CASS ... Too Little ... Too Late

Continuous Analysis and Surveillance FAR 121.373a: No surveillance ... no analysis

FAR 121.373a: “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.”


Several recent air carrier accidents, one in particular, focused attention on the FAA mandated Continuing Analysis and Surveillance System, (CASS) which all air carriers (FAR 121 and 135 with more than 10 seats) have been required to follow for more than 30 years.

Little attention was paid to the FAR, and in too many cases, it was simply ignored as too complex, time consuming, and or of little use. There appeared to be little surveillance or enforcement even though a monthly report is supposed to be filed with the FAA and some carriers had been cited through the years for failing to implement such a program. At times, even where they did, they did not follow their own approved surveillance program. Violations and fines against the carriers became an added threat against chief inspectors, directors of maintenance, and various company executives through the years, especially where data was false and or intentionally falsified.



We all remember the tragic loss of the ValuJet (now AirTran) DC9 in May of 1996 in the Florida Everglades. It was brought down because of a fire that started in a cargo compartment ignited by improperly stored oxygen canisters. This accident marked the start of a significant change in the FAA’s attitude toward enforcement and terminated the kinder and gentler era of David Hinson. (FAA Administrator). Enforcement was ramped up and the pressure was on maintenance in the air carrier business.

However, there was no significant focus on continuing analysis and surveillance during the investigation and congressional hearings simply because there was no clear maintenance failure regarding the accident. The oxygen canisters were being shipped to another station for re-certification and were not given the special handling they deserved. The accident was partly due to untrained workers who failed to handle and store the canisters with the care required of hazardous items.

But continuing analysis and surveillance does apply generally to inspection and performance of maintenance activities. Removal, inspection, packing and shipping of oxygen canisters is a continuing airworthiness maintenance and inspection function and hazmat handling should be included within the surveillance activities of an air carrier’s CAS committee. Since their replacement was required on a regular schedule it would be logical to have this item noted during CAS and perhaps focus attention on the extreme care required in their handling. The regular nature of the inspection of these canisters should have placed their surveillance under the CASS scrutiny and just maybe could have prevented the accident. The CASS did not work for this accident.

Alaska Airlines

A few years later the accident that changed everything regarding enforcement of FAR 121.373 was the Alaska Airlines crash where the MD80 horizontal stabilizer trim drive was defective and caused the aircraft to impact the ocean just north of Los Angeles. Clearly, a maintenance deficiency and clearly within the surveillance requirements of CASS.

When the inspectors converged on Alaska Airlines they focused their attention on the Alaska CAS program and found that it just did not exist or simply was not implemented. The problem with the trim drive was a particularly sensitive one and was a recurring wear problem that the airline should have included in its CASS. Here again the CASS did not work.

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