AI.III.C.K3iFAA-S-ACS-25 · Nov 2023Knowledge
i. Icing and freezing level information
Meteorology applicable to the departure, en route, alternate, and destination under visual flight rules (VFR) in Visual Meteorological Conditions (VMC), including expected climate and hazardous conditions such as: i. Icing and freezing level information
Bottom line
AIRMET Zulu is the inflight advisory code for icing and freezing levels. Under 14 CFR 91.527(a), no pilot may take off an airplane that has frost, ice, or snow adhering to any propeller, windshield, stabilizing or control surface.
Key numbers
| Number | What it means |
|---|---|
| moderate icing (AIRMET content) | AIRMET Zulu |
| 3 °C or less — fog may form | Dewpoint spread |
| 20 nm minimum distance | Thunderstorm |
| 6 hours or more before departure | Outlook briefing |
| standard briefing 1 hour or more old | Abbreviated briefing |
FAA references
- PHAK ch. 13 (p. 13-11) — FAA-H-8083-25C (2023)
- 14 CFR 91.527 (Operating in icing conditions.) — eCFR current as of 2026-03-05
- AC 91-92, paras. 7.6, 8.1, 8.2 — AC No: 91-92
- AC 91-92 Appendix A — AC No: 91-92
- AFH ch. 13 (pp. 13-9–13-10) — FAA-H-8083-3C
- RMH ch. 5 (p. 5-2) — FAA-H-8083-2A
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