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Deicing question

Old 3rd Feb 2019, 22:13
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Deicing question

Deicing has, as I understand it, to be undertaken within a specified time before takeoff or the plane has to be deiced again.

Is that time calculated from when the first drop hits the aircraft or the last drop or some other time? In the same vein must the take off roll be started within the alloted time or wheels off or some other measurement point?
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Old 3rd Feb 2019, 22:32
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Hold over time (time of protection) starts from the first drop.

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Old 4th Feb 2019, 19:07
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Do you have a calculator for the time from start of takeoff roll to takeoff? If not, use start of roll.
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Old 4th Feb 2019, 19:39
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Holdover times have usually a time range. Something like 25 minutes to 45 minutes. So for the first 25 minutes at the given conditions, protection is assured. Once those 25 minutes are over the flight crew needs to ascertain that the anti-ice protection is still holding, that can be done via a visual inspection. And yes, it is first drop to start of take off roll, during the take off rall the anti-icing fluid will flow mostly off the wings carrying with it the contamination and leaving the wing clean. Once in the air the aircraft installed ani-ice equipment has to take over if needed.
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Old 4th Feb 2019, 22:04
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That's rather what I suspected but it's nice to get the proper answer. Thank you all.
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Old 5th Feb 2019, 16:09
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Originally Posted by Intruder View Post
Do you have a calculator for the time from start of takeoff roll to takeoff? If not, use start of roll.
Holdover time is calculated using multiple factors such as fluid type/brand, fluid mix, OAT, current weather condition (frost, snow, no precipitation etc etc). There is not a "standard" time
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Old 10th Feb 2019, 16:38
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May be of some interest to the OP.

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Old 11th Feb 2019, 04:56
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Are we talking deicing or anti icing-
2 very different subjects with there own requirements, though both are normally carried out at the same time that is certainly not always the case in all parts of the world or airports.
Deicing is at it says-removing the contamination from the aircraft-thats it.
Anti icing however is a different ball game with many variables, ambient temperature, weather conditions-ie rain, sleet, snow etc, temperature and mix of the fluid being applied and of course the type of fluid-there not all the same-this will directly effect the "hold over time"...can be minutes to hours...once the hold over time has expired you have to "reapply anti/de icing fluid again if the weather conditions/aircraft require it.
And afterwards you need to wash the aircraft as its leaves a sticky mess...
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