De-ice technology develops

De-ice Technology Develops

New systems you can bet your boots on

By Greg Napert

October 1998

There are three basic types of ice prevention systems that have been in common use over the years: The rubber bladder type — typically used on corporate and general aviation aircraft airfoil leading edges, bleed air heat — used on commercial transport and business jets, and electric heating elements — used primarily on propellers and windshields. Ice detection, on the other hand has been virtually non-existent — the only system being one that consisted of a small probe which vibrated at a given frequency which changed as ice formed over it.

Researchers, over time, have developed new systems for detection and protection, but for the most part, manufacturers haven't incorporated the new technology into new aircraft. That still holds true.

However, an aircraft accident which happened in Oct. 31, 1994 — where an American Eagle ATR-72 in Roselawn, Indiana (Flight 4184) crashed due to icing problems — led industry icing experts, investigators, and manufacturers to study new ways to prevent and eliminate such incidents.

Although the de-ice manufacturers say they have been researching alternative approaches to ice detection and prevention for years, Supplemental Type Certificates (STCs) for new detection and prevention systems since 1994 seem to be on the rise.

The following pages give you a look at of some of the new detection and prevention systems that you will see appearing in the marketplace over the upcoming years as well as some new technology that is currently available.

SMARTboot
According to Bryn Young, customer service for BFGoodrich Aerospace Ice Protection Systems Division, the company's newest integrated ice detection/protection system called SMARTboot™, incorporates the ice detector into the de-ice boot. "Up until SMARTboot came along, the kind of ice detection systems that were on aircraft were probe-like, single point detectors. And so, they detected ice near the de-ice boot and not on the de-ice boot. Its disadvantages were twofold: its location, which wasn't in the critical area of the de-ice boot, and, it was a one-point sensor as opposed to SMARTboot, which is a wide area sensor," she says.

Dave Sweet, manager of research and development for BFGoodrich says the company received an STC on the SMARTboot on the Piper Malibu/Mirage in 1997. The product was in development for around three years.

Sweet continues, "BFG began working with a small company out of Ithaca, NY, which had adopted a system developed by NASA/Langly research. This system initially did not work, but it had merit and led us in the direction that we were able to solve the problems it had. The original capacitance technique that was used worked well if the ice was completely frozen. But, ice is often very wet in reality, especially when flying through clouds. So, in order to resolve the issue, we instead had to measure the impedance of the ice/moisture. Using impedance, we are able to sense the onset of ice at about .020-inch thickness, and the system tells us the thickness of the ice as it increases."

Sweet says the system is designed primarily for the tail of the aircraft — an area that is not visible to the pilots. "Tail icing was what drove the development of the SMARTboot," he says. "He can see the wing, so that's not really a concern when it comes to de-icing." He continues, "The horizontal stabilizer is also a smaller airfoil, so it is a more efficient collector of ice. The system is designed to alert the pilot when there is ice, and it also tells them when there is enough ice to activate the system. Once you've detected the ice, it works as a conventional boot does."