(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. This requirement applies --
(1) All aircraft. In Class A, Class B, and Class C airspace
areas;
(2) All aircraft. In all airspace within 30 nautical miles of an
airport listed in appendix D, section 1 of this part from the surface
upward to 10,000 feet MSL;
(3) Notwithstanding paragraph (b)(2) of this section, any aircraft
which was not originally certificated with an engine-driven electrical
system or which has not subsequently been certified with such a system
installed, balloon or glider may conduct operations in the airspace within
30 nautical miles of an airport listed in appendix D, section 1 of this
part provided such operations are conducted --
(i) Outside any Class A, Class B, or Class C airspace area; and
(ii) Below the altitude of the ceiling of a Class B or Class C airspace
area designated for an airport or 10,000 feet MSL, whichever is lower; and
(4) All aircraft in all airspace above the ceiling and within the
lateral boundaries of a Class B or Class C airspace area designated for an
airport upward to 10,000 feet MSL; and
(5) All aircraft except any aircraft which was not originally
certificated with an engine-driven electrical system or which has not
subsequently been certified with such a system installed, balloon, or
glider -- --
(i) In all airspace of the 48 contiguous states and the District of
Columbia at and above 10,000 feet MSL, excluding the airspace at and below
2,500 feet above the surface; and
(ii) In the airspace from the surface to 10,000 feet MSL within a
10-nautical-mile radius of any airport listed in appendix D, section 2 of
this part, excluding the airspace below 1,200 feet outside of the lateral
boundaries of the surface area of the airspace designated for that
airport.
(c) Transponder-on operation. While in the airspace as specified
in paragraph (b) of this section or in all controlled airspace, each
person operating an aircraft equipped with an operable ATC transponder
maintained in accordance with §91.413 of this part shall operate the
transponder, including Mode C equipment if installed, and shall reply on
the appropriate code or as assigned by ATC.
(d) ATC authorized deviations. Requests for ATC authorized
deviations must be made to the ATC facility having jurisdiction over the
concerned airspace within the time periods specified as follows:
(1) For operation of an aircraft with an operating transponder but
without operating automatic pressure altitude reporting equipment having a
Mode C capability, the request may be made at any time.
(2) For operation of an aircraft with an inoperative transponder to the
airport of ultimate destination, including any intermediate stops, or to
proceed to a place where suitable repairs can be made or both, the request
may be made at any time.
(3) For operation of an aircraft that is not equipped with a
transponder, the request must be made at least one hour before the
proposed operation.
(Approved by the Office of Management and Budget under control
number 2120-0005)