method of compliance with certain 14 CFR regulatory requirements. This method of compliance has been found to be acceptable to the Administrator of the Federal Aviation Administration (FAA). Instead of following this method, you may choose to follow an alternate or a different method. However, before you can use your alternate or different method, the FAA must make a finding that your alternate method is acceptable. Because using the method of compliance presented in this AC is not mandatory for those choosing not to follow this method, the term “should” used herein applies only to those who choose to follow this particular method.
c. FAA Expectations. This AC provides information about the FAA’s expectations regarding your development and implementation of a CASS. As required by part 121, §§ 121.373 and 135.431, your CASS monitors your maintenance program for compliance with applicable requirements.
d. Maintenance. As used in this AC, “maintenance” means inspection, overhaul, repair, alterations, preservation, and the replacement of parts. It is important to remember that your inspection functions are an integral part of your maintenance program. They are not separate from your maintenance program. This is consistent with the regulations.
1-2. APPLICABILITY.
a. Certificate Holders. The intended audience of this AC is any certificate holder that develops a CASS, whether required to do so or not. The following table explains which certificate holders must have a CASS and which certificate holders may choose to have one.
If you operate under 14 CFR— You— Part 121 must have a CASS as required by § 121.373.
Part 129 must have FAA approval for the maintenance program and may have a CASS if it is consistent with the regulations of the State of the operator.
Page 2 Par 1-2 If you operate under 14 CFR— You— Section 135.411(a)(2) applicability must have a CASS as required by § 135.431.
Section 135.411(a)(1) applicability or part 91, 125, 133, or 137 may be interested in developing a CASS because of the safety, efficiency, and other benefits a CASS affords.
b. Individuals. This AC is useful if you are directly involved in developing and implementing a CASS, or if you hold a senior management position where you exercise any control over maintenance operations.
Par 2-1 Page 3 CHAPTER 2. BACKGROUND ON CASS
2-1. HISTORY OF THE CASS. The CASS is one element of the Continuous Airworthiness Program (CAP) that was introduced in a rulemaking at 29 Federal Register (FR) 6522 on May 20, 1964. The rulemaking responded to safety concerns and discoveries of weaknesses in the maintenance programs of some air carriers revealed during accident investigations and FAA surveillance of air carrier maintenance activities. The CAP was designed to strengthen systemic requirements for safe air carrier operations. With its data collection, corrective action, and followup functions, a CASS is critical to the highest possible degree of safety in air transportation.
2-2. RELEVANT REGULATIONS.
a. Requirement to Have a CASS. This AC addresses certain key concepts in the CASS regulations, portions of which are in the regulatory text quoted here for discussion later in this AC. Title 14 CFR part 121, § 121.373(a), (b), and (c), and 14 CFR part 135, § 135.431(a), (b), and (c) state:
“(a) Each certificate holder shall establish and maintain a system for the continuing analysis and surveillance of the performance and effectiveness of its inspection program and the program covering other maintenance, preventive maintenance, and alterations and for the correction of any deficiency in those programs, regardless of whether those programs are carried out by the certificate holder or by another person.
“(b) Whenever the Administrator finds that either or both of the programs described in paragraph (a) of this section does not contain adequate procedures and standards to meet the requirements of this part, the certificate holder shall, after notification by the Administrator, make any changes in those programs that are necessary to meet those requirements.”
NOTE: The wording of § 135.431(a) and (c) is the same as that in § 121.373(a) and (c). There are slight differences between the text of §§ 135.431(b) and 121.373(b); however, they are substantively identical.
b. Requirement to Have a Maintenance Program.
(1) Regulatory Compliance. If you are a 14 CFR part 119 certificate holder conducting operations under § 121.367 requires you to have a maintenance program that consists of an inspection program and a program covering other maintenance, preventive maintenance, and alterations. In accordance with § 135.425, the same requirement applies if you are a part 119 certificate holder conducting operations under part 135 and operating or choosing to operate under § 135.411(a)(2) applicability.
