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United States Department of TransportationUnited States Department of Transportation

AC 121.321-1 - Compliance with Requirements of § 121.321, Operations in Icing

Document Information

Compliance with Requirements of § 121.321, Operations in Icing
Date issued
Office of Primary Responsibility
ANM-100, Aircraft Certification Service, Transport Airplane Directorate

This advisory circular (AC) describes an acceptable means for showing compliance with the requirements of Title 14, Code of Federal Regulations (14 CFR) 121.321, Operations in Icing. Part 121 contains the aircraft operating requirements applicable to domestic, flag, and supplemental operations. This AC provides guidance for:

a. Using visible moisture and temperature as a means for the flightcrew to know when the airframe ice protection system (IPS) must be activated.

b. Developing acceptable procedures for activating and deactivating the airframe IPS.

c. Installing a primary or advisory ice detection system.