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Airplane deicing: The how and why

'Tis the season for winter precipitation, and with that comes aircraft deicing procedures. Passengers often ask me about this process. This CNN piece will shed some light on the subject. Thanks again for reading. ( More...

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99NY 0
I've always wondered what happened to all the deicing fluid that rolls off the aircraft onto the tarmac. Is it treated in any way or just dumped into the public sewer system?
David Sims 0
The EPA regulates runoff from aircraft deicing. Bigger airports that use large quantities of deicing fluid are required to have reclaimation facilites to collect and reclaim the glycol before the fluid can get into storm water. Smaller airports that are under a threshold established by the EPA, such as where I work, are allowed to let small quantities enter the storm water system (not the sewer system). The amount used here is so small, it rarely if ever makes it across the ramp to the storm drain.
Most airport have a system in place allowing the runoff water and chemicals to be contained until it can be decontaminated. So in short NO the water dose not enter the public drinking supply in most cases. There are time that airports will not contain to save money. Which can result in large environmental fines if caught.
That's sounds like a lot of water for deicing planes, I wonder how they get all of the solution to the runway before the planes takeoff to prevent ice accumulation?
David Sims 0
Our airport has a bulk storage facility where glycol is stored and loaded into the deicing rigs. It is then mixed with water and heated before being used on aircraft. There are different types of fluids used, Type I is used most often to remove existing ice from aircraft. Type IV is a much thicker solution (like very thick syrup) that sticks to the aircraft better to prevent additional accumulation if frozen precipitation is still falling.
Iceman999 0
You are correct when you talk about the anti-icing fluid (Type II and Type IV) having thickeners, but that is only to ensure that it stays on the wing until you start your take-off roll.

The "Clean Wing" concept requires just that, so in a perfect world all of the anti-icing fluid should be gone BEFORE you rotate. As you accelerate down the runway the shear effect of the air over the wings and stabilizers causes the anti-icing fluid viscosity to be reduced so that it will flow off the wings before rotation. There will always be a little left in some of the more aerodynamically quiet areas, but eventually that should disappear as well.

Aircraft with low rotation speeds cannot use thickened fluids, so those Pilots have to hope that the minimal holdover time afforded by Type I will be enough or else they shouldn't be going.

Hope that helps.
Daniel Fahl Staff Writer 0
Ian - Exactly on point. In the finite space given in this article, my words are carefully crafted to explain what you just said in fewer words. It's very challenging. My intent with that sentence was to imply to the everyday airline passenger that the thickened fluid adheres to the aircraft up until the very last possible moment before takeoff. In essence, the fluid IS still coating the wing in some capacity until rotation speed. That's why it's thickened, to withstand "shearing" before taking flight. Hence, my explanation of once airborne, the aircraft systems take-over. Thanks for your insight.
GJT has a recovery system in place. We start the pump before de-icing. On most days we never see the fluid reach the drains. Question - do those several hunderd gallons of Type 1 evaporate with the water ?
Patrick Smith 0
I did a piece on winter flying that you might like, here...


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