21.A.435 Classification and approval of repair designs

1.Clarification of the terms ‘major’/‘minor’ In line with the definitions given in 21.A.91, a new repair is classified as 'major' if the result on the approved type design has an appreciable effect on structural performance, weight, balance, systems, operational characteristics, certified noise or emissions levels, other characteristics affecting the airworthiness of the product, part or appliance, or other characteristics affecting the environmental compatibility of the product. In particular, a repair is classified as major if it needs extensive static, fatigue and damage tolerance strength justification and/or testing in its own right, or if it needs methods, techniques or practices that are unusual (i.e., unusual material selection, heat treatment, material processes, jigging diagrams, etc.). Repairs that require a re-assessment and re-evaluation of the original certification substantiation data to ensure that the aircraft still complies with all the relevant requirements, are to be considered as major repairs. Repairs whose effects are considered minor and require minimal or no assessment of the original certification substantiation data to ensure that the aircraft still complies with all the relevant requirements, are to be considered ‘minor’. It is understood that not all the certification substantiation data will be available to those persons/organisations classifying repairs. A qualitative judgement of the effects of the repair will therefore be acceptable for the initial classification. The subsequent review of the design of the repair may lead to it being re-classified, owing to early judgements being no longer valid.

2.Airworthiness concerns for major/minor classification The following should be considered for the significance of their effect when classifying repairs. Should the effect be considered to be significant, the repair should be then classified 'major'. The repair may be classified as 'minor' where the effect is known to be without appreciable consequence. i) Structural performance Structural performance of the product includes static strength, fatigue, damage tolerance, flutter and stiffness characteristics. Repairs to any element of the structure should be assessed for their effect upon the structural performance. ii) Weight and balance The weight of the repair may have a greater effect upon smaller aircraft as opposed to larger aircraft. The effects to be considered are related to overall aircraft centre of gravity and aircraft load distribution. Control surfaces are particularly sensitive to the changes due to the effect upon the stiffness, mass distribution and surface profile which may have an effect upon flutter characteristics and controllability. iii) Systems Repairs to any elements of a system should be assessed for the effect intended on the operation of the complete system and for the effect on system redundancy. The consequence of a structural repair on an adjacent or remote system should also be considered as above, (for example: airframe repair in area of a static port). iv) Operational characteristics Changes may include: stall characteristics handling performance and drag vibration v) Other characteristics changes to load path and load sharing fire protection / resistance Note: Considerations for classifying repairs major/minor should not be limited to those listed above.

3.Examples of major repairs i) A repair that requires a permanent additional inspection to the approved maintenance programme, necessary to ensure the continued airworthiness of the product. Temporary repairs for which specific inspections are required prior to installation of a permanent repair do not necessarily need to be classified as major. Also, inspections and changes to inspection frequencies not required as part of the approval to ensure continued airworthiness do not cause classification as major of the associated repair. ii) A repair to life limited or critical parts. iii) A repair that introduces a change to the Aircraft Flight Manual.

(a)REPAIR DESIGN APPROVAL BY EASA

(1)Products first type-certified by EASA or first type-certified by a Member State (covering those type-certified through Joint Aviation Authorities (JAA) procedures or under national regulations and those nationally certified without a type certificate (TC)) EASA approval is required in cases of major repair designs proposed by design organisation approval (DOA) holders that do not hold the necessary privilege as per point 21.A.263(c)(5) to approve certain major repair designs, as well as in cases of minor repair designs proposed by persons or organisations that do not hold a DOA.

(2)Products first type-certified by the competent authority (CA) of a third country EASA approval is always required for major repairs on products first type-certified by the CA of a third country. Approval privileges granted to DOA holders (see point 21.A.435(b)) are not available to TC holders of products first type-certified by the CA of a third country unless this third country has since become an EASA Member State. TC holders of products first type-certified by the CA of a third country may need to be involved in a repair design when an arrangement with the TC holder has been determined to be necessary under point 21.A.433(a)(4). For repairs approved by the CA of a third country, the conditions for acceptance may be defined in the bilateral arrangement between EASA and the third country. In the absence of such an arrangement, the repair data should follow the approval route of Part 21.

(b)REPAIR DESIGN APPROVAL BY THE DOA HOLDER

(1)Approval by the DOA holder Approval of repairs through the use of procedures agreed with EASA implies that the DOA holder issues the approval without EASA’s involvement. EASA will monitor the application of this procedure within the surveillance plan for the relevant organisation. When the organisation exercises this privilege, the repair release documentation should clearly show that the approval is issued on the basis of its privilege.

(2)Previously approved data for other applications When it is intended to use previously approved data for other applications, it is expected that an appropriately approved design organisation has checked the applicability and effectiveness of this data. After damage identification, if a repair solution exists in the available approved data, and if the application of this solution to the identified damage remains justified by the previously approved repair design (structural justifications still valid, possible airworthiness limitations unchanged), the solution may be considered to be approved and may be used again.

(3)Temporary repairs These are life-limited repairs to be removed and replaced by permanent repairs after a limited service period. These repairs should be classified under point 21.A.435, and the service period should be defined when the temporary repair is approved.

(4)Fatigue and damage tolerance An approved design issued before the fatigue- and damage-tolerance evaluation has been completed should specify the limited service period.