Cold-Weather Flight Operations

When living in a locale with winter weather cold enough for clichs and wanting to commit aviation, there are three alternatives for coping: 1) Borrow a snowplow and drive south-when someone asks, “Whats that?” stay there and fly; 2) subdue the urge (as did 1920s barnstormers, realizing the oversupply in warmer climes would cause them to starve), secure the airplane, rent a hotel room and hibernate after contracting with a bootlegger for regular deliveries; or, 3) keep flying.

While not expressing a preference, our habit has been to continue flying while modifying our behavior. Among the changes is realizing winter means more than cold: It means fewer hours of daylight, so more-risky night flying also is likely. It means everything takes longer to accomplish, be it as mundane as putting on appropriate flying attire or as complex as readying a tied-down airplane for flight. It means hurrying means radically increasing the chance of making a small mistake and, in winter, small mistakes are far more likely to have a fatal outcome than in summer.

Winter weather has its own set of challenges requiring respect along with some considered planning before leaving for the airport. While the thunderboomers of summer are rarely a concern, any foray into the clouds carries a risk of airframe icing. Meanwhile, snow showers can erase horizontal visibility in seconds, and runway and taxiway conditions must always be respected. Night operations, especially at remote locations where weather information may be difficult to obtain, or just plain wrong, pose other challenges. At the same time, winter flying has its own powerful way of rewarding you for all the effort as a new fall of snow, viewed from the sky, will make the most run-down city look magical and the dreariest scenery dramatic.

Preparing the airplane for winter means removing wheel pants so they cant fill up with snow or slush and freeze, installing winterization kits to keep oil temperatures out of the basement, covering wing leading edge cabin air intakes to stop cold air leaks (on some Cherokees radio cooling air comes from a wing inlet-dont cover that one) and make sure the aft baggage or tailcone seals are in good shape (because airflow is forward through the fuselage-it brings in cold air and a surprising amount of engine exhaust). Finally, carry a good electronic carbon monoxide (CO) detector, not one of those worthless “spot” things that are supposed to turn dark when CO is around, but dont. We lose a few pilots every winter to CO-dont be one of them.

Each winter, questions arise about preheating: why its necessary and when. Because of poor lubrication, we recommend preheating a piston engine any time its below 40 degrees F. To ensure proper lubrication-cold starts can create more wear than any other situation-both the oil and the engine need to be warmed. And, once warmed up-as in a temporary shutdown between flights-the primitive magneto systems most of our airplanes use make a successful start without preheating the engine challenging below about 20 degrees F. And then theres the issue of how poorly a carburetor atomizes fuel in frigid conditions.

The best way to heat the engine is via one of the commercially available electrical block heaters. Plugging in the heater and tossing an old sleeping bag over the cowling should result in oil and engine temps in the 60s within about three hours. We are somewhat uncomfortable with leaving engines plugged in all winter unless the airplane is going to be flown fairly frequently. There is not a lot of data on whether it increases moisture in the engine and consequent corrosion; we tend to lean toward the “plug it in a few hours or the night before going flying” position on the subject, just to be safe.

Weve spent a lot of time out in the cold with propane-fired heaters ducting hot air into cowlings. They certainly throw off a bunch of hot air, although care should be taken as the warming tends to be localized, so blowing hot air into the front of the cowling, across the tops of the cylinders is less effective than blowing it into the bottom of the cowling where it can heat the entire engine. No matter how it is done, be there every moment and figure on a maximum of 20 minutes to avoid melting something important. Even so, its unlikely such a method will do much to warm the engines core, or its oil. Best to use a block heater or something similar.

No matter how the engine is being preheated, when you first get to the airplane put the ignition key on the top of the panel so people can see it is not in the ignition. This serves two purposes: First, checking to see if the engine is warm often involves rocking the propeller a little bit to see if things are freeing up. With the key out of the ignition and readily visible, you are reasonably assured the mags are not hot. Second, you wont be fumbling in your pocket or purse for the key after you get in and seated.

There is a huge tendency to hurry the preflight in the cold, especially if passengers are hopping from foot to foot and slapping their gloves together to keep warm. Our experience is a desire to hurry to get something done in cold weather should set off internal alarm bells. A pilot may be tempted to ignore small issues like a fuel quick drain that wont drain fuel on a bitterly cold day, but if you cant get fuel out of the low point in the system there may be an ice blockage. A quick drain that doesnt drain should be a no-go item in cold weather.

Once the preflight is done, open all the doors, put your charts in place, load your passenger and start the engine. If you close the doors, open the windows to try and keep cold air circulating so you dont frost up the windows. While what you cant see might not scare you, not seeing taxiway or landing traffic can seriously spoil your day.

Plan on starting the engine as near dead idle as possible so oil warms and circulates before you let the rpm rise. Some Lycomings seem to demand one cycle of the throttle to start. Dont do more than one, since pumping the throttle is an excellent way to create a carburetor fire during start. Instead, use the primer. Liberally. Then leave it out. Crank the engine. When it fires, use the primer to help it keep running. Dont shove the throttle into the rear cylinders, keep rpm below 1000.

