Cox: Using resonance to break the ice

With all the attention on pneumatic de-icing boots from the Colgan 3407 Q400 disaster in Buffalo last week, I was curious to see if any new technologies have been put to use to crack ice off the leading edge of lifting surfaces.

One very promising advance is a low-power "electro-mechanical expulsion deicing system" (EMEDS) built by Cox & Company and already in use on two Hawker Beechcraft models, the Premier 1A and the Hawker 4000, for the horizontal stabilizer. Boeing is also using the technology for the raked wing extensions of its P-8A Multi-Mission Maritime Aircraft, a variant of next generation 737.

Unlike a pneumatic system, which inflates rubber bladders on the leading edge of wings and tail surfaces....

...the EMEDS uses an aluminum or stainless steel leading edge with the guts of the deicing system behind the leading edge, protected from the elements. Actuators, driven by electro-magnetic forces, move at high frequencies, changing the shape of the leading edge such that ice thicker than 0.06in breaks off.

Benefits of having a metal leading edge include less drag and longer life compared to the rubber boots which wear away from abrasion.

Perhaps more beneficial is that EMEDS is immune to ice bridging, a phenomena where pneumatic boots, if activated too early in ice formation stage, can potentially form a "bridge" over the leading edge which cannot be removed by the boots on subsequent cycles.  

The video below, provided by Cox, shows how EMEDS works on the horizontal tail of a typical business jet. Note how the de-icing action takes place in sections, with the entire process repeating every 20 seconds.

Though jet powered aircraft use bleed air from the jet engines through piccolo ducts to pump hot air out onto the leading edge to melt ice before it forms (so-called anti-ice), some locations on the airframe are too difficult to reach with the hot air, and sometimes there simply isn't enough hot air left after servicing the main wing and the cabin.

Cox says it is in talks with multiple manufacturers about using the technology on a variety of new aircraft, and not just for the tail.