(a) All airspace: U.S.-registered civil
aircraft. For operations not conducted under part 121 or 135 of this
chapter, ATC transponder equipment installed must meet the performance and
environmental requirements of any class of TSO-C74b (Mode A) or any class of
TSO-C74c (Mode A with altitude reporting capability) as appropriate, or the
appropriate class of TSO-C112 (Mode S).
(b) All airspace. Unless otherwise
authorized or directed by ATC, no person may operate an aircraft in the airspace
described in paragraphs (b)(1) through (b)(5) of this section, unless that
aircraft is equipped with an operable coded radar beacon transponder having
either Mode 3/A 4096 code capability, replying to Mode 3/A interrogations with
the code specified by ATC, or a Mode S capability, replying to Mode 3/A
interrogations with the code specified by ATC and intermode and Mode S
interrogations in accordance with the applicable provisions specified in TSO
C–112, and that aircraft is equipped with automatic pressure altitude reporting
equipment having a Mode C capability that automatically replies to Mode C
interrogations by transmitting pressure altitude information in 100-foot
increments.
Link to the complete FAR 91.215
§ 91.217 Data correspondence between
automatically reported pressure altitude data and the pilot's altitude
reference.
(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 percent 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.
§ 91.413 ATC transponder tests and inspections.
(a) No persons may use an ATC transponder that is specified in 91.215(a),
121.345(c), or §135.143(c) of this chapter unless, within the preceding 24
calendar months, the ATC transponder has been tested and inspected and found to
comply with
appendix F of part 43 of this chapter; and
(b) Following any installation or maintenance on an ATC transponder where
data correspondence error could be introduced, the integrated system has been
tested, inspected, and found to comply with paragraph (c),
appendix E, of part
43 of this chapter.
(c) The tests and inspections specified in this section must be conducted by—
(1) A certificated repair station properly equipped to perform those
functions and holding—
(i) A radio rating, Class III;
(ii) A limited radio rating appropriate to the make and model transponder to
be tested;
(iii) A limited rating appropriate to the test to be performed;
(2) A holder of a continuous airworthiness maintenance program as provided in
part 121 or §135.411(a)(2) of this chapter; or
(3) The manufacturer of the aircraft on which the transponder to be tested is
installed, if the transponder was installed by that manufacturer.