AIRWORTHINESS PROCEDURES MANUAL CHAPTER 26. Modifications and Repairs

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1 November 2017 Page 1 of 10 CHAPTER Introduction Modifications and Repairs 1.1 CAR M states that a person or organisation repairing an aircraft or component should assess the damage against published approved repair data and the action to be taken if the damage is beyond the limits or outside the scope of such data. The modifications and repairs are carried out using data approved by the DGCA or by an approved CAR 21/EASA Part 21/FAA Part 21 Design organization, as appropriate. 1.2 AAC 1 /2017 stipulates the procedure to be adopted by the owners/operators for approval for carrying out modification and/or repair on an Indian registered aircraft, aircraft component and item of equipment of that aircraft. 1.3 This chapter stipulates the guidelines and procedure to be followed by DGCA officers for processing such cases for grant of approvals of major modification / repair on all aircraft for which Type Certificates have been issued/accepted by the DGCA. 2. References 3. Definition a) AAC 1/2017 b) CAR M c) Rule 52 of aircraft Rule 1937 d) Annex 6 e) ICAO Doc 9760 Repair: The restoration of an aeronautical product to an airworthy condition to ensure that the aircraft continues to comply with the design aspects of the airworthiness requirements used for the issuance of a Type Certificate for respective aircraft type after it has been damaged or subjected to wear. Major Repair. Any repair of an aeronautical product that might appreciably affect the structural strength, performance, power plant, operation flight characteristics or other qualities affecting airworthiness or environmental characteristics of an aeronautical product. 1

2 November 2017 Page 2 of 10 Minor Repair. A repair other than a major repair. Modification. A modification to an aeronautical product means a change to the type design which is not a repair. Major Modification. A major modification means a type design change not listed in the aircraft, aircraft engine or propeller specifications that might appreciably affect the mass and balance limits, structural strength, performance, power plant operation, flight characteristics or other qualities affecting airworthiness or environmental characteristics, or that will be embodied in the product according to non-standard practices. Minor Modification. A modification other than a major modification. Note. The term alteration is also used instead of modification. These terms, wherever used are intended to be synonymous. 4. Approval of modification and repair. 4.1 Minor modification approved by appropriately CAR 21 / EASA 21 / FAR 21 approved design organization may be accomplished by the Approved Maintenance Organization following documented procedures approved by Regional Airworthiness Office. 4.2 A repair which has been classified as minor has negligible effect on the airworthiness of the affected aeronautical product. The accomplishment of minor repairs normally involves use of standard or generally accepted practices. Repairs that are classified as Minor and approved by appropriately CAR 21/ EASA 21/ FAR 21 approved design organization may be accomplished by the Approved Maintenance Organization following documented procedures approved by Regional Airworthiness Office. 4.3 Procedures for accomplishment of modification / repair shall be established by operator / maintenance organisation and documented in CAME / MOE. The regional offices shall review the procedure and approve, if found satisfactory. 4.4 RAO / SRAO shall ensure that accomplishment of minor modification / repair are intimated by the operator / AMO to local Airworthiness Office. It shall be ensured that monthly engineering statistics report submitted by operator contains details of minor modification / repair accomplished on the operator fleet. 2

