Windscreen Anti-Ice  Propeller Anti-Ice  Other Anti-Ice and Deice Systems  Chapter Summary  7-41  Figure 7-50.  Prop ammeter and anti-ice boots.  Figure 7-49.  TKS weeping wing anti-ice/deicing system.  as a weeping wing. The weeping-wing design uses small  holes located in the leading edge of the wing to prevent  the formation and build-up of ice. An antifreeze solution  is pumped to the leading edge and weeps out through the  holes. Additionally, the weeping wing is capable of deicing  an aircraft. When ice has accumulated on the leading edges,  application of the antifreeze solution chemically breaks down  the bond between the ice and airframe, allowing aerodynamic  forces to remove the ice.  [Figure 7-49]  There are two main types of windscreen anti-ice systems.  The first system directs a flow of alcohol to the windscreen.  If used early enough, the alcohol prevents ice from building  up on the windscreen. The rate of alcohol flow can be  controlled by a dial in the flight deck according to procedures  recommended by the aircraft manufacturer.  Another effective method of anti-icing equipment is the  electric heating method. Small wires or other conductive  material is imbedded in the windscreen. The heater can be  turned on by a switch in the flight deck, causing an electrical  current to be passed across the shield through the wires to  provide sufficient heat to prevent the formation of ice on  the windscreen. The heated windscreen should only be used  during flight. Do not leave it on during ground operations, as  it can overheat and cause damage to the windscreen. Warning:  the electrical current can cause compass deviation errors by  as much as 40°.  Propellers are protected from icing by the use of alcohol or  electrically heated elements. Some propellers are equipped  with a discharge nozzle that is pointed toward the root of the  blade. Alcohol is discharged from the nozzles, and centrifugal  force drives the alcohol down the leading edge of the blade.  The boots are also grooved to help direct the flow of alcohol.  This prevents ice from forming on the leading edge of the  propeller. Propellers can also be fitted with propeller anti-ice  boots. The propeller boot is divided into two sections—the  inboard and the outboard sections. The boots are imbedded  with electrical wires that carry current for heating the  propeller. The prop anti-ice system can be monitored for  proper operation by monitoring the prop anti-ice ammeter.  During the preflight inspection, check the propeller boots for  proper operation. If a boot fails to heat one blade, an unequal  blade loading can result and may cause severe propeller  vibration.  [Figure 7-50]  Pitot and static ports, fuel vents, stall-warning sensors,  and other optional equipment may be heated by electrical  elements. Operational checks of the electrically heated  systems are to be checked in accordance with the AFM /POH.  Operation of aircraft anti-icing and deicing systems should be  checked prior to encountering icing conditions. Encounters  with structural ice require immediate action. Anti-icing and  deicing equipment are not intended to sustain long-term flight  in icing conditions.  All aircraft have a requirement for essential systems such  as the engine, propeller, induction, ignition systems as well  as the fuel, lubrication, cooling, electrical, landing gear, and  The boot is divided into two sections: inboard and outboard.  When the anti-ice is operating, the inboard section heats on  each blade, and then cycles to the outboard section. If a boot  fails to heat properly on one blade, unequal ice loading may  result causing severe vibration.  Prop anti-ice boot  20 0  10  PROP DEICER  AMPS  When the system is operating,  the prop ammeter indicates  normal operating range. As each  boot section cycles, the ammeter  fluctuates.  Prop anti-ice ammeter  Outboard section Inboard section 