Avionics News November 2015 - 13
Mode C transponder
The following information is from the
Federal Aviation Administration's ADS-B
frequently asked questions.
If a customer is choosing to satisfy the Jan. 1,
2020, ADS-B Out mandate with a UAT (978
MHz) solution, does the customer need to
change the Mode C transponder?
repaired as necessary, and reassembled.
(2) It has been tested in accordance with
approved standards and technical data, or in
accordance with current standards and technical
data acceptable to the administrator, which
have been developed and documented by the
holder of the type certificate, supplemental
type certificate, or a material, part, process, or
appliance approval under Part 21 of this chapter.
From the FAA's interpretation:
As you note in request for interpretation, in 1991,
we published a legal interpretation addressing the
logical and practical limitations of § 43.2 - namely,
that not all component parts can be disassembled.
At the time, a member of the public requested
clarification of "the term overhaul as it applies to
items or parts that are incapable of nondestructive
disassembly." In our response, we noted that, for
example, an engine can be disassembled, but not
all of an engine's component parts can be further
disassembled. We stated, "a part, component, or
subassembly of (a) larger assembly or product
should ... be deemed overhauled if it can be shown
to be airworthy by inspection, examination or tests
that do not require disassembly beyond (the part's)
normal state." In other words, if disassembly is
Not specifically because of UAT, but depending on
the age of the transponder the customer may need
to as a result of interface or compatibility issues to
ensure the same altitude encoder data is provided to
both the transponder and ADS-B Out avionics.
Checking with the transponder and UAT
manufacturers prior to installation is always
encouraged, especially when interfacing older
illogical or impossible, for example because it
would destroy the part, and if a mechanic can both
perform the required maintenance and confirm the
adequacy of that maintenance, then disassembly is
A similar rationale guides our analysis here. You
ask whether § 43.2 requires disassembly or repairs
if the design approval holder's overhaul instructions
or other data acceptable to the administrator
expressly requires only cleaning and inspection. The
answer is that, just as a mechanic is not required
by the term "disassembly" in § 43.2(a) to destroy
an aircraft part, neither is a mechanic required
by the phrases "disassembly," "reassembly,"
etc., to take maintenance action beyond what is
provided in the overhaul instructions. Of course,
this interpretation assumes that a mechanic follows
the entirety of the overhaul process and that, during
the overhaul, does not discover that additional
repairs are necessary. In all cases, a mechanic may
not label a part as overhauled if that mechanic
performs less than the entirety of the maintenance
process acceptable to the administrator.
This interpretation is imported to avionics as
well, since it clearly addresses the overhaul of
items that cannot be disassembled.
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