Management Matters: Continuing Analysis and Surveillance System

CASS is the acronym for continuing analysis and surveillance system; its primary role is to help air carriers put an airworthy aircraft on the gate each and every time. Like the safety management system (SMS), CASS uses a systems approach – it is a...


CASS is the acronym for continuing analysis and surveillance system; its primary role is to help air carriers put an airworthy aircraft on the gate each and every time. Like the safety management system (SMS), CASS uses a systems approach – it is a system, not a program.

Today, there is a “new” CASS, however, the initial regulation has not changed. The “new” CASS can help air carriers realize a positive return on investment (ROI) from the maintenance dollars spent.

The reader might ask: Why worry about the “new” CASS if the actual rule of CASS has not been changed? First, as noted above, an effective CASS can provide a positive ROI. Second, for the last five plus years, more than 1,000 FAA aviation safety inspectors have been trained in the new CASS. CASS training is planned to continue until all ASIs have been exposed to the “new” CASS. The FAA’s expectation of what CASS should look like and do has changed.  It is natural to expect that some air carrier’s CASS might need revision.

The rule of CASS was created in 1964 and is mandated by the FAA for Part 121 and Part 135 (10 seats or more) air carriers. The legal basis for CASS is the regulation: 14 CFR §§ 121.373 or 135.431. CASS is a three paragraph regulation and paragraph (a) is explicit to air carriers: “(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.”

Most Part 121 and Part 135 (10 seats or more) air carriers have convinced themselves and their FAA inspector(s) that they are in compliance to the CASS regulation. Because there had been no clear picture of what a CASS should look like, few questioned the issue of compliance. Figure 1 reflects how some air carriers feel they are addressing the requirements of a CASS. The air carrier’s quality group accomplishes audits, both internal and external (the surveillance side of CASS) and the reliability group accomplish data collection and analysis (the analysis side of CASS).

In the last decade the picture of CASS has changed. The FAA issued two Advisory Circulars:

  • AC 120-16 (Air Carrier Maintenance Programs, Rev. D on 03/20/2003 and Rev. E on 09/11/2008), and
  • AC 120-79 (Developing and Implementing a Continuing Analysis and Surveillance System (Original on 04/21/2003 and Rev. A on 09/07/2010). 

AC 120-16 (as revised) explains what a maintenance program is. For some people, this is quite a new definition. In essence, there are 10 elements that comprise an air carrier’s maintenance program. Some of those elements are the maintenance schedule, records, training, the manual, RII, and CASS.

AC 120-79 (as revised) advises that CASS is responsible for looking over an air carrier’s entire maintenance program (as defined by AC 120-16), not just the traditional operational data and audits. Examples of other items under the “new” CASS umbrella would include all 10 elements of the maintenance program, daily briefings, voluntary self-disclosures, pilot write-ups, non-routine write-ups, SDRs, and human factors. Figure 2 more closely resembles what can be covered by an air carrier’s “new” CASS.

Within the new guidance material for CASS, four major activities are identified that are inherent to any CASS, regardless the size, culture, or complexity of the air carrier. Those four major activities are surveillance, analysis of data, corrective action (when applicable), and follow-up (to corrective action). Most air carriers do the first three activities well. Very few air carriers accomplish the fourth activity well if at all, i.e., follow-up to determine if the corrective action(s) implemented are providing the desired/expected results. Figure 3 reflects the four major activities of a CASS.

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