Icing

Question 1

Ice can only form on an aircraft surface in flight if the temperature is below 0 degrees. With one exception. What is the exception?

Answer 1

SCWD will form ice upon contact with the airframe. Other SCWD will flow backwards and eventually cool on the air frame

Question 2

The smaller the water droplet the lower the temperature they reach and remain in liquid form. True or False?

Answer 2

True.

Question 3

What does aircraft icing depend on?

Answer 3

1) The size and temperature of the water droplet.

2) Shape and speed of the airframe

Question 4

List the 5 forms of ice

Answer 4

1) hoar frost
2) Cold soaker fuelling
3) Rime ice
4) Clear Ice
5) Rain Ice

Question 5

Describe Hoar frost

Answer 5

Created due to radiation cooling. Uniform white deposits of fine crystals. Forms on exposed surfaces that are below freezing. Can form on the top or bottom of an airframe and reduces lift and increases drag.

Question 6

Briefly describe Cold Soaked Fuel Cooling

Answer 6

Results from conductive cooling. Frost under the wing is a good indication of cold soaked fuel condiations

Question 7

What is Hold Over Time (H.O.T)?

Answer 7

The time de-icing fluid removes and prevents ice from returning for a set period of time.

Question 8

There are 4 fluid types. What are they?

Answer 8

1,2,3,4
I,II,III, IV
(Stated in Roman numerals)

Question 9

Anti-icing fluids are similar in composition except they contain?

Answer 9

Polymeric thickeners

Question 10

Which type of fluids are typically used for anti-icing?

Answer 10

Cat 2-4 as they can last for longer periods of time than cat 1

Question 11

Briefly describe Rime ice.

Answer 11

A rough, opaque coating produced by small SCWD that freeze almost completely on impact. Porous, weak and fragile. Unlikely to form accumulations. Can effect aerodynamics and block vents.

Question 12

Briefly describe Clear Ice.

Answer 12

Transparent/translucent ice formed by large droplets that are only just supercooled. Most droplets flow backwards and produce thick heavy ice. Breaks off in chunks and effects the flying characteristics of the aircraft.

Question 13

Briefly describe Rain ice

Answer 13

Most dangerous form of icing and caused by large rain droplets just above 0 falling into and airframe below 0 degrees. Only small amount freeze on impact the rest flow backwards causing a rapid buildup and weight penalty.
Occurs flying in cold air just ahead of a warm front

Question 14

What effects does ice have on aircraft?

Answer 14

• wings and controls
• propellers
• Tubes and vents
• Jet engines
• carburettors
• radio antennas
• wind screen

Question 15

What two types of clouds are associated with icing?

Answer 15

Cumulonimbus

Nimbostratus

Question 16

List the significant factors that effect ice

Answer 16

Temperature 
Drop size 
Airframe shape
Kinetic heating 
Concentration

Question 17

Which one (anti/de-icing) prevents ice from forming?

Answer 17

Anti-icing

Question 18

Which one (anti/de-icing) removes ice?

Answer 18

De-icing

Question 19

Suitable priority must be given to aircraft wishing to change level due icing

Answer 19

True

Question 20

Care must be taken to avoid undue delays to departures after de icing has been completed

Answer 20

True

Question 21

What cooking creates hoar frost?

Answer 21

Radiation cooling

Question 22

What type of cooling cause cold soaked fuelling frost?

Answer 22

Conduction cooling

Question 23

When are you going to encounter rain ice?

Answer 23

Flying in cold air just ahead of a warm front