How Does Snow and Ice Affect Passenger Aircraft?

Like so many things in flying the truth of what actually happens is very different from the public perception of what they think happens. The only connection that people have with bad weather and travel is usually their motor car. The logic is simple, if it's dangerous in a car, then it must be even more dangerous in a plane. But if we go step by step we can see that even from the very first things we do in poor weather, in driving or flying the two situations are worlds apart. But first lets deal with snow, we just bull doze it off the runways or clear it with snow blowers. Snow itself isn't a problem once it's been cleared. Weather reports are sent around the world so that a pilot can check the snow state of any airport before flying there.

Ice is the more important thing to deal with, because it affects the shape of the wing, so we pay very careful attention to clearing the wings. Imagine going out to your car after a cold night. The first thing most of us do is to scrape the frost from the screen, but the temptation is to scrape just enough off so that we can just see out, and then let the heater do the rest. By any standards this is madness because on a day when the conditions are bad we think it's OK to have a limited view through the screen. Then we roar off down the road using our 'experience and good judgment to decide how fast to go. Does anyone know what the road surface is really like? Do you really think that would be a safe way to operate a plane?

From the outset as I have said we do it differently in aviation. If a plane has been parked out overnight and has frost, ice or snow on it then it has, by law, to be de-iced. Every important part of the plane has to completely clear of any 'contamination' as we call it. But we don't just de-ice it. We de-ice it with approved de-icing fluids, which have a specified time of being effective. So if it's de-iced at a certain time and the plane isn't in the air within say 45 minutes it has to be de-iced again.

The captain always inspects the aircraft to make sure that it is completely clear of snow or ice. Before flight, information about the type of fluid used, its temperature and what time de-icing was started is all recorded officially in the aircraft's technical logbook. Runways too have to reach a minimum standard of clearance. The condition of the surface is then measured and broadcast to aircraft on the local information channel. When it has been cleared a special vehicle checks the braking effectiveness on it. The pilots have manuals that show the restrictions on the weight of the plane for take-off and landing. If there is any slush on the runway, take off is prohibited if it exceeds a certain depth. No such rules are applied to car drivers; we are allowed to do whatever we want with no information, no guidance and worst of all no training.

Let's review what we've done so far then. We've de-iced the plane with 'approved' procedures and fluids. We've limited the weight of the plane according to the conditions, and we've made sure that the runway is safe enough to use. That's why planes don't go skidding off the runways and off the taxiways or into terminal buildings!

You'd think that things would get a whole lot more difficult once we got into the air but in fact it gets a whole lot simpler. A commercial passenger carrying plane spends most of its life at temperatures a long way below freezing. So on almost every flight a plane will have its engine de-icers turned on.

It's only rarely that a jet aircraft will use its wing anti icing system. However planes that fly at lower altitudes will often collect ice on the front edge of the wings and tail plane when flying through cloud. One way of removing the ice is to blow hot air from the engines along the front edge of the wings and tail plane. Some planes have electrically heated warmers along the front of the wings and tail. But the one that you can see working in the air, if you can see the wings is the system that uses inflatable rubber tubes. The pilot waits for the ice to settle on the wings then turns the system on and air from the engines inflates then so that the ice breaks off mechanically. Flying in wintry conditions should not be compared with how we drive in the same conditions. - winter safety