Deicing Fluids

[vlamgat]

I have another question for you guys up north. As I have done most of my flying in the tropics and Africa I haven't encountered much icing (on the ground that is). Could someone explain to me the difference between the different types of deice fluids (ie. type I, II and IV). And the definition of holdover time? Is it the time that the fluid is effective? When does the timing start? This may sound like a dumb question but I would rather find out here from some of you guys who have vast experience with this problem than get a nasty surprise one cold winter morning when I discover that my aircraft is covered in two inches of snow and ice.

 

[cl-65link]

Here's an article from ALPA that might help. http://cf.alpa.org/internet/alp/2000/nov00p15.htm

 

[Tug Driver]

good article

however, in my opinion, Type I is pink, not orange.
Type I is applied hot. and it does not taste very good...fyi

Type IV is green, I agree, and it looks like jello. Pilots usually ask us to apply Type IV on the overnight a/c, when the forecast calls for a very heavy snow or freezing rain. That way the 1st outbound will have fewer problems departing in the morning.

In the event that the ground crew applies Type IV the night before...
make sure that they remove the Type IV with Type I before you go. I guess that jello substance can freeze, and give you problems on the control surfaces.

I have a vintage UAL instructional video on the subject, and your welcome to borrow it.

also, its slippery, so be carefull during your walk around.

 

[cargoflyr69]

Hold over time is the amount of elapsed time before you have to be airborn. Otherwise you are SOL and must deice again. Time usually starts when the first drop comes out of the nozzle. In light snow with type I fluid you usually get 11-15 minutes of "holdover" This is why you see the deice trucks near the departure end of the runway.

Type I: Pinkish color (if you inhale the mist it tastes like Big Red gum) usually around 50/50 mix diluted with water and heated to 160-170F. Called deicing fluid cause it melts the accumulated crud, does a relatively poor job of anti-icing. If there is very light or no precip, you are set and off you go.

If it is heavy snow, sleet, fz drizzle, you'll need type IV. This is anti-ice fluid and is always applied after type I fluid. This is green and looks like snot It is applied at ambient temperature as it doesnt have anything to melt. Type IV extends holdover time in heavy precip as the precip sticks to the fluid and not airframe. The fluid sloughs or falls off the airframe on T.O. roll around 70-80kts.

The above is usually how the 121 guys and gals do it. There is a type II fluid that I have seen in my 135 days in the upper midwest. It is a cross between to above 2 types. Its orange and is heated to 160ish and then sprayed with no dilution, ie 100%. It is a bit thicker than type I but not as thick as type IV. As for type III, never seen that one!

Most important though, Always refer to you companies APPROVED DE-ICING PROGRAM for reference. Thats the way the FAA OK'd it for you, so thats how you do it. you will have holdover tables and other goodies in your ops specs to help you with your decision making. If you are part 91, then do whatever is in your best judgement. If you have anyother questions, just shoot.

Hope this helps

 

[SkyWestCRJPilot]

Hold over time is the amount of elapsed time before you have to be airborn. Otherwise you are SOL and must deice again.

I disagree. Hold over time is not this at SkyWest. According to our Ground Deicing Program if you go beyond your holdover time then you must do a deice contamination check. At SkyWest that means looking out and making sure that the wings are still free of ice and snow. If they are then you have another 5 minutes to take off. If you don't take off before this time then you must do another check of the wings to see if they are still free of ice and snow. The only time you must go back to deice is if the wings have accumulated ice or snow and that is regardless of whether you've exceeded your holdover time or not. Also holdover times are presented as two maximums, not a maximum and a minimum. For example :10-:15 is zero to 10 minutes for heavy snow and zero to fifteen for light snow. We've exceeded our holdover time many times but still took off legally because we were free of ice or snow still. Most of the time it was because it was snowing when we deiced and then quit about ten minutes later.

 

[cargoflyr69]

I know what you are refering to. At my previous regional this was called a "tactile" inspection. We could actually touch the wing to see if there was accumulation. Also, we could leave the cockpit and walk back and have a look-see while on the taxiway too. Like I said that was my old company's way of dealing with exceeded holdover times. This is not the approved proceedure at my current company. Just one more reason to become familiar with your "approved deicing program" before winter really sinks in. There are many ways to get the same job done.

 

[saabtrash]

Has anyone ever heard of or seen type III? I always wonder that, it must be the long lost drunken cousin that got kicked out of the family or something.

 

[mullet]

Pilots usually ask us to apply Type IV on the overnight a/c, when the forecast calls for a very heavy snow or freezing rain.

huh...never heard that before.

 

[DDpaysoff]

good article

Pilots usually ask us to apply Type IV on the overnight a/c, when the forecast calls for a very heavy snow or freezing rain. That way the 1st outbound will have fewer problems departing in the morning.


Hmmm, they ask you to deice the a/c after they arrive at night. In the morning they will again deice w/ type I, and IV. That type IV is expensive sounds like just burning money to me, but I can't bash it becuase I haven't seen the results.
Do you notice a difference in the morning when deicing an a/c that was type IV'd the night before and on that was not?

 

[Tug Driver]

Indeed, Type IV is very expensive.

we only Type IV on the over-nighter by either
#1- the Captains request
#2- the forecast calls for very heavy snow or freezing rain.
or both #1 and 2.

however, there have been cases when the Captain will request it, when the forecast only calls for -SN. Those are the cases that the company burns money. Last winter it got to a point that we had to call the station manager at home and ask him for permission. Sometimes we told the crew that we would do, but ended up not getting approval for it anyways.

