Icing’s Electromagnetic Personality

Influenced by increasing fuel prices, the search for more profitability in every way, and a growing environmental movement, NASA’s aeronau­tics researchers during the 1980s sought to meet all of those needs in terms of propulsion, airframe design, air traffic control, and more. On the subject of aircraft icing, all three of the traditional de-icing meth­ods provided some drawbacks. The pneumatic boot added weight and disrupted the intended aerodynamics of an otherwise unequipped wing airfoil. Spraying chemicals onto the aircraft, whether on the ground or seeped through the leading edge in flight, contributed toxins to the envi­ronment. And bleeding off hot air to warm the interior of the wing and other aircraft cavities reduced the performance of the engines and added to the empty weight of the aircraft. Based on an idea first suggested in 1937 by Rudolf Goldschmidt, a German national living in London, NASA researchers investigated an Electro-Impulse De-Icing (EIDI) system that promised applications both on fixed-wing aircraft and on helicopters.[1234]

First tested during the 1970s, the EIDI system researched during the 1980s consisted of flat-wound coils of copper ribbon wire positioned near the skin inside the leading edge of a wing, but leaving a tiny gap between the skin and the coil. The coils were then connected a high – voltage bank of capacitors. When energy was discharged through the wiring, it created a rapidly forming and collapsing electromagnetic field, which in turn set up a sort of a vibration that rippled across the wing, creating a repulsive force of several hundred pounds for just a fraction of a second at a time. The resulting force "shattered, de-bonded and expelled ice instantaneously.”[1235]

Ground tests in GRC’s IRT and flight tests on aircraft such as NASA’s Twin Otter and Cessna 206 during 1983 and 1984 conclusively proved the EIDI system would work. The results set up a 1985 symposium with
more than 100 people in attendance representing 10 companies and several Government agencies. As participants observed test runs in the GRC IRT, program engineers stressed that EIDI operated on low energy (in some cases with less power than required to power landing lights), caused no aerodynamic penalties, required minimum maintenance, and compared favorably in terms of weight and cost with existing de-icing systems. Although it was hailed as the de-icing system of the future, the EIDI never found widespread acceptance or lived up to its expectations.[1236]

However, in 1988 an ARC engineer by the name of Leonard A. Haslim won NASA’s Inventor of the Year Award by coming up with the Electro­Expulsive Separation System (EESS), an apparent combination of the best of the EIDI and traditional rubber boot de-icing systems. In this configuration, the electrically conducting copper ribbons are embed­ded into the boot with tiny slits in the boot separating each conductor. When a burst of energy is discharged through the system, each conduc­tor pair repels one another in an instant and causes the slits in the boot to expand explosively, instantly breaking free any ice on the wing. In addition to the advantages the EIDI system offers, the EESS can remove ice when it is only as thin as a layer of frost, preventing the possibility of larger chunks of ice breaking free of the leading edge and then causing damage if the ice strikes the tail or tail-mounted engines. With applica­tions for removing ice from large ship superstructures or bridges, the EESS was licensed to Dataproducts New England, Inc. (DNE), to make the product available commercially.[1237]