When any pilot considers cold-weather flying, in-flight airframe icing is first and foremost on the list of worries. Icing is an important safety risk to all types of airplanes, and a great deal of cost and effort is spent to avoid icing or to safely remove it or prevent it from accumulating. But the cold months bring many more widespread threats to flying safety and cause many, many times more accidents than in-flight icing. They are the dangerous six, or winter weather's worst half-dozen threats.
Darkness
By last September, the hours of darkness caught and passed the amount of daylight in every 24 hours in the Northern Hemisphere. By the time the cold of winter set in, the number of daylight hours, depending on your latitude, shrank to eight or less in the northern parts of the contiguous United States. In Alaska, the sun barely made an appearance.
With such short days, we find ourselves flying trips in darkness that only a few months ago would have been routinely completed in daylight, or at least with twilight landings. And every study of general aviation accidents shows that a hugely disproportionate number of accidents happen in darkness compared with the total exposure of hours flown at night.
This added risk of night flying is not so apparent in scheduled airline flying, or even in the activities of the major freight lines that operate mostly at night. But if you think for a moment about the difference between how and where the major airlines fly, night or day, that situation makes sense.
The foremost difference in the night safety record is that the big airlines use big airports. And the airlines almost always use runways that have glideslope guidance, electronic or visual or both. Also, the airlines are almost always in radar contact and are being vectored to intercept the approach. The controller not only provides course guidance with the vectors, but also assigns safe altitudes and monitors the crew to be sure it maintains those altitudes.
Compare the pilot workload and attendant risks of being vectored to an ILS approach to a 7,000-foot or longer runway with the typical general aviation airport operation. The airline crew is well-trained and current in night operations and has every bit of help available from the system. The general aviation pilot might be a little rusty on night flight, is typically headed for a runway that is not served by an ILS or other vertical guidance, and often descends below radar coverage to intercept the final course.
Also, the runway lighting at airports used most often by general aviation pilots is minimal with only widely spaced edge lights of marginal brightness, no touchdown or centerline lights, and no approach-light system to help you align with the runway. It's not such a great mystery why the airlines post essentially the same safety record in darkness as they do in daylight, or why GA pilots don't.
Darkness is the one climate-related winter flying risk that is absolutely predictable, and the only way to minimize that risk is to operate differently than you would with longer days. An obvious risk mitigation is to go out and practice night flying as winter approaches. The required three takeoffs and landings to a full stop in order to be passenger-carrying current are a good start, but not really enough. It is much better to fly a few short trips in the system so you remember what it's like to deal with the cockpit lighting and how to scan the instruments when more visual clues are missing.
You should also reconsider airports you will use at night. For example, a nonprecision approach to a short runway surrounded by hilly terrain might make sense in daylight, but not darkness. Giving up some ground transportation convenience can be an excellent safety trade after the sun has gone down.
Wind
Winter weather systems are usually more potent than those in the summer, with higher pressure in the highs and lower in the lows. That means the wind blows harder as air rushes between faster moving weather systems, and surface wind is a significant risk to all pilots.
Crosswinds are the most apparent challenge, and every airplane has a limit. At some point a crosswind can overpower the control authority available to stop the airplane from drifting sideways. The best pilot in the world can move the controls only to the stops, and if that is not enough to keep you over the runway, the airplane has exceeded its crosswind limit.
There are also unpublished, but very real, overall wind limits for most airplanes. Again, a pilot can position the controls to counteract the force of the wind while taxiing, but at some point the wind can overpower those control inputs and flip the airplane. Even if the wind is more or less on the nose, a strong enough gust can knock many general aviation airplanes off of their wheels.
