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Training Tip: The ice of summerTraining Tip: The ice of summer

The temperature was well above average for a late spring afternoon in northern New England when a single-engine Cessna on a VFR cross-country made a forced landing on a remote lake after the aircraft began losing power.
Carb heat

Months from now, when the requisite inquiry is completed, any number of possible scenarios could emerge in the search for a probable cause. One possibility that always crosses a pilot’s mind based on the simple facts stated above—and to the incredulity of nonaviators and new members of the pilot-training ranks—is induction-system icing, or “carb ice.”

Wait—wasn’t it stated above that it was an unusually hot day? Doesn’t that contradict the notion of carburetor ice as a cause of the engine failure?

Not at all; in fact, quite the opposite is true, so bear that in mind, and keep a close watch on engine power readings as you head out on your summer cross-country flights.

“Carb ice can form over a wide range of outside air temperatures and relative humidities. While the word ‘icing’ typically brings to mind blustery winds and frigid conditions, carb ice can form when outside temperatures are as high as 100 degrees Fahrenheit with 50 percent relative humidity,” notes the AOPA Air Safety Institute’s “Combating Carb Ice” Safety Brief.

The safety brief adds that “certain aircraft types are also more prone to ice than others. For example, the pilot’s operating handbook (POH) for many single-engine Cessnas calls for the pilot to apply carb heat whenever power is reduced below the green arc on the tachometer.” On the other hand, most Piper singles with similar engines and carburetors may lack this restriction because of differences in engine heat and airflow through their cowlings. “Still, no aircraft with a carbureted engine is immune to carb ice.”

Does your trainer have a carbureted engine? What procedures does the manufacturer recommend for carb-ice avoidance? What indications would alert you that your engine’s intake of air might be becoming restricted by ice forming on the carburetor’s inner surfaces—and that (full) carb heat should be applied immediately?

Review as necessary to answer those three important questions. Then follow up by looking over this carburetor icing probability chart. It shows how ambient conditions may combine to elevate the carburetor-icing risk.

Carb ice can be a serious problem. Fortunately, the remedy, the carb-heat control, is right at your fingertips.

Dan Namowitz

Dan Namowitz

Associate Editor Web
Associate Editor Web Dan Namowitz has been writing for AOPA in a variety of capacities since 1991. He has been a flight instructor since 1990 and is a 30-year AOPA member.
Topics: Aircraft, Learn to Fly, Flight Training

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