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Winter Weather

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  • Winter Weather

    Anxious fliers feel safe when in control. When you go online to check the weather, that fits in perfectly with what would seemingly make sense. You do that to be on top of things. That's as close to being in control as you can be, and you hope what you find with reassure your about your safety.

    The problem is, non-pilots lack the expertise needed to interpret what they find and to accurately know it's meaning

    For example, when an anxious flier goes online or watches TV, they may find a weather person might reporting bad weather. But "bad weather" is far to vague for air operations. We don't think in such categories. We think in terms of MEASURED visibility, ceiling, temperature, and wind direction and velocity or FORECAST of those conditions for a SPECIFIC time.

    In weather conditions that reporters say call for persons to not drive, or to even go outside, may be completely fine for an airliner to takeoff, cruise, and land. Efforts to stay informed (a form of control) is only going to lead to disturbing conclusions if the person is not an aviation professional who knows how to read aviation weather reports and knows what they mean.

    For example, here is the forecast weather for Kennedy Airport:

    KJFK 041735Z 0418/0524 33032G45KT 1/4SM SN FZFG BLSN VV003 FM042100 31032G42KT 2SM -SN OVC020 TEMPO 0421/0423 BKN015 FM042300 31030G38KT 5SM BLSN SCT025 OVC040 FM050100 29027G35KT 6SM BLSN SCT050 BKN100 FM050600 29025G33KT 6SM BLSN SCT050 FM051300 28025G37KT 6SM BLSN SCT050

    KJFK 041735Z means Kennedy Airport at 1735 Greenwich Mean Time

    0418/0524 means the forecast covers the time from 1800 Greenwich Mean Time until midnight

    33032G45KT means the wind direction is 330 degrees, and the velocity is 32 knots gusting to 45 knots

    1/4SM means the visibility is one-quarter mile in snow

    The current weather:

    KJFK 041816Z 33036G43KT 1/8SM R04R/1800V2400FT -SN BLSN FZFG VV008 M05/M06 A2922 RMK AO2 PK WND 34043/1808 SFC VIS 1/4 P0000 T10501061

    Here it shows the vizibility at the moment (1816 Greenwich Mean Time, just six minutes ago) is down to one-eighth mile. It is still legal to land because the RVR (measured by a special instrument alongside the runway to measure visibility) for runway 4 Right is 1800 variable to 2400 in light snow and blowing snow.

    So planes can land. Whether or not an airline will go ahead to send their flights into JFK is up to the airline. I suspect domestic flights into JFK have been halted until conditions improve, but flights may still be coming in from Europe because it takes eight hours to get here and the forecast shows landing conditions are expected to be acceptable.

    Cold weather is with us, and with the cold weather I get emails asking about safety. One frequent question has to do with whether cold weather causes problems for the plane itself. No. Consider that at cruising altitude the average temperature is minus 55 degrees Celsius. That means the plane's normal flight environment is much colder than any place on earth in any season.

    Another question is about the effects of snow. Mainly, snow slows things down as the runway must be periodically closed for takeoffs and landings so the snow plows can and plow the snow off the runway. Since the plows do this in formation it takes only five to ten minutes. That causes delays.

    With residual snow on the runway, the plane's brakes are less effective. It takes planes longer to slow down on the runway. And they have to slow down to about five mile-per-hour to be sure they can make the turn off the runway onto the taxi-way without skidding. If they try to make the turn a bit too fast, the plane can slip off the taxiway into the dirt. That is embarrassing. No harm done though, other than the captain getting yelled at by the chief pilot for not slowing down enough before exiting the runway. Plus, yet more delay for other planes as the runway may have to be closed until that plane is towed away.

    Also delays are caused by the necessity of de-icing the planes before takeoff.

    All in all, winter operations are still safe. Even if a plane skids off the runway or the taxiway, there is no danger to passengers because these skids always happen at slow speed. Why? Because at high speed the plane is steered by the rudder. The rudder remains effective until below fifty or sixty miles-per-hour. So skids, if they happen at all, they happen at slow speed when the plane's direction needs to be controlled by the direction the nose wheel is turned, and if the runway or taxiway is too slippery, directional control is lost and the plane goes into the dirt. Again, the main problem is getting yelled at by the chief pilot. The biggest risk for passengers is delays.

    Some anxious fliers ask whether de-icing will be done properly. Yes. The FAA came down very hard - I would say too hard - on the airlines about de-icing back around 1990 following an accident at LaGuardia involving a Dutch-made airliner that we uniquely sensitive to ice on the wings. Since they, though other planes are not that sensitive, de-icing had to be done as though they were that Dutch-made plane in spite of the fact that none are flying in the U.S. anymore. So you just don't need to worry about de-icing.

    In the air, planes have built-in anti-ice systems. It is only on the ground that the planes need to be de-iced. The fluid used for de-icing is similar to the anti-free used in your car's radiator.

    All in all, there is nothing to worry about in the winter other than delays and possibly cancellations when the delays build up. And, of course, your safety on the ground in your car getting to and from the airport. There - in your car and on the ground - safety is a problem, so be careful.