AMC1 21.A.65 Continuing structural integrity programme for aeroplane structures

CAA ORS9 Decision No. 48

Type-certificate (TC) or restricted type-certificate (RTC) holders for large aeroplanes should implement a programme which includes a process to ensure the continuing structural integrity of the aeroplane’s structures following its entry into service.

For other large aeroplanes, the process should be established considering the points described below:

  1. Overall objectives

    The objective of point 21.A.65 of Part 21 is to ensure that the continuing structural integrity programme remains valid throughout the operational life of the aeroplane and will preclude unsafe levels of fatigue cracking and other forms of structural degradation.

    The intent is for (R)TC holders for large aeroplanes to monitor the continued validity of the assumptions upon which the ICA related to the aeroplane structures are based, and to ensure that unsafe levels of fatigue cracking or other structural deterioration will be precluded in service.

    To achieve this objective, (R)TC holders are expected to work together with aircraft operators.

    The process should apply to all structures whose failure could contribute to a catastrophic failure, and it is not limited to metallic structures or fatigue cracking, but should also encompass composite and hybrid structures and associated failure modes.

  2. Description of the process to maintain the validity of the continuing structural integrity programme

    The process to maintain the validity of the continuing structural integrity programme is either continuous with each service finding, or is a regular review following several findings, or a combination of both. It should include the following:

    1. a plan to audit and report to CAA the effectiveness of the continuing structural integrity programme, including the continuing validity of the assumptions upon which it is based, prior to reaching any significant point in the life of the aeroplane;

    2. criteria for summarising findings of fatigue, environmental or accidental damage and their causes, and recording them in a way that allows any potential interaction to be evaluated;

    3. criteria to assess and record the relevance of each potential contributing factor to the finding, including operational usage, fatigue load spectra, environmental conditions, material properties, manufacturing processes and the fatigue- and damage-tolerance analytical methods of analysis and their implementation;

    4. criteria for establishing and revising sampling programmes to supplement the inspections and other procedures established in compliance with the applicable fatigue- and damage- tolerance requirements;

    5. criteria for establishing when structures should be modified, or the inspection programme revised, in the light of in-service damage findings;

    6. sunset criteria: the extent to which the above elements of the process require definition may be tailored to the size of the fleet and its expected useful remaining life.

    7. Additional AMC which are relevant to the continuing structural integrity programme appear in paragraph 5 and Appendix 5 to AMC 20-20B.