Defining winter by the severity of cold weather on the North American continent can be a difficult task. In most years, anything south of a line through Atlanta, Little Rock, Oklahoma City, Santa Fe and Los Angeles has a good chance of a modest winter. Any location above 35 degrees north latitude can reasonably expect colder conditions. In this case, we’re not talking about the extremes of frigid temperatures, say, colder than -30 degrees F. It’s possible to operate in far more severe conditions—Alaskan bush pilots do it all the time—but we’re not considering those instances for the moment.
Perhaps contrary to popular belief, winter weather is often friendlier to an airplane than the atmospherics of summer. For one thing, the flying can actually be better. In winter, the lifting forces that produce thunderstorms and tornadoes simply aren’t present. That’s not to suggest that winter storms can’t be dangerous, but with the exception of inflight icing and an occasional slick runway, pilots and their airplanes see mostly positive benefits from winter weather. No question, icing is a real hazard, but it’s not in the same class as CBs and tornadoes.
Unfortunately, humans are less impervious to the ills of winter than the airplane. For that reason, you’ll want to check and service the heater before your flight. Long before the advent of GPS, a friend was flying a well-used Shrike Commander he’d just purchased in Wichita back home to California and got trapped on top in very cold temperatures with a malfunctioning heater. The airplane was running fine, but the avionics weren’t. Joe was forced to stay up high for four hours with an inoperative heater before he finally cleared the undercast and was able to descend and land in New Mexico, a very cold and humbled pilot. He hadn’t checked the heater before takeoff, and his one good navcom had failed shortly after level.
Survival gear requirements change with the season, and you can spend as much as you wish to provide a hedge in case you need to land off-airport in frigid conditions. I fly a four-seat retractable that almost never carries anyone in the back seat, so I have all the room and weight allowance I need for emergency gear. On winter flights across rugged terrain, I have a habit of loading my Mooney with enough survival gear to keep a squad of Marines alive for two weeks at the North Pole. (My friend, Doug Ritter, of Equipped To Survive, offers a more realistic variety of information and gear for every survival need. Doug edits and publishes a newsletter specifically dedicated to all aspects of survival. Contact him at dougritter.com.)
Winter brings with it fast-moving jet streams that can provide excellent tailwinds for those traveling east. “The Jet” was discovered in the mid-1940s when our B-29s, flying from Saipan and Tinian, first began saturation bombing of Japan. The ferocious westerly winds weren’t a new phenomenon, but they slowed our bombers by as much as 150 mph on the inbound run to Tokyo and other targets. At least the trip back to the Marianas was usually a quick one.
Here in North America, the jet stream migrates south out of Canada every winter, often bringing spectacular westerly winds to much of the United States. Those winds rarely descend much below 10,000 feet, but may still add an extra 20 to 30 knots in the bottom two miles of sky if you’re headed east. Pilots flying westbound, into the wind, can often mitigate the effect of headwinds by operating at the lowest possible height.
Back in March 1994, I took advantage of winter tailwinds to set eight new, city-to-city speed records between Los Angeles and Jacksonville, Florida, flying a new Mooney Bravo at FL250 all the way. The fastest leg was 338.32 mph, one hour and 59 minutes between LAX and Albuquerque. Total time coast-to-coast was seven hours and nine minutes, for an average speed of 300.2 mph over the 2146 sm course to Jacksonville. All those records still stand in class C1C.
The Bravo, predecessor to the current Acclaim, was/is the fastest piston, production airplane in the world, but such near-turboprop velocities wouldn’t have been possible without the help of the winter jet stream.
In addition to strong winds aloft, winter brings with it colder air (duh!), and that can be a major positive. The thick, dense air associated with winter temperatures is a wondrous thing for an airplane’s wing, prop and engine.
One slight negative of operating in cold temperatures is the occasional need for preheat. A standard start at 68 degrees F requires only about half the electrical power of one at 0 degrees F.
There’s little consensus on precisely when to preheat, but everything becomes easier when you bring the engine up to a reasonable temperature before engaging the starter.
Most experts on engine-operating techniques advise that it’s a false economy not to preheat if the overnight temperature fell below 20 degrees F the previous night. Most FBOs in northern locations do a steady diet of preheats in winter, and given an hour’s notice, they can have engine temps practically in the green when you show up and are ready to fly.
