Determining Icing Levels

meritflyer · July 28th, 2006, 22:47

What method do you use to determine icing levels? I typically use the winds aloft forecast.. Is there a better way?

Also, at 10,000' to figure out standard temperature, we'd decrease 15 degrees C by 2 degrees per 1000' correct?

Thanks all!

jtrain609 · July 28th, 2006, 22:50

PIREP's are another great way to figure out where the ice is. Also, to be accurate you never know where the ice is until somebody see's it on their wing; until then you just have the potential for icing.

B767Driver · July 28th, 2006, 22:55

Winds aloft is good. Pireps are good. Also there is a forecast freezing level chart that can be found on most internet weather sites or from FSS.

A good rule of thumb for standard temp is Altitude x 2 minus 15.

Standard temp at 10,000msl is -5c. So 10 x 2 = 20. 20 - 15 = 5. negative 5, of course.

fish314 · July 29th, 2006, 10:15

Keep in mind that those formulas for calculating the temperature at altitude are based on the "STANDARD DAY", and the rule of thumb that the altitude cools by 2 degress Celsius per 1000' is based on the STANDARD lapse rate.

So that means that using it to predict icing is probably not going to work...

You could fine tune it by using the temperature at field elevation today and applying standard lapse rate and that would probably get you a little closer, though. BTW, in Farenheit, the standard lapse rate is 3.6 degrees per 1000', in case you don't want to work metric.

So for example, if I live at 1200' and the temp when I take off is 90 degrees (F, of course). So the freezing level would be at 17,311' if the standard lapse rate applied.

here's the math:

90-32 (freezing temp)=58 degrees to cool

58 degrees to cool/3.6 degrees per 1000' =16.11111 or basically I have to climb from my present position by 16,111.11' feet to get to where it is 32 degrees (freezing).

1200' (where I'm starting from) +16,111.111= 17,311'

B767Driver · July 29th, 2006, 10:21

Quote:

Originally Posted by fish314

Keep in mind that those formulas for calculating the temperature at altitude are based on the "STANDARD DAY", and the rule of thumb that the altitude cools by 2 degress Celsius per 1000' is based on the STANDARD lapse rate.

So that means that using it to predict icing is probably not going to work...

The second part of his question asked for standard temp...not icing conditions.

fish314 · July 29th, 2006, 12:19

Oh, well........

Oops. Disregard then!

Van_Hoolio · July 29th, 2006, 20:19

How about checking out Airmet Zulu?

Mike

July 28th, 2006, 22:47	#1
meritflyer Old Skool Join Date: Dec 2005 Location: Winchestertonfieldville Posts: 6,802	Determining Icing Levels What method do you use to determine icing levels? I typically use the winds aloft forecast.. Is there a better way? Also, at 10,000' to figure out standard temperature, we'd decrease 15 degrees C by 2 degrees per 1000' correct? Thanks all! __________________ The simplest answer tends to be correct.

July 28th, 2006, 22:50	#2
jtrain609 Old Skool Join Date: Feb 2002 Location: Park City, UT Posts: 12,869	Re: Determining Icing Levels PIREP's are another great way to figure out where the ice is. Also, to be accurate you never know where the ice is until somebody see's it on their wing; until then you just have the potential for icing. __________________ "Jetlink 2940, on another radio, contact clearance for new airways..."

July 28th, 2006, 22:55	#3
B767Driver Old Skool Join Date: Sep 2003 Posts: 1,943	Re: Determining Icing Levels Winds aloft is good. Pireps are good. Also there is a forecast freezing level chart that can be found on most internet weather sites or from FSS. A good rule of thumb for standard temp is Altitude x 2 minus 15. Standard temp at 10,000msl is -5c. So 10 x 2 = 20. 20 - 15 = 5. negative 5, of course.

July 29th, 2006, 10:15	#4
fish314 Senior Member Join Date: Feb 2006 Location: (CBM) Columbus AFB, MS Posts: 1,306	Re: Determining Icing Levels Keep in mind that those formulas for calculating the temperature at altitude are based on the "STANDARD DAY", and the rule of thumb that the altitude cools by 2 degress Celsius per 1000' is based on the STANDARD lapse rate. So that means that using it to predict icing is probably not going to work... You could fine tune it by using the temperature at field elevation today and applying standard lapse rate and that would probably get you a little closer, though. BTW, in Farenheit, the standard lapse rate is 3.6 degrees per 1000', in case you don't want to work metric. So for example, if I live at 1200' and the temp when I take off is 90 degrees (F, of course). So the freezing level would be at 17,311' if the standard lapse rate applied. here's the math: 90-32 (freezing temp)=58 degrees to cool 58 degrees to cool/3.6 degrees per 1000' =16.11111 or basically I have to climb from my present position by 16,111.11' feet to get to where it is 32 degrees (freezing). 1200' (where I'm starting from) +16,111.111= 17,311' __________________ Dude, what are you trying to do? Land the airplane or adjust the field elevation?

July 29th, 2006, 12:19	#6
fish314 Senior Member Join Date: Feb 2006 Location: (CBM) Columbus AFB, MS Posts: 1,306	Re: Determining Icing Levels Oh, well........ Oops. Disregard then! __________________ Dude, what are you trying to do? Land the airplane or adjust the field elevation?

July 29th, 2006, 20:19	#7
Van_Hoolio Senior Member Join Date: Jan 2003 Location: Des Moines, Iowa (based in IAH) Posts: 1,083	Re: Determining Icing Levels How about checking out Airmet Zulu? Mike

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