Once the engine is reciprocating it will need a little warmup time (although less than one might suspect), so carry out the chores you might have omitted prior to start, such as securing restraint systems, donning headsets (put them on your leg just above your knee when you first get it and the earmuffs wont be ice cold when you put them on), and arranging maps. While it is uncomfortable, you may want to at least partially open one or more windows to prevent them frosting over.

Taxi a little slower than usual on a taxiway with patches of snow, ice or wind-blown snow. The centerline of the taxiway may not be the center of the open area; weave if necessary to stay on areas that have less snow or ice. Keep the ailerons positioned for the wind and cranked all the way to the stop. Adverse aileron yaw is your friend should you start to slide on the ice. On ice, you may find yourself taxiing in a crab, watching the world approach you through one side of the windshield rather than the front. Experimenting with power and rudder deflection may allow you to get where you want to go, rather than sliding into a snow pile after an unsuccessful attempt to stop.

If you taxi through any snow, assume it will melt on the brakes as you stop, then soon freeze. If possible, do the runup on a dry spot or where there is hard-packed snow and the tires wont slide. When doing the runup, dont waste time. Keep an eye out to make sure you arent sliding into something hard and expensive. This is no time to do a long runup with your head down. If you are not confident you can keep the airplane stopped, omit the runup and do a quick mag and carb heat check on the initial portion of the takeoff roll. Engine warmup time prior to takeoff varies: Check your POH-we like to see oil temps of at least 100 degrees F before applying full power.

If the brakes have frozen, add power slowly; they should break loose before you get to full power. They may not do so simultaneously, so be ready to do what it takes to make the airplane go where you want it, including a rapid power reduction. If full power does not free the brakes (which is unusual) shut down, get out and kick them unless you are wearing steel toed boots. It does wonders for frustration levels, and sometimes can free up a stuck brake.

On takeoff, make sure the ailerons are deflected into the wind; on a slippery surface it may make the difference between a smooth takeoff and loss of control. Stay in the center of the open area between snow piles and drifts-if there is wind-blown snow, the center of the open area probably wont correspond to the centerline. Open the throttle slowly, take five to eight seconds; after all, you are causing shock warming of the engine on a cold day.

If you roll through any loose snow or slush, assume the brakes are going to freeze again and be ready for it on landing. With a retractable, leave the gear down for about a minute to let the wind blow the snow and moisture off so you dont risk freezing it in the wells.

When setting power for cruise, check the power charts in the POH-the rpm you used in warm weather may produce over 75 percent power when its cold. Your airplane isnt any faster in the cold; you are just generating more power and the airspeed is indicating higher. Be kind to the engine as you approach for landing, make small power reductions and start early so it cools slowly. While theres no real data saying rapid cooling hurts the engine, why risk it?

If its an overcast, gray day, and there is a covering of snow on the ground, be alert for “flat light.” It can be impossible to tell your height above the ground in such conditions due to a lack of shadows or contrast on the ground. It is difficult to believe such a thing can happen until one experiences it, but flat light conditions are very real and have killed scores of pilots who thought they were flying well above the ground. Use the altimeter in the pattern and plan the turn from base to final to start no lower than 400 feet agl. Were not kidding: More than one pilot has stuck a wingtip into the ground on that turn while convinced he was still at least 500 feet in the air. Our experience is that in flat-light conditions, if the runway has been plowed and there are some tire or plow marks in the snow, depth perception returns at about 15 or 20 feet agl, and sometimes in a quite startling fashion: “Hey, there are snow piles beside this runway. Big ones.” Aim to flare a little way down the runway, crossing the threshold 10 or so feet in the air-every once in a while an inexperienced plow operator will leave a berm of snow at the end of the runway. Those have a way of teaching pilots about gear-absent landings in fixed-gear airplanes.

Assume the brakes are frozen and plan to touch down just a little firmly while being ready on the rudder. Use the center of the runways open area. If the brakes are frozen, you may hear a screech as the tire slides (if there is enough dry pavement to do so) and then a bang or pop as the ice lets go and the wheel starts to roll. The wheels usually free up at nearly the same time; however, if one wheel releases and the other doesnt, the airplane will swerve toward the locked wheel. The solution is to lock the other brake yourself, so you have two sliding tires, and steer with the rudders. Aileron into the crosswind is essential to this maneuver. You can do it. If/when the offending wheel releases, all you have to do is let go of the other brake. Inspect the tires afterwards.

Be cautious taxiing in, especially if landing at another airport. If in doubt about the condition of a taxiway, depth of snow, or presence of ice, especially at night, call ground control at a controlled field and get assistance. At an uncontrolled field, shut down and walk the area. After all, its a lot easier to walk into the FBO to get help clearing a way to taxi in than it is to get help because youve run off a taxiway and hit something.