Unit 3-3 Flashcards
How does ice form?*
Visible moisture + low temperature
Clouds
Fog
Rain
Sleet
Snow
Ice crystals
What problems can ice cause?*
Frozen control surfaces
Blocked “static system” and other ports (pitot)
Ice ingestion - into engines or engine sensing probes
Reduced Lift - Interfere with airflow, increase angle of attack
Added weight
Loss of visibility
Cause structural/system damage (antenna, fairings, etc.
How does a probe detect ice?
Vibrates at 40 Hz
Ice forming changes the frequency of vibration which causes light to illuminate in the cockpit
How does an electrical cutter detect ice?
If ice builds up, it begins to scrape against the adjacent knife edge
This change in torque activates a microswitch to illuminate the ice detected annunciator on the roof panel
What is the difference between anti-icing and deicing?
Anti-icing prevents the formation of ice
Deicing removes ice that has already formed
What systems can prevent ice on an aircraft?
Briefly describe each
Thermal anti-icing
Probe anti-icing
WAI system
Windshield ice control
Describe thermal anti-icing
Heated air
Engine bleed air (turbine powered aircraft)
Combustion heaters (piston engine aircraft)
Wing anti-ice system (WAI)
Flowing through leading edge, stabilizers, and engine cowling
Describe probe anti-icing
Electric heaters - keep probes (e.g., pitot mast, stall warning indicator, static ports, etc.) free from ice
How are anti-ice techniques applied to a windshield?
Heated windshield (electric or air)
Uses heated panel
Heated air between windshield surface
Spraying fluid on windshield to remove ice, and keep any more ice from forming (isopropyl alcohol)
Describe deicing boots
Inflatable rubber “boots” with several separate air passages
Inflation of the passages cracks any ice & it falls off due to wind speed
Uses low pressure air from an engine driven vacuum pump
What does a weeping wing (TKS) do?
How?
Anti-ice and deice the wing
Millions of laser drilled holes in the titanium leading edge of the wing that secretes fluid
What liquid is secreted by a weeping wing?
AL-5: a mixture of ethylene glycol, isopropyl alcohol, and water
How is the engine protected from ice?
Heated so ice does not enter the engine and cause damage
Anti-ice
Typically heated either using bleed air or electric coils
How can rain be removed/controlled?
Windshield wipers
Chemical repellents
A combination of the two
Pneumatic rain-removal system (jet blast system)
