AMT – 111 Ice and Rain Protec3on Chapter 15 Icing Icing Icing Icing Icing Icing Icing Types of Ice •  Clear ice – looks like sheets of glass Formed when large water droplets freeze   Heavy   Difficult for pilot to see and recognize the danger   Hard to remove 
•  Rime ice – looks like frosted glass Formed by small water droplets and snow   Lighter – contains more trapped air   Bulkier   Easier to remove 
•  Combina3on of both •  Increased drag •  Reduces liL •  Adds weight 
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Icing Effects Cause flight control surface imbalance Reduces visibility Reduces propeller performance Blocks pitot and sta3c ports Disturbs radio recep3on Blocks engine and carburetor intakes Breaks off and causes structural and engine damage Where Ice Forms •  Leading edges – wings plus horizontal and ver3cal stabilizers •  Engine inlets and cowl •  Carburetor •  Propellers and spinners •  Pitot and sta3c ports 
Angle of aOack (AOA) sensors •  Windows •  Water drain lines •  Antennas Ice Detec3on Ice Control Methods •  Hea3ng surface with hot air 
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Bleed air from turbine engine Hea3ng by electrical elements Breaking up ice forma3on by inflatable boots Chemical deicers Clean surface Ice Control Methods Heated Leading Edges Heated Leading Edge Heated Leading Edge Carburetor (Carb) Heat Electric Ice Control •  Heat is generated by electric power 
Tes3ng involves checking current draw when hea3ng element is turned on •  Limited to smaller components •  Air data/sensing probes Pitot & sta3c ports   Angle of aOack (AOA)   Turbine engine sensors 
•  Propellers •  Windshield •  Heated boots for leading edge Pitot/Sta3c Tube Heater Propeller Deicing Heated Windshield Heated Windshield Windshield Electric Ice Control •  Electricity is used to heat glass •  Hea3ng element is sandwiched between windshield layers 
Arcing is caused by breakdown in hea3ng element •  Windshield must be replaced •  Heat is regulated/sensed by thermistor The heat sensi3ve resistor   Embedded in windshield 
FAA Ques3on •  Which of the following are found in a laminated integral electrically heated windshield system? 1. Autotransformer. 2. Heat control relay. 3. Heat control toggle switch. 4. 24V dc power supply. 5. Indica3ng light. •  a. 1, 2, 4, 5. •  b. 2, 3, 4, 5. •  c. 1, 2, 3, 5. •  Answer: C Chemical Ice Control •  TKS Video •  Glycol mixture is dispensed on surfaces to lower freezing point •  TKS is a system that has 3ny holes on the leading edge – deicing fluid is pumped out the holes •  Sprayed on windshield 
Wipers help move ice •  Deicing fluid is “slung” on to propellers •  Deicing fluid is sprayed into intake system before carburetor Leading Edge TKS system Propeller Deicing Propeller Deicing Pneuma3c Deicing Boots Pneuma3c Deicing Boots Pneuma3c Deicing Boots •  Inflatable boots applied to leading edges •  Boot infla3on causes ice to breakup •  Boots are inflated in an alterna3ng sequence Minimizes airflow (flying) disrup3on   Minimizes the amount of airflow (pneuma3c)   Pulsing on pressure gauge indicates opera3on 
•  Boots are glued, riveted and screwed to leading edge 
When gluing, the surface must be perfectly clean and the correct adhesive used •  Don’t use solvents to clean boots 
Use soap and water Pneuma3c Deicing Boots Pneuma3c Deicing Boots Components •  Air supply Turbine engines – bleed air   Reciproca3ng engines 
•  Engine driven vane-­‐type vacuum pump •  Wet type 
Requires an oil separator •  Dry type •  Control valve – send air to system 
Routes air overboard when system not in use •  Deflate valve – send vacuum to system to deflate boots Pneuma3c Deicing Boots Components •  Distributor Valve Controlled by a 3mer or control unit   Directs the pressure and vacuum to the correct loca3on   Used to control the sequencing of infla3on 
•  Pressure regulator – regulates pressure by releasing excess pressure overboard •  Vacuum relief valve – regulates vacuum by allowing external air in when vacuum is too great 
External air must be filtered Rain Control •  Airflow created by aircraL moving forward or propeller •  Windshield wipers •  Pneuma3c – forced warm air 
From electric blower or bleed air •  Chemical rain repellent – fluid pumped on windshield to repel water 
Use on dry windshield will restrict visibility •  Windshield surface seal coa3ng Chemical coa3ng that repels water -­‐ hydrophobic   Requires periodic reapplica3on 
Ground Deicing •  Deicing fluids – ethylene glycol or isopropyl alcohol (rubbing alcohol) 
Usually heated •  Remove snow with brush or squeegee FAA Ques3on •  What method is usually employed to control the temperature of an an3-­‐icing system using surface combus3on heaters? •  a. Thermo-­‐cycling switches. •  b. Thermostats in the cockpit. •  c. Heater fuel shutoff valves. •  Answer: A