(2) Elements of Your Maintenance Program. Your air carrier maintenance program includes the following 10 elements:
• Airworthiness responsibility,
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• Air carrier maintenance manual,
• Air carrier maintenance organization,
• Accomplishment and approval of maintenance and alterations,
• Maintenance schedule,
• Required Inspection Items (RII),
• Maintenance recordkeeping system,
• Maintenance providers,
• Personnel training, and
• A CASS.
NOTE: You can find additional, more detailed information about the 10 elements of a maintenance program in the current edition of AC 120-16, Air Carrier Maintenance Programs.
2-3. STANDARD DEFINITIONS USED IN CASS.
a. Definitions.
(1) Audit. Scheduled or unscheduled formal reviews and verifications to evaluate compliance with policy, standards, and/or contractual requirements.
(2) Authority. The power to design or change fundamental policy or procedures without having to seek higher level management approval. Authority is permission; it is a right coupled with an autonomous power to accomplish certain acts or to order others to act. Often, one person grants another authority to act as an employer to an employee, a corporation to its officers, or as a governmental empowerment to perform certain functions.
(3) Carried Out by the Certificate Holder or Other Person. This refers to your ability as a certificate holder to accomplish maintenance yourself or to make arrangements with someone else to accomplish maintenance on your behalf. However, you always retain the responsibility for the performance of maintenance, and you must always maintain operational control over any maintenance that any other person performs on your aircraft. Operational control includes independently determining the scope and type of maintenance that may be required, when to accomplish that maintenance, and if the maintenance was done in accordance with your manual and program, regardless of who accomplished the maintenance.
(4) CASS. The elements of the system are always working. For example, continuing surveillance means someone is always looking and collecting information. Continuing analysis means that someone is always analyzing the information that the system is always collecting.
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(5) Corrective Action. An action designed to eliminate or mitigate a deficiency that has been identified within your maintenance program.
(6) Deficiency. A condition which is insufficient or incomplete, or where something required is lacking. In a CASS, it is something that is missing from your maintenance program that should be there, or it is something that is there but not producing the desired results.
Alternatively, it could indicate that your maintenance program documentation is not being followed. For example, a program element that has failed and is not working, or a program element that has faults and is not working as it should, are deficiencies.
(7) Effective. Producing or capable of producing a result. The maintenance program is producing the desired results when it realizes the following objectives:
• Airworthy aircraft have been properly maintained for operations in air transportation;
• Personnel are competent;
• Facilities and equipment are adequate; and
• All maintenance, preventive maintenance, and alterations are always performed in accordance with your maintenance program and manual.
(8) Establish and Maintain. To establish means that you develop a CASS that is appropriate for the type and scope of your operation. To maintain means that you keep your CASS current and appropriate in response to changes in the type and scope of your operation.
(9) Maintenance Program. The programs outlined in §§ 121.367 and 135.425 are outlined in other sections of part 121 subpart L and part 135 subpart J, and the current edition of AC 120-16 describes them in some detail.
(10) Maintenance. Inspection, overhaul, repair, preservation, and the replacement of parts, excluding preventive maintenance.
(11) Performance. The act of doing something successfully; the successful execution of an action. In CASS, performance means your maintenance program is being accomplished or executed as outlined in your air carrier manual.
(12) Person. An individual, firm, partnership, corporation, company, association, joint-stock association, or governmental entity. It includes a trustee, receiver, assignee, or similar representative of any of them.
(13) Preventive Action. Action to eliminate or mitigate the cause or to reduce the effects of potential nonconformity or other undesirable situation.
(14) Program. An organized list of procedures.
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(15) Responsibility. The obligation to ensure that a task or function is successfully carried out. Responsibility includes accounting for actions related to the task or function. This is a key attribute of operational control.
(16) Risk. Risk is the degree of probability that hurt, injury, or loss will occur over a specific period of time or number of operational cycles. Risk has two elements: severity and likelihood. With regard to air carrier maintenance operations standards, the relationship between these two elements must be inverse.
