Avionics News March 2017 - 12

In this monthly column, Ric Peri of the AEA's Washington, D.C., office, informs members of the latest regulatory updates.

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A EA V I C E P R ES I D E N T O F G OV E R N M E N T & I N D U ST RY A F FA I RS

The simplicity of
major and minor
D
uring the Aircraft Electronics Association's Repair
Station Training Course in January, a course that is
offered semiannually by the association, the students
got around to discussing alterations and the issue of major or minor.
In general, the evaluation of major and minor is hugely simple.
It doesn't warrant the effort put into it, and more importantly, it
doesn't warrant the "cost" associated with it.
I admit there are certain factions that will disagree with my
simplified approach, but they are in a minority; the FAA guidance
for the past two decades follows this logical approach. The
minority argues that no "in-service" aircraft should ever need
a supplemental type certificate. They argue that the approved
"type design" is frozen in time when the aircraft receives its
type certificate and that all in-service modifications are simply
alterations. Unfortunately, this opinion has not taken off and
does not align with the international norms. As mechanics, we
were all taught Part 43 and the installation of alterations. But in
the late 1980s and early 1990s, the environment (and guidance)
changed to where we are now required to do a top-down analysis
of modifications beginning in Part 21; should the modification
warrant an STC, we would apply for an STC.
During the early 1990s, the Federal Aviation Administration
found itself with a number of aircraft that had some extreme
modifications performed under "field approvals." These
modifications included changes such as increasing the maximum
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gross weight, extending the wings and changing the ailerons.
When reading the definition of a major alteration ("might
appreciably effect ...") independent of anything else, you can (and
we routinely did) come to that same conclusion.
However, when reading Part 21, these types of modification
mandate an STC. The applicant was receiving a field approval in
lieu of an STC, which has never been the intent of the regulations.
So with the publication of change 15 to FAA Order 8300.10
(predecessor to the current FAA Order 8900.1) in the mid-1990s
and FAA AC 43-210 on Field Approvals, it clarified the need for
a top-down analysis of a modification beginning with the highest
level of certification and working down to the lowest level - a
logical approach.
Note: I'm using the generic term "modification" to
mean both type design changes (governed by Part 21)
and alterations (governed by Part 43). We will get into
changes in type design and alterations when we talk
about the individual regulations.
Let's start with the systematic regulations. It is important to
know that what we discuss is fundamentally regulatory. We start
with the regulatory definition of a minor alteration. It is critically
important to understand where the floor is. While there may be
debate on the scope of the criterion, the criterion itself is well
defined by, yes, the regulations. 14 CFR Part 1 defines a minor
alteration as follows: "Minor alteration means an alteration other

Table of Contents for the Digital Edition of Avionics News March 2017