Avionics News June 2022 - 19

FREQUENTLY ASKED QUESTIONS
United States
Installation of altitude
reporting equipment and
transponder systems
The following information is from an inquiry
to FAA Advisory Circular 43-6D.
Question: Who may install altitude reporting
equipment and transponder systems?
Answer: The FAA answered the question
in AC 43-6D:
Any appropriately rated person (as specified in
§ 43.3) may perform an aircraft alteration that
consists of installing or reinstalling equipment
(following maintenance). The equipment may
consist of an encoding or non-encoding altimeter,
air data system components, remote encoding
devices (blind encoder), or transponders. ADS-B
equipment includes an ADS-B transponder
or UAT and the associated source system's
components to broadcast the aircraft's identity,
altitude, velocity, and other information. Only
after the performance of the suitable functional
check to determine that the altered system
will perform its intended functions can an
appropriately rated person grant approval of the
aircraft for return to service.
Additionally, if applicable, test and inspections
requirements described in §§ 91.411 and 91.413
and Part 43 appendices E and F must be satisfied.
There are additional considerations.
14 CFR section 91.411 (a) (3) requires that no
person may operate an airplane, or helicopter, in
controlled airspace under IFR unless, " Following
installation or maintenance on the automatic pressure
altitude reporting system of the ATC transponder
where data correspondence error could be introduced,
the integrated system (emphasis added) has been
tested, inspected, and found to comply with paragraph
(c), appendix E, of Part 43 of this chapter. "
Also, 14 CFR section 91.411 (c) states, " Altimeter
and altitude reporting equipment approved under
technical standard orders are considered to be tested
and inspected as of the date of their manufacture. "
However, this would not replace the " integrated
system test " required by 14 CFR section 91.411 (a)
(3); 14 CFR section 91.411 (c) applies only to the new
equipment.
14 CFR section 91.413 (b) requires that, " Following
any installation or maintenance on an ATC transponder
where data correspondence error could be introduced,
the integrated system (emphasis added) has been
tested, inspected, and found to comply with paragraph
(c), appendix E, of Part 43 of this chapter. "
Keep in mind that while an appropriately rated
person (as specified in § 43.3) can install and return to
service altitude reporting equipment and transponder
systems, the tests and inspections required by §§
91.411 and 91.413, with few exceptions, require an
appropriately rated repair station.
And finally, 14 CFR section 91.217 contains
important instructions regarding data correspondence
between automatically reported pressure altitude data
and the pilot's altitude reference. In this section, there
are two essential paragraphs:
(a) No person may operate any automatic pressure
altitude reporting equipment associated with a radar
beacon transponder -
(1) When deactivation of that equipment is directed
by ATC;
(2) Unless, as installed, that equipment was
tested and calibrated to transmit altitude data
corresponding within 125 feet (on a 95% probability
basis) of the indicated or calibrated datum of the
altimeter normally used to maintain flight altitude,
with that altimeter referenced to 29.92 inches of
mercury for altitudes from sea level to the maximum
operating altitude of the aircraft; or
(3) Unless the altimeters and digitizers in that
equipment meet the standards of TSO-C10b and
TSO-C88, respectively.
(b) No person may operate any automatic pressure
altitude reporting equipment associated with a radar
beacon transponder or with ADS-B Out equipment unless
the pressure altitude reported for ADS-B Out and Mode
C/S is derived from the same source for aircraft equipped
with both a transponder and ADS-B Out. q
avionics news * june 2022 19
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