(a) Severity is the type of harm inflicted if a particular event occurs. For air carrier maintenance programs, severity should be expressed in qualitative terms as a consequence of failure, such as catastrophic, hazardous, etc.
(b) Likelihood is the estimated probability or frequency, in quantitative or qualitative terms, of an occurrence related to the hazard; it is an expression of the probability that a specific unsafe event will occur. Likelihood is always an estimate.
(17) Risk Mitigation. A risk control measure. It refers to the process of modifying the system in order to reduce the risk.
(18) Risk Management. A formal process composed of identifying hazards, analyzing risk, assessing risk, and controlling risk. This process, embedded within the processes used to provide the product/service, is not a separate process.
(19) Root Cause Analysis (RCA). The analysis of deficiencies to determine their underlying root cause.
(20) System. A functionally related group of elements. In CASS, the elements are:
• Surveillance,
• Analysis,
• Corrective action, and
• Followup.
2-4. PURPOSE OF A CASS.
a. High Level Purpose. If you do not accomplish your maintenance program according to your manuals and applicable requirements, or if your maintenance program itself has deficiencies, your aircraft might be approved for return to service when it is not airworthy. The high-level purpose of a CASS is to reduce or eliminate the likelihood of your aircraft being approved for return to service when it is not airworthy through the continuous, system safety-based, closed-loop cycle of surveillance, investigation, data collection, analysis, corrective action, monitoring, and feedback of a CASS.
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b. CASS Design. The FAA expects you to design your CASS to ensure that you conduct your maintenance program according to regulations and your manuals, and that your program is effective in achieving the desired result of consistently having airworthy aircraft approved for return to service. For the CASS to yield this safety benefit, the FAA expects your senior management to establish safety as its top organizational priority. All personnel need to embrace your organizational goals and act jointly to achieve them.
2-5. STRUCTURE OF A CASS.
a. Overall Objective. The overall objective of the air carrier regulations governing maintenance programs is to ensure that you maintain at least the level of safety originally designed into an aircraft and that each aircraft used in air transportation is always in an airworthy condition.
b. Questions a CASS Addresses. There are two basic questions the regulations require a CASS to address:
(1) Are you following your maintenance program as you have documented in your maintenance manuals and procedures? The CASS of the performance of a maintenance program refers to the process of collecting and evaluating information to determine that the execution of the maintenance program is done according to the regulations, your manuals, and other applicable requirements. This portion of the CASS consists of conducting audits and analyzing audit findings and trends to verify that you are following your maintenance program as you have written it and are properly performing maintenance on your aircraft. The analysis conducted in this area of your CASS should also identify weaknesses, if any, in the systems and procedures used to carry out your maintenance program.
(2) In following your manuals and procedures, are you producing the results that you want? The CASS of the effectiveness of the maintenance program refers to the process of collecting and evaluating operational data that you need to verify that your maintenance program is producing the desired results.
(a) Under the regulations, your primary desired results should be those defined results found in §§ 121.367 and 135.425. There are three:
1. You, or any of your maintenance providers, perform all maintenance, preventive maintenance, and alterations in accordance with your manual.
2. You and your maintenance providers provide competent personnel and adequate facilities and equipment for the proper performance of maintenance, preventive maintenance, and alterations.
3. Each of your aircraft released to service is airworthy and properly maintained for operations in air transportation.
(b) Another desired result is that your aircraft operate with a level of reliability that is consistent with the goals of your maintenance program. “Reliability” is a broad term in this context and is an expression of dependability and the probability that an item, including an
Page 8 Par 2-5 aircraft, engine, propeller, or component, will perform its required function under specified conditions without failure, for a specified period of time. Testing for effectiveness usually consists of collecting and analyzing operational performance data, such as:
• Maintenance-related delays and cancellations,
• Failure rates of parts and components after they are approved for return to service,
• Discrepancy rates of aircraft after heavy maintenance, and
• Related trend analysis.
c. Correcting Deficiencies. The regulations require you to include, as part of your CASS, provisions to correct any deficiencies in your maintenance program, regardless of whether your maintenance program or any part of it is actually conducted by you or by your maintenance provider. The regulations also provide authority for the FAA to require you to make necessary changes in the program if you do not make them on your own.
