Airliners and Icing/deicing

skier

skier

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Skier
I recently flew commercially (Southwest on a 737) and there was freezing rain predicted from 11pm to 9am. My flight was at 5:30am. As a result I didn't think we would end up taking off, but we did make it out with "only" a 60 minute delay. I started doing some research which quickly led me to discussions of holdover times, type IV deicing fluid, etc. and shortly thereafter got in over my head.

After boarding the aircraft, there was a visible layer of ice covering the wings and the freezing rain was increasing in intensity. They went around the aircraft spraying something on it that appeared to blast all the ice off the surfaces. That was followed up with a green fluid that my research suggests is Type 4 deicing fluid. We then taxied to the runway and took off.

Can someone more familiar with the airline-world explain the process in a way that a VFR only private pilot can understand?
 
Yup. And generally type 1 is heated to a fairly high temp. Type 4 has a sheer factor. The ice can actually build on type 4 (not too much) but the layer of green fluid will sheer off the wing at a certain speed. That’s why many small airplanes with low rotational speeds are not approved for type 4.

Type 2 & 3 are pretty rare. I’ve seen (used) type 2 in Canada but never seen it in the States. Different properties of protection.
 
skier said:
Can someone more familiar with the airline-world explain the process in a way that a VFR only private pilot can understand?
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Type I fluid is a glycol based fluid. It is good for deicing airplanes but it does not last long. It is used in the first step of a two step process to make sure an airplane has no ice on it when it takes off. (Sort of oversimplified. The length of time that it is effective is called hold over time.) The green fluid is Type IV fluid. It has a longer hold over time and is usually used when there is visible moisture of varying intensities. The lighter the intensity, the longer the hold over time. The crew has a table in their manuals that allow them to determine how long a hold over time the fluid has based on a number of factors, including temperature and precipitation intensity.

That is a basic overview of how the deicing process works. Any questions, please be sure to ask.
 
Type and intensity of precipitation is a factor also. We use a computer based system whereby we insert the holdover start time (time they start application of one wing) and the computer determines liquid water equivalent and spits out a no later than takeoff time or start the whole process again AND then that is only if there is present precipitation in which the drop dead time can be extended. Big, thick boring manual to cover this procedure. They want the Captain to have no say in the matter. Us old farts kinda throw a kink in their ideal world.

Rules states that no frost allowed so this is why you will see them spraying just the wings when it is warm out. Cold fuel, warm wing.
 
MD11Pilot said:
Type and intensity of precipitation is a factor also. We use a computer based system whereby we insert the holdover start time (time they start application of one wing) and the computer determines liquid water equivalent and spits out a no later than takeoff time or start the whole process again AND then that is only if there is present precipitation in which the drop dead time can be extended. Big, thick boring manual to cover this procedure. They want the Captain to have no say in the matter. Us old farts kinda throw a kink in their ideal world.

Rules states that no frost allowed so this is why you will see them spraying just the wings when it is warm out. Cold fuel, warm wing.
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Are you not allowed frost on the upper fuselage? I understand some carriers may have different procedures on this. We are allowed frost on certain areas, but obviously not critical surfaces.
 
Timbeck2 said:
Stole my thunder. I was going to ask what happened to types 2 and 3. As a follow up however, what happened to Preparations A-G?
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No clue about A-G, but it’s my belief that types 2&3 became outdated before they were widely used. Type 4 came along and that was that.
Someone may correct me there....??
 
The idea behind the anti-ice fluids, Types II, III, and IV, is that they are thick and provide a protective layer that prevents contaminants from adhering to the surfaces. They are designed to shear off the surfaces, taking the built up contaminants with them, prior to rotation during the takeoff roll.

Type II was widely used for quite a few years. Type IV, when introduced, provided significantly longer holdover times and has almost completely replaced Type II.

Type III is for aircraft that rotate at slower speeds (generally under 100kts) and does the same job as type II or IV but shears off the surfaces at a lower speed.
 
Kritchlow said:
Are you not allowed frost on the upper fuselage? I understand some carriers may have different procedures on this. We are allowed frost on certain areas, but obviously not critical surfaces.
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Technically no due to the possible injestion into number two engine.
 

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^^^^ that picture is badass!
 
Let'sgoflying! said:
What is the typical cost of full deice/anti-ice; say...737?
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I believe it’s somewhere around $12 a gallon. That was years ago so that May have changed. Much of the cost is wrapped up into environmental recovery.

How many gallons??? It really depends on how coated the plane is. I’m guessing 50 gal for a quick squirt, and several hundred for a full mess.... plus the type 4.
 
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I remember discovering it's a lot more expensive than an overnight hangar fee!
 
They deiced when I was with my 3 yo and she figured it out. "IT'S SOAP!" she announced to the entire cabin!!! Must be soap!
 
Let'sgoflying! said:
What is the typical cost of full deice/anti-ice; say...737?
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As someone posted not cheap. Back when I was flying a Hawker I seem to recall a deicing bill of around $800 for a relatively quick spray with Type I to remove ice/frost. Lot of places don't have the Type IV, which would have added to the bill.
 
