Why Ice and Airplanes Don't Mix

Today's jets can handle most weather, but pilots of smaller aircraft sometimes need to sidestep trouble.

Modern jets take most fog, rain and wind in stride. Even violent thunderstorms are usually easy to sidestep with today’s radar and other storm-detection gear. And come winter, what used to be dangerous icy clouds are generally no match for the latest ice-protection systems. 

In fact, today’s jets are usually immune to icing concerns, since they have sophisticated systems that use hot air bled from their engines to keep engine inlets, wings and control surfaces warm. The exception is when the airplane has sat on the ground for an extended period, either parked or with the engines idling at low power. Then the aircraft may require a hosing down with hot deicing fluid to remove ice buildup before takeoff.

In the early days of aviation, many airplanes were lost to ice before its dangers became known. Since the ice that accumulated in flight would usually melt after a crash, investigators were baffled as to the cause of the pilot’s loss of control. After a few pilots survived harrowing encounters with heavy ice, they realized the only defense against the hazard was staying out of clouds altogether or learning by experience what an icy cloud might look like. 

In the film The Spirit of St. Louis, Charles Lindbergh (played by Jimmy Stewart, himself an experienced pilot) is horrified to see ice building up on the wings and struts of the little monoplane far out over the Atlantic. With the added weight of the ice, and the way it changes the carefully engineered shape of the wings and other control surfaces, Lindbergh knew that the airplane could not sustain flight for long under those conditions. The film does a marvelous job of depicting how he found warmer air at the last moment, narrowly avoiding the need to ditch—probably to his death. The footage of thick ice breaking off in chunks is enough to cause any pilot to breathe a sigh of relief.

It’s the unpredictability of icing conditions that can cause pilots of smaller aircraft to give suspect clouds a wide berth. And that doesn’t go only for cold-weather months. For example, last August, I was flying home to New Jersey from Wisconsin with my friend Patrick Bradley in his turbocharged Cirrus SR22T—the personal-airplane equivalent of a souped-up Range Rover. With the turbo, we were at 17,000 feet, hitching a boost from high-altitude tailwinds that would shorten our trip to just a little more than three hours. He was even able to text his wife via the inflight phone to let her know our estimated time of arrival.

As we droned through the air, a mountainous, foreboding cloud blocked our path. It wasn’t a thunderstorm, and we were certainly equipped and trained to fly without being able to see outside the windshield. But Patrick asked the controller for a vector to go around the system, rather than right on through. “That looks icy,” he said to me, never taking his eye off the cloud. It was as if he was afraid it might sneak up on him if he turned away. 

Patrick flies in weather a lot more than I do, and I took his word for it. Even with his Cirrus’s “flight-in-known-icing” approval, Patrick is wise to avoid testing that envelope. Ice has been known to accumulate faster than the system can handle. Even airliners can occasionally encounter conditions that call for a speedy descent to warmer air.

Such extreme conditions are hard to predict by looking at the cloud from the outside. Sometimes, it’s just a feeling. But as the saying goes, “The superior pilot uses superior judgment to avoid situations requiring superior skill.

Mark Phelps, a private pilot, writes BJT's Exit column.