Module 11.12 Ice and rain protection

Question 1

What are the conditions for ice formation?

Answer 1

• Supercooled water droplets
• Below freezing aircraft skin

Question 2

What are the 3 types of ice?

Answer 2

• Rime ice
• Clear ice
• Mixed ice

Question 3

What is clear ice caused by?

Answer 3

Large water droplets
- Looks smooth

Question 4

What is rime ice caused by?

Answer 4

Small water droplets
- Rough surface

Question 5

What is the problem with mixed ice?

Answer 5

Rapid formation

Question 6

What areas should have ice protection?

Answer 6

• Leading edges of wings, stabs and engines
• Props and spinners
• Air data probes
• Flight deck windows
• Water and waste system lines and drains
• Antennae

Question 7

What are the types of ice detectors?

Answer 7

• Visual
• Hot rod
• Accretion or pressure
• Rotary ice
• Vibrating ice

Question 8

What are the two methods of visual detection?

Answer 8

• Wing inspection lights
• Visual ice indicators

Question 9

How does a hot rod detector work?

Answer 9

In icing conditions ice will form. Pilot can then see the formation from his window, the pilot will then switch on the heating element to reset it.

There is also a light for night ops

Question 10

What is the angle of the hot rod detector?

Answer 10

30°

Question 11

How does the pressure operated ice detector work?

Answer 11

Leading edge of the probe has 4 holes and trailing edge has 2. under normal conditions there will be a pressure build up.

Under icing conditions there will be negative pressure created, this will trigger a warning in the cockpit

Question 12

What occurs after ice formation has occurred and warnings have been issued?

Answer 12

The heating element will automatically turn on

Question 13

What does the rotary ice detector consist of?

Answer 13

• Single phase AC motor to spin a rotor
• Knife edge placed less than 0.002” from the rotor

Question 14

What occurs when ice forms on the rotary detector?

Answer 14

Ice forms and the torque will increase due to the knife edge having to shear this off. The motor will then rotate slightly in its housing. This movement is detected and issues a warning

Question 15

Why doesn’t a rotary detector have a heater?

Answer 15

As the knife edge shears of the ice and resets it

Question 16

What happens to the resonating frequency when ice forms on the vibrating probe ice detector?

Answer 16

It decreases

Question 17

What does the element ice sensing unit/Sangamo Weston ice detector detect?

Answer 17

It detects icing conditions and not formation

Question 18

What are the 3 main components of the element ice sensing unit?

Answer 18

• Moisture detector controller
• Moisture sensing heads
• Thermal switch

Question 19

What occurs when ice forms on the probe of a beta particle ice detection probe?

Answer 19

The geiger mueller readings go down, then the heater will be actuated

Question 20

What is the difference between anti-ice and de-ice?

Answer 20

• Anti-ice is to stop the formation
• De-ice is to remove formation

Question 21

How may a surface be anti-iced?

Answer 21

• Keep it dry
• Heat it enough to evaporate water or prevent freezing

Question 22

Where is the thermal pneumatic anti-icing?

Answer 22

Generally leading edges of aerofoils

Question 23

How does the warm air get to the leading edge?

Answer 23

Ducts (piccolo tubes) with holes to direct hot air to leading edge

Question 24

What is done to ensure the slat LE doesn’t have ice build up?

Answer 24

The Wing Anti-Ice (WAI) moves air from the leading edge to the slat via a telescopic pipe

Question 25

What is shown on the WAI indication system?

Answer 25

• Wing manifold pressure
• Valve
• Air pressure
• Air flow

Question 26

When would the Engine Anti-Ice (EAI) system be turned on automatically?

Answer 26

Before the WAI

Question 27

The bleed air is directed to the LE like WAI, where is this heated channeled out?

Answer 27

Through outboard vents

Question 28

What does the electrical windshield anti-ice do?

Answer 28

Removes ice formation and improves the impact resistance

Question 29

What are wings with chemical anti-ice systems also called?

Answer 29

Wet wings or TKS system (Brand name)

Question 30

What concept does TKS use?

Answer 30

Freezing point depressant concept

I.e. it makes the freezing point lower

Question 31

What is the drawback to TKS?

Answer 31

Limited use as only a finite amount of fluid can be stored on board the aircraft

Question 32

How do de-icer boots work?

Answer 32

They are rubberised section of LE’s and after ice formation the boots are inflated which removes the ice

Question 33

What is the purpose of the suction in de-icer boots?

Answer 33

To keep a flat LE surface

Question 34

How are the boots operated?

Answer 34

Manually via a switch

Question 35

What are electric de-ice boots?

Answer 35

They have electric heating elements on the LE instead of rubber inflatable channels

Question 36

How may windshields be de-iced?

Answer 36

• Chemically, de-icer sprayed on via nozzle

Question 37

How is rain repellent applied?

Answer 37

Sprayed on with the wipers on, only in really wet conditions

Liquid used is banned

Question 38

when should rain repellent never be applied?

Answer 38

Dry conditions

Question 39

What does a hydrophobic coating do?

Answer 39

Allows water to bead and run off

Question 40

What are the challenges wipers face?

Answer 40

• Slipstream reduces effectivity
• Oscillation speed may be too slow to keep up with the downpour

Question 41

Removal via pneumatic rain removal systems has two purposes, what are they?

Answer 41

The heated air:
- Breaks water into small particles to be blown away
- Heats windshield, stops freezing

Question 42

What are the 3 types of rain removal?

Answer 42

• Chemical
• Pneumatic
• Coating

Question 43

How are probes anti-iced?

Answer 43

Using heating elements

Question 44

When would the heating elements around a water tank and drains be turned on?

Answer 44

When a temperature of below freezing is detected

Question 45

How are windshield wipers actuated?

Answer 45

Electrically via a motor