Ice And Rain Protection

Question 1

De icing definition

Answer 1

Process where ice is allowed to build prior to it being removed

Question 2

Anti icing

Answer 2

Where the object is to prevent any ice accumulation

Switched on before entry into an area with an ice risk

Question 3

Types of ice detection devices

Answer 3

Hot rod 
Vibrating 
Pressure 
Rotary 
Inferential

Question 4

Hot rod ice detector operation

Answer 4

Ice will build up on narrow sections with a small surface area first

Detector consists of an aerofoil shape mast

No ice on the detector = no ice on the wing

Heater is incorporated to melt the ice so it can be used again

Question 5

Vibrating ice detector

Answer 5

Consists of a short cylindrical probe mounted on a vibration housing - vibrate axially about 40Khz

As the ice builds - freq of the vibration changes

Question 6

What gets rid of the ice warning light

Answer 6

Switching the anti ice on or cancelling the light

Question 7

When is the ice boots system switched on

Answer 7

Until a specific depth of ice has been built up

Typically given as 1.5m

Question 8

Mechanical de icing are employed on

Answer 8

Mechanical de icing systems are employed in certain types of piston eng a/c and twin prop a/c

Use pneumatics

Question 9

2 different types of de icing tubes in a mechanical de icing system

Answer 9

Chord wise

Span wise

Question 10

What happens to the de icing tubes when the system is switched off

Answer 10

Vacuum is created - makes a tight seal with the l/d edge

Question 11

Mechanical de icing system operation

Answer 11

When it is switched on - cyclically applies pressure and vacuum to one of the groups - needs for the ice to build a little bit for it to throw it off cleanly

Question 12

Fluid used for fluid based ice protection

Answer 12

Isopropyl alcohol

Question 13

Fluid based ice protection operation

Answer 13

Fluid is pumped from the reservoir into perforated strips

Spreads back to melt the ice - weeping wing, fluid comes out in tiny tear drops

Sequence is controlled by a timer

Question 14

Fluid based ice protection system can only be used on

Answer 14

Straight, one curved leading edges

Question 15

Purpose of the head compensating valve

Answer 15

Ensures fluid goes to all parts of the system

Question 16

Micronic filter in the fluid ice protection system

Answer 16

Takes out the tiny bits in the fuel - protects the tiny holes of the leading edge

Question 17

Types of fluid distributors and their use on different wings

Answer 17

Strip - curved leading edge

Panel - Straight leading edge

Question 18

Advantages ad disadv of panel distribution for fluid ice protection

Answer 18

Economical and efficient

Covers a larger area of the leading edge

Not suitable for surfaces with double curvature

Question 19

Thermal anti icing operation

Answer 19

Taking hot bleed air from the compressor states of the turbine and throwing it down the wing

Modern transport - airframe

Question 20

Thermal anti icing what does it protect

Answer 20

All l/d edges inc slats and wing fences

Does not protect Krueger flaps

Question 21

When will thermal anti icing not be used

Answer 21

In the ground - will cook the wing

On t/o and l/d

Question 22

How does a turbo prop get its thermal anti icing system

Answer 22

Ram air is warmed by exhaust gasses though a heat exchanger which is sent around the a/c

Does not loose thrust unlike the modern jet transport thermal system

Question 23

Anti icing for the jet engine has 2 separate systems which are and the operation

Answer 23

One for the engine itself

One for the intake area of the engine nacelle

Uses hot engine oil/ internal engine air to heat fan and nose cone areas - crew have not control about this

Question 24

Effect of ice on the prop and 2 ice protection systems

Answer 24

Distortion to the aerofoil, vibration in balance and a loss of efficiency

Protected by
Anti ice fluid system
Electrical thermal de icing system

Question 25

Electrical prop de icing protection

Answer 25

Resistance wire heating elements bonded to the leading edges of the blades

Turbine eng prop - wire woven or sprayed elements are also bonded to the shell of the spinner

Spinner is constantly kept warm to warm the air coming into the intake - still called de icing

Question 26

Indications in the flight deck for the operation of prop and airframe ice protection

Answer 26

Normally operate at 2 cycle speeds

Fast = light icing 
Slow = heavy 

Green light = indicates the system is in operation

Question 27

Prop fluid anti icing system operation

Answer 27

Provides a film of freezing point depressant fluid to the prop blade surfaces

Distributed by slinger rings - centrifugal force forces it out - spreads and sticks to the prop

Question 28

Windscreen electrical anti ice system is powered by ? And controlled by ?

Answer 28

Powered by AC but controlled by DC

Question 29

Overheat sensor purpose - windscreen

Answer 29

Senses overheat and will cut the power - senses normal temp controller has failed

Question 30

Windscreen rain repellent system operation

Answer 30

System delivers rain repellent fluid to the screen, makes the water droplets coalesce into big drops so it can be blown away

Question 31

What happens if you use the rain repellent system on a dry screen

Answer 31

Will reduce visibility

Question 32

Windscreen wipers are operated

Answer 32

Electrically or hydraulically powered

Should not be operated on a dry screen