Keeping ice off airplane wings

Keeping ice off airplane wings

by Greg Paula, Associate Editor

Sophisticated devices such as magnetostrictive, electromagnetic, and ultrasonic sensors are helping to increase the safety of air travel by preventing ice buildup on aircraft

In conventional deicing, crews use heated glycol-based fluids to remove existing ice, then coat the airplane with ice suppressants to prevent new ice from forming

The accumulation of ice on airplane wings, because of inadequate ground deicing or ice accumulation in-flight, is one of aviation’s most insidious problems. In-flight ice is removed with engine heat or by inflating rubber bladders, called pneumatic boots, installed along the wings. For planes on the ground, various chemicals are used to melt ice and prevent it from reforming. Ice can be difficult to see, so airlines increasingly rely on devices such as magnetostrictive, electromagnetic, and ultrasonic sensors to alert them to the need for deicing.

The SmartBoot developed by BF Goodrich Aerospace in Uniontown, Ohio, has a magnetostrictive system that determines when the pneumatic boot should be activated. A coil inside a probe vibrates ultrasonically; as ice builds up, the probe’s vibrational frequency decreases. The SmartBoot is the primary ice-detection system in all Boeing aircraft.

To detect icing on the ground, Jacques Padawer and Robert M. Goldberg used a number of discrete light sources and electro-optical sensors installed at various points on the aircraft surface. When a reflecting material, such as ice, covers one or more of these sensors, signals are generated to alert the crew.

The C/FIMS system from AlliedSignal Aerospace Canada in Toronto uses the principle that an electric field is affected by a material’s conductivity and permissivity to discriminate between layered materials, identifying and displaying all common contaminants found on an aircraft surface, such as ice, snow, and deicing fluids.

The HALO ice-detection system being developed by Rosemount Aerospace in Burnsville, Minn., includes four wing-mounted ultrasonic sensor assemblies that use short ultrasonic pulses, composed of both vertical and horizontal shear-wave components that travel along curvatures in the structure and yield data on surface contaminants. The system is especially effective in detecting ice in hard-to-see areas, such as cold areas on a wing due to low fuel temperatures.

The above was adapted from an article by Greg Paula, Associate Editor. The full text may be found in the May 1997 issue of Mechanical Engineering magazine. © 1997 ASME International.© To obtain a copy of this issue, click here.