CA.III.A.K4FAA-S-ACS-7B · Nov 2023Knowledge
Appropriate use of transponder(s).
Appropriate use of transponder(s).
Bottom line
When required to operate their transponder/ADS-B, pilots must always operate that equipment with altitude reporting enabled unless otherwise instructed by ATC or unless the installed equipment has not been tested and calibrated as required by 14 CFR section 91.217.
Key numbers
| Number | What it means |
|---|---|
| Mode 3/A Code 1200, regardless of altitude, unless otherwise instructed by ATC | VFR code |
| 4,096 possible codes, four digits from 0 to 7 | Codes |
FAA references
- PHAK ch. 14 (p. 14-25) — FAA-H-8083-25C (2023)
- AIM 4-1-20 (Transponder and ADS-B Out Operation) — AIM Basic 2/20/25 w/ Change 1 (8/7/25) & Change 2 (1/22/26)
- 14 CFR 91.413 (ATC transponder tests and inspections.) — eCFR current as of 2026-03-05
- AIM 6-2-2 (Transponder Emergency Operation) — AIM Basic 2/20/25 w/ Change 1 (8/7/25) & Change 2 (1/22/26)
- AIM 6-4-2 (Transponder Operation During Two‐way Communications Failure) — AIM Basic 2/20/25 w/ Change 1 (8/7/25) & Change 2 (1/22/26)
- 14 CFR 91.215 (ATC transponder and altitude reporting equipment and use.) — eCFR current as of 2026-03-05
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