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This video says (at 25:06) that you should do it as soon as possible. but I just learned in class that you should wait for an ice build up then turn it on vs just turning it on. This would prevent an ice bridge to form:

enter image description here

But in the clip it says modern de-ice boots don't have the problem mentioned in the picture.

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    $\begingroup$ That video also says that every icing encounter is different. It's a 55minute video, so unless you can narrow the scope and give some context for your remarks you're not likely to get much help. $\endgroup$ – user11516 Oct 17 '15 at 0:16
  • $\begingroup$ Sorry I meant to go to 25:26. It talks about bridging over the deice boot and how it can be dangerous. in class we learned to wait for a ice build up then turn it on vs just turning it on. here is the example. but in the clip it says modern deice boots don't have the problem mentioned in the picture. lessonslearned.faa.gov/Comair3272/deicing_still.jpg $\endgroup$ – Tango India Mike Oct 17 '15 at 0:48
  • $\begingroup$ @TangoIndiaMike Explain all that and some more in the question :) $\endgroup$ – digitgopher Oct 17 '15 at 1:47
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There was a belief that activating de-icing boots too early could result in an ice bridge forming over the boot and rendering it ineffective. This led to a recommendation that de-icing boots should not be activated until a significant build-up of ice had occurred.

enter image description here (Source: FAA)

Recent testing has established that modern de-icing boots are not susceptible to this problem, and advice from the FAA has been changed.

In InFO9007 (dated 5th May 2009) the specific advice given is:

Pilots should follow the boot activation and operating procedures specified in the AFM or FAA approved operator’s manual for the airplane they are flying

And further:

If the AFM does not have specific boot operation procedures or if ice thickness is difficult to judge, pilots should not be reluctant to cycle modern boots at the first sign of ice accretion and then as needed.

A 'modern boot' is defined in the same publication as having

less than 1.75 inch diameter tubes, operating pressures of 15 psig or greater, and fast inflation/deflation times

It also suggest that any aircraft built later than 1960 is likely to have modern boots.


Essentially, for most cases that you might encounter the video clip is correct, and your class instructor is wrong.

That said, the definitive guide should always be the Pilot's Operating Handbook for the aircraft you are flying.

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