Popular Mechanics contributing editor Jeff Wise, a private pilot and long-time aviation writer, takes on his biggest challenge yet: Flying withoutan engine. Follow along as Jeff learns that no matter how experienced the pilot, getting a glider license is no easy sail.
Today's lesson: If you have no expectations, you'll never be disappointed.
For most of my life, I had no interest in the weather. Low-pressure systems, cold fronts—I just didn't care, except to decide if I needed to take an umbrella to work. But when I started working towards my private pilot license, the weather became an obsession. I was only allowed to fly under visual flight rules, (VFR), which require that you can see at least three miles, and that the cloud ceiling is higher than 1000 feet (the rules are actually far more complicated than that, with loopholes and stipulations depending on different altitudes and airspaces and time of day, but who cares). Legally, you can fly in rain, and in high winds, but in a small plane a little bit that sort of weather goes a long way. If you're jonesing to get up into the air, you start to care if there's a low pressure system two states over, because, most likely, it will bring bad weather tomorrow, and you'll be SOL [a technical aviation term that translates, roughtly, to "You're Grounded" —Ed].
When I started getting interested in gliders, the weather mattered even more. As I mentioned earlier, the kind of lift we look for at Nutmeg is usually thermal. The sun heats a patch of ground, and the ground warms the air above it, and the air starts to rise. So if there's no sun, you can forget about thermals.
Glider pilots also care about a phenomenon unknown even to many private pilots: the lapse rate of the atmosphere. A pocket of air will only rise if it's warmer than the air around it. As it rises, the air cools as its thermal energy is translated into potential energy. The rate of cooling is called the "dry adiabatic lapse rate," and it's equal to 5.4 degrees Fahrenheit per thousand feet of elevation. (Which means, if it's 94 degrees at sea level and you climb a 10,000 foot mountain, the temperature at the summit will be 40 degrees. This is why people vacation in the mountains in the summer).
In practice, the air temperature at higher altitudes is rarely what you'd calculate from the lapse rate. Sometimes, the air up there is warmer, which means that as air from the ground rises and cools, it just sinks back down again (it's a phenomenon called an inversion, and it's why smoggy air gets stuck in the LA basin for weeks at a time). And sometimes, the air above is cooler, and that rising air just keeps rising. When this happens, the atmosphere is unstable, and thermals form easily. (Thunderstorms can form, too; come mid-summer, glider pilots dance a careful dance between having not enough lift and too much—since thunderstorms are among the most dangerous of all meteorological forces aloft).
Which brings us today: From the forecast, I was expecting the weather today to be much the same as yesterday, with summer's typical hazy sun and thunderstorms cooking up in the afternoon. In the morning it looked like the forecast shaped up as I'd hoped. But as I drove west toward Freehold, the clouds got thicker and grayer. I stopped in Hudson for lunch and shopping, hoping things would improve. They didn't. I contemplated going to Freehold anyway, since the creek that runs along the airstrip was recently stock with trout, and I have a fishing pole in the trunk. But I knew that being there, with the gliders tied down under a gloomy gray ceiling, would just make me antsy. So I drove home. As I headed east, the skies grew clear again. Puffy clouds and thick sunshine filled the sky. It looked like great gliding weather.
Well, maybe it was. But it's also great gardening weather, great bicycling weather, great lying-in-the-hammock weather. Because when you're into gliding, you have to make the best of whatever nature gives you.—Jeff Wise
Next: The Sun Will Come Out... Tomorrow?
Earlier: Learning To Glide
Glide The Lightning: Gliders ride rising currents of warm air. Extreme updrafts form cumulonimbus clouds such as the classic, anvil shaped thunderhead (center). Updrafts such as these rise many thousands of feet and release massive amounts of energy, causing violent thunderstorms, or even mesocyclones. There will be no gliding here.