Operations in icing

This regulation applies to Part 121 operations using aircraft under 60,000 pounds maximum takeoff weight when flying in conditions conducive to icing (visible moisture at or below 5°C static air temperature or 10°C total air temperature).

Operators must use one of three compliance methods:

1. Primary ice detection system that automatically or manually activates ice protection when needed 2. Advisory ice detection system combined with visual cues, activating protection at first indication 3. No detection system: Activate ice protection before and during specific flight phases (takeoff climb after second segment, enroute climb, go-around, holding, approach maneuvering, and operations at approach/holding speeds), plus at first sign of ice during other phases

Each method requires following additional AFM procedures for icing operations. The regulation ensures systematic ice protection activation rather than relying solely on pilot judgment, particularly important for smaller Part 121 aircraft where ice accumulation can quickly degrade performance.

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