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383 

Federal Aviation Administration, DOT 

Pt. 25, App. C 

A

PPENDIX

TO

P

ART

25 

Part I—Atmospheric Icing Conditions 

(a) 

Continuous maximum icing. 

The max-

imum continuous intensity of atmospheric 
icing conditions (continuous maximum 
icing) is defined by the variables of the cloud 
liquid water content, the mean effective di-
ameter of the cloud droplets, the ambient air 
temperature, and the interrelationship of 
these three variables as shown in figure 1 of 
this appendix. The limiting icing envelope in 
terms of altitude and temperature is given in 
figure 2 of this appendix. The inter-relation-
ship of cloud liquid water content with drop 
diameter and altitude is determined from 
figures 1 and 2. The cloud liquid water con-
tent for continuous maximum icing condi-
tions of a horizontal extent, other than 17.4 
nautical miles, is determined by the value of 
liquid water content of figure 1, multiplied 

by the appropriate factor from figure 3 of 
this appendix. 

(b) 

Intermittent maximum icing. 

The inter-

mittent maximum intensity of atmospheric 
icing conditions (intermittent maximum 
icing) is defined by the variables of the cloud 
liquid water content, the mean effective di-
ameter of the cloud droplets, the ambient air 
temperature, and the interrelationship of 
these three variables as shown in figure 4 of 
this appendix. The limiting icing envelope in 
terms of altitude and temperature is given in 
figure 5 of this appendix. The inter-relation-
ship of cloud liquid water content with drop 
diameter and altitude is determined from 
figures 4 and 5. The cloud liquid water con-
tent for intermittent maximum icing condi-
tions of a horizontal extent, other than 2.6 
nautical miles, is determined by the value of 
cloud liquid water content of figure 4 multi-
plied by the appropriate factor in figure 6 of 
this appendix. 

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