Avionics News February 2015 - 60

TOOLS AND TEST EQUIPMENT
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approve or determine equivalency of tooling and
test equipment. Neither the FAA nor a DER may
approve equipment or test apparatus. The FAA and
DERs may only make a finding that the functional
equivalency for special equipment or test apparatus
is acceptable. It is important to emphasize that the
repair station, not the FAA, bears the burden of
demonstrating equivalency.
3.

If the repair station uses a manufacturer's test and
measuring equipment as an equivalent for equipment
recommended by a component's manufacturer, verify
that the equipment meets the calibration standards
recommended by the component's manufacturer.
This type of calibration must be traceable to a
standard acceptable to the FAA.

Tools and test equipment equivalency files are
strongly recommended to document and substantiate
TTE equivalency. Although they are not required by
regulation, or explicitly mentioned in FAA Order 8900.1,
they demonstrate that the repair station has exercised due
diligence in the determination of TTE equivalency and
facilitate the work of FAA DERs and FSDO inspectors in
the equivalency-acceptance process.
The contents of these files may be simple or complex,
depending on whether the TTE is classified as general
purpose (DMM, oscilloscopes, pressure Gauges) or
specialized (test panels, semiautomatic test stations, ATE).
The TTE equivalency file also may include
airworthiness test results obtained from a "golden"
component using the proposed equivalent TTE to
facilitate the equivalency verification process. A "golden"
component is defined as a new or used serviceable
component that has been approved for return to service
using the TTE recommended in the manufacturer's
component maintenance manual.
The test results obtained for the "golden" component
using the manufacturer's recommended TTE are compared
to those obtained using the proposed "equivalent"
TTE; and both sets of test results are kept in the TTE
equivalency file to substantiate the equivalency. A
copy of the FAA Form 8130-3 that is applicable to the
"golden" component should also be included in the file for
traceability purposes.
Unfortunately, some repair stations do not have enough
technical information in their TTE equivalency files to
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fully substantiate that their "equivalent" TTE complies
with applicable CMM requirements or that it is calibrated
to a standard acceptable to the FAA. This increases
the risk of noncompliance with 14 CFR 43.13 and the
probability of inadvertently approving for return to service
an unairworthy component.
Aeronautical Radio Inc. has published industry
guidance report ARINC 668, Guidance for Tool and
Test Equipment Equivalency, which provides excellent
and comprehensive guidance on this subject, including
substantiation of equivalency. Repair stations that plan to
use equivalent TTE should have a copy of this document
readily available for reference and follow its guidelines.
Calibration of equivalent of test equipment
Improperly calibrated tools and test equipment also may
cause a component that is approved for return to service to
be outside their manufacturer's prescribed specifications
and tolerances.
It is important to understand the meaning of the words
"calibration to a standard acceptable to the FAA" (used
in 14 CFR 145.109 (b) and FAA Order 8900.1, Volume 6,
Chapter 9, Section 9, Paragraph 6-1800C) have a specific
connotation when applied to specialized test panels,
semiautomatic test stations or automatic test equipment.
Locally manufactured specialized test panels,
semiautomatic test stations or automatic test equipment
cannot be proven to be equivalent to those recommended
by the component manufacturer unless the applicable
airworthiness test and calibration procedures are verified
to be equivalent.
This includes substantiation that the "equivalent" TTE
interface requirements, test signals and measurement
parameters meet the component manufacturer's standards
and specifications in all respects regarding tolerances,
repeatability and accuracy.
General purpose TTE is usually provided with
calibration procedures that are readily available to the
calibration laboratories subcontracted by the repair
station. However, these laboratories normally do not have
available the calibration procedures for the "equivalent"
specialized test panels, semiautomatic test stations and
automatic test equipment fabricated by a repair station.
To comply with 14 CFR 145.109 (b), repair stations
must provide to their TTE calibration subcontractor(s)
the calibration procedures that are applicable to their
"equivalent" specialized test panels, semiautomatic test
stations and automatic test equipment.
Continued on page 62
Avionics News February 2015

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