Annex 3 to Appendix 3 to AMC 20-20A Repairs and modifications to removable structural components

1.         DETERMINING THE AGE OF A REMOVABLE STRUCTURAL COMPONENT

Determining the actual component’s age or assigning a conservative age provides flexibility and reduces operator burden when implementing DT data for repairs and modifications to structural components. In some cases, the actual component’s age may be determined from records. If the actual age cannot be determined this way, the component’s age may be conservatively assigned using one of the following fleet leader concepts, depending upon the origin of the component:

(a)       If component times are not available, but records indicate that no part changes have occurred, aircraft flight cycles or flight hours can be used.

(b)       If no records are available, and the parts could have been switched from one or more older aircraft under the same maintenance programme, it should be assumed that the time on any component is equal to the oldest aircraft in the programme. If this is unknown, the time should be assumed to be equal to the same model aircraft that is the oldest or has the most flight cycles or flight hours in the world fleet.

(c)       A manufacturing date marked on a component may also be used to help establish the component’s age in flight cycles or flight hours. This can be done by using the above reasoning and comparing it to aircraft in the affected fleet with the same or older manufacturing date.

If none of these options can be used to determine or assign a component age or total number of flight cycles or flight hours, a conservative implementation schedule can be established by using the guidelines applied in paragraph 3 of this Appendix, for the initial inspection, if required by the DT data.

2.         TRACKING

An effective control or tracking system should be established for removable structural components that are identified as FCBS or that contain FCS. This will help ensure compliance with the maintenance programme’s requirements specific to repairs and modifications installed on an affected removable structural component. Paragraph 4 of this Appendix provides options that could be used to alleviate some of the burden associated with tracking all repairs to affected removable structural components.

3.         DEVELOPING AND IMPLEMENTING DT DATA

(a)       Repairs

Accomplish the initial repair assessment of the affected structural component at the same time as the aircraft level repair survey for the aircraft on which the component is installed. Develop the DT data according to the process given in Annex 2 and incorporate DTI into the maintenance programme.

(b)       Modifications

Accomplish the initial modification assessment of the affected structural component at the same time as the aircraft level modification assessment for the aircraft on which the component is installed. Develop DT data and incorporate the DTI into the maintenance programme.

If the actual age of the repairs or modifications installation, or the total number of flight cycles or flight hours is known, use that information to establish when the initial inspection of the component should be performed. Repeat the inspection at the intervals provided by the TCH or STCH for the repair or modification against the component.

If the actual age of the repairs or modifications installation, or the total number of flight cycles or flight hours is unknown, but the component’s age or total number of flight cycles or flight hours is known, or can be assigned conservatively, use the component’s age, or the total number of flight cycles or flight hours to establish when the initial inspection of the component should be performed. Repeat the inspection at the intervals provided by the TCH or STCH for the repairs and modifications against the component.

As an option, accomplish the initial inspection on the affected component at the next C‑check (or equivalent interval) following the repair assessment. Repeat the inspection at the intervals provided by the TCH or STCH for the repairs and modifications against the component.

4.         EXISTING REPAIRS AND MODIFICATIONS — COMPONENTS RETRIEVED FROM STORAGE

(a)       If the time on the component (in flight cycles or flight hours) is known, or can be conservatively assigned, perform the following:

(1)       survey the component;

(2)       dispose repairs and modifications;

(3)       implement any DTI in accordance with the approved schedule;

(4)       accomplish the initial inspection using the actual age of the repairs or modifications, or the total number of flight cycles or flight hours, if known. If the age of the repairs or modifications is not known, use the component’s age. Repeat the inspection at the intervals given for the repairs or modifications against the component.

(b)       If the time on the component (in flight cycles or flight hours) is unknown and cannot be conservatively assigned, perform the initial repair or modification assessment of the affected component prior to installation, and perform the following actions:

(1)       develop DT data according to the process given in paragraph 3 or 4 of Appendix 3to this AMC as applicable;

(2)       incorporate any DTI into the maintenance programme;

(3)       accomplish the first inspection on the affected component at the next C‑check (or equivalent interval) following the repair or modification assessment;

(4)       repeat the inspection at the intervals given for the repair or modification against the component.

5.         IMPLEMENTATION OPTIONS TO HELP REDUCE TRACKING BURDEN

The following implementation techniques could be used to alleviate some of the burden associated with tracking repairs to affected removable structural components. These techniques, if used, would need to be included in the maintenance programme and may require additional EASA approval and TCH or STCH input for DTI.

(a)       Upgrading existing repairs

As an option, existing repairs may be removed and replaced with new parts of the same design revised as necessary to support the new installation. This practice would permit the DTI requirements of the repair to be set to zero and to re-establish an initial tracking point for the repair. Normally, this would be done at or before the survey for maximum benefit. The initial and repetitive inspections for the upgraded repair would then be accomplished at the intervals given for the repair against the component.

A repair could also be upgraded to one whose inspection requirements and methods are already fulfilled by an operator’s maintenance or inspection programme. That repair would then be repetitively inspected at each routine inspection interval applicable to the repair. Specific tracking would not be required because that area of the aircraft would have already been normally inspected on each aircraft in the fleet as part of the existing approved maintenance programme. If the operator’s programme intervals were changed, the effect on requirements for specific tracking would have to be re-evaluated.

(b)       Special initial and/or routine inspections

As an option, existing repairs may have special initial inspections accomplished during the component survey. This initial inspection establishes an initial tracking point for the repair. Following this initial inspection, the DTI requirements (e.g. repetitive inspections) of the repair would be implemented.

In addition, special routine inspections could be defined for typical repairs that could be applied at a normal interval. In this case, an operator could check the affected components on each aircraft for this type of a repair at the defined interval. If the repair is found, the special inspection would be applied to ensure its airworthiness until the next scheduled check. This alleviates the need to specifically track affected components for every repair, especially typical ones.

[Amdt 20/2]

[Amdt 20/20]