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Modification of Canadian Aircraft

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

A DAR or DAO should be a value added service that supplements a maintenance or manufacturing organization. Consider a DAR or DAO as an engineering department on demand. Any individual may obtain an aeronautical product design change approval directly from Transport Canada. However, obtaining the same approval though a DAR or DAO offers the following benefits:

• Speed of approval issuance. Transport Canada’s mandate is clearly to have private sector perform this service. Transport Canada is becoming more and more hesitant to complete approvals for non-delegated individual that they have little experience with.
• A clear concise design change package defining the design change modification. Many times the operator knows exactly the design change they wish and exactly how to do it. This is good, but unfortunately many times the certification and documentation part of the modification seams like a burden to the operator. However, years down the road good documentation can prevent many headaches.
• Experience guidance and engineering analysis. How many rivets are needed? Is that bracket strong enough? What about an electrical load analysis, flight testing, ect ect ect. Clear information and helpful guidance should help to avoid the many land mines. When I was an apprentice mechanic I welded up an aluminum tow bar from 6061-0. Looked good from far, but was far from good. The moral of the story is that mistakes can be costly in this industry and that mistakes are best kept to ground support equipment.

One note on why even bother? We all have our stories and I have spent my time in remote locations were you end up doing what ever it takes to get the machine flying. Airplanes have to fly to make money, yes that is very true, but the practice of “doing whatever it takes” can catch up to you. Consider the potential cost of an unapproved design change in the event of a Transport Canada inspection, buyer inspection or an accident.

Standards and Approvals
Mechanics, Engineers and good design
Whose responsibility is the aircraft modification
Change Product Rule and the basis of certification