Regulation Text
(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.
[Docket 18334, 54 FR 34311, Aug. 18, 1989, as amended by Amdt. 91-267, 66 FR 21066, Apr. 27, 2001; Amdt. 91-269, 66 FR 41116, Aug. 6, 2001]
Research Notes
Section 91.413 — ATC transponder tests and inspections — establishes the 24-calendar-month transponder testing requirement.
The 24-calendar-month rule: No person may use an ATC transponder UNLESS, within the preceding 24 calendar months, the transponder has been tested and inspected per Part 43 Appendix F.
What gets tested: Transponder operation including the Mode A code response, Mode C altitude encoding, antenna performance, and (for Mode S and ADS-B equipped systems) the additional data integrity tests.
The combined § 91.411 + § 91.413 inspection: Most aircraft owners combine the altimeter/static check (§ 91.411) with the transponder check (§ 91.413). Both have 24-month intervals and both are typically performed at the same shop visit — often during an annual.
ADS-B Out testing: When ADS-B Out is required (§ 91.225), the ADS-B Out function is tested as part of the § 91.413 transponder check. Additional ADS-B-specific tests verify position accuracy and integrity.
Reference: Part 43 Appendix F; AC 90-115 on ADS-B Out installation.
Amendment History
Amendment History Coming Soon
Every time this regulation changes, we'll record it here — the date, what was amended, and a plain-English summary of what shifted.