Another possible benefit of a preheat is that you may be able to warm up the cabin. Under some circumstances, you can ask the FBO to channel one of the heat ducts through the storm window to warm the cabin while the engine tubes are bringing cylinder head and oil temps off the bottom peg.
Icing in all its forms is a subject worthy of an entire book, in fact, dozens of books. For that reason, we’ll confine our examination of winter flying to problems on the ground and leave inflight icing for another time.
If you’re traveling and need to park the airplane overnight, you’ll need to decide between leaving it outside or parking inside a hangar. Obviously, a heated hangar is the preferred option. It’s also the most expensive one. In some places, you’ll pay $250 to $300 to house a single in a heated hangar overnight, $350 to $400 for a twin.
A cheaper alternative may be to have the airplane pulled inside for perhaps two hours just before departure, long enough to bring everything up to a reasonable temperature. That may not be much cheaper than leaving it inside all night, since the big fee is for the power to reheat the hangar rather than the occupied floor space.
If that’s not an option, you can leave the airplane outside and take your chances on frost. Should you step out in the morning and find your Piper has been transformed into a popsicle, all may not be lost.
A full deice with type IV ethylene glycol is usually fairly expensive, and that isn’t always available unless you can move the airplane to a specific deice pad, plumbed to drain away deice fluid safely.
Some pilots carry a few gallons of antifreeze with them, but that’s a bad idea. Antifreeze is sickeningly sweet and will kill any animal that licks it up. Additionally, most airports frown on pilots pouring anti-freeze on the wings and tail, inconveniently leaking some on the ground. As you might imagine, antifreeze and ground water combine into toxins you don’t want to think about.
The next option is to use a standard credit card to remove frost and snow. I have a long-outdated Long Beach Airport access card that’s thick and strong, and will blade away most snow and frost fairly quickly without shattering or damaging the paint. A standard American Express card may also work, but you stand a good chance of breaking it and having to rely on cash for the rest of your trip.
Once the airplane is clear of ice and it’s time to depart, winter may offer you too much of a good thing. You may develop a density altitude problem that’s exactly the opposite of what you might imagine.
Cold starts should obviously follow your airplane’s start procedure, but a universal rule is not to over-prime. Using too much prime can wash the cylinder walls clean of any residual oil and result in metal-on-metal contact when you engage the starter. The jury is still out on pulling the prop through before initiating start. Personally, I do it on any cold-weather start.
Everyone who operates an airplane in mountainous terrain understands the concept of high-density altitude. Fly into Leadville, Colorado, in summer, and the temperature can seem very comfortable at, say, 50 degrees F. The “yeah, but…” comes when you start calculating what the temperature “should be” at Leadville’s 9,927 feet MSL elevation. Standard temp at that height works out to roughly 29 degrees F. If the actual temperature is 50 degrees F, the air is considerably thinner than standard, equivalent to about a 12,000-foot density altitude.
Nonstandard temperatures can cut both ways, however. Pilots address this problem on a regular basis in the Far North at more typical, near-sea-level airports when the winter temp drops to -40 degrees F or colder. Since standard temperature should be 59 degrees F, they’ll be operating at about 100 degrees F below normal temperature. That produces a density altitude of almost -7,000 feet (note the minus sign). That represents a kind of natural supercharging.
Now, see what happens when you translate that density altitude to engine power. A perfectly tuned, normally aspirated piston engine, operating in sea-level, standard conditions, should deliver something like 28.5 to 29.0 inches of manifold pressure. Ideally, induction systems should produce 29.90 inches, but no induction system is perfectly efficient. Most lose at least an inch of pressure to inefficiencies in the system.
Go to full power at conditions that simulate 7,000 feet below sea level, and your engine will suddenly deliver more like 36 inches MP at full power. For most engines, that means you’re technically over-boosting the engine.
If you monitor the manifold pressure and are careful to maintain it at 30 inches or less, winter temperatures can allow you to enjoy slightly more power and performance without the risk of engine damage.
That much power might feel great under your right palm, but it could also be destructive if maintained for more than a few minutes.
Conversely, such dense air is wonderful news for most airfoils. Wings love a compressed sky, and propellers produce more thrust as the air becomes thicker and they can take a bigger bite with each passing blade.
Climb also benefits from cold weather, since there’s little convective activity. The ride uphill is usually smooth and quicker than normal. Traditional wisdom suggests cruising higher than you normally do if there are tailwinds available.
