Ice And Rain Protection Flashcards
De icing definition
Process where ice is allowed to build prior to it being removed
Anti icing
Where the object is to prevent any ice accumulation
Switched on before entry into an area with an ice risk
Types of ice detection devices
Hot rod Vibrating Pressure Rotary Inferential
Hot rod ice detector operation
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
Vibrating ice detector
Consists of a short cylindrical probe mounted on a vibration housing - vibrate axially about 40Khz
As the ice builds - freq of the vibration changes
What gets rid of the ice warning light
Switching the anti ice on or cancelling the light
When is the ice boots system switched on
Until a specific depth of ice has been built up
Typically given as 1.5m
Mechanical de icing are employed on
Mechanical de icing systems are employed in certain types of piston eng a/c and twin prop a/c
Use pneumatics
2 different types of de icing tubes in a mechanical de icing system
Chord wise
Span wise
What happens to the de icing tubes when the system is switched off
Vacuum is created - makes a tight seal with the l/d edge
Mechanical de icing system operation
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
Fluid used for fluid based ice protection
Isopropyl alcohol
Fluid based ice protection operation
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
Fluid based ice protection system can only be used on
Straight, one curved leading edges
Purpose of the head compensating valve
Ensures fluid goes to all parts of the system
Micronic filter in the fluid ice protection system
Takes out the tiny bits in the fuel - protects the tiny holes of the leading edge
Types of fluid distributors and their use on different wings
Strip - curved leading edge
Panel - Straight leading edge
Advantages ad disadv of panel distribution for fluid ice protection
Economical and efficient
Covers a larger area of the leading edge
Not suitable for surfaces with double curvature
Thermal anti icing operation
Taking hot bleed air from the compressor states of the turbine and throwing it down the wing
Modern transport - airframe
Thermal anti icing what does it protect
All l/d edges inc slats and wing fences
Does not protect Krueger flaps
When will thermal anti icing not be used
In the ground - will cook the wing
On t/o and l/d
How does a turbo prop get its thermal anti icing system
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
Anti icing for the jet engine has 2 separate systems which are and the operation
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
Effect of ice on the prop and 2 ice protection systems
Distortion to the aerofoil, vibration in balance and a loss of efficiency
Protected by
Anti ice fluid system
Electrical thermal de icing system
Electrical prop de icing protection
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
Indications in the flight deck for the operation of prop and airframe ice protection
Normally operate at 2 cycle speeds
Fast = light icing Slow = heavy
Green light = indicates the system is in operation
Prop fluid anti icing system operation
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
Windscreen electrical anti ice system is powered by ? And controlled by ?
Powered by AC but controlled by DC
Overheat sensor purpose - windscreen
Senses overheat and will cut the power - senses normal temp controller has failed
Windscreen rain repellent system operation
System delivers rain repellent fluid to the screen, makes the water droplets coalesce into big drops so it can be blown away
What happens if you use the rain repellent system on a dry screen
Will reduce visibility
Windscreen wipers are operated
Electrically or hydraulically powered
Should not be operated on a dry screen
