1989-04-01

Fatique and Electromagnetic Interference Test for Electro-Impulse De-Icing 891062

Electro-Impulse De-Icing (EIDI) has been studied and developed at Wichita State University for the past six years in ten icing wind tunnel tests and three sets of flights tests. However, questions remained about the system endurance over a lifetime of use and about electromagnetic compatibility. These were addressed in tests of both metal and composite leading edges. Energy levels used were those determined necessary in the earlier tunnel and flight tests. Failures for the aluminum leading edges were found only in poorly designed coil brackets and in a pre-stressed rivet hole. No damage could be found with the composite model. Electromagnetic radiation was found to be well contained in an aluminum wing. Exposed lead wires were high power emitters and these had to be fully shielded for the composite model to meet the specifications. The emissions were broadband with no significant peak frequencies.
ICE ACCUMULATION IN FLIGHT is a well recognized danger. Although ice normally is accrued only a few centimeters thick-on the forward 2% of the wing, this is enough to cause flow separation and destroy lift. For engine inlets, choking of the flow or asymmetric flow may result. For helicopters, the added power requirements when ice forms on rotors has severely limited the cold weather usefulness.
Although several methods of de-icing or anti-icing are available, all have some undesirable aspects in regard to energy requirements, reliability, maintenance needed, weight or space requirements. The electro-magnetic impulse phenomenon holds the promise of ice removal with very low energy, minimal maintenance, great reliability, with weight and costs competitive with existing methods.
During 1982 to 1986, the EIDI method was studied, tested and developed by a NASA/University/Industry consortium. The NASA Lewis Research Center funded Wichita State University to do the basic research and to coordinate the efforts of ten industrial aerospace firms in developing the EIDI system. Twelve series of tests were performed in the Icing Research Tunnel of NASA in Cleveland, and three sets of flight tests were conducted. A continuing series of AIAA papers reported the status and progress of the EIDI project. References 1 and 2 gave the underlying electrodynamic and structural dynamic principles, problems and approach. References 3 and 4 reported on flight tests in NASA's DeHavilland DHC-6 Twin Otter and in a Cessna 206. The Cessna flight tests led to the equipping of a C-206 with a production prototype EIDI system for wings, struts and empennage. Flight tests in natural icing were conducted in February 1985. Reference 5 and 6 reported on additional icing tunnel tests. In June, 1985 a symposium for invited representatives of U.S. industry was held as NASA/Lewis to report results of three years work. Reference 7 is a comprehensive report. Reference 8 addresses system design and Referencing 9 gives a mathematical modeling.
From 1980 to 1988, the Federal Aviation Administration supported testing to evaluate the potential problems of fatigue damage and electromagnetic interference. It is primarily this latter work which will be reported here. But first, a general description of the EIDI system will be given.

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