Par 11-1 Page 45 CHAPTER 11. CONTINUING ANALYSIS AND SURVEILLANCE SYSTEM
11-1. BACKGROUND OF THE CASS. Introduction of the CASS requirement resulted from an FAA industry study of a series of maintenance-related air carrier accidents occurring during the 1950s. The study found that, in many cases, the primary causal factor of an accident was a fundamental weakness or weaknesses in the air carrier maintenance program. The study found that in some cases maintenance personnel failed to accomplish required maintenance tasks or failed to accomplish the task correctly. They simply didn’t follow the manual. In other cases, the study found that the maintenance program, even when followed as planned and documented, was not effective in preventing the situation that led to the accident. It did not produce the desired results.
a. Regulations. Responding to this finding, we introduced regulations (§§ 121.373 and 135.431) that require you to establish and maintain a system for the CASS of the performance and effectiveness of your maintenance program.
b. Correcting Deficiencies. These regulations further require that you include a process in your CASS to correct any deficiency identified in your maintenance program, regardless of whether you did the work or had a maintenance provider do the work.
11-2. CASS IS A SAFETY MANAGEMENT TOOL. A CASS is your system for managing safety as it relates to maintenance functions. As a tool to manage safety, it is part of your overall structure of policies and procedures that you use to ensure your operations are to the highest possible degree of safety. It is a structured, methodical process that helps you reach your maintenance program objectives. CASS is the only management system that we currently mandate by regulation. If you use it properly, your CASS becomes an inherent way of doing business for you, and helps you to promote a culture of safety in your company by providing a formal process for your employees to identify and correct safety deficiencies. As you will see in the following brief discussion of the structure of a CASS, the same objectives of measuring and continuously improving the performance (program execution) and effectiveness (program results) of a major function (maintenance) apply equally to all safety-related maintenance program functions that you must manage.
11-3. BASIC CASS PROCESSES.
a. CASS Processes. Your CASS is a risk-based, closed-loop system that has four basic processes:
(1) Surveillance. An information gathering/audit process you use to collect data to measure your program execution and measure your program results.
(2) Analysis. An analysis process you use to identify any maintenance program deficiencies and any necessary corrective actions.
(3) Corrective Action. A planning process you use to ensure that your corrective actions are implemented.
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(4) Followup. A performance measurement process that you use to verify that your corrective actions are effective. This is also an information gathering and analysis process, thereby closing the loop.
b. Using an Audit Program.
(1) During the first step, surveillance, you will gather and obtain data using an audit program to support measurement of performance (program execution). Your audit program should be well structured, based on risk assessment, and accomplished by individuals trained and skilled specifically at auditing. Consistent with the wording of the regulation, your primary type of audit should be work-in-progress audits that evaluate if the worker is following the manual.
Your auditors would also look at areas such as manuals and other maintenance technical data, aircraft condition, actual in-process maintenance practices, training, publications, and ground operations.
(2) In addition, information gathering to obtain data that will support the measurement of effectiveness (program results) is generally a collection of flight operational data such as accidents/incidents, mechanical delays and cancellations, in-flight engine shutdowns, unscheduled landings, engine performance, pilot log book writeups, and unconfirmed component or part removals.
c. Data Analysis. In the second step, you will analyze the data to identify indications of maintenance program weaknesses. Your data analysis should be accomplished by individuals experienced and/or trained as analysts. One of your key objectives here is to not only identify a weakness, but to determine its root cause. This is where your knowledge of human factors becomes critical.
d. Developing Corrective Action. Based on the results of your analysis, the third step is for you to develop a corrective action, if necessary, again taking into account human factors so that your corrective action is likely to be successful. Once you determine what the corrective action is, you will develop and implement a corrective action plan.
e. Conduct a Followup Measurement Process. To close the loop, the fourth step of your CASS will have you conduct a followup measurement process using surveillance and analysis to verify that your corrective action has effectively corrected the deficiency that you identified. You can design this followup data-gathering process specifically for the issue of interest, or you can make it a part of your continuing surveillance that is the first step of your CASS. Determining if you need a special information gathering procedure is part of your analysis that you accomplished in step three.
