Winter flying might be considered better or worse than summer flying, dependi

Elegant Escapes

For private jet travelers intent on satisfying their own "urge for going," winter flights south often begin with a quick, cold dash from the limo or terminal across a wind-blown, icy ramp to a toasty preheated cabin. The rest of the flight passes in climate-controlled comfort until you emerge-relaxed and refreshed-to take on the sun.

For pilots, however, winter flying involves a host of differences when compared with plying the summer skies. For sure, there are liabilities beyond the simple discomfort of battling wind and elements. But there are also positives that come with the sinking mercury readings. On balance, winter flying might be considered better or worse, depending on your perspective. But it is certainly different.

Ensuring that the airplane is free of accumulated ice and snow is the first and most obvious safety concern. After some high-profile takeoff accidents over the past few years, the FAA has rewritten regulations regarding preflight deicing. And in any case, only the most out-of-touch flight crews would ignore even trace amounts of wing ice, now that everyone throughout the industry is so painfully aware of how much it can degrade lift at the most critical stages of flight.

There are other, perhaps less obvious, concerns for winter takeoffs. Slush on a runway can degrade acceleration more profoundly than any other form of runway contamination. Icy water splashing up into wheel wells and coating flap attach points has been known to freeze solid in flight, leaving the airplane unable to extend flaps or wheels for landing.

Even in summer, jets fly at altitudes where temperatures are almost always well below zero Fahrenheit. For that reason, many jets have fuel heaters. Even trace amounts of water in a jet fuel tank can freeze, creating crystals that can block fuel lines and cause engine failure. Another way to combat fuel icing is blending in an additive at the pump that acts as an antifreeze within the fuel supply. (Some fuel suppliers pre-blend their additives.) Either way will keep the go-juice flowing under the most frigid conditions.

While the passengers have a quick run across the tarmac, flight crews aren't so lucky. Doing a thorough preflight inspection in the predawn hours when the wind is howling is never a walk in the park, and frankly it is sometimes not done as thoroughly as it should be. This is one good reason the expense of putting the airplane in a hangar-if not overnight, than at least for the time it takes to do the preflight-is worth it.

Pilots must also consider varying weather-formulating flight plans with strong west winds in mind. At typical business-jet cruise altitudes, it isn't uncommon for the jet stream to flow at close to 200 miles per hour. Since the jet stream flows mainly west to east in the Northern Hemisphere, you can expect relatively quick west-to-east flights-but a long day's journey into night when you're headed west for some "California dreamin'." Sometimes, however, the jet stream will curve southward on its track from western Canada and make a U-turn over the southern U.S., before bending back toward the northeast. Depending on one's route, this can cause north-south flights to be faster or slower than normal and subject east-west flights to more-than-normal turbulence.

Certainly, not all aspects of winter weather are negative. Systems and fronts tend to move more quickly than they do in warmer weather, leaving less chance of long periods of stagnant low visibility. Thunderstorms, among the deadliest of aviation hazards, are virtually nonexistent in winter. And cold air is significantly denser than warm air, meaning that engines develop more power and wings provide greater lift. A high-altitude runway that might have been marginal for a midday summer takeoff at 90 degrees is no problem when the air is crisp and frosty.

Of course, there is such a thing as too cold, even for an inanimate airplane. That is why new models must be tested under natural conditions at low temperatures to achieve certification.

Consider that an airplane-especially a modern business jet-is much more than engines and airframe. It's a complex mechanical organism made up of electrical, hydraulic and computer systems that must work in flawless, triple-redundant harmony-even when the mercury goes deep into hibernation at the bottom of the thermometer. Think about how well you'd be able to trust your laptop computer if it had been sitting for three days on an airport ramp at 40 below during a blizzard. Most PC monitors lapse into cardiac arrest at anything much below room temperature. For an airplane, all systems must prove workable first time, every time, or they are not certified. Toll-free help lines aren't much help at 51,000 feet.

So a modern jet really is a marvel-not just in its speed, luxury and beauty. Each one also represents innumerable engineering feats, many of them worthy of coverage in Scientific American, let alone Business Jet Traveler. So as you board your airplane at some frigid northern airport on your way to the balmy Bahamas, think about what has gone into the design of this remarkable machine, and what it takes to fly it safely under these trying conditions. Then remember those geese in chevron flight-and consider how elegantly you've assuaged your own "urge for going."

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