3 November 2017 Page 3 of Examination of Application for Major modification / repair The nominated officer at the regional airworthiness office shall examine the application received from the owner/operator, as per CA Form -2 (MR) given in AAC 1 / 2017, for approval of major modification/repair The application shall be examined to ensure that: a) The description of the proposed modification or repair correctly and accurately describes the modification or repair; b) Documents are complete and if not, advice applicant what additional information is needed; c) The applicant has conducted and submitted an acceptable conformity evaluation statement that ensures the proposed modification or repair will not impact the airworthiness of the aircraft including mass and balance and other technical aspects such as noise level. d) There is proof that the modification or repair is compatible with previously approved modification or repairs; e) The proposed modification or repair has no unsafe features; f) The applicant has met the requirements for the provision documentation as stipulated in the AAC 1 / Procedure for approval of Major Modifications and Repairs 5.1 The regional airworthiness office shall examine the cases in two categories as follows: a) Modifications and repairs for which Modification/Repair data has been prepared by the aircraft, component or equipment manufacturer and approved by State of Design and certified by Authorized Representatives (AR)/Designated Engineering representatives (DER) of the State of Design of the aircraft. b) Modifications and repairs for which Modification/Repair data prepared by the owner/operator without any approval/certification from State of Design/Authorised Representatives (AR)/Designated Engineering representatives (DER) of the State of Design of the aircraft. 5.2 All cases where design data approved by organizations holding DOA approval from State of Design or their designated representatives are not available, the Regional Airworthiness Office will examine the proposal and forward the same to the Airworthiness Directorate at DGCA Headquarters. The Airworthiness Directorate at 3

4 November 2017 Page 4 of 10 DGCA Headquarters will review the case and forward the same for detailed analysis and approval of the modification/repair scheme data to the Aircraft Engineering Directorate (AED). The operator/owner may have to provide necessary data to AED in line with requirements stipulated in Part-3 of AED Hand Book of Procedures (available on DGCA website at On receipt of approval from the AED, the same shall be conveyed to the Regional Airworthiness Office for grant of approval to owner/operator. 5.3 All cases where design data for the intended modification/repair approved by organizations holding DOA approval from the State of Design or their designated representatives are available, the Regional Airworthiness Office will examine the proposal and if satisfied that all the applicable documents are submitted and the proposal is acceptable, may permit to carry out the modification/repair on the basis of the repair proposal and the design data. 5.4 In case an aircraft is grounded awaiting approved repair data from the DOA of state of design and the data is received by the operator / owner on Saturdays / Sundays, the regional airworthiness office may permit the operator / owner to submit the proposal through . On being satisfied that all the applicable documents are submitted and the proposal is acceptable, the RAO /SRAO may permit to carry out the modification/repair on the basis of the repair proposal and the design data through The formal approval shall be granted on FORM CA-2(MR) to the owner/operator by RAO, after ensuring the following: a) Modification/Repair has been completed as per the approved data. b) If there are any deviations during the practical implementation of the Modification/ Repair, they are duly authenticated by the manufacturer/ organisation holding DOA approval of the state of design. c) The modification/repair completion report has been accepted by the DOA / manufacturer. d) The accomplishment of major repair/modification should be verified/ accepted by the Regional Airworthiness Office (RAO) 4

5 November 2017 Page 5 of Approval of major modifications / Repair at Regional Airworthiness Office shall be granted by an officer not below the rank of DDAW. 5.7 Check list for processing of application is given as an Annexure. 6. Compatibility of Modifications And Repairs 6.1 While assessing the requests for approval of modification or repair it is required to ensure that it is compatible with all other design changes installed on that aircraft. Modifications or repairs designed separately may conflict or interfere with each other, despite having been individually analysed, tested and shown to comply with all applicable standards of airworthiness. Interaction between different modifications or repairs may be of a physical, aerodynamic, structural or fatigue strength, electromagnetic or any other nature. Such interaction may jeopardize the airworthiness of the aircraft. An example of potential incompatibility would be a repair installed in close proximity to an existing repair. While the two repairs individually may be completely satisfactory if separately installed on an aircraft with no other design changes in the vicinity, the combination in close proximity may introduce additional stress concentrations which cause fatigue cracks to occur after a period of time in service. The Authority approving the repair scheme may survey the aircraft to be repaired to establish whether there are any other design changes in the vicinity which may interfere. In the case of an existing repair in close proximity to the new damage, it may be necessary to remove the old repair and install a new repair encompassing both damage areas, designed in a manner to reduce any stress concentrations to a level that will not produce fatigue cracking. 6.2 In a more general situation, modifications may be separately designed for the same basic aircraft type by different organizations with no knowledge of the other s work. The modifications may be shown separately to comply with all applicable airworthiness standards; however, on attempting to install them on the same aircraft, it may be found that they physically interfere with each other. Alternatively, no problems may be encountered with the installations, but it may be found in service that the combination causes aerodynamic buffeting, stability or control problems, fatigue cracking, structural failure, electromagnetic interference, or any number of other problems. If the concurrent installations of different modifications are not rigorously assessed for compatibility, there exists the possibility that in combination they may cause serious airworthiness hazards Modifications and repairs design may be prepared by the same organization that operates the aircraft into which they are incorporated. In the more general case, however, the organization that designs and obtains design approval for the modification or repair, the operator of the aircraft, and the organization that incorporate the design change on the aircraft may all be different. Their separate responsibilities are discussed below. 5

