For any maintenance task, including AD required actions, the date of release is the date when the Certificate of Release to Service (CRS) is signed by duly authorised certifying staff. Only certifying staff is competent to make the final airworthiness determination and therefore the CRS reference date does not necessarily coincide with the date when the individual maintenance task was actually performed and signed off by maintenance staff.
In the EASA system, the owner/CAMO is not required to keep the (so called) dirty finger prints, i.e. the exact time of the performance of the maintenance (e.g. AD action) work card. However, the owner/CAMO must consider the specific cases of tasks with repetitive action having a calendar limit, where a significant lag could occur between the date of task performance and the date of the CRS (which “legally speaking” determines the effective date of accomplishment). In such cases, the owner/CAMO must coordinate with the maintenance organisation the issuance of a release specifically and without undue delay to cover the particular task that is subject to a calendar limit when it has been applied, to avoid any distortion regarding limits associated with such repetitive actions or, as an alternative, record the date of AD accomplishment in the CRS.
In determining if a lag between the date of task performance and the date of the CRS is “significant”, engineering judgment and common sense must be used. The following questions should be considered:
- how long is the time lag between the ‘due date' (calendar time limit required for the next AD action) and the actual date of (planned) accomplishment? For example, 2 days are significant for a monthly interval task, and obviously insignificant for a 5-year interval task);
- what is the technical content (e.g., inspection for corrosion) of the AD task?; where (e.g., inside hangar, or outside, salty or otherwise erosive/corrosive environment) will the aircraft be parked after AD action completion?;
- other factors may also be considered, affecting that single aircraft and/or operator etc.
It is also to be noted that AD compliance verification (enforcement) is not an EASA responsibility, but that of the National Aviation Authority of the State of Registry of the aircraft, and it is always recommended, if in doubt, to seek their advice.