There are some steps a pilot can take to prevent, recognize,
and respond to carburetor icing.
To prevent carburetor icing, the pilot should:
• Assure the proper functionality of the carburetor heat
during the ground check (before takeoff).
• Use carburetor heat on approach and descent when
operating at low power settings, or in conditions where
carburetor icing is probable.
To recognize carburetor icing, the warning
• A drop in rpm in fixed-pitch propeller airplanes.
• A drop in manifold pressure in constant-speed
• In both types, usually there will be rough engine
The pilot should respond to carburetor icing by
applying full carburetor heat immediately. The engine
may run rough initially for a short time while the ice
melts. The recommendations are general suggestions.
The pilot should consult the AFM or the pilot’s operating
handbook for the proper use of carburetor heat.
The references below, and their associated links,
provide more information:
• AC 20-113, Pilot Precautions and Procedures to
be Taken in Preventing Aircraft Reciprocating Engine
Induction System and Fuel System Icing Problems
• AC 91-51A, Effect of Icing on Aircraft Control and
Airplane Deice and Anti-Ice Systems
• AOPA Safety Advisor—Aircraft Icing
• AOPA Safety Advisor—Aircraft Deicing and Anti-
For more information contact Peter L. Rouse, aerospace
engineer, Small Airplane Directorate, at 816-329-4135
or e-mail firstname.lastname@example.org.