6 November 2017 Page 6 of Responsibilities of Holders of Approvals In the case of a design change intended as a unique installation on a single aircraft, the aircraft records and the aircraft itself should be surveyed to identify all other design changes to the aircraft which may in any way interfere with the proposed installation. All such existing installations should be considered in the analysis and testing conducted to demonstrate compliance with the standards of airworthiness In the more general case where a design change is intended to be sold to many aircraft operators and incorporated on multiple aircraft, it may not be feasible for the designer of the modification or repair to obtain knowledge of the modification status of every aircraft affected. The designer should account for the effects of any potential incompatibilities between the proposed design change and any known existing or reasonably foreseeable modifications or repairs when conducting analyses and tests to demonstrate compliance with the standards of airworthiness and obtain design approval. Alternatively, limitations may be placed on the design change, explicitly advising potential users that it has not been cleared for compatibility with other modifications or repairs and that the installer should obtain separate design approval for installation in combination with those others The holder of a design change approval has a responsibility to assist the DGCA to correct airworthiness deficiencies discovered in service which relate to the design change. If, during the course of investigating a perceived unsafe condition related to the design change, the approval holder determines that the unsafe condition results from an incompatibility between the design and another modification or repair, the approval holder should notify the DGCA immediately and recommend corrective measures. If the DGCA determines that the design change must be altered to prevent the unsafe condition from occurring in other aircraft on which it is installed, it will normally require the approval holder to develop the corrections and issue instructions for the installer. These instructions should provide corrective measures for existing installations and revisions to the installation instructions for future installations. 6.5 Responsibilities of Installers Because the holder of a design approval for a particular modification or repair cannot be expected to be aware and to have conducted analyses and tests for all the possible design changes installed on all aircraft of a given type, the installer has a responsibility to verify compatibility with other modifications and repairs before installing any design change. The installer should survey the aircraft records and the aircraft itself to determine what other design changes exist on the aircraft. Any 6

7 November 2017 Page 7 of 10 questions of incompatibility with other modifications or repairs arising from the survey should be referred for resolution to the operator. 6.6 Responsibilities of Operators Operators have the overall responsibility to ensure the compatibility of all design changes incorporated in their aircraft. The operator contracting with an installer for incorporation of any aircraft modification or repair should provide the installer with information on all existing design changes to the aircraft so that compatibility may be verified. Any questions of design change incompatibility which may arise during installation or in service should be thoroughly investigated by DGCA in association with the approval holder. In case of any incompatibility between modifications or repairs, the problem must be corrected. In addition to correction of the problem on the aircraft on which it is established, it is necessary that any incompatibilities between modifications or repairs be addressed on all other affected aircraft. The operator should promptly report any design change incompatibilities detected during installation or in service to the approval holder to the installer and to DGCA. 7. Oversight 7.1 RAO / SRAO shall carryout periodic surveillance to ensure that documented procedures for approval of modifications and repair are being followed and all the modifications / repair accomplished by the operator without formal approval by DGCA are classified as minor by appropriately approved DOA. 8. Record Keeping The DAW (Region) and DAW (Hqrs) will establish a system to maintain records of all documents generated and received. It may be ensured that all related records are maintained in chronological manner and all the pages are appropriately numbered. Traceability of all records should be ensured for future reference. ******** 7

