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De-Icing Procedures

Sun Dec 31, 2000 2:06 pm

What are the parameters in the weather that requires and aircraft to be de-iced before departure? Does it have to do with how long the aircraft was staionary in winter precipitation? or are there other factors that affect when de-icing begins/stops?

Thanks in Advance,
"Courage is not the absence of fear, but rather the judgement that something else is more important than fear"
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RE: De-Icing Procedures

Sun Dec 31, 2000 2:28 pm

1/ FARs prohibit takeoffs with snow ice adhering to the aircraft.

2/ Once an aircraft has been de-iced, the time interval before it must again be de-iced is based on many variables, such as:

* Type of precip falling (snow, ice pellets, freezing rain).

* Intensity of precip (light, moderate, heavy),

* Type of de-ice fluid (Type-1, -2, -3, -4),

All of these things (and others) affect the effectiveness of the de-icing fluid, since the precip (water) is diluting the fluid. This effective time of the fluid is called "holdover time" and it's really brief (2-3 minutes) in some freezing rain conditions, and much longer for dry snow conditions.

After USAir lost 405 at LGA back in 1992 (F-28 on takeoff, iced up) Faa held a major industry conference on de-icing, and lots of loopholes and gray areas were tightened up, and folks have a better understanding about the threat(s) if procedures are properly followed.
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RE: De-Icing Procedures

Sun Dec 31, 2000 2:43 pm

It any frozen visible moisture is adhering to the uppersurface of the wing the aircraft will be de-iced. Sometimes the captain will choose not to de-ice if it is only a thin layer of frost.

Most large aircraft are de-iced with type I fluid then anti-iced with type IV if precipitation is falling to increase hold over times.

Type 4 is a fluid only applied to large aircraft. It is designed to blow off the wing at a predetermined speed (120 kts) before the aircraft is airborne.

Type I is usually 50/50 fluid/water applied between 170 degrees and 180.

Type IV is applied cold.

Hold over times only apply if precip is falling. If no precip there is no hold over time.

The other day we had a storm in IND. There were 747's on the ramp de-icing. They took over 2 1/2 hours to de-ice. Our 727 took over an hour.

Topic Author
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Joined: Mon Nov 22, 1999 5:37 am

RE: De-Icing Procedures

Mon Jan 01, 2001 6:08 am

Thank you gentlemen for the replies
Have a good new years,
"Courage is not the absence of fear, but rather the judgement that something else is more important than fear"
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RE: De-Icing Procedures

Sat Jan 22, 2005 4:33 am

Just curious about de-icing (but you'll have guessed that already!).

At airports where there can be long queues and which are also susceptible to extreme cold - eg JFK, ORD, DTW, YYZ, how long before t/o can the aircraft be de-iced. It occurs to me that if it's de-iced at the gate, but is then in a 20+ aircraft queue, it might need more de-icing before it takes off - particularly if jet blast from aircraft in front affects surfaces such as leading edges, which have already been de-iced.

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RE: De-Icing Procedures

Sat Jan 22, 2005 9:06 am

Most modern jets have heated leading edges so once they are de iced and the engines are started the leading edges stay clean. The tops of the wing and the control surfaces are the real problem while waitng on the ground. Some weather prone airports de ice near the end of the runway, so re applying isn't an issue. PIT I think was the first to use this system.
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RE: De-Icing Procedures

Sat Jan 22, 2005 10:27 am

Originally posted by JETPILOT:
"Type 4 is a fluid only applied to large aircraft."

How big does the airplane need to be before Type IV is applied. I've seen Beech 1900s get Type IV after being deiced with Type I.

On another note, does anyone know how much Type IV costs per gallon? I've always wondered how much it'd typically take to spray down a 777 and how much all that stuff costs.
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RE: De-Icing Procedures

Sat Jan 22, 2005 10:54 am

"Type 4 is a fluid only applied to large aircraft."

I personally have put it on 25/35 series lears.

But getting back to the original subject. There is no set standard rule for de-icing. The rules will be laid out in the companies ops manuals, and that is a negotiated document with the FAA. There are certain things they like to see, but their hard and fast rule, is simply the airplane has to be clean. Unless noted in that ops-spec there is no limitation on how to do it.
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RE: De-Icing Procedures

Sat Jan 22, 2005 10:55 am

It doesn't matter what size the plane is. Its the conditions that dictate the type, unless the deicing company does not have type IV. Type IV holds over longer than type I, thats why they did it with type IV.
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RE: De-Icing Procedures

Sat Jan 22, 2005 3:35 pm

Whats the Duration of Application prior to Departure or risk reapplication of DeIcing Fluid Type 1,2,3 & 4.
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