Winter is fully upon us and it’s time for snow, ice and de-icing. Why de-ice? When ice, frost, snow or anything else is stuck to the wings it will cause the wings to lose lift. Lift makes the airplane fly and if you lose lift, well, you’re going to have a really bad flight! There are many documented cases in recent aviation history where planes either ran off the end of the runway or crashed because of icing. Two notable instances are: Air Florida in Washington DC back in 1982. When the plane could not attain adequate speed to takeoff (because of ice) from a snowy runway and ended up in the Potomac River. Continental Airlines in Denver, CO in 1987 had snow and ice on the wings that prevented the plane from being able to generate the lift required to takeoff. Though the pilots tried to get the plane in the air, it did not happen and crashed off the end of the runway.
Luckily, under today’s rules ALL aircraft must be free of contaminants before taking off. Most airlines operate under the “clean aircraft” concept. This simply means that the aircraft is completely clean of all frost, snow, ice etc.
So, you are sitting in your seat and the Captain announces that “…we will be de-icing today.” Here’s an inside look at what is happening up front. The pilots will determine where the de-icing will take place. Normally, this location is up to the airport as each one has their own rules on how and where to de-ice. At some airports such as Boston, the de-icing will take place at the gate due to minimal space on the airport. If you are in Denver, or Pittsburgh, it will take place at a remote pad designated for de-icing.
When the pilots arrive at the de-ice pad, they will get the airplane configured for the de-icing process. The configuration is specific for the type of aircraft. Typically, the pilots will shut off the air conditioning system causing the plane to get a bit stuffy. This is done because if the fluid got into the A/C intakes outside, it would cause not only a very strong and nasty smell, but likely lots of smoke and we all know that smoke in a plane is a bad thing. So, the stuffy feeling is definitely the better option.
The people in the de-ice truck will drive around and spray an orangish-red colored fluid that knocks off the snow and ice. That fluid is known as ‘Type 1’. It is essentially a heated anti-freeze mixture, much like what you put in your car. Type 1 is heated to around 150 degrees F and that helps to knock off the snow and ice much faster which means a quicker de-ice and less fluid is used. If it’s snowing or there is freezing rain, they will follow with another fluid called ‘Type 4’. Type 4 is a green, thick, fluid that is not heated. This allows for a longer protection time against the snow. Because the fluid is cold, it stays on thick which prevents snow and ice from accumulating on the wings. The amount of time that the fluid protects the plane is called a ‘Hold Over Time’. The amount of hold over time is based upon a combination of temperature, and snow fall intensity. These times, though they vary, are anywhere from 20 minutes to 1 ½ hours. If the plane is still on the ground when the hold over time is exceeded, then the pilots have to go back and get de-iced again. Though it’s not a fun process to repeat, it is imperative for safety.
A few questions come up out of the whole process. First, people want to know if it is safe to fly in the snowy weather. As I explained above, it is if you take the right precautions before take off. Once in the air, the plane has its own ability to remove ice from the wings by way of heat. Second, the burnt sugar smell that almost always accompanies a de-icing. That smell is actually a trace amount of the fluid being sucked into the air conditioning system. By trace amount, I mean a few drops here and there. That’s enough to go through the heater (it is winter, the heater is going to be on) and burn up and give off the smell. The fluid is not actually being pumped into the cabin, just a bit of the smell from the drops burning up.
Hopefully, this answers any questions you had about de-icing. That flight you have coming up or just had, where you saw this entire operation take place will now make a little more sense.
As always, if you have a question, feel free to submit it and I’ll get you an answer.
Happy Holidays!!
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