0. GM - Acceptable Means of Compliance
By complying with the AMC the corresponding requirement is considered complied with. Deviations may be accepted by CAA-NL, provided that the applicant demonstrates that an equivalent level of safety is obtained.
1. GM - Effective date
Sufficient implementation time is provided to update aircraft maintenance programmes in an annual cycle, and company expositions. After the effective date, all one-time variations applied and all maintenance programmes and expositions should comply with this MD. Before the effective date, compliance with this MD is accepted as a means to comply with current regulation.
2. GM – Limitation on aircraft operation
As specified in the applicable regulations, an aircraft shall not be flown when one or more maintenance tasks exceed their intervals as specified in the Aircraft Maintenance Programme. This includes any one-time variation applied. No variation may be applied that is outside the one-time variation limitations specified in the Aircraft Maintenance Programme. If the Aircraft Maintenance Programme does not specify any limitations on one-time variations for a specific task, then one-time variations may not be applied to that task. Note that in the AMP, limitations may also be specified per task group or task type. For example: 'C check to be performed at 1000 flt hrs +/-100 flt hrs', 'a one-time variation of 10% may be applied to all lubrication task intervals', 'no extension may be applied to any life limit'
3. AMC - National requirements
Extensions may be applied to Maintenance Directives, unless otherwise specified in the Maintenance Directive.
4. AMC – Reasons for applying one-time variations
Acceptable reasons for applying a one-time variation may include an unforeseen workload peak in the maintenance organisation, an unforeseen unavailability of staff, an unforeseen delay in the parts provisioning, an unforeseen unavailability or unserviceability of a required tool or equipment, or the aircraft not being able to arrive at the maintenance location.
5. GM - One-time variations outside the scope of this MD
In case an interval extension outside the scope of this MD is required, an application for approval can be sent to the authority, together with substantiating documents and a No Technical Objection from the design holder. Note that only the Agency (EASA) may grant approval for a variation of an AD or an Airworthiness Limitation Section task.
6. GM – Non-cumulation of variations
The application of variations will not result in the task being performed less often. After a variation has been applied, the maintenance task next due should be calculated as if the last compliance was at the original due date (so without the variation being applied).
Example:
A 100 hour inspection was originally due at 200 flight hours (hrs) TSN, but performed at 210 hrs TSN, with a variation of 10% applied. Next maintenance should then be due at 200+100=300 hrs TSN.
7. AMC – Cumulation of variations to calendar time intervals
When an aircraft is grounded, maintenance tasks controlled by calendar time other than parking or storage maintenance tasks may be accepted to be overdue. After performance of the maintenance task before flight, the next due may then be calculated from this last performance of the maintenance task.
Example:
An aircraft is grounded for a major repair for 8 months, from 1 February till 1 October. The Aircraft Maintenance Programme specifies a 3 monthly inspection. This inspection is performed only once during the ground time, on 30 September. The inspection is next due at 30 December.
8. AMC – Application of one-time variations in line maintenance
In order to maintain continuity in the inspection pattern, it is allowable to apply the maximum variation as a tolerance as detailed below. If a maximum variation of 10% applies, then tasks may be performed at the interval +/-5%, so within the bracket of 5% before and 5% after the task being due, with the next task due being calculated as last compliance + interval. Note that no additional variation can then be applied. The Aircraft Maintenance Programme must specify such use of variations.
Example:
Tasks with a 100 flight hour (hrs) interval and a maximum variation of 10%, may be performed in a 10 hrs bracket between 95 and 105 hrs. If last task compliance is at 200 hrs TSN, then next due is at 300 hrs. If the task is performed at 295 hrs, then next compliance is due at 400 hrs. If then performed at 405 hrs, it is still within the 10% tolerance (405-295=110 hrs).
9. GM – Variation of intervals reduced for planning purposes only
Reducing a task interval may be more efficient, for example in cases where performing specific maintenance tasks during maintenance checks reduces labour by limiting the number of times that access needs to be provided.
Example:
The design holder specifies a 500 hour interval for a task, with no specific requirement regarding variation. An operator has an inspection cycle based on 100, 200 and 1000 hour inspections. This operator has included this task in its 200 hour inspection. The operator has included a maximum one-time variation of 350 flight hours in the Aircraft Maintenance Programme for the task (200 + 350 = 500 + 10%).
