Accident analysis: ‘None for me, thanks’

To put it plainly, no part of the aircraft was designed to work while frozen over. If the engineers knew what they were doing (and we hope they did!), it follows that those pieces won’t perform better frosted up.

Ice accumulation degrades airworthiness by disrupting the flow of air over the exterior and/or blocking its path to the engine. The two aren’t mutually exclusive, but one usually bites first. The turbocharged Beechcraft Bonanza that came up short of an attempted dead-stick landing at a backcountry Idaho strip that had closed for the winter first began losing altitude because of airframe icing, then had its engine strangled when the alternate air door apparently froze shut. The engines of the Beechcraft Baron that went down in a national forest in Kentucky, on the other hand, produced full power right up to the moment of impact—but the combined thrust of a pair of 285-horsepower Continentals wasn’t enough to overcome the loss of lift once the contours of its airfoils were altered.

Pilot reports of ice along your route are an automatic no-go.The Baron was equipped with pneumatic boots and windshield and propeller alcohol systems, reminding us that known-ice certification provides broader options for escaping icing conditions rather than license to linger in them indefinitely. That point was driven home more emphatically by the crash of a Daher TBM 700 onto a New Jersey highway after just a couple of minutes in icing much more severe than forecast. That accident—the subject of the AOPA Air Safety Institute’s “Delayed Reaction” case study—also serves to point out that any anti-icing system can eventually be overwhelmed by sufficiently intense accumulation. Airline crews in the vicinity reported picking up as much as four inches while climbing through the layer that caught the TBM, “hot wings” notwithstanding.

The solution is to be both realistic and cautious. Without icing protection, it’s best to avoid both instrument meteorological conditions and precipitation in temperatures below 5 degrees Celsius. Pilot reports of ice along your route are an automatic no-go. Zulu airmets should be taken seriously despite their frustratingly high false-positive rate. Any accumulation in flight requires immediate response. Don’t count on being able to climb through it unless you know the layer’s thin and you’re blessed with an abundance of thrust; otherwise, descend or turn around. And don’t forget that ice doesn’t only accrue in flight. Airplanes have been lost to innocuous-looking layers of frost that left them unable to climb out of ground effect. Keeping the airframe ice-free helps preserve the option of deciding whether to enjoy your beverages chilled.