Modifications and repairs
Modifications and repairs for General Aviation aircraft This page provides guidance on applying for modifications or repairs to UK registered General Aviation aircraft. Modifications and repairs are categorised as either minor or major.
Minor modifications and minor repairs
A minor modification or repair is one that has no appreciable effect on airworthiness but still requires CAA approval. All other changes are major. The criteria and guidance material for determining the correct classification are stated in 21.A.91of the UK Initial Airworthiness Regulation. For repairs there are additional criteria and guidance in 21.A.435.
For non-Part 21 aircraft, such as amateur-built microlights, gyroplanes, historic aircraft or replicas 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.
CS-STAN
Before applying for a minor modification or repair, check whether the intended task may be accomplished via CS-STAN , without CAA approval. On completion of a Standard Change (SC) or Standard Repair (SR), the CAA Form 123 must be completed for the aircraft records. CS-STAN may be used for both Part 21 and non-Part 21 aircraft.
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.
For Part 21 aircraft minor modifications (minor changes) and minor repairs refer to the changes or modifications and repair to Part 21 aircraft page.
Application
Anyone may apply for CAA approval of a minor modification or minor repair.
Applications for approval of minor modifications or minor repairs to:
- other-than complex motor-powered aeroplanes or helicopters; and
- other ELA2 aircraft;
should be submitted by email to apply@caa.co.uk through the SRG1723 form.
Applications concerning complex motor-powered aircraft should use SRG1726NR – refer to the changes or modifications and repairs to aircraft page for more details.
Complex motor-powered aircraft means:
- an aeroplane:
- with a maximum certificated take-off mass exceeding 5700 kg, or
- certificated for a maximum passenger seating configuration of more than nineteen, or
- certificated for operation with a minimum crew of at least two pilots, or
- equipped with (a) turbojet engine(s) or more than one turboprop engine, or
- a helicopter certificated:
- for a maximum take-off mass exceeding 3175 kg, or
- for a maximum passenger seating configuration of more than nine, or
- for operation with a minimum crew of at least two pilots, or
- a tilt rotor aircraft.
1. an aeroplane with a maximum take-off mass (MTOM) of 2,000 kg or less that is not classified as a “complex motor-powered aircraft”;
2. a sailplane or powered sailplane of 2,000 kg MTOM or less;
3. a balloon;
4. a hot air ship;
5. a gas airship meeting all of the following elements:
· 3% maximum static heaviness,
· Non-vectored thrust (except reverse thrust),
· Conventional and simple design of: structure, control system and ballonet system
· Non-power assisted controls;
6. a Very Light Rotorcraft.
Supporting Documents
The applicant must provide an initial 'data pack', to include:
- Definition of the change, (applicability by product type/model and description)
- Accomplishment instructions for the embodiment of the change/repair
- Instructions for Continued Airworthiness
- Flight Manual Supplement (if applicable)
- Record of compliance with the applicable (and appropriate) airworthiness, environmental and OSD requirements
Applicants are recommended to use the provided proforma template for compiling the data pack.
CAP 1419 contains examples of the following to assist applicants:
- Compliance statement
- Instructions for Continued Airworthiness
- AFM supplement
Note CAP 1419 still refers to ‘EASA’ and ‘non-EASA’ aircraft – this should be read as ‘Part 21’ and ‘non-Part 21’ aircraft respectively.
Approval
On receipt of the application, the CAA will confirm that the change/repair can be classified as Minor. The 'data pack' will then be checked to ensure that compliance with the appropriate airworthiness requirements has been demonstrated. The applicant may be asked to provide further information if required.
After confirmation that compliance has been demonstrated, the CAA will issue the Minor Change/Repair approval certificate.
Major Modifications and major repairs
A major modification or major repair to a UK registered aircraft is one that has a larger overall effect on the airworthiness of the aircraft and requires CAA approval.
Major modifications or major repairs are those with:
an appreciable effect on any of the following:
- mass, balance
- structural strength
- reliability
- operational characteristics
- noise/fuel venting/emissions
- operational suitability data
- any other characteristics that may affect airworthiness
or those which may:
- require adjustment of the certification basis
- require new interpretation of the certification basis
- create new methods of demonstration
- require considerable re-evaluation
- alter airworthiness or operating limitations
- effect AD terminating action
- affect a function with a hazardous or catastrophic failure condition
The approval is usually achieved through the release of a Major Change approval certificate, STC certificate or an Airworthiness Approval Note (AAN). Details of individual AANs can be found here.
For major modifications (major changes to Type Certificates (TCs), Restricted TCs (RTCs) and Supplemental Type Certificates (STCs)) refer to the changes or modifications and repairs to aircraft page.
Fees
Information on current fees can be found in the Scheme of Charges (Airworthiness, Noise Certification and Aircraft and Aircraft Engine Emissions.
Contact details
Email: ga@caa.co.uk
Telephone: 01293 573988