Considering Corrosion Prevention and Control Programme (CPCP) Airworthiness Directives (ADs)

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Sofema Online (SOL) considers the role of CPCP ADs and the responsibility for updating the Aircraft Maintenance Program (AMP)


Each CPCP, whether originally mandated by AD or later incorporated into the MPD for an aircraft, includes certain definitions to lay the groundwork and baselines for the programs.

Corrosion is a progressive condition and generally becomes more serious as it moves deeper into the grain of the affected metal. Therefore, different levels of corrosion are defined: Level 1 being the least serious, Level 2 being increasingly problematic, and Level 3 being the highest. However, these definitions were never standardized, although they are largely well-understood by CAAs, manufacturers, and the industry.

A typical CPCP AD requires an operator to incorporate a baseline CPCP into its maintenance or inspection program.

>> The baseline CPCP, developed by a manufacturer for all operators of a particular model of aeroplane, consists of

o corrosion prevention and control tasks;
o definitions of corrosion levels;
o compliance times (implementation thresholds and repeat intervals); and
o reporting requirements.

>> After an operator has incorporated a baseline CPCP into its maintenance or inspection program, the ADs allow adjustment to the required repeat intervals of the CPCP, provided the maintenance program is maintaining corrosion at an acceptable level.
>> The FAA has determined that corrosion damage occurring between successive inspections that are local and can be reworked or blended out within allowable limits (as defined by the manufacturer or the FAA) is an acceptable level of corrosion.

In broad terms, these allowable limits of corrosion damage are defined as Level 1 corrosion.

Originally, CPCP ADs were issued when approved CPCPs did not exist or were not part of an operator’s maintenance program.

Today, in most cases, the implementation of the original ADs has succeeded in their goal of reducing corrosion and has also provided a means to integrate corrosion prevention practices into Maintenance Review Board Reports (MRBRs) and MPDs.

>> Over the years, CPCP ADs have been modified as a result of safety information reported by operators to manufacturers, whereas other ADs have been revised by adopting terminating actions that were found to be effective.
>> The FAA issued CPCP AD 90-25-05, Amendment 39-6790 (55 FR 49268, November 27, 1990), which requires implementation of a CPCP contained in Boeing Document Number D6-35999, titled “Aging Airplane Service Bulletin Structural Modification Program –Model 747.”

CPCH Incorporation in the Aircraft Maintenance Program

>> To prevent structural failure due to corrosion.
>> The TCH is required to develop a baseline corrosion prevention and control programme (CPCP).
>> The operator incorporates a CPCP in the AMP taking into account the baseline CPCP.

Next Steps

Please see the following course (currently available as classroom or webinar): FAA & EASA Corrosion Protection and Control Program – 2 Days

For additional information please see or

Please email [email protected] for any questions or comments

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