Winter IMC

But few general aviation aircraft are equipped for prolonged exposure to icy clouds, and avoiding them is the surest way to prevent ice accumulation in flight.

Preflight weather planning should include satellite images showing cloud coverage, freezing levels, and pilots reports of ice encounters.

Once you get to the airplane, preheating the engine, cabin, and avionics can reduce wear and increase reliability of electronic and mechanical items. If the airplane you’re flying is equipped with deice, or anti-ice systems, make sure they’re serviced (with TKS fluid or alcohol) and working properly. TKS systems, in particular, require that the pumps are primed, and even when they’re working properly, it can take several minutes to move fluid from the tanks to the portions of the airplane you’re trying to protect.

If you rely on a tablet computer or smartphone for IFR charts, the cabin has to be warm enough for your tablet to work, and cold temperatures drain battery power faster than normal. (Bringing a separate, external battery pack for your devices can keep them working happily for many hours—provided that the battery pack itself is fully charged.)

If clouds are unavoidable in flight, realize they’re not all created equal. Cumulous clouds with extensive vertical development carry the most moisture, and they can create clear ice that may accumulate rapidly and present an immediate threat. Relatively thin, stratiform clouds tend to produce lighter rime ice that isn’t such an immediate hazard.

Pay close attention to the outside air temperature—and realize it’s likely to drop when you enter the clouds. If you’re in cruise flight in clear skies with an outside air temperature of 38 degrees Fahrenheit and then enter clouds, the temperature is likely to drop to the freezing point almost immediately. It’s like stepping into the shade on a sunny day.

Even if the airplane you’re flying doesn’t have deice or anti-ice equipment, you can reduce the hazards by making sure the pitot heat is on and working (look for a jump in amperage when you turn the heat on) before entering clouds, and that should keep the pitot-static system free of ice. Also, turn on the windshield defroster well in advance. It’s better to prevent frost from forming on the windshield than to clear it once it’s there.

When pilots encounter ice, they should report it to air traffic control and find an expeditious way out. Usually, that means climbing or descending. If there’s sunshine and clear air above and within the airplane’s reach, go to it—but not too quickly. It’s usually better to fly fast and make a relatively shallow climb to avoid flying at high angles of attack. This helps keep ice from forming behind the wing and horizontal tail leading edges, and it provides a greater margin over the critical angle attack where aerodynamic stalls take place.

Winter brings cold, dense air that gives airfoils and piston engines seeming superpowers. Enjoy the enhanced performance the cold months bring.

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