Kritchlow said:
No clue about A-G, but it’s my belief that types 2&3 became outdated before they were widely used. Type 4 came along and that was that.
Someone may correct me there....??
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Not really a correction, but... I was reading this thread yesterday and really didn’t have much to add that hadn’t been said already. Until last night, when I had to de-ice in East Midlands (UK) and wouldn’t you know... all they have there is Type II. So, I guess it is still in use.
 
I always used to wonder about this. Specifically, you guys are pilots and many here are airline pilots, and know the specs for de-icing.

My question is, if you were a passenger on a flight, and saw when they de-iced, and all, and say the takeoff was delayed for a time period long enough that you were very sure the de-icing had lost its effectiveness and yet the plane began to line up for takeoff..what would you do? Would there ever be a case where you would try to alert the crew, or possibly refuse to fly and demand to deplane?

Stupid question probably, but then too, mistakes can happen. Do they have de-icing on a checklist, with some kind of timer set, or does de-icing never need to be reapplied after a certain amount of time on the ground?
 
LongRoadBob said:
Stupid question probably, but then too, mistakes can happen. Do they have de-icing on a checklist, with some kind of timer set, or does de-icing never need to be reapplied after a certain amount of time on the ground?
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Take a look at he third link that I provided in post #8 above.
 
In addition to what Larry in TN posted, we now use a computer based system that takes the present weather and analyzes it for Liquid Water Equivalents I.e. how wet is the precipitation and derives a no later than takeoff time. Seems to be very accurate. If the precipitation stops then the times stop.
 
MD11Pilot said:
we now use a computer based system that takes the present weather and analyzes it for Liquid Water Equivalents.
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To avoid confusion, the LWE doesn't come from the standard weather report. It is additional weather data that is only available at participating airports. The LWE can not be derived from a standard METAR. There are only a handful of airports that have it now.

Here's an FAA AC on the certification of LWE systems, for those who are interested.

https://www.faa.gov/regulations_pol...fm/go/document.information/documentID/1027819
 
LongRoadBob said:
I always used to wonder about this. Specifically, you guys are pilots and many here are airline pilots, and know the specs for de-icing.

My question is, if you were a passenger on a flight, and saw when they de-iced, and all, and say the takeoff was delayed for a time period long enough that you were very sure the de-icing had lost its effectiveness and yet the plane began to line up for takeoff..what would you do? Would there ever be a case where you would try to alert the crew, or possibly refuse to fly and demand to deplane?

Stupid question probably, but then too, mistakes can happen. Do they have de-icing on a checklist, with some kind of timer set, or does de-icing never need to be reapplied after a certain amount of time on the ground?
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It wouldn't be just one airplane out there and they stay on top of the time of anti ice effectiveness. If you want to start a rukus based on your ignorance of deicing procedures I'm sure they'll accommodate you and get you off the plane and put you up in the airport gray bar hotel.
 
Kritchlow said:
Are you not allowed frost on the upper fuselage? I understand some carriers may have different procedures on this. We are allowed frost on certain areas, but obviously not critical surfaces.
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"Critical surfaces" for us is everything except for the engine pylons...
 
Larry in TN said:
To avoid confusion, the LWE doesn't come from the standard weather report. It is additional weather data that is only available at participating airports. The LWE can not be derived from a standard METAR. There are only a handful of airports that have it now.

Here's an FAA AC on the certification of LWE systems, for those who are interested.

https://www.faa.gov/regulations_pol...fm/go/document.information/documentID/1027819
Click to expand...

Agree with this but it seems that the number of participating airports has dramatically increased the last couple of years.
 
In Europe all I see is type I for the first step and type II for the second. I 've never seen type IV in EU.
 
I roughly remember inserting the number of liters of deicing fluid into the FMGC on the A320/321. It depends how much contamination we have on the airplane, and the water/deicing fluid ratio such as type I 50/50 ratio, type II 75/25 ratio. Numbers like 170 liters, 265 liters comes to mind. So that would be around 45, 70 gallons respectively of deicing fluid, water excluded. So let's say 60 gallons at $15 per gallon. Roughly, I would venture it costs about $1000 to deice/anti-ice an A320/321. Next time I do it I will note how much of what and I'll ask about the cost.
 
Hmm. We don’t care how much was used, only the type of fluid and the time the last application was started.
 
Yea Greg, same here, though we do insert the quantity into the FMGC.
 
Greg Bockelman said:
Hmm. We don’t care how much was used, only the type of fluid and the time the last application was started.
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It was odd. At East Midlands, they gave us the amount and temperature of the Type II (74 liters at 80.4°C). I hadn’t heard that before. Don’t need that information. I guess some carriers/airframes do.
 
Sluggo63 said:
It was odd. At East Midlands, they gave us the amount and temperature of the Type II (74 liters at 80.4°C). I hadn’t heard that before. Don’t need that information. I guess some carriers/airframes do.
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Why are they heating the Type II? That would reduce its anti-icing effectiveness.
 
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