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

To determine the certification requirements for an aeronautical product design change (the basis of certification) the starting point is the original certification basis of the aircraft. You can find this listed on the aircraft’s Type Data Sheet. Think of the basis of certification like a building code, as time goes on the code gets more stringent increasing the cost and effort for certification of new designs. The trade off is increased minimum level of safety for new designs. The basis of certification is the point in time (at what amendment level) the design change will comply to.

Prior to the Change Product Rule, which is effect now in CAR 511 and 513, the design change certification basis was usually always the original certification basis of the aircraft. Now the Change Product Rule has to be considered when determining the basis of certification for a modification. The effect of this is that some modifications may be required to comply with a more current basis of certification. This could make some modifications much more costly that they were in the past.

Why has this happened you might ask? Imagine that you are an aircraft manufacture and you wish to develop a new aircraft. Very costly, at the time of design conception you have to comply with the latest regulations. So why not take an existing airframe and extensively modify it creating a new derivative. This new derivative is therefore not a “new design” but a design change. The basis of certification remains with the older regulations of the original aircraft design thus significantly reducing the cost of certification. This is the practice that the Change Product Rule is aiming at stopping.

So now we have the Change Product Rule to make life even more fun. Airworthiness Manual Advisor AMA 500/16 has been created by Transport Canada defining a recommended procedure to follow when applying the Change Product Rule. The interesting part about this is that it introduces new terms that have to be considered. If you thought understanding major and minor modification was fun now we have new terms such as; is the design change “substantial” and is the design change “significant”. The consolation is that mechanics will not be exposed to this. The decision of the basis of certification for a modification is the DAR, DAO or Transport Canada. The second consolation is that the Change Product Rule does not apply to repairs and the issuance of an RDC.

The long and the short of it is that the Change Product Rule is not going to affect 90% of the day to day design change modifications that occur.