As winter arrives, airports dust off their deicing equipment and ready for another season of cold, snow, and ice. While a car may be safely operated partially covered in ice or snow, aircraft must be completely free of contamination to assure a safe flight. Deicing can sometimes lead to flight delays, but the alternative is far worse. We spoke with Andrew Poure, a former aircraft deicer, to learn more about what goes in to deicing a plane and how the orange or green liquid being sprayed on the plane actually works.

What exactly are deicers doing?

Deicers are there to ensure that there’s no frozen contamination, be it frost, ice, or snow on the critical surfaces of the aircraft. The trucks they use carry about 2000 gallons of deicing fluid and are equipped with hydraulic lifts, pumps, and heaters that allow deicers to accomplish their task of removing any and all frozen material from the aircraft, from the leading edges of the wings to the top of the tail.

What sort of training do they receive?

In the United States, the FAA regulates and approves each airline’s deicing procedures and policies. Deicers are in turn required to be trained to these standards. In addition there will normally be computer-based training conducted on the basics of deicing: fluid, equipment, airport operations, relevant aircraft systems and aircraft identification, among other things. All that will usually be followed by on-the-job training with an individual deicing provider’s particular trucks, infrastructure, and so on. All told, training to the point of being allowed to independently operate a deicing truck can take up to a month or so.

What do the different colors of deicing fluid mean?

The vast majority of deicing around the world is done with two fluid types: Type I and Type IV, both of which primarily consist of propylene glycol. Type I is the orange or reddish fluid used to actively deice the aircraft by melting and knocking off contamination. Heated up to 82 degrees Celsius (180 degrees Fahrenheit) and mixed with water, the chemical properties of the glycol lower the freezing point of water, while the heat and high pressure can melt and remove contamination. Type IV, the bright green fluid you’ll see aircraft covered in while taxiing, is often referred to as anti-icing fluid. It’s not mixed with water and is much thicker than Type I. Type IV sticks to the aircraft and is used during active snowfall or precipitation to prevent accumulation of additional ice or snow. It can provide a holdover time of up to 45 minutes, allowing aircraft to depart safely after an extended taxi or ground delay.

When does a plane need to be deiced?

The FAA promotes what they call the Clean Aircraft Concept. No air carrier aircraft may take off with any frozen contamination. This is why you could be sitting on a plane as the sun comes up, with the temperature even a degree or two above freezing, and still need to deice. If there’s a layer of overnight frost, you’ll hear the captain come on and say you’ll be deicing before departure. One important note though is that the responsibility for requesting deicing—or not—lies with the captain, so while deicing crews can certainly give their input, it’s his or her ultimate decision.

What are some things deicers need to be aware of?

To be effective and efficient at deicing requires attention to detail. The weather and type of contamination are big factors, constantly changing conditions have a big impact on how deicing operations are carried out. The aircraft itself also requires close attention at all times; at many airports, particularly those with special areas specifically for deicing as opposed to gate deicing, the entire process is conducted with engines running. Given how close deicers and their vehicles get to the aircraft (as close as 3-5 feet / 1-2 meters at times), being aware of engines, APUs, as well as moving control surfaces on the aircraft is very important.

What’s one thing you’d want a passenger to know about deicing?

It really is all about safety. Sometimes you might have a delay for baggage, catering, cabin cleaning and the like, and think things like “get on with it, it shouldn’t take this long.” Don’t think of deicing in the same way. Without deicing, planes crash. It sounds extreme, but there are a number of accident reports to readily back it up. Proper ground deicing can be held right up there with things like proactive maintenance and professional, well-trained crews in terms of it being a visible representation of how committed airlines are to safely getting you from place to place.

And if you happen to see a deicing crew outside your window, give them a wave or a thumbs up, they appreciate it.

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