In parts of the U.S. where snow falls, pilots frequently have to decide whether or not to go flying after accumulation stops and the skies clear. “It’s only a little snow cover,” the hardy aviators will say, “looks like we can handle it.” The problem is, there’s snow, and then there’s SNOW. What we could handle easily last time may not match today’s conditions. Much depends on the snow’s depth and composition.
One inch of dry, powdery snow on clean pavement is navigable for most airplanes fitted with standard six-inch tires. That same inch composed of wet, slushy snow is much more difficult to handle. That is, it’ll take more power to push through it and it’s more likely to accumulate on brakes, wheels and landing gear fairings and in wheel wells. So, be prepared to learn just show much of what kinds of snow your particular airplane can negotiate safely.
Where and when will frozen white stuff present the greatest problem? Most new-to-winter pilots are concerned about trying to stop after landing, but over the years of operating from snow I’ve seen more challenges during takeoff than in the landing roll-out. Brake-dependent high performance aircraft obviously need a dry runway to meet their normal landing distance numbers, while light airplanes slow down reasonably well with the added drag of snow accumulation. On the other hand, taking off from a snow-covered runway, particularly with low-horsepower planes, may find you plowing along at terminal velocity well short of unstick speed.
Packed snow and ice on the runway, often the result of attempted snow removal, provides much less braking traction than loose snow. On such surfaces, one should double the usual dry-surface stopping distance, just for starters, and you need to be aware of a significant crosswind component’s effect on your ability to hold the airplane straight. A wet, melting snow/ice surface presents a “nil” braking action. Snow can also lead to “reverted rubber hydroplaning” when locked-up tires under panicky braking generate heat from sliding, creating steam under the immobile tire that melts away the tread while providing no braking.
If at all possible, check out the runway conditions at a little-used airport on the ground with a four-wheel drive vehicle before attempting flight. Look for varying snow accumulation, hidden drifts, ruts and previous removal debris. On the other hand, assessing the suitability of a landing surface from above, with no input from observers on the ground, is difficult when all you can see is unbroken white. Be not the first to try a landing; look for tracks left by previous users, and note the difference between tricycle landing gear and four-wheeled vehicles. Snow depth is tricky to ascertain, even from a low pass; if you can’t tell for sure, don’t try to land. I have made experimental touch-and-goes on an unbroken snow-covered runway, but that technique carries some risk.
If starting from your shoveled-out hangar, don’t assume all taxiways have been plowed full width; observe before entering. As you proceed, watch for changing snow depth and hidden drift fingers emanating from “push piles” along the runway sides. Taxi carefully, pretending you have no brakes, and be ready to advance power if you feel the aircraft bogging down in the snow; keep it moving, because if you let it stop you can not be able to start again. Try not to let one main wheel run through a patch of deeper snow, which can slew you off track before you can correct.
Be particularly aware of the danger posed by flat lighting on snow-covered landscapes. With a fresh snowfall on top of piles of “used” snow and old drifts, paired with a lack of shadows on an overcast day, you will not see a snow berm or other obstruction until you run into it.
It’s best to limit brake use when taxiing through snow. Heating up the brakes invites accumulating slush on the calipers, which then refreezes. If the snow surface is turning slushy, the tires will pack those pretty wheel fairings tight with frozen aggregation, perhaps locking up the wheel. Turn around and park on cleared surfaces for the run-up if at all possible.
Review your soft-field takeoff and landing procedures when operating out of snow. Plan to lift off and touch down at the lowest acheivable speed, anticipating the clutch of billions of snowflakes grabbing at your wheels. For takeoff, maximize your wing’s lift by configuring flaps for producing lift and get the nosegear up out of the snow as early as you can, then level off in ground effect once you’ve lifted off. Delay touchdown until at or stalling speed and be ready to use lots of rudder for steering until weight is on the wheels.
Operating in a little snow merely adds to the sense of accomplishment during winter flying. Just make sure that it’s only a “little,” and that your developing experience leads you to an understanding of your aircraft’s snow limitations.
