Flashcards
Weather Protection System
Cards in this deck (35)
- 1When can ice appear?Under certain atmospheric conditions, ice can build rapidly on airfoils and air inlets. Ice can form on aircraft leading edge surfaces at altitudes where freezing temperatures start.
- 2What happen with supercooled droplets?Water droplets in the air can be supercooled to below freezing but without turning into ice due to the surface tension of the water droplet not allowing the droplet to expand and freeze. When aircraft surfaces distrurb theses droplets, they immediately turn into ice
- 3When is ice expected to form?Whenever there is visible moisture in the aiir and the temperature is near or below the freezeing one. An exception is carburetor icing, which can occur during warm weather with no visible moisture.
- 4Icing Effects- Increases drag (fuel consumption) and reduces lift - Higher than usual stall speed - Destructive vibration - Hampers true instrument readings - Unbalanced or frozen control surfaces - Fixed slots filled and movable slots jammed
- 5Icing Effects (bis)- Radio reception is hampered and engine performance is affected - Reduce takeoff, landign, climb performances - Reduced maneuverability of the aircraft - Possible engine failures and structural damage when ice breaks-off
- 6Surfaces equiped with ice protection- Wing and stabilizers leading edges - Engine cowl leading edges - Propellers - Propeller spinner - Air data probes -Water and waste system lines and drains
- Antenna - 7Icing conditions- Moisture: liquid water content (0-3 g/m3)
- Temperature (-40 - 0º C)
- Droplet size (from a few microns to hundreds of microns) - 8Small DropletsHave smaller mass and momentum and thend to follow better the airflow streamlines: high probability of impact and ice formation mainly on the leading edge (prevalently at -40 < T < - 15ºC)
- 9Larger DropletsCross the streamlines and can impact farther aft along the airfoil. Large droplets are far more dangerous: de-icing and anti-icing systems are usually on the leading edge.
- 10Supercooled Large Droplets (SLD)They have diameter larger than 40 microns. Flow along the airfoil for long distances before frezing
- 11How are SLD formed?One mechanism is the freezing rain. Temperature decreases with altitude but sometimes, layer of cold air lie under warmer layers. When snow falls into the warm layer, it melts and then droplets become supercooled when passing through cold air. To over come this, climb descend to avoid cold layer
- 12Type of ice. List- Clear/glaze ice
- Rime ice
- Mixed clear and rime icing - 13Clear/ glaze ice(Large droplets). Remaining water drop flows out over the aircraft surface, gradually freezing as a smoothe sheet of solid ice. Its removal by de-icing equipment is specially difficult.
- 14Rime ice(Small droplets). Rapid freezing on leading edge. lighter and more easily removed. Its irregular shape and rough surface reduces lift and increases drag
- 15Mixed clear and rime icingwater drops vary in size or when liquid drops are mixed with snow or ice particles
- 16FrostDoes not change the basic arodynamic properties but the induced roughness determines an upstream displacement of the abscissa of separation (5/10% increase of stall speed: impossibility to take-off, reduced margin to gusts during climb)
- 17Means to prevent or control ice formation- Heating surfaces with hot air
- Heating by electrical elements
- Breaking up ice formations, usually with the use of inflatable boots
- Chemical application - 18Anti-icing definitionEquipment turned on before entering icing conditions and designed to precent ice from forming (keeping the surface dry, heating to a temperature that evaporates impinging water or precent solidification)
- 19De-icingEquipment designed to remove ice after it begins to accumulate typically on the wings and stabilizer leading edges
- 20Thermal pneumatic anti-icing PurposePreventing the formation of ice or for de-icing airfoil leading edges usually using heated air ducted spanwise along the inside of the leading edge of the airfoil and distributed wound its inner surface
- 21Thermal pneumatic anti-icing Where it is used?- Wings
- Leading edge slats
- Horizontal and vertical stabilizers
- Engine inlets - 22Thermal pneumatic anti-icing Sources of hot air- Hot air bled from the compressor
- Engine exhaust heat exchangers
- Ram air heated by a combustion heater - 23Thermal electric anti-icing FunctioningThe component temperature is elevated by Joule effect above the freezing point of water
- 24Thermal electric anti-icing Where it is usedSmall components: pitot tubes, static air ports, AOA probes, ice detectors, engine pressure/temperature sensors, water lines, waste water lines, turbopropo inlet cowls, windshields
- 25Chemical anti-icing. FunctioningIce protection is based upon the freezing point depressant concept. A gycol based fluid is pumped from a reservoir through a mesh screen embedded in the leading edges of the wings and stabilizers. It is also capable of de-icing
- 26Chemical anti-icing UseLeading edfes of the wing
Stabilizers
Windshields
Propellers - 27How are the wing and stablizer chemical anti-icing systems called?Weeping systems or TKS tm systems (Tecalemit-Kilfrist Sheepbridge Stokes). Some aircrafts with these systems are certified to fly into known icing conditions
- 28Pneumatic de-icingThe leading edges of the wings and stabilizers have inflatable boots attached to them. The boots expand when inflated by pneumatic pressure, which breaks away accumulated ice on the boot. They are deflated by vacuum suction which is continously applied to hold the boots tightly against the aircraft while not used.
- 29Propeller de-icing systems Electrically heated boot in each bladeThe boot receives current from a slip ring and brush assembly on the spinner bulkhead. The centrifugal force of the spinning propeller and air blast breaks the ice particles loose from the heated blades
- 30Propeller de-icing systems Chemical de-icingIce usually appears on the propeller before it does on the wing. The propeller system can be a stand-alone system, or it can be part of a chemical wing and stabilizer deicing system such as TSK tm weeping system
- 31The presence of ice on an aircraft may be the result of...- Direct precipitation
- Formation of frost on integral duel tanks adter prolonged flight at high altitude
- Accumulations on the landing gear following taxiing through snow or slush - 32Under which conditions may the aircraft take off if authorized by the FAAWith frost under the wing in the area of the duel tanks
- 33What happen with the measures taken when de-icing on groundThey must also prevent the possible redreezing of the liquid
- 34Ground icing contaminants can cause:- Longer take-off
- Failure to lift-off
- Lift-off but no climb capabilities
- Climb but roll or pitch uncontrollability
- Engine power loss - 35Problems of lightning- Expected at any time of the year
- Can damage structure locally and induce very high transient voltages in aircraft cables
- Induced effects can destroy entire systems
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- Sistemas Flashcards on Weather Protection System, created by Ana Castilla on 16/06/2020.
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- Ana Castilla
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