so, I travel in the colder parts of the world, and I’m familiar with the de-icing procedures. I (think I) understand about airfoils shape as the reason that they de-ice the wings of the plane, but why do they de-ice the fuselage?
here’s a related question: how long does de-icing last? on a recent trip we got de-iced at the gate, then pushed back and sat on the runway for about half an hour. At what point would we have had to go back for another dose?
Weight, drag, and you don’t want a piece of ice to break off at speed and damage something behind it. There might be antennas, vents, or instrument sensors on various parts of the fuselage whose function could be impaired by ice.
In addition to aerodynamic reasons, they de-ice the wings so that the control surfaces (all of those flaps, air brakes, etc) can move because if those freeze up you can’t control the plane.
It varies quite a bit depending on conditions. The FAA has guidelines about how long to wait between de-icings based on weather conditions, what type of de-icing fluid is used, and other factors. Even then though the pilot is the one making the ultimate decision on when to de-ice the plane. It can be as short as 5 minutes in really bad freezing rain conditions. In my very limited experience fifteen minutes to half an hour is common but it could easily be longer than that.
I’ve de-iced aircraft before. That’s a job I never want to do again. Wet, cold, smelly fluids, miserable.
The problem is that the top surface of a wing can accumulate a lot of ice or snow. First, there’s the weight issue. Then, there’s the problem that a significant build-up can change the shape of teh airfoil, which affects flight characteristics (how much lift, where the stall point is, etc.)
Also, many aircraft today are “laminar flow” and particularly sensitive to irregular wing skins. I have heard of some, like the Grumman Tiger (low wing, laminar flow 4-seater) where the warning was that damp grass clipping from a fresh-cut grass field might stick to the leading edge during takeoff and affect airflow (and hence lift and stall speed) to the point that it could cause a crash.
The shape and smoothness of a wing are very important, and the amount of weight that could accumulate if it is freezing rain or sleet coats the entire upper wing might be significant.
I assume if the accumulation on the top of the fuselage were significant as a weight issue, that would be de-iced too. the main job, however, is to keep the flight surfaces - wings, stabilizer, and tail - clean of build-up.
The only de-icing process I know was that James Cagney movie. The surface of the plane is a rubberized fabric that can be inflated with air to “break” the ice formation, allowing it to fall into the slip stream.
Those are inflatable deicing boots and completely different from ground deicing. They are used in the air and literally break off chunks of accumulated ice from essential control surfaces in the air.
They aren’t meant to take the place of ground deicing treatments and, depending on the plane, may be considered emergency use equipment only. They tend to work well but they can only deice small sections of the plane and that is only after they have accumulated enough ice to be in breakable sheets. It is bad news if you are in conditions that require using them and the deicing boot doesn’t work correctly.
Well, now I know. As I understood it before, the crucial de-icing process is done in-flight.
That phrase turned out to refer to something that wasn’t nearly as dramatic as what I was picturing.
