Aircraft Systems

and dirt. Aircraft with permanently installed oxygen tanks usually require two persons to accomplish servicing of the system. One should be stationed at the service equipment control valves, and the other stationed where he or she can observe the aircraft system pressure gauges. Oxygen system servicing is not recommended during aircraft fueling operations or while other work is performed that could provide a source of ignition. Oxygen system servicing while passengers are on board the aircraft is not recommended. Anti-Ice and Deice Systems Anti-icing equipment is designed to prevent the formation Tubes deflated of ice, while deicing equipment is designed to remove ice once it has formed. These systems protect the leading edge of wing and tail surfaces, pitot and static port openings, fuel tank vents, stall warning devices, windshields, and propeller blades. Ice detection lighting may also be installed on some aircraft to determine the extent of structural icing during night flights. Most light aircraft have only a heated pitot tube and are not certified for flight in icing. These light aircraft have limited cross-country capability in the cooler climates during late fall, winter, and early spring. Noncertificated aircraft must Tubes inflated exit icing conditions immediately. Refer to the AFM/POH for details. Figure 6-48. Deicing boots on the leading edge of the wing. Airfoil Anti-Ice and Deice also incorporate an annunciator light to indicate proper boot Inflatable deicing boots consist of a rubber sheet bonded to operation. the leading edge of the airfoil. When ice builds up on the leading edge, an engine-driven pneumatic pump inflates the Proper maintenance and care of deicing boots are important rubber boots. Many turboprop aircraft divert engine bleed for continued operation of this system. They need to be air to the wing to inflate the rubber boots. Upon inflation, carefully inspected during preflight. the ice is cracked and should fall off the leading edge of the wing. Deicing boots are controlled from the flight deck by Another type of leading edge protection is the thermal anti-ice a switch and can be operated in a single cycle or allowed to system. Heat provides one of the most effective methods for cycle at automatic, timed intervals. [Figure 7-48] preventing ice accumulation on an airfoil. High performance turbine aircraft often direct hot air from the compressor In the past, it was believed that if the boots were cycled section of the engine to the leading edge surfaces. The hot too soon after encountering ice, the ice layer would expand air heats the leading edge surfaces sufficiently to prevent the instead of breaking off, resulting in a condition referred to as formation of ice. A newer type of thermal anti-ice system ice “bridging.” Consequently, subsequent deice boot cycles referred to as ThermaWing uses electrically heated graphite would be ineffective at removing the ice buildup. Although foil laminate applied to the leading edge of the wing and some residual ice may remain after a boot cycle, “bridging” horizontal stabilizer. ThermaWing systems typically have does not occur with any modern boots. Pilots can cycle the two zones of heat application. One zone on the leading edge boots as soon as an ice accumulation is observed. Consult receives continuous heat; the second zone further aft receives the AFM/POH for information on the operation of deice heat in cycles to dislodge the ice allowing aerodynamic forces boots on an aircraft. to remove it. Thermal anti-ice systems should be activated prior to entering icing conditions. Many deicing boot systems use the instrument system suction gauge and a pneumatic pressure gauge to indicate proper boot An alternate type of leading edge protection that is not as operation. These gauges have range markings that indicate common as thermal anti-ice and deicing boots is known the operating limits for boot operation. Some systems may 7-40