Question(s) re deicing fluid

[Hartington]

Flew out of LHR on Thursday (BA Boeing 757). Before take off we were deiced. Can anyone answer the following for me:

1) In the conditions at about 1300 local what was the maxiumum time between deicing being applied and need to re-apply?
1a) How do the conditions affect that time (if at all)
2) What is the deicing fluid made up of?
3) Does the fluid affect the flying characteristics of the plane?
4) I was surprised to note what appeared to be the fluid still flowing very slowly and stickily accross the top of the wing on approach to Rome. Does the rate at which the fluid "washes off" the wing vary according to altitude (or other coditions) and how long might it still be present after flying (if not providing any protection any more)?

Man thanks.

[flapsforty]

Hartington, being a Wagon Dragon I have no idea of the answers to questions 3 and 4, but no doubt some kind soul will answer those for you.
In the mean time, for information on the so-called holdover time, click on any of the links on this (http://www.tc.gc.ca/CivilAviation/commerce/HoldoverTime/menu.htm) page.

For your second question, try here (http://www.cryotech.com/dfplus88.htm) for an example.

And if you really want to delve into the matter, go and have a look at the Deicing Forum (http://www.agse.com/forum/deicing/) ;)
Good luck!

[Hartington]

Wonderful web sites, thank you.

Need some concentrated reading when I have time, am not tired, and on an unmetered line!

[BOAC]

H - Q3/4 (hopefully you'll get the rest from Flaps' links!)

3) It degrades the performance of the surface due to its viscous nature which affects the airlow (not as much as ice/snow!). An adjustment is made to take-off performance to allow for this. Effect on landing/cruise performance judged negligible.

4) I have operated several flights, many over 1:30 long, where de-icing fluid is still evident on the surfaces at the end. It IS viscous! Regarding dissipation (the fluid, not me!) I guess speed and rain would do that more quickly, but I'm guessing. I cannot see altitude having much effect unless it gets so cold it freezes itself during the cruise?


Hmm! Some "wagon dragon", Flaps!:eek:

[Dragon Knight]

4) I have operated a flight 4 flights after last deicing, and the fluid was still "trailing of the wing" during flight.
And a comment on your last remark: The fluid giving you holdover time, is designed to protect the flight from the begining of the treatment until the flight is in the air. There is no protection from the fluid airborne, there are other means for that, and there is no protection on the following flight without a new fluid treatment.

[Rote 8]

De icing fluid, I gather is one of 3 types - Type I, Type II and Type IV. The different types have different hold over times (the time after which the application commenced before which it can no longer be regarded as giving protection).

Type I is 80% glycol diluted with water. The high percentage of glycol means that it is effective as a de icer, but is less viscous than other types so it has a correspondingly reduced hold over time.
Type II is 50% glycol, so not so effective as a de icer, but also contains a thickening agent, which improves its viscosity and so increases its hold over times.
Type IV is similar to type II but contains a more advanced thickening agent for even greater hold overs.

You may recall the colour of the agent that was used on your flight - if so Type I is a clear liquid, Type II is straw coloured and Type IV is green.