Avionics News October 2016 - 14
Continued from page 13
A part design approval is issued when a third
party designs a replacement part for a type-designed
aeronautical product. There are a few situations
where a PDA cannot be issued for a replacement
part. Does a change in manufacturing process make
a replacement part ineligible for a PDA?
The answer is not straightforward. The easiest
way to look at this is to review when a PDA
can be issued and then address each case. CAR
"(2) A part design approval shall not be
issued if the replacement part
(a) is subject to an airworthiness
(b) is a standard part or a
(c) constitutes a change to the type
design of the aeronautical product.
(d) creates an airworthiness limitation."
Sentence (b) is clear if you refer to CAR 101
for the definitions of these items; (a) and (d)
are straightforward in that any change to an
airworthiness limitation (including adding one) is
a major design change. Or as it is stated in CAR
521.152, a "change to a type design." This is
essentially covered by (c).
Sentence (c) is the tricky one. Keep in mind
that a change in type design does not mean
both major and minor. CAR 521 removed the
use of the terms major and minor. However,
CAR 521.152 and CAR 521.154 are essentially
major and minor design changes, respectively.
Therefore, (c) refers to a major design change
only. Now the question is, does the change in
manufacturing process constitute a major design
change? In many cases, the answer would be no.
Consider the fact that, in most cases, a
third party would not know exactly what the
manufacturing processes are. The requirement
is to show that the replacement part continues
to meet the certification basis for the part being
replaced. In doing so, this does not make it
a major design change. As long as the part
performs the same function and can be installed
in essentially the same manner, it is not a major
What about the case where the replacement
part affects the structural strength, which is a
basic part of when something is a major design
change? This may be true, but the premise of
the PDA is that the applicant still has to show
compliance to the design standard for the
replacement part. Therefore, showing that the
part meets the structural requirements is integral
to the PDA and does not make it ineligible.
So when does a change to the manufacturing
process constitute a major design change?
When a maintenance manual or flight manual
supplement is required, when there is a change
to the installation procedures or when additional
instructions are required to operate it are some
of the examples that may constitute a major
design change. Each case must be carefully
reviewed. However, as stated above, a change in
manufacturing process is most likely not a major
If you are having issues with the interpretation
of this, contact the AEA to help you through the
Note: The AEA offers "Frequently Asked Questions" to foster
greater understanding of the aviation regulations and the rules
governing the industry. The AEA strives to ensure FAQs are as
accurate as possible at the time of publication; however, rules
change. Therefore information received from an AEA FAQ should
be verified before being relied upon. This information is not
meant to serve as legal advice. If you have particular legal questions, they should be directed to an attorney. The AEA disclaims
any warranty for the accuracy of the information provided.