11.12 ICE AND RAIN PROTECTION 👌🏼 Flashcards
3 most common types of ice encountered during flight
- Clear ice
- Rime ice
- Mixed ice
Explain clear ice
- formed by large supercooled water droplets
- freeze gradually
- smooth, hard, glossy, transparent
- heavy and difficult to remove
Explain Rime ice
- formed by small supercooled water droplet
- freezes before it has time to spread
- white appearance
- lighter than clear ice, irregular shape, rough
- brittle but easier to remove than clear ice
Explain mixed ice
- combination of clear and rime ice
List the Ice detection systems
- Visual detection
- Hot rod detector
- Accretion/pressure detector
- Rotary ice detector
- Vibrating ice detector
What are the 2 methods of visual detection
- wing inspection lights
- visual ice indicators
Explain wing inspection lights
- located on each side of fuselage forward section
- enable flight crew to view and detect ice build up
- during night operation or low ambient light conditions in flight
Explain visual ice indicators
- small posts
- usually mounted between windshields
- Ice will be collected on post
Which of the following is a visual ice detector
- hot rod
- pressure operated
- rotary operated
- hot rod ✅
What are Hot rod detectors
- external (where it can be observed by flight crew)
- light illumination for dark conditions
- deicing achieved by heater element within rod
- operated by press button in cockpit
What is a pressure operated ice detector
- 4 holes in leading edge, 2 holes in trailing edge
- leading edge holes blocked by ice and negative pressure is created
- relay closes and triggers ice warning
- relay also activates heating element to melt ice from probe
- when deactivated, probe is able to freeze again until aircraft is out of icing conditions
Explain a rotary ice detector
- external (forward fuselage)
- consists of single phase AC motor
- has knife edge cutter with clearance less than 0.002 inches
- As ice builds up, greater rotational torque is required as it shaved
- This movement gives a ice warning
Explain vibrating probe ice detector
- vibration caused by electric current of approx 40khz
- Ice accumulation on probe causes vibration frequency to decrease
- Flight crew is then alerted
- probes internal and external heater cycles on and off to clear ice accumulation
Which ice detector is NOT built with a heating element?
- Hot rod
- Pressure operated
- Rotary detector
- Rotary detector✅
Which ice detector is de-iced independently?
- hot rod detector
- pressure operated detector
- visual detector
- pressure operated detector✅
Explain Element ice sensing unit (Sangamo Weston ice detector)
- It detects moisture or freezing temp separately to prevent ice formation
3 main components:
- Moisture detector controller
- Moisture sensing head
- Thermal switch
Manufacturers of ice detectors produce sensors that fall under 3 certification types
- Primary automatic
- Primary manual
- Advisory
How are ice detection alerts provided?
- visual or audio alerts in cockpit
- designed to draw FC attention immediately
How are WARNING lights indicated
- corresponding WARNING light is illuminated to notify FC
What must be done when the master caution system is activated
- FC needs to address the situation (has to respond to it)
What are EICAS (Enhanced Indication and Crew Alerting System) ?
- essential engine and system info to FC
- Icing related warnings etc can be displayed on central display
How can a surface be anti-iced?
- keeping it dry
- heating enough to evaporate water
- heating surface to prevent freezing
How can a surface prevent and remove ice?
- heating surface with hot air
- heating by electrical elements
- breaking ice that has formed (inflatable boots)
- applying chemicals to prevent adhesion of ice
What is the preferred anti-ice method on large turbine aircraft
- Thermal pneumatic anti-icing, with engine bleed air
- wing leading edges, empennage, engine inlet cowls
Explain thermal pneumatic anti-icing
- prevents ice formation on aero foil LE
- warm air enters duct which travels lengthwise along inside of leading edge of aero foil and exits through holes
Explain wing anti-ice (WAI) system
- Thermal wing anti-ice utilise hot air from engine bleed
- hot air routed through ducting, manifolds, and valves to LE of the wings
- joints of ducting is ‘hermetically sealed’ to prevent loss of hot air
Explain the WAI valve
- controls flow of bleed air from pneumatic system to WAI ducts
- ## electrically controlled and pneumatically actuated
What information is shown on WAI indication system
- WING MANIFOLD PRESS
- VALVE
- AIR PRESS
- AIR FLOW
Explain engine anti-ice (EAI)
- large turbine powered aircraft have thermal pneumatic engine (inlet cowl)
- bleed air is ducted to LE of engine inlet cowls, and then exits through overboard vents
Explain pneumatic de-ice boots
- commonly used for de-icing wings and stabilisers on small/reciprocating engines
- expand when pneumaticcally inflated, breaking away any formed ice
- Boots inflated 6-8 seconds then deflated by vacuum suction
Explain electric de-ice boots
- contain electric heating elements which are bonded to leading edge
- when activated, boots heat up and melt ice
What systems are used to control rain on windshield
- Chemical rain repellent
- Pneumatic rain removal (Jet blast)
- hydrophobic surface seal
Explain windshield surface coating
- ‘hydrophobic’ coating (layer that repels water)
- long term
Explain pneumatic rain removal systems
- removes rain by directing a flow of heated air over windshield
What 2 purposes do heated air serve in a pneumatic rain removal system
- breaks raindrop into small particles
- heats windshield to prevent moisture from freezing
In pneumatic rain removal systems, how can the air be supplied
- electric blower
- bleed air
Explain probe anti-ice
- current flows through integral conductive element that generates heat
- temp of system kept above freezing point of water
Aircraft with water and waste systems have ———- to prevent ice from forming in water lines
- electrical heaters
What does a windshield wiper assembly consist of
- a wiper
- a wiper arm
- a wiper motor
Windshield wiper systems are powered by
- electrical motors
- hydraulic motors (old aircraft)