8 November 2017 Page 8 of 10 ANNEXURE Note: While filling up the following checklist, either SAT or UNSAT Column to be filled up, in case of any item of inspection is UNSAT, then the reason to be mentioned in the remarks column. CHECKLIST FOR APPROVAL OF MAJOR MODIFICATION/REPAIR S.No. ITEM OF INSPECTION SAT UNSAT REMARKS 1. Check the Application Form CA 2(MR) received is duly filled up with all relevant information. 2. Check classification of modification/repair as minor or major either by DGCA on appropriately approved DOA. 3. Check detailed description of the proposed modification or repair submitted. 4. Check that the master documentation list detailing the individual drawings and specifications which define the modification or repair submitted. 5. Check that all relevant documents bear modification/repair reference number, title, issue number and date. 6. Check all drawings and instructions necessary for incorporation of the modification or repair submitted. 7. Check that copy of Repair and Deviation Record (RDR) &/or Repair Design Approval Sheet (RDAS), as applicable, is attached along with the repair data. 8. Check that modification/repair data has been received from organization holding Design Organization Approval by State of Design. 9. Check that data is certified by Authorized Representatives (AR)/ Designated Engineering representatives (DER) of the State of Design of the aircraft. Note: AR/DER shall be a regular employee of the organization holding DOA approval. Certifications by independent representative shall not be acceptable. 10. Check that the applicant has conducted and submitted an acceptable conformity evaluation statement that ensures that the proposed 8

9 November 2017 Page 9 of 10 modification or repair will not impact the airworthiness of the aircraft. 11. Check that a proof is submitted that the modification or repair is compatible with previously approved modification or repairs. 12. Check that a statement is submitted that proposed modification or repair has no unsafe features. 13. Check detailed design standards, to ensure that the operator has considered all applicable design requirements and acceptance engineering reports, including expected test results to be used in determining the compliance of the modified or repaired product. 14. Check whether any test or inspection is required to be conducted during the progress or after the completion of the modification/repair. Such tests/inspection may include but are not limited to flammability, noise requirements, EMI, Electrical load check etc. Check the results of such tests, as applicable. 15. Check, if applicable, the record of the change in electrical load when the modification or repair is performed in the aircraft. 16. Check, if applicable, Ground check done on the aircraft. 17. Check, if applicable, whether Test flight is required, if so check the test flight report and observation. 18. Check any significant changing the weight and centre of gravity position of the aircraft. Also check a. Whether weight of aircraft is required; b. Whether weight and balance computation has been done; c. Whether weight schedule has been amended; d. Whether after revision of weight schedule Load & Trim sheet has been amended, if applicable. 19. Check, whether amendments of particulars in the Certificate of Airworthiness or associated documents have been done, if applicable. 20. Check, if required, whether amendments on the following have been done: 9

10 November 2017 Page 10 of 10 a. Maintenance program b. Maintenance manual c. Repair manual d. Parts manual e. Wiring Diagram f. Inspection schedule g. MEL h. Any other affected Maintenance data 21. Check, if required, whether amendments are done to data specified in the AFM and /or Flight crew operating manual. 22. Physical inspection of repair/modification carried out, if considered necessary. DISCREPANCIES/ DEFICIENCIES: S.No. DISCREPANCY/ DEFICIENCY REMARKS NOTE: Cases where design data is not approved by organisations holding DOA from State of Design or their designated representatives, refer Checklist given as appendix-iii in Part-3 of AED Hand Book of Procedures to be evaluated by AED. Recommended/Not recommended Signature: Signature: Name & Designation: Date: 10