Anti-icing & De-icing

       Anti-icing And De-icing System

✈ATA-30

✈Negative Effects of  Ice Buildup

☂Negative effects of ice buildup

☂Destroys  smooth  flow  of  air  over  wing, leading  to  severe  decrease  in  lift  and increase  in  drag  forces.

☂Can change pitching  moment 

☂ As  angle  of  attack  is  increased  to compensate  for  decreased  lift,  more accumulation  can  occur  on  lower  wing surface.  

☂Causes  damage  to  external  equipment such  as  antennae  and  can  clog  inlets, 

and cause  impact  damage  to  fuselage  and engines  

☂Considered  a  cumulative  hazard    because as  ice  builds  up  on  the  wing, it  increasingly changes  the  flight  characteristics.
✈Causes of Icing
There is three cause;

✈Effects of Icing

✈Types of Ice

☂Rime:  Has  a  rough   milky  white appearance and  generally follows  the  surface  closely.

A milky white colored or opaque ice that deposits on the surface of the aircraft when it's flying through filmy clouds is classified as rime ice. It is usually formed because of small supercooled droplets when the rate of catch is low. Rime ice accumulates on the wings' leading edges and on pilot heads, antennas, etc.

☂Clear/Glaze:  Clear  and  smooth but  usually  contain  some  air pockets  that  result  in  a  lumpy translucent  appearance,  denser, harder  and  more  difficult  to break  than  rime  ice

Clear ice or glaze ice is a heavy coating of glassy ice which forms when flying in areas with high concentration of large supercooled water droplets, such as cumuliform clouds and freezing rain. It spreads, often unevenly, over wing and tail surfaces, propeller blades, antennas, etc.

☂Mixed: It forms when both small and large supercooled droplets are present. The appearance of mixed ice is irregular, rough and whitish. Favorable conditions for forming of this type of aircraft ice include frozen and liquid particles present in the wet snowflakes and cumuliform cloud's colder portion.

✈Ice Prevention Methods

☂Heating  surfaces  using hot air

☂ Heating  by  electrical  elements 

☂ Breaking  up ice  formations, usually by  inflatable boots 

☂Alcohol spray.

✈Methods of Ice Control

 Location of Ice    ✈      Method of control  

☂Leading edge of the wing  >Pneumatic, Thermal

☂L/E of Horizontal & vertical stabilizer> Pneumatic,Thermal

☂Windshields, windows, radomes> Electrical, Alcohol

☂Heater & Engine air inlet> Electrical

☂Stall  Warning Transmitters> Electrical

☂Pitot tubes> Electrical

☂Flight controls > Pneumatic, Thermal 

☂L/E of propeller blade> Electrical,

Alcohol

☂Carburetors> Thermal, Alcohol 

☂Lavatory drains>Electrical.

✈Types of Ice Removal

☂Anti-Icing

•Preemptive, turned on before the flight enters icing conditions 

•Includes: thermal heat, prop heat, pitot heat, fuel vent heat, windshield heat, and fluid surface    de-icers.

☂De-Icing

•Reactive, used after there has been significant ice build up

 •Includes surface de-ice equipment such as boots, weeping wing systems, and heated wings.

✈Propeller Anti-Icers

☂Ice  usually  appears  on propeller  before  it  forms  on the  wing 

☂Can  be  treated  with chemicals  from  slinger rings  on  the  prop  hub 

☂Graphite  electric  resistance heaters  on  leading  edges  of blades  can  also  be  used.

✈Windshield Anti-Icers
☂Usually  uses  resistance  heat to  clear  windshield  or chemical  sprays  while  on the  ground
☂Liquids  used  include:  ethylene  glycol, propylene  glycol,  Grade  B  Isopropyl  alcohol, urea,  sodium  acetate,  potassium  acetate, sodium  formate, and  chloride  salts
☂Chemicals  are  often  bad  for  the  environment.

✈Thermal Heat

Air Heated 

☂Bleed  air  from  engine  heats  inlet cowls  to  keep  ice  from  forming 

☂ Bleed  air  can  be  ducted  to  wings to  heat  wing  surface  as  well 

☂Ice  can  also  build  up  within engine,  so  shutoff  valves  need  to be  incorporated  in  design 

☂ Usually  used  to  protect  leading edge  slat, and  engine  inlet  cowls  Resistance  heater 

☂ Used  to  prevent  ice  from  forming on  pitot  tubes,  stall vanes, temperature  probes,  and  drain masts.

✈Boots 

☂Inflatable  rubber  strips  that run  along  the  leading  edge  of wing  and  tail  surfaces  

☂When  inflated,  they  expand knocking  ice  off  of  wing surface  

☂After  ice  has  been  removed, suction  is  applied  to  boots, returning  them  to  the  original shape  for  normal  flight  

☂Usually  used  on  smaller planes.

✈Weeping Wing

☂Fluid  is  pumped  through mesh  screen  on  leading edge  of  wing  and  tail 

☂Chemical  is  distributed  over wing  surface, melting  ice 

☂Can  also  be  used  on propeller blades windshields.

✈Typical Anti-Icing

C-130:  

☂Engine  bleed  air  used  for  anti-icing  wing  and empennage  leading  edges, radome, and  engine  inlet air  ducts.  

☂Electrical  heat  provides  anti-icing  for  propellers, windshield, and  pitot  tubes. 

777: 

☂Engine  bleed  air  used  to  heat  engine  cowl  inlets.  If leak  is  detected  in  Anti-Ice  duct,  affected  engine Anti-Ice  valves  close.  

☂Wing  Anti-Ice  System  provides  bleed  air  to  three leading  edge  slats  on  each  wing.  Wing  Anti-Ice  is only  available  in  flight.

✈ You can watch this https://youtu.be/JpvSEiPyIZM