De-icing Safewing

Deicing fluid – a mixture of a chemical called glycol and water, is generally heated and sprayed under pressure to remove ice and snow on the aircraft.

Holdover Time (HOT) – the estimated time for which an anti-icing fluid will prevent the formation of frost or ice and the accumulation of snow on the protected surfaces of an aircraft, under specified weather conditions.

Grab some vocab:

to spray de-icing fluid
to interfere with lift
to hinder smooth air flow
to remove ice deposits
to protect from icing
to prevent from freezing
to consist of glycol and water
it takes some minutes (for new deposits to form)
to extend holdover time

Innovation spotlight. Safewing for a safe takeoff in ice and snow.
Worldwide more than 41 million airplanes with over four billion passengers take off in the course of a year.
During the winter months additional precautions are necessary.
In icy and snowy conditions the planes are sprayed with colored de-icing fluids especially on the wings.
Planes need lift to fly.
This means that air must be able to flow around the wings unhindered.
For this they have to be completely smooth and free from any deposits.
Even relatively small amounts of ice or snow on the wings interfere with lift and can potentially lead to crashes.
For this reason special fluids are used to de-ice planes and protect them from re-icing before takeoff. Their color makes it easier to tell them apart and see whether they’ve been spread evenly.
Red Type I de-icing fluid consists of about 80 to 88 percent glycol, 12 to 20 percent water and a small amount of additives such as surfactants, corrosion inhibitors and de-foamers.
The glycol lowers the freezing point of the de-icing fluid and thus prevents it from freezing.
To remove ice and snow the fluid is sprayed on under high pressure and at a temperature of about 50 to 80 degrees Celsius.
Depending on weather conditions, however, it can take only 2 to 5 minutes for new deposits of ice and snow to form.
This is prevented by a second fluid, a so called anti-icing fluid.
These yellow Type II or green Type IV fluids consists of roughly equal parts glycol and water, to which up to 5% additives are added.
They greatly extend the time window for takeoff up to 4 hours.
The anti-icing fluids form a viscous protective film on the wings.
Since ice crystals instantly melt when they fall on this film it prevents deposits of ice and snow from forming on the surface of the plane.
Even when the plane taxis to the runway the fluid remains in place.
On the runway the viscosity drops significantly due to various mechanical forces.
Thus the film flows off completely before the plane leaves the ground.

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