• Approval must be sought when performing a modification or repair on a CAA regulated aircraft or importing a CAA regulated aircraft fitted with modifications.

    Failure to do so will invalidate the Certificate of Airworthiness or Permit to Fly.

    The length and cost of the approval investigation is determined by the complexity of the modification and how accurate and comprehensive the information submitted by the applicant is.

    The procedures for approving repairs are essentially the same as those for approving modifications.

    Major modification and repairs

    Approval must be sought when performing a major modification or repair on a CAA regulated aircraft or importing a CAA regulated aircraft fitted with modifications.

    Failure to do so will invalidate the Certificate of Airworthiness or Permit to Fly.

    The length and cost of the approval investigation is determined by the complexity of the modification and how accurate and comprehensive the information submitted by the applicant is.

    The procedures for approving repairs are essentially the same as those for major modifications.

    Approval of a major modification

    Please complete and submit Form SRG 1726, together with the appropriate fee.

    Your application should include an initial payment equal to the cost of three hours investigation. If the investigation time exceeds three hours, the additional costs will be invoiced to the applicant.

    Details of the hourly rates are listed in the Scheme of Charges - Airworthiness, Noise Certification and Aircraft and Aircraft Engine Emissions.

    Where the investigation specifies that a CAA Supplemental Type Certificate (STC) is required, approval will be granted largely upon the basis of the STC Definition Document submitted by the applicant.

    CAP 562 - Civil Aircraft Airworthiness Information and Procedures section 11-44 provides further details.

    The CAA may request any further information or ask to conduct any inspection required in order to be satisfied with respect to compliance. Once satisfied that compliance has been demonstrated to the CAA, the STC will be issued.
    Where the application does not state that a CAA STC is required, the major modification approval procedures will be based upon Airworthiness Approval Notes (AANs).

    An AAN will be produced detailing the modifications and the requirements with which they must comply.

    The AAN will record the evidence supplied by the applicant to demonstrate that the modifications comply with the set requirements.

    Once completed and signed, the AAN is the statement of approval by the CAA.

    Records are kept of all AANs. Most can be viewed using the AAN Database.

    Minor modifications and standard changes or repairs 

    A minor modification to a UK registered CAA Regulated/non-EASA aircraft is one that has no appreciable effect on airworthiness, but still requires CAA approval.

    CAP 1419 - Guidance to applicants when preparing applications for the approval of minor modifications to non-EASA aircraft outlines how to achieve a minor modification approval.

    It also covers an alternative process to enable the use of CS-STAN for 'standard' changes (modifications) and repairs, and includes CAA Form 123 as the Standard Change/Standard Repair (SC/SR) embodiment record for an aircraft.

    EASA is responsible for providing equivalent guidance (CS-STAN) for the approval of standard changes and standard repairs to EASA aircraft.