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SESK: Stuff Everyone Should Know · sesk.info/pilot-transponder-24-months

Before using a required ATC transponder, how recently must it have been tested and inspected?

Within the preceding 24 calendar months.

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  1. Within the preceding 24 calendar months ✔
  2. Every 12 calendar months
  3. Every 100 hours

Why: No one may use a required ATC transponder unless, within the preceding 24 calendar months, it has been tested and inspected and found to meet Part 43, Appendix F.

Huh, didn't know that: The test may be done by a properly rated repair station, an approved maintenance program holder, or the aircraft manufacturer if it installed the transponder.

The dad joke
My transponder passed its test. It squawked about it all the way home.
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References

Answer: Within the preceding 24 calendar months. No one may use a required ATC transponder unless, within the preceding 24 calendar months, it has been tested and inspected and found to meet Part 43, Appendix F.

  1. 14 CFR 91.413 ATC transponder tests and inspections www.ecfr.gov/current/title-14/section-91.413
    within the preceding 24 calendar months, the ATC transponder has been tested and inspected
    Checked 2026-10-09.

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