Wednesday, November 14, 2007


There are two main types of windscreen anti-ice systems. The first system directs a flow of alcohol to the windscreen. By using it early enough, the alcohol will prevent ice from building up on the windshield.

The rate of alcohol flow can be controlled by a dial in the cockpit according to procedures recommended by the airplane 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 cockpit, at which time electrical current is passed across the shield through the wires to provide sufficient heat to prevent the formation of ice on the windscreen. The electrical current can cause compass deviation errors; in some cases, as much as 40°. 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.

Propellers are protected from icing by 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 makes the alcohol flow down the leading edge of the blade. 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 grooved to help direct the flow of alcohol, and they are also imbedded with electrical wires that carry current for heating the propeller. Monitoring the prop anti-ice ammeter can monitor the prop anti-ice system for proper operation. 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.

Pitot and static ports, fuel vents, stall-warning sensors, and other optional equipment may be heated byelectrical elements. Operational checks of the electrically heated systems are to be checked inaccordance with the AFM or POH.

Operation of aircraft anti-icing and de-icing systems should be checked prior to encountering icing conditions. Encounters with structural ice require immediate remedial action. Anti-icing and de-icing equipment is not intended to sustain long-term flight in icing conditions.

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