Avionics News October 2015 - 11

Occasionally, an inspector will argue that the alteration isn't listed in the
aircraft specifications; therefore, it must be major. Or the inspector argues
the modification is not on part of the type design; therefore, it must be major.
Both of these approaches are simply wrong!

While this seems strong and damaging language in
the debate on major and minor, I will offer that it is not.
This is speaking of the effect of the alteration on the type
certificated product. In other words, when the alteration is
completed and you return the aircraft to service, could the
alteration just completed have had a "measurable" effect on
these seven critical areas? If so, then the alteration is major.
Why these seven categories? Because any measurable
change in the certificated levels of each category might
affect the ability of the aircraft to safely fly and needs to be
reviewed by an engineer. In most cases, it's simply having
a second set of eyes reviewing your proposed alteration.
But, because the effect of missing something is so great, the
alteration requires "approved data."
But what are these seven categories - weight and
balance, structural strength, performance, powerplant
operation, flight characteristics, or other qualities affecting
airworthiness?
Since these can be interpreted as broad categories, what
is the intent of each characteristic? Back in 2002, the FAA
published Order 8110.46, Major Alterations that Require
Supplemental Type Certificates. In this order, the FAA gave
the best explanation of six of these seven critical categories
of change.
Before you make the argument that the order applies
to STCs and not major alterations, 14 CFR 21.93 (a)
defines a "minor change" in type design as one that has
no appreciable effect on the weight, balance, structural
strength, reliability, operational characteristics or other
characteristics affecting the airworthiness of the product.
You will notice that five of the seven characteristics are the
same. A major alteration looks at "flight characteristics,"
while 21.93 focuses on "operational characteristics" that
accounts for the sixth. Both deal with the ability of the
aircraft to fly, not operational "credit" of the installation.
The only characteristic not specifically addressed is
powerplant operations, although this is addressed in the
context of other characteristics. So the definition from
Order 8110.46, although this order was rescinded, provides

the best description of these characteristics.
As a note, Order 8110.46 was rescinded following the
2002 publication of Change 15 to FAA Order 8300.10 that
provided guidance to the FAA workforce on performing
field approvals of major repair and major alterations. The
reason was that the logic of 8110.46 was incorporated into
Change 15. Unfortunately, we lost the words in the process.
For this discussion, the original words are important.
So what were these words?
For general aviation aircraft with a certification basis of
14 CFR Parts 23 and 31, or Joint Aviation Regulation 22:
FAA Order 8110.46 described typical alterations that may
appreciably affect "weight and balance" as changes that
increase the certificated maximum weight limits (increases
in the maximum gross weight, maximum takeoff or landing
weights), or changes in the certificated center of gravity
range limits (for example, decreasing the forward limit or
increasing the aft limit).
The Order described typical alterations that may
appreciably affect "structural strength" as alterations that
include changes to primary structures (structure that carries
flight, ground or pressure loads as defined in AC 25.571-1,
Damage Tolerance and Fatigue Evaluation of Structure), or
substituting an engine, propeller, rotor or airframe primary
structural materials (such as replacing a reciprocating
engine with a turbine engine or increasing horsepower
output by 10 percent or more).
The FAA described typical alterations that may
appreciably affect "reliability" as alterations that make
changes to manifolding, air induction systems or air intake
doors, engine cowling or baffle that affect the flow of
engine cooling air and carburetor/fire ignition heat rises;
changing the basic engine or propeller design, controls,
and operating limitations, or changes that include engine/
propeller adjustments and settings limitations that affect
power output.
The FAA also described typical alterations that may
Continued on page 73
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Table of Contents for the Digital Edition of Avionics News October 2015

Avionics News October 2015 - Intro
Avionics News October 2015 - Cover1
Avionics News October 2015 - Cover2
Avionics News October 2015 - 1
Avionics News October 2015 - 2
Avionics News October 2015 - 3
Avionics News October 2015 - 4
Avionics News October 2015 - 5
Avionics News October 2015 - 6
Avionics News October 2015 - 7
Avionics News October 2015 - 8
Avionics News October 2015 - 9
Avionics News October 2015 - 10
Avionics News October 2015 - 11
Avionics News October 2015 - 12
Avionics News October 2015 - 13
Avionics News October 2015 - 14
Avionics News October 2015 - 15
Avionics News October 2015 - 16
Avionics News October 2015 - 17
Avionics News October 2015 - 18
Avionics News October 2015 - 19
Avionics News October 2015 - 20
Avionics News October 2015 - 21
Avionics News October 2015 - 22
Avionics News October 2015 - 23
Avionics News October 2015 - 24
Avionics News October 2015 - 25
Avionics News October 2015 - 26
Avionics News October 2015 - 27
Avionics News October 2015 - 28
Avionics News October 2015 - 29
Avionics News October 2015 - 30
Avionics News October 2015 - 31
Avionics News October 2015 - 32
Avionics News October 2015 - 33
Avionics News October 2015 - 34
Avionics News October 2015 - 35
Avionics News October 2015 - 36
Avionics News October 2015 - 37
Avionics News October 2015 - 38
Avionics News October 2015 - 39
Avionics News October 2015 - 40
Avionics News October 2015 - 41
Avionics News October 2015 - 42
Avionics News October 2015 - 43
Avionics News October 2015 - 44
Avionics News October 2015 - 45
Avionics News October 2015 - 46
Avionics News October 2015 - 47
Avionics News October 2015 - 48
Avionics News October 2015 - 49
Avionics News October 2015 - 50
Avionics News October 2015 - 51
Avionics News October 2015 - 52
Avionics News October 2015 - 53
Avionics News October 2015 - 54
Avionics News October 2015 - 55
Avionics News October 2015 - 56
Avionics News October 2015 - 57
Avionics News October 2015 - 58
Avionics News October 2015 - 59
Avionics News October 2015 - 60
Avionics News October 2015 - 61
Avionics News October 2015 - 62
Avionics News October 2015 - 63
Avionics News October 2015 - 64
Avionics News October 2015 - 65
Avionics News October 2015 - 66
Avionics News October 2015 - 67
Avionics News October 2015 - 68
Avionics News October 2015 - 69
Avionics News October 2015 - 70
Avionics News October 2015 - 71
Avionics News October 2015 - 72
Avionics News October 2015 - 73
Avionics News October 2015 - 74
Avionics News October 2015 - 75
Avionics News October 2015 - 76
Avionics News October 2015 - 77
Avionics News October 2015 - 78
Avionics News October 2015 - 79
Avionics News October 2015 - 80
Avionics News October 2015 - Cover3
Avionics News October 2015 - Cover4
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