Learn to Beat the Hazards of Winter Flying
By Alan Smith
When summer and fall have passed and the hard cold of winter has set in we have to be careful in setting up our airplanes for safe operation. Fuel, oil and flying surfaces need special care and preflight preparation will take a lot longer than it did in the days of warm sunshine. Flying through winter skies, whether gray or blue, also needs special care as cold temperatures get colder with altitude.
On preflight being careful with your fuel is important. Never park your airplane with partial or fully empty tanks. We all know that on a cool summer night condensation will occur in partially full tanks, but, in winter, you could have ice in the tanks that would not show up in a cursory drain check in preflight inspection. Drain each tank separately by at least a quart into a transparent container and look for any solid contamination along with water. In winter, storage tanks, even those underground, can acquire rust. Fuel delivery from them drops off during the cold season and the reduction of underground temperatures can cause a slight shrinkage in metal storage facilities and let internal surface corrosion work into stored fuel. These tanks can also acquire water through condensation.
For these reasons, during winter, use of a filtered funnel when refueling is wise. There are better filters available than the traditional chamois. For one thing imitation chamois will not filter water.
Starting the engine on a cold winter day presents another set of problems. Its oil has congealed into molasses, a hand crank is impossible and a starter on a cold-weakened battery is not up to the job. Find some kind of safe heater to warm the engine for some time before the start is attempted again. Above all, don’t over-use the primer. This will just wash oil off the cylinder walls and leak raw fuel into the exhaust system – a real fire hazard when the engine fires.
If there is ice or snow on the wings and control surfaces, remember that there will be ice or frost under the snow. Don’t count on everything blowing off during the takeoff run. Try to get into a heated hangar and don’t use water to get rid of any frozen matter on the aircraft. Water will run into all the hinges and freeze again when you take the plane outside again. Use alcohol or some commercial ice remover.
When you have the engine running don’t let the airplane sit there idling for a long time. It won’t generate enough heat to keep cylinder head temps up to operating levels. It will quit and won’t want to restart. You’ll find the plugs in the heads will have iced over.
When taxiing don’t go through snowdrifts, even small ones, that you find at the edge of the runway or taxiway. There is likely ice under the snow that will make directional control difficult.
Use carburetor heat on the takeoff run. Because of the extremely low-density altitude of cold weather, your engine could generate more horsepower. Power increases are about one percent for each 10 degrees lower temperature. At minus 40F, your engine will have about 10 percent more horsepower at normal RPM and MP. Watch the head temperature on climbout. If you see it heading for the red, lower the nose a bit to pick up airspeed and open the cowl flaps.
Once on the way, remember that winter weather changes fast. You can be in clear conditions and then, a few minutes later be in the blind. One winter day trick is the whiteout. Suddenly you can no longer see the ground or the horizon. You can either go IFR immediately or do a 180 and get the hell out of there. It’s not smart to press on into what could be rapidly worsening conditions. Accept the fact that not every winter day trip can be completed. Don’t become a statistic. Snow showers can also be a trap. They start with light flurries and then – wham! You’re blinded in a blizzard.
Carburetor ice is another winter hazard and it doesn’t need subzero temperatures to happen. If the weather is just very cool and you’re ready to let down and land at your destination, your carburetor could start to plug up with ice. On fixed pitch props you’ll see a drop in RPM; in constant speed props there will be a drop in manifold pressure. Apply the carb heat immediately and inch the throttle up a bit. There will be a little roughness and then it will smooth out. Throttle back and continue your descent to final approach with the carb heat on.
All in all, take your time in preparation, watch your engine instruments in flight, and remember winter weather changes can be abrupt and severe. If the weather is messy in any way, don’t go near the mountains no matter what kind of forecast you saw or heard. During the winter, attempts to forecast mountain weather are educated guesses. Above all, be willing to retreat and land when faced with uncertainty. Let the folks at your destination know you may or may not make it (let them know if you stop short or turn back). That way you’ll still be alive come springtime.
