Page 22 - Twin and Turbine December 16

20 • TWIN & TURBINE DECEMBER 2016
From the Flight Deck by Kevin R. Dingman Let It Snow
Above average snowfall is forecast
“A day without sunshine is like, you know, night.”
– Steve Martin
For all life on earth, nothing is as fundamental as the length of daylight. The tilt of the Earth’s axis affects the duration of daylight and plays a major role in our weather. It’s tilted at an angle of 23.44° to the plane of its orbit and because of this, at certain times during the orbit, it’s dark longer and we get cold weather. It’s a time of the year that produces fast moving fronts, icing conditions, strong and gusty winds with drifting snow and it’s like, you know, winter.
It took me a lifetime, but I have a nice airplane, a private hangar with an office, pre-heat equipment out the wazoo and reliable snow plowing. For this pilot, who keeps an artificially- lighted Christmas tree up all year long and cold weather gear at the ready, it’s a great season. My dad raised me to be an outdoorsman, to love the seasons. I have clothes for rain, cold, snow and wind – some might even get me through a torrent of frogs and locusts. Cold never bothered me as much as does heat and humidity. Just as southerners think we’re crazy to put up with cold and snow shoveling, the heat, humidity and bugs endured in the south are perplexing to a northerner. That’s why God made air conditioning – y’all say. And that’s
fine if you like living in a cubicle indoors, but not me. Part of why we fly is freedom and the view. Let not a little thing like planetary tilt interrupt our flying schedule.
Tilted
In the northern hemisphere, winter solstice always occurs around December 21st or 22nd. In the Southern hemisphere, it’s around June 20th or 21st. This year, it’s on December 21st at 5:44 A.M. EDT (10:44 UTC) and marks the official start of winter in the Northern Hemisphere and summer in the Southern Hemisphere. Winter solstice is the day with the fewest hours of sunlight during the whole year. Our shortest day this winter will last just nine hours and 15 minutes. The word solstice comes from the Latin words for “sun” and “to stand still.” In the Northern Hemisphere, the points on the horizon where the sun rises and sets advances southward each day and the high point across the sky, which occurs at local noon, also moves southward each day. At the winter solstice, the sun’s path has reached its southernmost position. The next day, the path will advance northward. However, a few days before and after the winter solstice, the change is so slight that the sun’s path seems to stay the same, or stand still – to “solstice.” The sun is directly overhead at high- noon on winter solstice along only one planetary marker: the latitude called the Tropic of Capricorn – it’s a bit south of the equator. Now that we’re astronomically up to speed
about why it’s so cold and dark cold outside, onward to its relevance on our operations.
The Forecast
Temperatures in the North cause nostrils to momentarily stick closed and thin layers of snow will create a squeaky noise when you walk. Flying can be a bit more work for pilots: snow removal and preheating are added to the preflight list, taxi speeds are slower and low visibilities can be widespread. On the other hand, it’s the kind of weather the airplane loves: cold, dry air for the motor to breathe and tightly-packed molecules for the wings to finesse into lift. Compared to the hot, humid days of summer, it’s ideal. Traveling in our airplanes exposes us to wide- ranging temperatures and weather. This year, the National Weather Service is forecasting above-average temperatures and below-average precipitation for the southern part of the U.S. People in northern states should expect below-average temperatures and above-average precipitation. Forecasters expect the remaining U.S. to experience an average winter. The biggest wintertime changes for us occur during planning and preflight: preheating motors, adding a fuel system icing inhibitor (FSII) like Prist to our jet fuel when needed, using deice fluids, calculating holdover times and selecting alternates. When inflight, we’ll be using fuel heat and the anti- ice equipment. On arrival, flying low-visibility approaches and computing landing distances will be the norm and we’ll be diverting a couple of times. You’ve heard it all before, but stay with me; here comes the mandatory wintertime preflight stuff: