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william
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De icing

Tue Jan 09, 2018 12:44 am

I know there are two formulas, two different colors, one lasting longer than the other. My questions are
1. How hot is the fluid when sprayed onto the aircraft?

2. Say an aircraft sat overnight and it sleeted. How does the sprayer/mechanic know when all of ice is gone? Does the fluid make a certain color when contacting ice?

3. Are there no spray areas? Such as the engine outlet? Or rudder (fragile)?

4. Is the goal no ice at all, such as on fuselage?

Thank you in advance.
 
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Starlionblue
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Re: De icing

Tue Jan 09, 2018 2:50 am

The two fluids are de-ice and anti-ice (the latter can also be used in the de-icing function). The names describe the function. The first one removes stuff. The second one prevents new stuff from forming/lingering. In some cases you would only use de-ice. For example if there's ice/snow on the plane but no risk of further icing you could de-ice then skip the anti-icing.

There are many different brands and types. Concentration can be varied depending on conditions.

1. Hot enough to steam? Honestly I don't know.

2. The aircraft is visually inspected and in some cases by touch. Fluids are dyed to assist in determining coverage, and colour varies by fluid type.

3. The procedure is to close exterior valves and turn the packs off. Engine inlets are a no go. The rudder is fine, and is certainly not fragile.

4. The goal is no ice or snow on anything with some exceptions. A light coating of hoar frost on the fuselage is acceptable as long as vents and ports are clear. The rule of thumb is if you can clearly see the lettering on the fuselage it's fine. Up to 3mm of ice on the lower wing surface under the fuel tanks is acceptable.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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Acey559
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Re: De icing

Tue Jan 09, 2018 6:01 am

There are four types of fluid: Type I-IV. In the US, Type I (orange) and Type IV (green) are most common. Type I is heated to about 180 degrees F before being applied and is used as a de-icing fluid. Type IV is used as anti-ice and is applied unheated. I’m less familiar with Type II and Type III as I have no experience with them directly. Perhaps someone from outside the US will enlighten.

No-spray areas include windows, engine/APU inlets, probes (pitot, TAT, AOA, etc) and doors.

A tactile check must be performed before the process is complete to ensure the aircraft is in fact clean.

As mentioned, some ice is acceptable but generally, most operators subscribe to the “clean aircraft “ concept and won’t depart with any contamination (except small amounts of frost under the wings).
 
slcguy
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Re: De icing

Tue Jan 09, 2018 7:11 am

There are some instances where engine inlets get deiced. Usually done with a small cart to spray at low pressure and a small amount of fluid (a gallon or so) to ensure stators and probes aren't iced over. AA is real big on this with the JT8Ds on the MD-80s, the fixed stator vanes at the front of the JT-8D can accumulate frost and ice at low power settings like taxiing in freezing fog after landing. They want that gone before the plane starts back up and departs.
 
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CARST
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Re: De icing

Tue Jan 09, 2018 7:42 am

Acey559 wrote:
As mentioned, some ice is acceptable but generally, most operators subscribe to the “clean aircraft “ concept and won’t depart with any contamination (except small amounts of frost under the wings).


Two weeks ago when taking of at Helsinki (evening of December 30th) to NRT on a JAL 787 we had lots of thin ice on the wing. We didn't got any de-icing and anti-ice and proceeded right to the runway. The ice was still on the wing, when we lifted off and then disappeared / flew off the wing once we came through the first cloud layers and the aircraft doing some stronger banking while flying the departure route.

So, reading what you describe about the "clean aircraft" concept, do you think it was right for JAL to depart without getting the aircraft deiced? Could it have been so warm, that they said "the ice will fly off after take-off anyway"? Or was it something that should have been done?

The layer of ice was very thin and the phone did no good job in showing it in this photo I took while boarding:
Image
 
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zeke
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Re: De icing

Tue Jan 09, 2018 4:37 pm

Sounds like ice that forms from cold soaked cold fuel from the previous sector. Often when you land fuel can be -10 or -20 degrees. With humid air ice will form over the fuel tank area.

When fuel is added to the tanks the temperature of the fuel in the tanks rises towards the temperature of the fuel that is added. The skin temperature rises and a layer of water forms under the ice and the ice just slides off.
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N353SK
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Re: De icing

Tue Jan 09, 2018 5:49 pm

Acey559 wrote:
I’m less familiar with Type II and Type III as I have no experience with them directly. Perhaps someone from outside the US will enlighten.


I believe type II is basically a predecessor to type IV in that it's mostly an anti-ice fluid for aircraft rotating above 100 KIAS with lower holdover times than type IV. I've read that heated type II can also be used as a deice fluid, but I don't know much about this technique.

Type III is a modern anti-ice fluid for aircraft that rotate at speeds below 100 KIAS. I believe it is chemically similar to type IV except that it's not as thick so it can shear at a lower speed.
 
