Chapter 7.2 Annex D - Repair Design Approval Scenarios

Introduction

This Annex provides examples of approval processes for repairs IAW DASR 21 Subpart M, with a focus on major repairs. Within the Defence context there are a number of scenarios that are applicable for different repair development circumstances. These scenarios are defined herein as an aid for explanation, rather than as a series of strict application processes. This Annex contains detailed guidance, and highlights how processes vary, for the following scenarios:

Scenario 1 – Major Repair developed by an organisation holding an approval under DASR 21 Subpart J, and approved by DASA. An application for DASA approval of a major repair processed by an organisation holding an approval under DASR 21 Subpart J. 

Scenario 2 – Major Repair approved by an organisation holding an approval under DASR 21 Subpart J with major repair privileges. The process by which an organisation holding an approval under DASR 21 Subpart J, and holding the privilege to approve certain major repairs, may approve a major repair design. 

Scenario 3 – Major Repair which has not been approved by a CAA/MAA and which has been developed by an organisation which does not hold an organisational design approval issued by a DASA recognised CAA/MAA. The process by which a major repair developed by an organisation such as OEM, which has not been approved by a recognised CAA/MAA, may be approved.

Scenario 4 – Approval of unrepaired damage utilising major repair provisions where compliance can be shown with the Type Certification Basis (TCB). The process by which unrepaired damage11See AMC 21.A.445 – Unrepaired Damage (AUS), which can be shown to be in compliance with the TCB with specific maintenance action (for example with an additional inspection program), is subject to approval via the major repair arrangements of DASR 21.A.435(b). These arrangements are also applicable where an individual aircraft is to be flown beyond an AwL item and where compliance with the risk level inherent in the TCB can be demonstrated. In cases where compliance with the TCB cannot be shown a major repair approval is not an appropriate authorisation22A Military Permit to Fly (MPTF) is the appropriate authorisation for flying activities outside the limits encompassed by the valid Certificate of Airworthiness, including flights where the aircraft is not conforming to the Type Design. Further details regarding use of a MPTF can be found in Section 7.5.. 

Scenario 5 – Staged approval of damage tolerant repairs. The process by which approval of repairs which include fatigue and damage tolerance evaluation, may be staged to allow an operator to return its aircraft to service before all the fatigue and damage tolerance data have been developed and approved. The staged process is not applicable to propulsion systems and dynamic systems for helicopters.

Scenario 6 – Approval of new repairs based on pre-approved repairs contained in the type data set. The process by which new repairs are developed based on those contained in the aircraft type repair manual, or based on repairs previously developed for the aircraft type, but outside of the limitations of the existing repair approval, are approved.

Scenario 7 – Approval of changes to the approved type design repair data. The process by which changes to approved data for repairs for the platform are approved (typically changes to the aircraft type Structural Repair Manual).

As a reminder, CAMOs may be able to directly consume repair data approved by a CAA/MAA recognised by DASA as competent for the approval of major repairs or approved by an organisation privileged by such a CAA/MAA. Refer to the Section 8.2 for further information.

Scenario 1 – Major Repair developed by an organisation holding an approval under DASR 21 Subpart J, and approved by DASA

The process for major repair design development and approval for the case of a major repair developed by an organisation holding an approval under DASR 21 Subpart J and approved by DASA is outlined in Table D.1.

Table D.1: Detailed process for Scenario 1

Scenario 2 – Major Repair approved by an organisation holding an approval under DASR 21 Subpart J with major repair privileges 

In Scenario 2 the organisation holding an approval under DASR 21 Subpart J has the privilege to approve certain major repairs IAW AMC2 21.A.263(c)(5). As part of this privilege, major repair approvals will be conducted under a procedure approved by DASA, which will include steps to ensure the privilege is only exercised when valid (refer Section 7.2.4 for further guidance). In cases where the MDOA cannot approve the specific major repair design under their current privilege they must either seek expansion of their privilege (refer AMC2 21.A.263(c)(5), (8) and (9)), or submit an application for DASA to approve the major repair (as per Scenario 1). The MDOA should also consider a means to provide a list of approved major repairs to DASA during surveillance activities (see AMC2 21.A.263(c)(5), (8) and (9) and GM 21.A.435(b)). The process for major repair approval for scenario 2 is outlined in Table D.2.

