30 Questions
What happens to the contacts when ice forms on the diaphragm?
They close, supplying current to an ice warning light and a heater.
What is the purpose of the heater in the probe mentioned in the text?
To melt any ice formed on the probe.
How is a warning light signal activated in case enough ice forms on the rotor?
By increasing the motor torque and twisting it slightly.
Why does ice forming on the rotor cause an increase in motor torque?
To shave off the formed ice.
How is icing cessation detected in relation to the rotor-driven motor?
By sensing an increase in current draw.
What happens when the drum slows down and draws more current?
The current draw is sensed by a current metre.
What source of power is used to supply the drain mast heater circuit when the ground handling bus is powered?
42.5 volts AC from the drain mast heater transformer
What happens to the windshield wipers on the aircraft when the windshield is dry?
They stop working to avoid damaging the windshield
Which motor type is NOT commonly used to power aircraft windshield wipers?
Steam motor
What voltage is supplied to the heaters of the drain mast when the aircraft is in operation?
115 volts AC from the ground service transfer bus
What is the purpose of ensuring that the windshield is clear of foreign matter before operating the wipers?
To prevent damage to the windshield
Which relays control the supply of power to the drain mast heaters when power is provided to the main airplane buses?
R8277 and R731
What is the purpose of inflating the de-ice boots on an aircraft?
To break the ice by protruding out
How long do the de-ice boots inflate for during a 'cold' sequence?
6 seconds
What is the timeframe for deflating the de-ice boots in a 'warm' sequence?
2 minutes and 54 seconds
How should de-icer boots be cleaned according to the text?
Using mild soap and water
What is used to remove oil and grease from the surface of de-icer boots?
White spirit or lead-free gasoline
Why is it important to keep de-icer boots clean?
To prevent damage to the aircraft surface
Where are the worst continuous icing conditions typically found?
In stratified clouds near the freezing level
At what altitude range do most catastrophic in-flight icing accidents occur?
Between 3,700 m and 4,900 m ASL
In which type of clouds can structural icing occur at altitudes above 30,000 ft?
Cumuliform clouds with strong updrafts
What is the main reason that icing is rare above altitudes of 16,000 ft?
Cloud droplets at those altitudes are already frozen
What is a characteristic of glaze or clear ice?
It is transparent and smooth
What can distort the freezing level in cumuliform clouds causing severe icing potential?
Both strong updrafts and downdrafts
What component changes the rotary motion of the motor to the oscillating motion required by the wiper blades?
Converter
Which part determines the stroke arc of the wiper blades?
Converter
What part keeps the wiper blade vertical and governs the wiper pattern?
Guide arm
How is the spring tension against the windshield obtained?
Using a steel pin inserted through a pinhole in the arm
What supports the end of the guide arm?
Pivot stud
How can one remove the wiper for maintenance?
Inserting a 1/8-inch-diameter steel pin through a pinhole in the arm
Test your knowledge on the worst continuous icing conditions, common altitudes for icing accidents, and the impact of different cloud types on aircraft icing incidents.
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