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Guest cliff

Icing problems at 37,000 ft?

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Guest cliff

Cruising at 37,000 ft I noticed that the outside temperature was minus 34 degrees C.On checking I noted that I'd forgoten to activate anti ice for the wings.Should the aircraft have experienced problems or is this not yet programmed? Cliff

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Guest frankathl

Hi Cliff,Clear or cloudy?In or near precipitation(clouds, snow, hail, etc), you should anticipate icing conditions and activate wing and engine anti-ice. In clear skies, you don't need to worry.The effect of icing conditions is simulated on the PMDG 737NG, AFAIK.BR,Frank

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Guest cliff

Hey this can can only have come from my Mentor! (This is Cliff in Spain)I didn't want to bother you with this sort of basic query but you've still found a way to help via the Forum............... We ascended through some pretty heavy cloud (actual weather thanks to "Active Sky" but the cruise was way above the clouds in a clear blue sky.It's fascinating to learn that ice conditions have indeed been modelled. What happens in those conditions if we forget to turn the anti ice on?Cliff

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>Cruising at 37,000 ft I noticed that the outside temperature>was minus 34 degrees C.OT: minus 34

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>outside temperature>was minus 34 degrees C.It is really too cold for any danger of icing. Icing can only happen at or above approximately minus 10 C.Michael J.WinXP-Home SP2,AMD64 3500+,Abit AV8,Radeon X800Pro,36GB Raptor,1GB PC3200,Audigy 2


Michael J.

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I didn't know that icing was simulated. pretty cool. This topic has raised a question that I was too embarassed to ask previously but anyway now that I've mustered the courage I'd like to know the difference between the true outside air temperature vs. the temperature displayed on the EICAS. Sometimes I'm flying using activesky and it's supposed to be for example -31C at FL300 but the display I get is much warmer. So from what I could deduce the reading we get is not the true outside air temp (TAT) but the Indicated Air temperature (IAT) correct? http://www.precisionmanuals.com/images/forum/800driver.jpg


Cheers,
Victor M. Lima
 

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What you are seeing is TAT = Total Air Temperature (not true air temperature). TAT is the SAT(Static Air Temp.) + Ram Air Rise. As the aircraft gets faster, there is kenetic heating of the airframe and this is what the TAT probe measures.Cheers,JohnBoeing 727/737 & Lockheed C-130/L-100 Mechanichttp://www.precisionmanuals.com/images/forum/ng_driver.jpg

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Actually TAT stands for (if I am not mistaken) "Total Air Temp." and this is higher since it indicates temperature of a slightly compressed air and compression generates heat. What you call "true" is normally called SAT (Static Air Temp.) or OAT (Outside Air Temp.). I don't think there is such a thing as IAT.Michael J.WinXP-Home SP2,AMD64 3500+,Abit AV8,Radeon X800Pro,36GB Raptor,1GB PC3200,Audigy 2


Michael J.

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Guest frankathl

>It is really too cold for any danger of icing. Icing can only>happen at or above approximately minus 10 C.I don't understand how it can be "too cold" for icing conditions, Michael? If moisture freezes at -10C, it will also freeze at -34C, won't it? Or is it that you won't get precipitation when the temperature drops below a certain point? Are there never any clouds at 37,000 ft, where OAT is regularly in the -50C range?BR,Frank

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I'll try to answer that for you Frank. We can have clouds in the tropical region as high FL640. And I'm not talking about CBs but actually Cirrus formations which are solid clouds made of ice crystals. It is known that icing occurs between 10 to -10C. However some icing conditions have been observed at temps as low as -40C.It occurs when very small water vapor particles suspended in the air (clouds for example) and who ere semi-stationary collide with the aircraft. Once collision occurs they immediately freeze upon impact, creating the icing effect. The more pure and smaller the water particles the more resistant they are to lower temperatures. I'm not sure but I think you don't get icing in these Cirrus clouds above mentioned because they are actually solid ice crystal clouds (no moisture), and thus there is no freezing of any particles upon impact.Hope it helps,Victorhttp://www.precisionmanuals.com/images/forum/800driver.jpg


Cheers,
Victor M. Lima
 

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>it will also>freeze at -34C, won't it?It won't because it won't exist. As Victor explained given temperature cold enough an airplane won't encounter any moisture that will 'wait' to freeze on the wing. It is already all ice.Michael J.WinXP-Home SP2,AMD64 3500+,Abit AV8,Radeon X800Pro,36GB Raptor,1GB PC3200,Audigy 2


Michael J.

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Guest frankathl

Oh, very good explanation, Victor.I'm grateful to you!By the way, what happens if an aircaft encounters a "solid ice cloud"?:-)Thanks,Frank

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Guest frankathl

Yes, I understand now, Michael. I live and learn every day :-)Thanks,Frank

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