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Acey559
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Re: De icing

Tue Jan 09, 2018 5:56 pm

N353SK wrote:
Acey559 wrote:
I’m less familiar with Type II and Type III as I have no experience with them directly. Perhaps someone from outside the US will enlighten.


I believe type II is basically a predecessor to type IV in that it's mostly an anti-ice fluid for aircraft rotating above 100 KIAS with lower holdover times than type IV. I've read that heated type II can also be used as a deice fluid, but I don't know much about this technique.

Type III is a modern anti-ice fluid for aircraft that rotate at speeds below 100 KIAS. I believe it is chemically similar to type IV except that it's not as thick so it can shear at a lower speed.


That rings a bell, thanks for the info. I remember reading about Type II and III during annual de-ice/anti-ice training but don’t remember much outside of I and IV since that’s all we use.
 
StarAC17
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Re: De icing

Wed Jan 10, 2018 7:11 pm

CARST wrote:
Acey559 wrote:
As mentioned, some ice is acceptable but generally, most operators subscribe to the “clean aircraft “ concept and won’t depart with any contamination (except small amounts of frost under the wings).


Two weeks ago when taking of at Helsinki (evening of December 30th) to NRT on a JAL 787 we had lots of thin ice on the wing. We didn't got any de-icing and anti-ice and proceeded right to the runway. The ice was still on the wing, when we lifted off and then disappeared / flew off the wing once we came through the first cloud layers and the aircraft doing some stronger banking while flying the departure route.

So, reading what you describe about the "clean aircraft" concept, do you think it was right for JAL to depart without getting the aircraft deiced? Could it have been so warm, that they said "the ice will fly off after take-off anyway"? Or was it something that should have been done?

The layer of ice was very thin and the phone did no good job in showing it in this photo I took while boarding:
Image


I have left YYZ in similar circumstances when there is some ice on the wind that came off as the plane took off. Basically the intention is to smooth out the wing, that volume of ice is nothing but if you have ever seen your car after a snowstorm with ice caked to it and have to pull out the scraper to clear your windows that is what de-icing is getting rid of as that affects the airflow over the wings. The crystallization on a metal surface as shown in the image is nothing to worry about, also it was probably cold and dry and there was no risk of additional ice forming also.

IIRC there have been many instances where aircraft at YYZ in a snowstorm are stuck in line and have to go back to get it done again because the fluid has worn off.
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Whiteguy
Posts: 1263
Joined: Sat Nov 29, 2003 6:11 am

Re: De icing

Wed Jan 10, 2018 7:24 pm

CARST wrote:
Acey559 wrote:
As mentioned, some ice is acceptable but generally, most operators subscribe to the “clean aircraft “ concept and won’t depart with any contamination (except small amounts of frost under the wings).


Two weeks ago when taking of at Helsinki (evening of December 30th) to NRT on a JAL 787 we had lots of thin ice on the wing. We didn't got any de-icing and anti-ice and proceeded right to the runway. The ice was still on the wing, when we lifted off and then disappeared / flew off the wing once we came through the first cloud layers and the aircraft doing some stronger banking while flying the departure route.

So, reading what you describe about the "clean aircraft" concept, do you think it was right for JAL to depart without getting the aircraft deiced? Could it have been so warm, that they said "the ice will fly off after take-off anyway"? Or was it something that should have been done?

The layer of ice was very thin and the phone did no good job in showing it in this photo I took while boarding:
Image


Or it could’ve been so warm that it was actually dew on the wing. If you didn’t perform a tactile test, scratch with your finger nails, you wouldn’t know for sure!
 
BlueLine
Posts: 124
Joined: Sat Jun 30, 2012 8:48 pm

Re: De icing

Sat Jan 13, 2018 2:21 am

william wrote:
I know there are two formulas, two different colors, one lasting longer than the other. My questions are
1. How hot is the fluid when sprayed onto the aircraft?

2. Say an aircraft sat overnight and it sleeted. How does the sprayer/mechanic know when all of ice is gone? Does the fluid make a certain color when contacting ice?

3. Are there no spray areas? Such as the engine outlet? Or rudder (fragile)?

4. Is the goal no ice at all, such as on fuselage?

Thank you in advance.


1. Type I fluid used for the removal of contamination is heated to 160-180 degrees Fahrenheit. Type IV fluid used to prevent contamination from forming is unheated.

2. They know when the ice is gone by the texture, reflectivity, and opacity of the surface that was treated. The fluid does not change color on ice.

3. Windows and doors cannot be directly sprayed. You must spray above them and let the fluid trickle down. It's the same with pitot tunes, AOA vane, and other sensors. You also can't spray directly in an engine or APU inlet. You also have to use a fan spray and a 45 degree angle spraying winglets.

4. There is a FAR (114.something I believe) that states that no aircraft can depart with frozen contamination on the wings, tail, engines, cockpit windshield, or any other critical surface. The only exception is a very thin layer of frost under the wing from being filled with cold fuel.

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