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Modification of Canadian Aircraft

What is a design change
The maintenance release for a modification design change

You have made a change to the type design of the aircraft and it is time to make the logbook entry so the aircraft can go flying. The decision that the person completing the maintenance release has to make is if design change is a major or minor modification? Remember that the purpose of this exercise is to determine the type of applicable data that the design change has to “comply” with. Hopefully this exercise was thought about before the work was completed.

Here are the definitions straight from CAR 571.06:

major modification” - means an alteration to the type design of an aeronautical product in respect of which a type certificate has been issued that has other than a negligible effect on the weight and centre-of-gravity limits, structural strength, performance, power plant operation, flight characteristics or other qualities affecting its airworthiness or environmental characteristics;

"major repair" - means a repair to an aeronautical product in respect of which a type certificate has been issued, that causes the aeronautical product to deviate from the type design defined by the type certificate, where the deviation from the type design has other than a negligible effect on the weight and centre-of-gravity limits, structural strength, performance, power plant operation, flight characteristics or other qualities affecting the aeronautical product's airworthiness or environmental characteristics;

Don’t feel bad if these definitions leave you more confused than before. The determination of a minor and a major design change has been a gray area for many people since its conception. If you are having a hard time about this one I recommend one of two approaches, call Transport Canada and ask, or feel free to call AV8 Design.

Here is the data that Transport Canada allows to be used for major and minor modifications CAR 571.06:

The criteria to be used to determine which data applies to modifications and repairs is as follows:

(a) All major modifications and major repairs shall be performed in accordance with either “approved” data or “specified” data. A statement of “No technical objection”, or similar wording, by the manufacturer does not constitute “approved”, “acceptable”, or “specified” data and shall not be used without further approval by the Minister.

(b) All other modifications and repairs shall be performed in accordance with “acceptable” data.

Sparing you any more definitions here is how it breaks down in regards to what data can be used to complete the maintenance release for a design change.

Minor
Major
Acceptable Data
Specified Data
Approved Data


OEM Data

TC Advisory Material

Advisor Documents of foreign authorities which Canada has airworthiness agreements with


Manufactures SRM

AC 43.23-1 and 43.13-2 with conditions

AD’s

SB’s with regulatory approval

STC’s

LSTC’S

RDC’S

If the design change is a major modification or major repair don’t forget to report the design change to Transport Canada. This is a requirement as stated in CAR 571.12. You can find a report form in CAR 571 Appendix L.

The AC 43.13 as specified data for major modifications
Approved data for major modifications
How do you obtain a design change approval
What is a DAR and a DAO
Why use a DAR or DAO
Standards and Approvals
Mechanics, Engineers and good design
Whose responsibility is the aircraft modification
Change Product Rule and the basis of certification