Avionics News February 2015 - 57

Type design includes drawings and specifications,
Equivalency of test equipment
and a listing of those documents that are necessary to
Repair stations that deviate from the component
define the configuration and design features of a product.
maintenance manual by using "equivalent" tools and test
It also includes the drawings and specifications of the
equipment must verify that all applicable airworthiness
components that are installed in that product, as explained
tests and adjustments prescribed in the CMM are
in FAA Advisory Circular 20-154, Paragraph 5.a (1).
performed, and that the manufacturer's specifications and
Type design therefore includes component
tolerances are in compliance. Otherwise, the maintenance
airworthiness test specifications, allowable
work may have to be classified as a major repair because
tolerances, environmental requirements and other
"... other qualities affecting airworthiness ..." as defined
documentation that is required to demonstrate
in 14 CFR Part 1 may be affected.
compliance with the applicable aircraft or engine FAA
It is difficult to establish whether the use of
type certification requirements,
"equivalent" tools and test equipment
including the calculation
changes the classification of the
of failure probabilities that
maintenance work to a major
IT IS IMPORTANT TO
demonstrate compliance with
repair unless clear and detailed
EMPHASIZE THAT THE REPAIR
14 CFR 23.1309, 25.1309 and
documentation is available to
STATION, NOT THE FAA,
similar regulations.
substantiate conformance with all the
It is evident a component that is
applicable component maintenance
approved for return to service slightly
manual requirements.
outside the tolerances and specifications
The component maintenance
published by the manufacturer does
manual must clearly define the
not comply with its type design
interface between a component
requirements, and is therefore
and the recommended tools and
unairworthy regardless of whether the
test equipment, and also include
action is inadvertent or not.
detailed test signal and measurement
The manufacturer's component
parameter specifications and
maintenance manual includes airworthiness specifications
tolerances, as well as the expected results. If this
and test parameters that are FAA-approved technical data
information is available, then it is relatively easy to
and part of the component type design. It also includes
substantiate equivalency by comparison methods.
recommended maintenance methods, techniques and
However, some component maintenance manuals are
practices, which are FAA-accepted data.
not sufficiently detailed to clearly identify all the required
Component maintenance manuals generally include
airworthiness tests and adjustments, or the specifications
recommended tools and test equipment, which the
and tolerances, especially when the complexity of the
manufacturer considers to be adequate to perform
component requires the use of specialized test panels,
applicable airworthiness tests and adjustments with
automatic test equipment and/or airworthiness test
sufficient accuracy to ensure that the component
software.
being approved for return to service meets its required
The missing information can sometimes be obtained
specifications and tolerances.
from manufacturer's tools and test equipment manuals
The component maintenance manual provides all the
applicable to those specialized test panels and/or automatic
type design information necessary to approve for return
test equipment, including their calibration procedures.
to service an airworthy component, provided the repair
Continued on following page
station does not deviate from its contents.

BEARS THE
BURDEN OF
DEMONSTRATING
EQUIVALENCY.

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february

2015

57
Avionics News February 2015

Table of Contents for the Digital Edition of Avionics News February 2015
