Aircraft Systems

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