Table D.2: Detailed process for Scenario 2

Scenario 3 – Major Repair which has not been approved by a CAA/MAA and which has been developed by an organisation which does not hold an organisational design approval issued by a DASA recognised CAA/MAA

This scenario documents the process by which major repair data developed by an organisation from outside of an airworthiness framework for which recognition is applicable, or from within an airworthiness framework for which the recognition scope, conditions and caveats do not allow for direct consumption of major repairs. In this scenario there is no scope to leverage a recognition framework for direct consumption; however, the data may be used to support an application for approval by DASA or by an appropriately privileged organisation holding an approval under DASR 21 Subpart J. The detailed process is shown at Table D.3.

Table D.3: Detailed Process for Scenario 3

Scenario 4 – Approval of unrepaired damage utilising major repair provisions where compliance can be shown with the TCB

This scenario documents the process by which unrepaired damage can be shown to be in compliance with the TCB. This process may also be applied to the case when an individual aircraft without damage is to be flown beyond an existing AwL. 

This scenario may be used for managing the demonstration of compliance with the TCB of unrepaired damage for which a repair is required, and for which implementation of additional maintenance inspections or limitations would allow demonstration of compliance with the TCB. In this case, the CAMO seeks an approved design from an organisation holding an approval under DASR 21 Subpart J with access to appropriate type design data. 

The limitations may be related to the limit of duration of the approval; however, operational limitations such as flight restrictions are not managed within this scenario. Flight restrictions are to be managed via the Military Permit To Fly (MPTF) process.

Where an individual aircraft without damage is to be flown beyond an AwL item and where compliance with the risk level inherent in the TCB can be demonstrated, and is approved via a major repair approval for unrepaired damage, the arrangements described in this scenario are also applicable. In this case, it constitutes a major repair88IAW the major/minor considerations detailed in Section 7.2.4 and follows the approval process outlined herein. Where compliance with the TCB cannot be shown, a major repair approval is not an appropriate authorisation. In this case a MPTF should be considered99As documented in Section 7.5 an example of DASR MPTF usage is “Flights where an individual aircraft is not conforming to the Type Design. Predominately include ferry to maintenance venue when damaged beyond approved limits (and un-repaired damage assessment is not an option), for operation with overdue scheduled servicing or ADs not incorporated, and for operation outside ICA, including operational limits”. 

Table D.4: Detailed Process for Scenario 4

Scenario 5 – Staged approval of damage tolerant repairs

The process by which approval of repairs that include fatigue and damage tolerance evaluation may be staged, to allow an operator to return an individual aircraft to service before all of the fatigue or damage tolerance data has been developed and approved. Note that such repairs are considered major repairs and a staged approach for repairs which include fatigue and damage tolerance evaluation may only be applied for aircraft types for which the basis for fatigue or damage tolerance evaluation is part of the TCB1111In cases where the aircraft TCB does not incorporate damage tolerance, but the applicant wishes to take advantage of damage tolerance as part of a staged repair approval process, DASA agreement is required as part of the approval of the CP.. Note, propulsion systems, and dynamic systems for helicopters, are not eligible for the staged approval process. The general approach outlined below follows the 3-stage approach documented in FAA Advisory Circular 120-93 Appendix 5: Approval Process for New Repairs; however, it is noted that the implementation of the stages is to be outlined as part of the CP, and the combination of stages into a one or two-staged delivery may be appropriate depending on the repair requirements. The stages are described below:

The first stage is approval of the static strength data and the schedule for submittal of the fatigue or damage tolerance data. This approval is required prior to returning an aircraft to service. For a staged approach to be considered acceptable, good damage-tolerant design practices are required. Prior to a staged approach being invoked, an assessment of the suitability of a damage-tolerant approach with staged approval is to be considered and documented in the CP.