f. Aspects of Surveillance. Note that both the initial and followup surveillance can and should have proactive and reactive aspects to them. In the case of audits, by auditing systems and procedures, as well as specific transactions, the analysis of audit results can identify weaknesses in a process. Correcting these weaknesses before a problem results is a proactive approach. An audit also may uncover a missed or improper maintenance action. Investigating this finding and correcting the immediate problem is a reactive process. Developing and implementing a corrective action to prevent a similar future event is equally important for improving the
Par 11-3 Page 47 maintenance program, and the regulations require it. Similarly, your analysis of operational performance data from a systems point of view can result in identification of a system’s weakness before a specific unwanted event, such as a cancellation, occurs, which is a proactive process. Investigating and correcting an undesirable operational event related to the maintenance program after it has occurred, though reactive, also is a necessary and desirable procedure.
11-4. RISK-BASED DECISIONS. All effective CASSs take into account the need to manage risk to an acceptable level, as well as the practical limitations that you must face when addressing deficiencies. Consequently, you must set priorities and make choices for planning audits and other information gathering activities, analyzing data, and selecting and implementing corrective actions. You should tie setting such priorities directly to a risk assessment process so that the resulting maintenance program achieves its objectives.
11-5. SCOPE OF A CASS. The CASS monitors all 10 elements of your maintenance program:
• Airworthiness responsibility,
• Air carrier maintenance manual,
• Air carrier maintenance organization,
• Accomplishment and approval of maintenance and alterations,
• Maintenance schedule,
• RII,
• Maintenance recordkeeping system,
• Contract maintenance,
• Personnel training, and
• CASS.
11-6. CASS DESIGN PRINCIPLES.
a. Attributes of System Safety.
(1) Clear authority,
(2) Clear responsibility,
(3) Specific written procedures,
(4) Effective controls,
(5) Performance measures, and
(6) Well-defined interfaces.
b. CASS Design. These six system safety attributes should be the starting point for the design of your CASS. It should be clear who in your organization is responsible for and who has authority over the CASS. You should not divide responsibility/authority into two or more parts due to the likely possibility that activity such as auditing and operations data analysis are poorly
Page 48 Par 11-6 coordinated. Typically, in addition to an individual with overall CASS responsibility, you should have a management board or committee to ensure good communications and coordination of all CASS functions and to maintain regular senior level management involvement. This oversight group also can provide a form of control over critical aspects of your CASS operation and measure the performance and effectiveness of the CASS itself.
c. CASS Interfaces. In addition to the many elements within your maintenance organization, there are many interfaces between the CASS and functions or organizational elements of a typical air carrier that are outside maintenance. Some of the more obvious examples are engineering, flight operations, purchasing, safety, and the FAA. It also is important that you clearly define and coordinate your CASS relationships to your other programs (if they exist) such as Internal Evaluation Programs (IEP), flight operations quality assurance (FOQA) programs, voluntary disclosures, and Aviation Safety Action Programs (ASAP).
11-7. CASS PERSONNEL REQUIREMENTS.
a. Effective CASS Skills. An effective CASS requires certain skills that you may not have readily available within your maintenance organization. For example, auditing skills are not automatically inherent in those skilled in accomplishing maintenance. Analysis capability, particularly related to root cause determination, risk analysis, and consideration of human factors, is specialized and generally requires specific training and experience.
b. Sharing Personnel. For all operators, but particularly for the smaller ones, required CASS personnel can be shared. You may choose to have your personnel perform CASS functions as a collateral duty, and you may choose to hire someone outside your organization to accomplish some or all of your CASS functions. However, it is essential that you recognize the need for knowledge and skills in your CASS that do not necessarily coincide with those knowledge and skills resulting from many years of maintenance experience repairing airplanes.
NOTE: You can find more detailed information concerning developing and implementing a CASS in AC 120-79.
Par 12-1 Page 49 CHAPTER 12. ADMINISTRATIVE
12-1. WHOM TO CONTACT. If you have questions about the material in this AC or would like to provide feedback, you may use the following communication links. By mail: Manager, Air Carrier Maintenance Branch, AFS-330, Federal Aviation Administration Headquarters, 5th Floor, 950 L’Enfant Plaza, S.W., Washington, DC 20024. By phone at: 202-385-6435.
