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Changes (or modifications) to an aircraft, engine or propeller are any change to the approved type design. The change may be physical such as the installation of a new system or replacement of a part for one of a new part number but could also only be a change to documentation such as the Aircraft Flight Manual (AFM) or Operational Suitability Data (OSD).
Repairs are the result of design activities for the elimination of damage and/or restoration of the aircraft/engine/propeller to an airworthy condition. This could also include the assessment of damage to allow continued operation without physical repair of that damage.
All changes and repairs need to be CAA approved. The means of approval depends on the classification of the change or repair and whether Design Organisation Approval (DOA) privileges can be used. These pages address the case when the DOA privileges are not used and the change or repair is approved directly by the CAA.
Changes and Repairs are classified as major or minor.
A minor change has ‘no appreciable effect’ on airworthiness or environmental characteristics. All other changes are major. The criteria and guidance material for determining the correct classification is in 21.A.91. For repairs there are additional criteria and guidance in 21.A.435.
Anyone may apply for the approval of a minor change or repair by following the process shown below.
The Applicant for the approval of a major change or major repair must (usually) hold an appropriate design organisation approval. The process for major change or repair approval is shown below on this page.
Note: For some classes of light aircraft, the change or repair may not need CAA approval if it has been classified as a Standard Change or Standard Repair and is embodied as per CS-STAN.
A minor change or repair is one that has 'NO appreciable effect' on airworthiness or environmental characteristics.
Modification of data and documentation such as the Aircraft Flight Manual (AFM) and Operational Suitability Data (OSD) will be processed as changes/repairs to the type design. There is no separate application.
Anyone may apply for the CAA approval of a minor change or minor repair.
An application is made using CAA Form SRG1726NR
Submit an application on CAA Form SRG1726NR and provide the initial 'data pack' which should include:
Further guidance may be found in CAP 1419
CAP 1419 was originally developed for non- Part 21 changes, but the intent of the guidance within is still applicable for minor changes to Part 21 aircraft.
A major change or repair is one that has 'an appreciable effect' on airworthiness or environmental characteristics.
The approval process for Major Change and Supplemental Type Certificate (STC) is essentially the same.
A Major Repair Approval format is common to the TCH and non-TCH alike.
Modification of data and documentation such as the Aircraft Flight Manual and Operational Suitability Data will be processed as changes/repairs to the type design. There is no separate application.
Applicants for the CAA approval of a Major Change, Supplemental Type Certificate (STC) or Major Repair must hold an appropriate design organisation approval such as:
In the case of a STC on ELA1 aircraft (European Light Aircraft as defined in EU Reg 748/2012), in the absence of an organisation approval, the applicant's capability may be shown through the Certification Programme as per 21.A.112B(c).
If DOA or ADOA is required, the scope of the certification project must be within the approved scope and Terms of Approval (TOA) of the DOA/ADOA. Applications are also accepted in cases when the certification project is simultaneously being used to demonstrate applicant competence for the issue of or extension to the scope or ToA of the DOA/DOA.
For further information on DOAs and ADOAs see our guidance on how to apply for a Part 21 Subpart J approval.
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