Topic Author
Posts: 1689
Joined: Tue Sep 10, 2002 2:23 am


Sat Oct 18, 2003 5:51 am

often, in winter, I hear the pilots asking for de-icing and mentioning some sort of ratio:
(example) 25% and 75% of something (concerns the fluid used in de-icing).

What does this mean? Does it have any effect on the performance of slats and flaps?
How much A is there is Airliners Net ? 0 or nothing ?
Mr Spaceman
Posts: 2723
Joined: Thu Mar 15, 2001 5:09 am

RE: De-icing

Sat Oct 18, 2003 6:42 am

Hello Codeshare.

I used to de-ice corporate bizjets & turboprops. The fluid (I forget what it's called) we used came pre-mixed in 50 gallon drums & was died the colour pink to help you see where it was being applied to an aircraft. So we had no control over the percentage ratio of the de-icing fluid.

We simply pumped it from the drums into our de-icing machine's tank, where it was heated to around 230 degrees F (if I remember correctly). From there we would spray as much of the fluid as the customer could afford. We would concentrate on coating the wings first, and then their control surface hinge areas as well as soaking the landing gear. Basically after all the lifting surfaces were coated, we would spray any areas where ice & slush could accumulate during the takeoff roll, then "freeze" during intial climbout and prevent the movement of the elevator, rudder and ailerons or the retraction of the landing gear, flaps & slats. We also sprayed clear of the cockpit windows.

I suspect that a pilot would request a certain de-icing fluid ratio (if he could) based on the weather conditions he'd encounter during takeoff & climb. The better the weather, the lower the ratio, the lower the cost. Just a guess on my part though.

Chris  Smile
"Just a minute while I re-invent myself"

RE: De-icing

Sat Oct 18, 2003 10:39 am

There are two types that I'm aware of, that they use here in YYZ. Type I, and Type II. Type one is a de-icing fluid, and type two is an anti-icing (more thick gelly like that Type I.) I believe these are a more modern type if de-icing fluid, older ones I believe were given a ratio of fluid to water. Someone correct me if I am wrong on that though. The only data we are given these days is which type was used (I or II), the amount used, and the start and stop times for de-icing. Hope this helps?
Posts: 2830
Joined: Fri Sep 19, 2003 3:26 pm

RE: De-icing

Sat Oct 18, 2003 11:25 am

Hey westjet, it sounds like the stuff you were using was TKS fluid. It's this thick, nasty fluid that is not fun to use and costs like $70 a gallon. A few early bizjets used it in weeping wing anti-ice systems (Citation SII, and all Hawkers).

As for the other fluids there are three kinds I know of. Type I, II, and IV(no idea where III went). WestJet has it right on type I and II. Type IV has an even more viscous soulution and has a higher holdover time. Holdover time is the amount of time an aircraft can sit on the ground after being deiced. All air carriers have holdover charts in their ops manuals.
Posts: 391
Joined: Sat Mar 30, 2002 3:34 am

RE: De-icing

Sat Oct 18, 2003 7:34 pm

On recent de-icing trucks, there are 2 tanks. One is for water, the other for the killfrost (de-icing fluid). The truck has a heater system and the driver can select the mixture as per crew request, depending on type of weather and degree of ice snow, as this affects the holdover time (already mentioned above)
Posts: 29881
Joined: Wed Jul 07, 1999 11:27 am

RE: De-icing

Sat Oct 18, 2003 10:35 pm

Just the mixture of fluid and water. Some fluids can't be mixed others can. The type one stuff we used is mixed.

When I worked out in the bush all of our de-ice fluid had to be brought in on the aircraft, in 55 gallon drums.

We old got pure and then mixed it out there on site to a 50/50 mix for the homebrewed de-ice machine that we had.

It worked out pretty well, at 744rules notes most real de-ice trucks have a selector that will allow the mixture to be adjusted.

You can run allmost pure hot water for de-ice for example and then follow it up with a fairly high percent mix for an anti-ice coating.

Posts: 182
Joined: Wed Jun 04, 2003 9:18 pm

RE: De-icing

Sun Oct 19, 2003 8:13 am

As said by the other it means how many water and fluid the ground staff have to spray on the aircraft. Our SOP require in it is possible the type 2 o 4 fluid.
e.g. in a classic winter day taking off from EWR or YUL with light to moderate snow we ask for a two step de-icing (de-icing plus anti-icing).
the de-icing will be 0% fluid 100% warm water. The anti-icing mix depend on the temperature and also the expected delay, if we expect some delay after the end of operation we ask for 75% fluid or also 100%.
Posts: 29881
Joined: Wed Jul 07, 1999 11:27 am

RE: De-icing

Mon Oct 20, 2003 6:23 pm

The real slick deicing system now, isn't hot water but hot air.

Posts: 99
Joined: Sun Oct 05, 2003 11:49 am

RE: De-icing

Thu Oct 23, 2003 7:21 am

Typically, deicing fluid comes in two "flavors", Type I and Type IV.

Type I is usually orange in color, and is mixed 1 part water to 1 part glycol ( i.e. 50/50 mix). Depending on the airline and the circumstance, this fluid either comes pre-mixed or is mixed in the deicing truck itself. This fluid is heated in the deicer to at least 140 degrees at the nozzle, and is sprayed on the aircraft to remove contaminants ( i.e. frost, snow, slush).

Type IV is green in color, is 100% glycol, and has the consistency of the Nickolodeon slime. Its not necessary to heat Type IV, but it always can only be applied to a "clean" aircraft ( one that has already been sprayed with Type I). Due to the thick consistency of the fluid, it is not sprayed, but instead squirted out of the nozzle. Typically, it is only applied to critical surfaces of the aircraft, such as the wings and horizontal/vertical stabilizers.

As somebody mentioned earlier, the start/stop time of the deicing event is recorded and given to the pilot-in-command to determine the holdover time of the deicing fluid. This time starts when the final application of fluid (either Type I of IV begins) and extends until the fluid is no longer able to prevent accumulation on the ground. The aircraft must be airborne by the time that the holdover time is expired. I know that for light freezing rain, the holdover time is like 18 minutes. Therefore, if the aircraft is not airborne in 18 minutes from when the Type IV application began, the aircraft will need to return to the deicing pad and the whole process will need to begin again.

In a deicing event, the ground controllers will talk to each flight and find out when their holdover time expires, and then try to expedite and get the aircraft airborne before the time is up.

Hope this helps you out

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