IR.I.B.K3kFAA-S-ACS-8C · Nov 2023Knowledge
k. Frost
Meteorology applicable to the departure, en route, alternate, and destination for flights conducted under Instrument Flight Rules (IFR) to include expected climate and hazardous conditions such as: k. Frost
Bottom line
Frost is a crystallized deposit formed from water vapor on surfaces at or below 0 degrees C (32 degrees F). Frost disrupts airflow over the wing and can drastically reduce lift production.
Key numbers
| Number | What it means |
|---|---|
| 30 percent lift reduction from frost, snow, or ice no thicker or rougher than coarse sandpaper on the leading edge or upper wing surface | Lift loss |
| up to 40 percent drag increase from sandpaper-thin contamination on the leading edge or upper wing surface | Drag increase |
| 80 percent or more drag increase from larger accretions | Large accretions |
| 110 knots minimum rotation speed for Type II and IV anti-icing fluids | Fluid rotation speed |
| within five minutes prior to beginning takeoff | Contamination check |
FAA references
- AC 135-17 — AC 135-17
- PHAK ch. 12 (p. 12-15) — FAA-H-8083-25C (2023)
- AWH ch. 20 (p. 20-7) — FAA-H-8083-28A
- AC 91-74, para. 7-1 — AC No: 91-74A
- AWH ch. 21 (p. 21-5) — FAA-H-8083-28A
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