The east USA was closed for much of the early week due to snow. Why?
A common question at this time of year is why do we de-ice airplanes on the ground, and how?
And what happens in the air?
Remember the 1958 Munich air crash in the fifties when the Man United football team was decimated? Only if you are my age probably but, it was a watershed in understanding snow and ice. That sort of thing would never happen today due to our total understanding of the danger that snow and ice would pose.
Pilots and Planes don’t like snow and ice for lots of reasons-
- Snow on the runway slows down the takeoff due to resistance on the wheels – this is what happened in the Munich incident.
- Snow or even a little bit of frost on the wings reduces lift (which makes the plane fly) and can create massive problems during takeoff.
- Engines can suffer icing which affects their performance.
- The sheer weight of snow and ice can affect the performance of the plane.
So what can be done on the ground?
First the plane is brushed clear of snow and then a mixture of antifreeze and water is hosed on hot to clear any remaining ice. Then a layer of strong de-icing fluid is sprayed on to protect the plane for up to an hour – its called the holdover time. It depends on the rate that snow is falling and the strength of the mixture which are carefully calculated.
The engines have heated air pumped into the intakes to ward off any ice.
The taxiways and runways are cleared by specialized machines which clear the snow and reduce its depth to about 3mm or less so it does not create a problem.
When you are on the plane you can sometimes see the de-icing machines spraying the fluid and it takes about 15 minutes. There is a massive cost to all this – it can cost thousands to de-ice a Jumbo, but there is no alternative.
The Pilot will always check to make sure that the de-icing is carried out correctly and will assess its effectiveness prior to takeoff. There is never a chance takes with snow and ice.
A bad winter can result in millions of extra costs for airlines but it is done no matter what since safety is paramount.
As this week sometimes the snow is so heavy that all airports on the East Coast of USA were closed for much of the time due to the intensity of the snow. This is when the volume of snow outstrips the ability of the airport staff to clear runways, taxiways and planes of snow. Heathrow is 3 miles long and 2 miles wide. That’s 6 square miles of snow or 4000 acres. 21 million cubic feet of snow – you need a big shovel for that.
Why do some airports cope better?
Because they are used to snow and have more equipment – don’t expect Rome to have extensive snow removal facililties because it only snows occasionally. Vice Versa Montreal would be so used to heavy snow that they have massive facilities.
But, the most important factor is the kind of snow! Dry snow at -40 degrees is easy to clear – it blows away. London and other similar cities, have snow that is the worst kind. Just below freezing, slushy and thick. We all know this when it first snows in winter, the snows is light and fluffy but soon turns into a thick and unpleasant heavy goo which is hard to brush away on your driveway – so it is at such airports.
Once airborne, the plane has its own deicing systems. The wings are heated by hot air to prevent ice forming, or to shed ice that has formed and it is very effective. The engines are heated too to prevent any ice formation in the air intakes. The pilots avoid areas of known heavy icing which can be forecast by the Met Office and the radar on board can pick out areas of intense rain / hail activity.
Happy and safe flying