Icing

Question 1

What are the 3 types of icing?

Answer 1

1. Hoar frost
2. Rime ice
3. Clear ice

Question 2

What conditions create hoar frost on the ground and in the air?

Answer 2

1. If aircraft skin falls below 0c in high humidity conditions such as overnight.
2. An airborne aircraft where skin falls below 0c and flies in to a warm moist layer of air.
   - will usually disappear quickly but may obscure windshield

Question 3

What is RIME ice?
What type of droplets?
What temperature range?
What cloud is associated?

Answer 3

A white opaque rough deposit of ice.

Formed by SMALL supercooled water droplets that freeze on impact with the aircraft surface.

Common temperature is -10c to -20c

The cloud type generally associated are STRATIFORM cloud
— the exception is NIMBOSTRATUS because it’s droplets are normally larger forming CLEAR ICE

Question 4

What is CLEAR ice?
What type of droplets?
What temperature range?
What cloud is associated?

Answer 4

A transparent sheet of ice

Formed by LARGE super cooled water droplets

Temperature range is 0c to -15c

IT IS THE MOST DANGEROUS FORM OF ICING

It is generally associated with CUMULIFORM cloud ABOVE THE FREEZING LEVEL (when Temp is below 0c)

***Also possible with THICK ALTOSTRATUS AND NIMBOSTRATUS and OROGRAPHIC CLOUD

Question 5

Two hazards posed to aircraft around a thunderstorm could be

A. Icing and hail
B. Icing and turbulence
C. Turbulence and hail
D. Lightning and icing

Answer 5

C. Turbulence and hail

Question 6

The min OAT at which clear airframe icing would be unlikely is

A. 0c
B. -25c
C. +5c
D. +10c

Answer 6

C. +5c