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United States Department of Transportation United States Department of Transportation

AC 20-73A - Aircraft Ice Protection

Document Information

Aircraft Ice Protection
Date issued
Office of Primary Responsibility
AIR-120, Aviation Safety - Aircraft Certification Service, Aircraft Engineering Division
This advisory circular (AC) tells type certificate and supplemental type certificate applicants how to comply with the ice protection requirements of Title 14 of the Code of Federal Regulations (14 CFR) parts 23, 25, 27, 29, 33, and 35. It also provides guidance for aircraft type certificate holders on how to maintain the aircraft’s airworthiness when operating in an icing environment. Applicants seeking an FAA type certificate for their aircraft, aircraft engines, or propellers, or a supplemental type certificate for an existing aircraft model or an aircraft component must adhere to ice protection regulations. You will find these requirements embedded throughout 14 CFR parts 23, 25, 27, 29, 33, and 35. (Ice protection regulations are listed in tables 1 through 4 in section 6 of this AC.) This AC also directs you to other ACs providing guidance for compliance with specific icing-related regulations.
Number Title Date
20-73 Aircraft Ice Protection Provides information relating to the substantiation of ice protection systems on aircraft. 1971-04-21