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US-FAA14 CFR 91.413

ATC transponder tests and inspections

Read the official rule

In plain English

The ATC transponder must be tested and inspected within the preceding 24 calendar months to be used. The tests must be performed by an appropriately authorized person or facility and recorded in the maintenance records.

Key points

  • Transponder test/inspection every 24 calendar months.
  • Performed by an authorized person/facility.
  • Recorded in the maintenance records.

Common pitfalls

  • Confusing this with the pitot-static/altimeter test (also 24 months, see 91.411).

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation.*

This is an original plain-English explanation for training and reference, not legal advice and not for navigation. Always rely on the current official rule linked above. Last reviewed June 8, 2026.