In winter, visibility is typically better than during the haze of summer when you’re not fighting a snowstorm. In fact, much of the time, you’ll be greeted by clear air and sunshine, even if it’s a little chilly.
On a recent Columbia 400 delivery to Geneva, Switzerland, I encountered something I’d never seen before: an oil temperature of what I interpolated as 50 degrees F, well off the bottom of the gauge. (I say “interpolated” because there were no markings below 135 degrees F.) Flying out of Bangor, Maine, for Goose Bay with an outside air temperature of -30 degrees F, I first assumed it was simply a malfunctioning oil temp gauge. Everything was running well, the weather was severe clear and the engine didn’t seem unhappy. I continued to Goose Bay, landed and immediately taxied to the maintenance shop. The mechanic said he’d seen that before, and it wasn’t unusual when conditions were what he termed “brisk.”
Trouble was, my next three legs were across the North Atlantic, and I wasn’t about to contend with a possible engine failure in such “brisk” conditions.
A few phone calls later, I determined that such amazingly low readings weren’t that unusual in northeastern Canada in winter, and the Columbia 300/350/400 had experienced the problem before. The Goose Bay mechanic installed some metal deflectors that partially blocked the cooling air intake, and the oil temperature climbed to about 135 degrees F on my next leg, warm enough to justify continuing the trip.
Winter takeoffs and landings can also present some special problems you won’t encounter in summer. If there’s snow on the runway, most any idiot can figure there might be ice underneath, but if the runway looks clear….
In reality, you may be better off when there’s visible snow available for taxi and takeoff. In some parts of the Far North, it’s not always possible to keep the taxiways and runways clear because of the rate of snow accretion. For that reason, you’ll often taxi by reading the guide poles that rise a foot or more above the taxiway/runway edges to help delineate aircraft movement areas.
Sometimes, even that isn’t enough. A few years back, I was delivering a 58P Baron to Cleveland Hopkins following a double-engine overhaul by Victor Aviation in Palo Alto, California. The snow at Cleveland was heavy, but the air was characteristically smooth when I arrived at 9:00 p.m.
The Baron made the approach look easy as I broke out near minimums, touched down in heavy snow and almost immediately lost all forward visibility to low-lying mist and snow. With plenty of runway ahead, I stayed off the brakes and let the airplane roll out straight ahead. After I’d stopped, the tower called and said they couldn’t see me, only fair since I couldn’t see them, either.
The controller started sending everyone around, but it barely mattered as the airport had dropped below minimums. They advised me to hold position, turn on every light in the airplane and wait for a follow-me truck.
It took about 10 minutes before the truck found me, starting from the opposite end of the runway and driving very slowly toward me. He came up on ground and told me to stay right behind him as we taxied to the ramp at a slow walk.
It seemed to take forever until a huge hangar with an open door and welcome floodlights materialized in the snow. Fortunately, Cleveland was my destination, so I didn’t need to contend with snow on ice the next day.
The point is, don’t trust snow covering a runway or taxiway on the premise that there’s no ice underneath. You may not know it’s there, but if it is, the airplane will find it for you.
Understandably, airports always clean their runways first, and taxiways/ramps are a second priority. Keep taxi speeds as slow as practical, and don’t automatically try to take high-speed turnoffs just because you think you can. Make all turns as gently as possible, and stay off the brakes, especially if you’re unfamiliar with the airport layout or if visibility is marginal.
Even what looks to be a clean runway can be deceptive. Many years ago, during a Christmas flight from Long Beach, California, to Tampa, Florida, I landed at perpetually windy Amarillo, Texas, with a slight crosswind and what looked to be a clear runway, only to discover it was covered with black ice.
My tailwheel Bellanca Cruisemaster started a slow turn to the left and kept right on going through a full 360, tracking the centerline and ignoring whatever I was doing wrong with rudder and brakes. It finally stopped, once again pointed down the centerline just as if I’d planned it that way. I hadn’t.
As I sat there with my heart still racing and the airplane totally undamaged, the droll controller felt compelled to ask, “Bellanca 85 November, do you require assistance to taxi?”
As of January 1, 2016, Senior Editor Bill Cox has logged 15,100 flight hours in 321 types of aircraft.
He also holds 28 world city-to-city speed records, has made 211 international delivery flights, and owns
and flies a LoPresti Mooney. You can email Bill at [email protected].