AIRFOIL ICE CONTROL

Inflatable de-icing boots consist of a rubber sheet bonded to the leading edge of the airfoil. When ice builds up on the leading edge, an engine-driven pneumatic pump inflates the rubber boots. Some turboprop aircraft divert engine bleed air to the wing to inflate the rubber boots. Upon inflation, the ice is cracked and should fall off the leading edge of the wing. De-icing boots are controlled from the cockpit by a switch and can be operated in a single cycle or allowed to cycle at automatic, timed intervals. It is important that de-icing boots are used in accordance with the manufacturer's recommendations. If they are allowed to cycle too often, ice can form over the contour of the boot and render the boots ineffective.

Many de-icing boot systems use the instrument system suction gauge and a pneumatic pressure gauge to indicate proper boot operation. These gauges have range markings that indicate the operating limits for boot operation. Some systems may also incorporate an annunciator light to indicate proper boot operation.

Proper maintenance and care of de-icing boots is important for continued operation of this system. They need to be carefully inspected prior to a flight.

Another type of leading edge protection is the thermal anti-ice system installed on airplanes with turbine engines. This system is designed to prevent the build-up of ice by directing hot air from the compressor section of the engine to the leading edge surfaces. The system is activated prior to entering icing conditions. The hot air heats the leading edge sufficiently to prevent the formation of ice.

An alternate type of leading edge protection that is not as common as thermal anti-ice and de-icing boots is known as a weeping wing. The weeping-wing design uses small holes located in the leading edge of the wing. A chemical mixture is pumped to the leading edge and weeps out through the holes to prevent the formation and build-up of ice.