In the morning, we spray the Type IV off with the hot Type I. Also when we apply Type IV, its only for the wings and tail. Only Type I is appiled to the whole airplane.

Type I = deicing
Type IV = anti-icing

 

[grog_sit_reserv]

Wow! I can't believe it! An actual, honest to goodness helpful thread.

Wait, before it gets too useful let me just throw in a "Mesa Sucks" so it can deteriorate.

 

[LuvMyJob]

Tug Driver,

In your opinion does it really help to spray the type iv the night before? i also have never heard of this and frequently find myself walking up to an aircraft that needs much de icing in the morning because of overnight precip.

 

[jobear]

I didnt think anyone would waste that kinda of money for an overnight set. Type4 is probably the most expensive stuff in the world to waste like that. In the morning the ramp will sweep the A/C just to cut back on the amount of Type1 being used and to speed up the de-ice process. Besides I love the way it Smells ..it smell like... like.....LIQUID GOLD!

Jobear
"THE AUTHOR IS NOT RESPONSIBLE FOR ANY REMARKS HE MAY OR MAY NOT HAVE MADE"

 

[Tug Driver]

Tug Driver,

In your opinion does it really help to spray the type iv the night before? i also have never heard of this and frequently find myself walking up to an aircraft that needs much de icing in the morning because of overnight precip.

I dont think that Type IV is worth it, if its a powder snow. Even a heavy wet snow can removed easily by sweeping the wings first then spraying Type I. But if it is freezing rain, then its a must.

Both types of gycol are expensive, but Type I is usually a 50/50 mix with water. Type IV is pure 100%. When we apply Type IV, we dont have to spray a ton on there, because it expands to cover the wing surface on its own. However, when we de-ice first thing in the morning, we have to use a TON of Type I, in most cases dealing with snow. But, in the case of freezing rain, if we did the anti-ice spray the night before, we use much less Type I in the morning.

Hope that helps. I have a good video tape on it, if you want to take a look.

 

[WrightAvia]

USING TYPE I & TYPE IV FLUIDS -- WHICH TO USE- WHEN & WHY...

During normal operation hours, when the weather turns foul and triggers the Winter Operations Plan, four (4) options are available to ensure that aircraft are clean and ready for dispatch.


For overnights (RON) and prolonged layovers, Type IV is used in order to reduce the volume of Type I needed to deice an aircraft before its dispatch, and to speed up deicing of the first bank during the morning rush.



OPTION ONE

It is snowing and the outside temperature is at or below freezing. The snow is dry. The aircraft is cold and dry. Under these conditions, the snow may melt on the upper surface of the fuselage due to cabin heat transfer. This can be ignored.


If the snow can be seen swirling on the ground, either because of wind, or because the air is being moved by aircraft or vehicle - This is a good sign and observable by the cabin crew. If the ground deicing inspector also confirms the wings and control surfaces are cold and dry, and that no precipitation is adhering - proceed to take off - confident the snow will not adhere to the lift or control surfaces.


In this scenario, the use of deicing or anti-icing fluid would give the snow a wetted surface to stick to - just what you do not want. It would also be a considerable waste of both time and money.



OPTION TWO

The precipitation is wet snow, sleet (snow mixed with rain), freezing rain, or the aircraft is subject to snowfall from its arrival at the gate until the time when the deicing coordinator gives the order to start deicing.


Under these conditions, the aircraft should be deiced with heated Type I fluid followed by anti-icing with cold undiluted Type IV fluid. This will provide extended holdover permitting the captain in command to the use appropriate holdover tables.


REMEMBER: THE HOLDOVER TIME BEGINS WITH THE APPLICATION OF THE TYPE IV FLUID.



OPTION THREE

The snowfall or freezing precipitation has stopped, but, the lift and control surfaces are contaminated. There is no forecast for precipitation before the time that the aircraft is scheduled to be released to the active runway for departure. Deice the aircraft with heated, diluted Type I fluid immediately prior to push back. Under these conditions, the use of Type IV fluid is not required.



OPTION FOUR

During a hailstorm, apply Type IV only - to protect the aircraft skin from dents. As soon as the storm has passed, deice the aircraft with heated, diluted Type I fluid. Do NOT rely on the Type IV fluid looking OK. It is probable that the hailstones will have penetrated the film of fluid, and if the temperature of the wing is low, they may freeze to the wing. Hailstorms are generally very short in duration.

A typical storm cell will be obvious to weather reporters, who will probably be able to give you advance warning of its onset, allowing the ground crew time to protect the upper surfaces of the airframe.



RON AIRCRAFT - SAVING TIME & MONEY

Type IV Anti-icing fluid offers a major benefit when applied to above aircraft in that if it is applied to surfaces free from adhering contaminants (either before the onset of precipitation, or after the aircraft has been deiced with heated, diluted Type I fluid) it will significantly reduce the volume of Type I fluid needed to clean up the aircraft prior to pushback.

If the weather forecast calls for freezing precipitation preceded by a period of rain, apply the Type IV fluid only when the rain turns to freezing precipitation. Obviously any fluid applied during the rain event will be washed off and provide no protection. Significant snowfall and/or ice accumulation may form on top of the film of Type IV fluid without freezing down to the airframe. The best way to remove the majority of this accumulation is with the use of brooms or squeegees.

 

[Tug Driver]

I think I covered that

 

[ShyFlyGuy]

I think it's the glycol that makes the deice fluids taste funny. I tried a tactile inspection once and then ate my lunch inflight. It wasn't too bad, though... kinda seemed like it might belong on a taco moreso than a PBJ sandwich.