LEADING EDGE DEICING

Shape memory alloys, which can be trained to generate a compressive strain upon application of an electric current, show promise for deicing applications.

Icing conditions can occur as aircraft fly through clouds with supercooled water droplets. These water droplets can freeze immediately upon impact or flow back along the surface as a liquid film before freezing. Accumulation of ice can greatly degrade aircraft aerodynamic performance. Small amounts of ice can decrease lift, increase drag, and significantly change pitching moment, thus potentially causing loss of control.

Current deicing systems either prevent ice accumulation via heating or break the ice layer after it is formed using surface deformation. Turbofan aircraft often use hot bleed air from the engine for anti-icing, while on propellers and helicopter rotors, resistive electric heaters are commonly used. However, such systems have high input requirements: high bypass-ratio turbofans have limitations on the amount of available bleed air, while resistive heating requires excessive electrical power input. Pneumatic boots consist of a flexible material that is glued to the leading edge in strips, leaving unbonded passages. Pressurized air is forced into these passages, causing the boot to swell outward and the ice to be shed. Although the input requirements for a boot system are much less than those for a thermal heating system, the boot system may only be effective in a narrow range of operating conditions. Such a system may also have high maintenance costs due to deterioration and erosion of the boot material with time.