The second stage is approval of the fatigue or damage tolerance data. The fatigue or damage tolerance data should be submitted no later than agreed as part of the stage 1 approval . Damage tolerance data might only contain the threshold where inspections are required to begin as long as a process is in place to develop the required inspection method and recurring intervals before the threshold is reached. In this case, the submittal and approval of the remaining damage tolerance data may be deferred to the third stage. 

The third stage is approval of the damage tolerance data not submitted and approved in the second stage. This would typically involve the inspection method and the recurring intervals. This data would need to be submitted and approved prior to the inspection threshold being reached. Operation beyond the threshold would not be allowed unless the data are submitted to and approved by DASA.

Organisations with major repair approval privileges who wish to approve damage tolerant repairs in a staged process, are to have documented the process via which these approvals will be conducted in the Handbook as per DASR 21.A.435(b)2.

Table D.5: Detailed Process for Scenario 5

Scenario 6 – Approval of new repairs based on pre-approved repairs contained in the type data set

This scenario documents the process by which new repairs developed based on those contained in the aircraft repair manual, or based on repairs previously developed for the aircraft, but outside of the limitations of the existing repair approval, are approved. When repairs are developed that are outside of the limitations (for example effectivity and location) of the previously-approved repair scheme they are treated as new repairs, and follow the processes documented in Scenarios 1 and 2. This scenario may leverage compliance demonstration documents developed for previously approved repairs, where applicable, as part of the demonstration of compliance. This may make the repair certification and approval steps more straightforward, but these steps are still required to be conducted.

Table D.6: Detailed Process for Scenario 6

Scenario 7 – Approval of changes to the approved type design repair data

Manuals and other Instructions for Continuing Airworthiness (ICA) (such as the Manufacturer’s Structural Repair Manual (SRM), Maintenance Manuals and Engine Manuals provided by the holder of the type-certificate, supplemental type-certificate, design approval or Auxiliary Power Unit (APU) AUSMTSO authorisation as applicable) for operators, contain useful information for the development and approval of repairs. When these data are explicitly identified as approved, they may be used by operators without further approval to respond to anticipated in-service problems arising from normal usage, provided that they are used strictly for the purpose for which they have been developed. 

The process by which changes to any pre-approved repairs, as documented in the aircraft ICA (such as the SRM), are approved is considered a change to the type certificate (i.e. DASR 21 Subpart D). 

Changes to the approved repair schemes provided for the platform are to be treated as changes to type and classified / managed IAW DASR 21 Subpart D1414Approved Repair Schemes in this context, refers to those repairs that require the introduction of additional material or altered fastening systems (e.g.; doublers, straps, angles, welding, bonding etc.) in order to restore the type-certified limit load capability of the affected structure. Applicability of these repairs is usually constrained by the size of the damage (termed Repairable Damage Limits). Hence changes to those Repairable Damage Limits (i.e. increase in applicable damage size), also constitute a change to the related Approved Repair Scheme. However, changes to Allowable Damage Limits, ‘Repair by Replacement’ or Standard Operating Procedures (such as those described in the ‘General’ section of an SRM), are considered updates to ICA and managed by the organisation holding the MTC via DASR 21.A.61 and DASR 21.A.57.. When developing standard repairs as changes to the type certificate, the developer should also take into account GM 21.A.435(a) and AMC 21.A.433(a) respectively for classifying and substantiating the design. In the case of changes to the previously-approved data being developed by the aircraft OEM, a CRE assessment is required to be included as part of the application for approval of the change to the type certificate. Note that, once the change to the type certificate for the repair is approved, updates to the ICA (such as SRM), which promulgates that repair data, is managed by the organisation holding the MTC, under a procedure agreed with DASA IAW DASR 21.A.61 and DASR 21.A.57 by the organisation holding the MTC.