Anti-icing of aircraft is accomplished by applying a protective layer, using a viscous fluid called anti-ice fluid , over a surface to absorb the contaminate. All anti-ice fluids offer only limited protection, dependent upon frozen contaminant type and prevailing weather conditions. A fluid has failed when it no longer can absorb the contaminant and it essentially becomes a contaminant itself. Even water can be a contaminant in this sense, as it dilutes the anti-icing agent until it is no longer effective.
For those who do not like to read, they can listen and enjoy the beautiful shots. Upon inflation, the ice is cracked and should fall off the leading edge of the wing. Deicing boots are controlled from the flight deck by a switch and can be operated in a single cycle or allowed to cycle at automatic, timed intervals.
Pilots can cycle the boots as soon as an ice accumulation is observed. Many deicing 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 deicing boots are important for continued operation of this system. They need to be carefully inspected during preflight. Another type of leading edge protection is the thermal anti-ice system.
Heat provides one of the most effective methods for preventing ice accumulation on an airfoil. High performance turbine aircraft often direct hot air from the compressor section of the engine to the leading edge surfaces.
The hot air heats the leading edge surfaces sufficiently to prevent the formation of ice. A newer type of thermal anti-ice system referred to as ThermaWing uses electrically heated graphite foil laminate applied to the leading edge of the wing and horizontal stabilizer. ThermaWing systems typically have two zones of heat application.
One zone on the leading edge receives continuous heat; the second zone further aft receives heat in cycles to dislodge the ice allowing aerodynamic forces to remove it. Thermal anti-ice systems should be activated prior to entering icing conditions. An alternate type of leading edge protection that is not as common as thermal anti-ice and deicing boots is known 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.
This is done by first melting the ice at the interface of the surface and then shedding it from the aircraft. The main advantage of anti-icing is that it generates less aerodynamic disturbances than de-icing. On the other hand, de-icing requires significantly less energy than anti-icing.
Energy-efficiency is very important for UAV ice protection systems, because the energy used for ice protection reduces the range and endurance of the UAV.
Combining anti-icing and de-icing. A larger area works in de-icing mode, periodically detecting and removing ice from the surface by exploiting the kinetic energy of the wind. This operation mode combines the advantages of anti-icing and de-icing, leading to low power requirements and low aerodynamic disturbances.
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