Definition
An FAA Advisory Circular (AC 91-74) that provides pilots with practical information on the hazards of flight in icing conditions, how aircraft icing forms, how to recognize and avoid it, and how to use anti-ice and de-ice equipment safely. It is a non-regulatory guidance document intended to supplement aircraft flight manuals and pilot training.
Plain English
An FAA-published guide that teaches pilots what icing is, why it is dangerous, how to spot it, and what to do about it before and during flight.
Context Anchor
Seen as a recommended FAA reference when studying weather hazards, especially winter flying and flight near clouds or precipitation.
Why Pilots Care
Ice on wings or control surfaces reduces lift and can lead to loss of control, making this knowledge essential for cold-weather flight decisions.
Grounding Statement
If moisture freezes onto the aircraft in flight, the airplane may no longer fly the way its clean, dry shape was designed to fly.
Intuition Check
Do not assume icing conditions mean only obvious ice already on the airplane. In aviation, the concern is any weather situation where ice could form on the aircraft during flight.
Example Sentence 1
Before her first winter cross-country, she reread the Pilot Guide: Flight in Icing Conditions to refresh her memory on how to recognize structural icing in flight.
Example Sentence 2
The guide stresses that even a thin layer of ice can increase stall speed noticeably.