Aircraft Ice Detection and De-icing Systems

Stall Warning Systems

• Stall warning systems indicate to the crew that a stall is imminent and is a critical aspect of flight safety
• These systems provide a warning before the stall is reached

Ice Detectors

• Ultrasonic ice detectors vibrate at a lower frequency when they accumulate ice

Stall Identification Systems

• Stall identification systems contain an actuator that pulls the control column rearward

Pneumatic De-icing Boots

• Pneumatic de-icing boots are deflated and kept flush with the airframe when not in use

Weeping Wing De-icing Systems

• Weeping wing de-icing systems rely on pumping repellent fluid from a reservoir onto the surface to prevent the buildup of ice

De-icing Fluids

• De-icing fluids contain propylene glycol and additives
• De-icing is the process of removing existing ice buildup

Windscreen Ice Protection

• Windscreen ice protection relies on an electrical heating element embedded within the glass layers to prevent ice from forming
• This type of system does not require the use of ice repellent fluids

Angle of Attack (AoA) Sensor Vane

• An AoA sensor vane aligns itself with the prevailing airstream

De-icing De-misting

• De-icing is the prevention of ice formation
• De-misting is the removal of moisture from surfaces such as passenger windows, which is achieved by an electrical heating element

De-icing Boots

• De-icing boots are completely bonded to the leading edge to prevent electrical static buildup
• When a de-icing boot is fully inflated, it disrupts airflow over the leading edge and can reduce lift

Windshield Heaters

• Windshield heater systems utilize an autotransformer to step up output in severe weather conditions

Windshield Rain Repellent

• Windshield rain repellent is applied before rain and spread on the window surface by wipers

Pneumatic Rain Removal Systems

• Pneumatic rain removal systems use engine bleed air at high velocity to remove water droplets from the windscreen
• These systems are not permitted on large transport aircraft, as they may have undesirable effects on aircraft performance
• They are commonly used on smaller, general aviation aircraft

Windshield Wiper Torque Tests

• Windshield wiper torque tests are carried out at the shaft end

Types of Ice

• Glaze ice forms when liquid water flows over the airframe before freezing, resulting in a dense, tough ice deposit that sticks closely to the surface
• Rime ice forms when supercooled water droplets freeze on impact with the airframe, and is typically less dense and more porous than glaze ice
• Hoar frost forms when water vapor freezes directly onto a surface, leading to a white, feathery ice deposit

Pitot Head Heaters

• Pitot head heaters must only be switched on for the minimum time required to check serviceability

Ice Formation on Wings

• Ice formation on wings is due to supercooled water changing state on contact with the wing

Vibrating Rod Ice Detectors

• When a vibrating rod ice detector has de-iced, the warning lamp on the flight deck goes out after a set period of time

De-icing Boot Securement

• Prior to securing a leading-edge de-icing boot, you must shave rivets to prevent further abrasion

Leading Edge De-icing

• The advantage of leading edge fluid de-icing is that it does not disturb the aerodynamic shape

'Hot Rod' Type Ice Detectors

• 'Hot Rod' type ice detectors are switched on when selected by the crew

Windshield Wiper Systems

• On large transport aircraft, the windshield wiper system is independent on each side with different power sources
• Each side has its own system with its own power source, for reliability and safety reasons