d. Systems Safety. A well-structured CASS can assist you in taking a systems safety approach to your maintenance program through recognition of the interaction of all the elements within your program systems and subsystems. The systems consist of interrelated processes that comprise of personnel, procedures, materials, tools, equipment, facilities, and software operating in a specific environment to perform a specific task or to achieve a specific purpose, support, or mission requirement for an air carrier.
e. Organizational Functions. An unairworthy aircraft can be the result of the actions of a wide variety of organizational functions, in addition to those associated with maintenance. These organizational functions include senior management decisions, flight operations, ground operations, and others. An effective CASS would consider the potential role of these organizational functions through effective surveillance and complete RCA. Chapter 5, paragraphs 5-2 through 5-4 covers these issues in greater detail.
f. System Safety Categories. When performing their surveillance and analysis functions, we encourage individuals responsible for a CASS to use the system safety categories of safety attributes, safety culture, communication, accountability, training programs, and potential problem areas when identifying hazards and managing risks. The FAA defines safety attributes as the following:
(1) Authority. You have a clearly identifiable, qualified, and knowledgeable individual with the authority to establish and modify your CASS or a process within your CASS. Authority means the power to design or change fundamental policy or procedures without having to seek a higher level approval. Authority is permission; it is a right coupled with an autonomous power to accomplish certain acts or order others to act. Often one individual grants another authority to act, such as an employer to an employee, a corporation to its officers, or a governmental empowerment to perform certain functions.
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(2) Responsibility. You have a clearly identifiable, qualified, and knowledgeable individual who is accountable for the quality and accomplishment of your CASS or a process within your CASS. Responsibility means the obligation to ensure a task or function is successfully carried out. Responsibility includes accountability for the action to carry out a task or function. There is overall responsibility and direct responsibility.
(3) Procedures. You have documented methods for accomplishing a process. The procedure description should answer the basic questions of who, what, when, where, and why, as appropriate.
(4) Controls. You design checks and restraints into a process to ensure you get the results that you want. Controls may not be necessary for every process; however, if a process is critical to meeting your overall system goals, specific controls to ensure proper accomplishment of that process generally are indicative of a well-designed system.
(5) Process measurement. This is where you measure and assess your processes to identify and correct problems or potential problems. You should identify specific measures and the data that you require to be collected.
(6) Interfaces. You identify and manage the interactions between processes, and the interfaces between your CASS and other systems or programs, whether within or outside your maintenance organization.
g. Risk Management. System safety and, therefore, CASS functions are built around principles of what is commonly referred to as risk management. Risk has two elements: severity and probability. Risk management includes identifying hazards, evaluating how severe the hazards’ consequences would be, and how likely they are to occur (probability). After you do that, you can develop, implement, and evaluate measures to address the identified risks and program deficiencies throughout a system’s life cycle to achieve the level of risk that you deem acceptable. All operators currently perform these functions on some level, although the degree of formality and sophistication depends on the size and scope of the operation as well as the level of training your personnel have in risk management. In your CASS, the FAA expects a formal risk management process (system safety) with safety, regulatory, and program compliance as the top priorities. Your formal risk management process should be structured, but not necessarily complex or expensive.
h. Safety Enhancement versus Disciplinary Action. The intention of a CASS is to give you (and the FAA) a realistic picture of the frequency and nature of deficiencies occurring in your maintenance program, and the opportunity to correct them. If your personnel at any level perceive that their jobs are at risk by collaborating in this system, they are likely to withhold information or bias the analysis for self-protection. You should design your CASS to emphasize the end goal of enhancing safety by evaluating and improving your maintenance program. You should not carry out your analysis and surveillance so that others perceive it or its intention as a method of identifying individuals who have committed errors simply to take some sort of disciplinary action. Human error is inevitable, but the question for your CASS to answer is how to better design your maintenance program to preclude errors from encroaching on operational safety or resulting in noncompliance.