Posted by: Bryan Anderson
Aircraft repairs are no longer static displays that can be immediately forgotten after return to service
Due to aviation's complex regulatory environment, repairs to aircraft structure can no longer be treated as static data points once they are completed and returned to service. A large percentage of the repair activity on Primary Structure requires ongoing attention to remain in an Airworthy condition. For example, certain Repairs and/or Alterations require a Damage Tolerance Evaluation to determine their impact on the fatigue resistance of the structural element being repaired or altered. Furthermore, repair activity can occur in areas that are already covered by mandatory inspection programs or supplemental inspection requirements. If repair activity impacts the accomplishment of a previously mandated procedure, the effect of the repair on accomplishment of the specified procedure must be considered.
In the RepairMaps system, a Restriction will generally be used to keep track of any item that requires continued attention and/or effort to be allowed to remain in service. In the case where repair activity does occur in an area of a previously mandated inspection procedure, but is found to have no impact, it is good policy to note that this has been assessed and found to have no impact. A good way to do this is to raise a Restriction in RepairMaps, which acknowledges the potential impact and can include any details as to why the mandated inspection is not impacted:
The DTA process is often broken down into three distinct Stages:
- Stage 1 is typically called 'static strength' and remains valid for a short time.
- Stage 2 is static strength plus a threshold. Normally the threshold is the point at which you need to have Stage 3 in hand.
- Stage 3 consists of the inspection method to be used starting at the threshold and the interval that the supplemental inspection must be repeated.
You can receive just one or all three Stages at once. Normally, any SRM repair figure used to repair Fatigue Critical Baseline Structure (FCBS), will contain the information needed for all three stages or instructions for how to derive them using currently published data. Let's assume, for this example, that we have repaired the L1 bearstrap. Further, let's assume that the aircraft had 47273 cycles on it at the time of repair. The repair was completed using instructions from the manufacturer. The manufacturer only gave us a Stage 1 approval initially so that we could return the aircraft to service. A Restriction should be raised to this effect:
This acknowledges that we have received the Stage 1 equivalent strength approval and can release the aircraft for service for continued operation until the 'Next Due' limiter is reached. For purposes of this example, let's assume that the Manufacturer allowed operation of the aircraft for 6000 cycles from the time of the repair before the Stage 2 DTA was required. There is no further activity required on the Stage 1 approval, so the Restriction can be terminated and a new Restriction raised for the still needed Stage 2 approval:
This Restriction would then be an open tracked item due by 53273 TAC, (47273 + 6000), as shown in the 'Next Due' attribute. Upon receipt of the Stage 2 approval, the Restriction can be edited to look like this:
And terminated. Then, a fresh Restriction should be raised for the still-open Stage 3 requirement:
The Restriction for the Stage 3 portion of the DTA process remains an open item and must be addressed at the appropriate time, as noted in the Restriction. The Restrictions area would look like this, (assuming all the above was accomplished as described):
Note that there are three terminated Restrictions and one active Restriction. This gives a full picture of any impact the repair has on FCBS structure or previously mandated inspections, as well as the current status of any open items that may affect the ongoing Airworthiness of the repair.
Any number of Restrictions can be raised. It is suggested that one Restriction be raised for each impacted required inspection, or element of an inspection. For example, a lap seam modification may impact several SSI inspections. A Restriction should be raised for each individual impacted inspection such as 'F-38A, Internal DVI'; 'F-38A, Internal NDT'; 'F-38B'; 'F-38C'; 'F-38D, Internal DVI'; 'F-38D, Internal NDT,' and so on. Along these same lines, a DTA supplemental inspection may be broken into several steps, such as 'HFEC around periphery of repair doubler'; 'Internal DVI for cracking' that occur at the same time. This would benefit from two separate Restrictions. Any reference documents for accomplishing the denoted inspections should be uploaded to the documents section and called up in the Restriction.
These are just a small handful of examples that illustrate the value proposition of RepairMaps' Restrictions module. Given the complicated regulations that every operator must now routinely navigate, the filebox-and-clipboard approach to tracking this dynamic data is no longer enough to ensure airworthiness and regulatory compliance.
To learn more, contact us today.