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IFR Fix: The shape of iceIFR Fix: The shape of ice

Name a component of most airframes that is aerodynamically critical, is not visible from most cockpits, and is an all too efficient collector of ice.

Photo by Mike Fizer

Next, explain how your aircraft might behave if the component became ice-laden and stalled, and what you would do to recover. (Hint: This is no garden-variety stall recovery.)

The airframe component is the tailplane, which when flying at its normal angle of attack exerts a downward force. If icing causes the tailplane to exceed its normal—that is, negative—angle of attack, tail-down force is lost, causing the nose of an aircraft with its center of gravity forward of its center of lift (like your Skyhawk) to pitch down.

“Since the tailplane is ordinarily thinner than the wing, it is a more efficient collector of ice. On most aircraft the tailplane is not visible to the pilot, who therefore cannot observe how well it has been cleared of ice by any deicing system. Thus, it is important that the pilot be alert to the possibility of tailplane stall, particularly on approach and landing,” notes the Instrument Flying Handbook (page 4-15).

With fall approaching and freezing levels aloft descending toward general aviation’s common cruising altitudes, airframe icing in clouds or precipitation becomes a regular consideration for flight planning. (Check the Aviation Weather Center’s interactive graphic of the lowest forecast freezing levels.)

It’s fundamental that if you fly an aircraft not certified or equipped to handle icing you must avoid such conditions, period. Even the briefest flirtation—perhaps you are fixated on flying by instruments and are not monitoring outside air temperature—invites aerodynamic aggravations.

Escaping an icing encounter into the clear may not melt away the risk. When a Cessna 182 flying in instrument conditions in Colorado began accumulating ice, air traffic control issued vectors to a nearby airport.  Unfortunately, “Following completion of the instrument approach, while the airplane was about 10 ft above ground level, the airplane stalled and then landed hard on the runway,” notes the official accident report, linking the stall to airframe-ice accumulations.

Mishaps have had far worse outcomes—the probable causes sometimes determined by accident-scene evidence including ice fragments “shaped consistent with wing and tailplane ice accumulations.”

Another word about tailplanes and their temperamental tendencies: Neither the symptoms of an approaching tailplane stall nor the recovery procedures are intuitive. Be sure to reacquaint yourself before your ice-season IFR flying gets going.

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: Training and Safety, Accident, IFR

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