Thursday, January 1, 2004
Get The Most Out Of Winter Part 1
With cool temperatures and great visibilities, autumn-to-spring flying requires a different set of rules—and it all starts on the ground
Winter doesn’t lend itself to preflights. When the temperature is well below zero, the wind is blowing snow in your face and you’d rather be sipping hot chocolate in front of a fire, it’s sometimes tough to do a thorough preflight. Ironically, winter is the time you need to be more meticulous in preflight rather than less. It’s also ironic that the most apparent aspect of winter preflights often is the most neglected. Cleaning accumulated snow and ice from aerodynamic lifting surfaces is critical if you expect to get the bird airborne and keep it there. The weight of the white stuff isn’t the major problem (though it can be in extreme situations), deformation of the airfoil is. Cleaning the wings and tail of contamination can be a vexing problem, especially if you fly a high wing.
The best solution is to put the airplane in a hangar for the night, if you have that option. I’ll always try to rent a hangar (preferably heated) for my Mooney when I’m on the road in winter. It’s a false economy to save money on a hangar and then pay it back out in preheat and de-ice charges, not to mention the wear and tear a super-cold night can exact on avionics, tires, door locks, upholstery, door seals, etc.
If you’re forced to scrape away snow and ice from the wings and tail yourself, you sometimes can do so with a credit card without damaging the finish, though the process may be a long one. In the Far North, many bush pilots carry cans of standard automotive antifreeze to pour over the wings and tail and rid them of accumulated frozen goo. According to the labels, antifreeze can damage some paint finishes, but I’ve used this trick a dozen or so times on ferry airplanes and my Mooney (when there was no alternative short of waiting for spring), and never had a problem.
The question sometimes arises, “How much snow and ice do you really need to remove?” A better question might be, “How much are you willing to gamble on leaving?” Take it off, take it all off. Any significant frozen accumulation could compromise lift, lengthen takeoff run, reduce climb and, in the worst asymmetric case, cause the airplane to become uncontrollable in flight. Don’t just be content to remove ice from airfoils, however. Static ports need to be open and all air intakes, engine, cooling and even cabin air should be clear.
Most manufacturers recommend preheat when the temperature drops below about 20 degrees F, especially when the engine has been cold-soaked overnight. Personally, I use 30 degrees F as my preheat limit—it’s just much easier on the airplane—and I’ll consider preheating at 35 degrees F if the bird has been sitting for a few days. In the long run, the wear and tear on rings and cylinder walls can be far more expensive than the price of preheats.
I don’t hesitate to mix Prist with the airplane’s fuel in very cold weather. Prist originally was intended to help prevent ice crystals from forming in jet fuel, since most jets operate at altitudes where temperatures are -30 degrees F or colder. A specially formulated Prist is now available for piston engines, and many pilots of turbocharged/pressurized singles and twins that fly in the 20,000- to 25,000-foot range and any airplane operated in extreme cold use it regularly.
Once again, our bush-pilot advisors suggest carrying blankets to cover the cowling and trap whatever residual heat remains after shutdown, and to cover the windshield and keep it from freezing over.
Next month, we’ll examine operational considerations of winter flying.
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