12-2. REGULATORY REFERENCES. You can find the regulations that underlie this AC in 14 CFR. A summary of specific regulations:
• Scope of Regulatory Applicability, §§ 119.1(c), 121.1(b), and 135.1(a)(2);
• Air Carriers’ Responsibility for Airworthiness, and for Performing Maintenance, §§ 121.363 and 135.413;
• Air Carrier Maintenance Programs, § 119.5, § 119.49, § 121.133, § 121.367, or § 135.21;
• Air Carrier Maintenance Program Manual, §§ 121.133, 121.137, 121.367, 121.369,
135.21, and 135.427;
• Air Carrier Maintenance Organization, §§ 119.65, 119.67, 119.69, 119.71, 121.365, and
135.423;
• Air Carrier Maintenance Time Limitations, §§ 119.49, 121.135, and 135.23;
• Performance and Approval of Maintenance and Alterations, §§ 43.3(f), 43.7(e), 91.403,
91.407, 91.413, 119.1(c), 121.1(b), 121.379, 135.1(a)(2), and 135.437;
• Performance and Approval of Maintenance and Alterations Performed by Other Persons, §§ 119.1(c), 121.1(b), 121.379, 135.1(a)(2), and 135.437;
• Air Carrier CASS, §§ 121.373 and 135.431;
• Air Carrier Personnel Training, §§ 121.367(c), 121.375 and 135.433;
• Air Carrier Maintenance Recordkeeping and Reports, Part 121 Subpart V, §§ 43.9(b),
121.369(c), 121.380, 135.415, 135.417, 135.427, and 135.439(b);
• Maintenance Log, §§ 121.563, 121.701, 121.709, and 135.65;
• Service Difficulty Reports (SDR), §§ 121.703 and 135.415;
• Required Inspection Items (RII), §§ 121.365, 121.369, 121.371, 135.427, and 135.429;
• Mechanical Interruption Reports, §§ 121.705 and 135.417; and
• Alteration and Repair Reports, §§ 43.9(b), 121.707, and 135.439(a)(2)(vi).
12-3. OTHER RELATED REGULATIONS AND GUIDANCE MATERIAL. For more information, consult current editions:
• Title 14 CFR parts 1, 3, 43, 26, 91, 119, 121, and 135;
• Title 49 U.S.C. § 46310, Reporting and Recordkeeping Violations;
• AC 120-59, Air Carrier Internal Evaluation Programs;
• AC 120-73, Damage Tolerance Assessment of Repairs to Pressurized Fuselages;
• AC 120-77, Maintenance and Alteration Data;
• AC 120-78, Acceptance and Use of Electronic Signatures, Electronic Recordkeeping Systems, and Electronic Manuals;
• AC 120-79, Developing and Implementing a Continuing Analysis and Surveillance System;
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• FAA Order 8110.103, Alternative Methods of Compliance (AMOC);
• FAA Order 8620.2, Applicability and Enforcement of Manufacturers’ Data;
• FAA Order 8900.1, Flight Standards Information Management System (FSIMS);
• Air Transport Association (ATA) MSG–3, Operator/Manufacturer Scheduled Maintenance Development; and
• Report Number AD-A066-579, Reliability-Centered Maintenance.
12-4. OBTAINING REFERENCE MATERIAL (current editions):
• You can find this AC at http://www.faa.gov/regulations_policies/advisory_circulars/.
Operators can find this AC and FAA Order 8900.1, Flight Standards Information Management System (FSIMS), at http://fsims.faa.gov. The public can find this AC and FAA Order 8620.2, Applicability and Enforcement of Manufacturers’ Data, at http://www.faa.gov/regulations_policies/orders_notices/.
• You can request MSG-3 information from the Airlines for America (A4A); 1301 Pennsylvania Ave., NW, Suite 1100, Washington, D.C. 20004. You can also contact A4A online at https://publications.airlines.org/.
• You can get Report Number AD-A066-579, Reliability-Centered Maintenance, from the U.S. Department of Commerce, National Technical Information Service (NTIS), 5301 Shawnee Road, Alexandria, VA 22312. You can reach their Sales Desk at 1-800-553-6847 or 703-605-6000, 8 a.m.—6 p.m. EST, Monday—Friday. You can also access NITS information online at http://www.ntis.gov/.