Microwave device for de-icing, or keeping hollow bodies free from ice and method for the operation of the device

A method of de-icing and keeping the surfaces of hollow body structures free of ice which structures are exposed to atmospheric influences and which have leading edge areas which consist of fiber compound material, said edge areas consisting of a fiber reinforced material provided at its outer exposed surface with a metallic material coating and each of said hollow body structures being microwave-tight, and wherein each of said hollow body structures includes at least a power supply connected to an electrical energy source, at least one microwave source operable by said power supply, a hollow conductor connected to said at least one microwave source, for conducting microwave energy to a wall area of said hollow body in order to heat said wall area, said wall area being divided into equal surface sections disposed adjacent one another along said leading edge and being defined by ribs extending normally from the leading edge in the hollow body structure in spaced relationship and further by spars extending parallel to said leading edge so as to form microwave-tight chambers, and an uncoupling conductor structure supported in each chamber on said spars in a position parallel to said front edge and being connected to said microwave source, with the geometry of the chamber and the frequency of the microwaves being selected so that in each chamber an electromagnetic field with excess modes is generated when the microwave source is switched on for uniform heating of the equal-size surface segments of fiber reinforced material, metallic double lines of conductive material extending in the area to be kept ice free along the leading edge and forming, together with cooling coils of said microwave sources, a cooling circuit with the coolant in the double lines flowing in opposite directions and the cooling coils of said microwave sources being arranged in a series circuit,

• said method comprising the steps of:
• maintaining the coolant flow through the cooling circuit for a certain area of the equally sized surface segments along the leading edge in order to maintain the structure along the double line free of ice, operating said microwave sources mounted in said hollow spaces such that, within a cycle period, at least one microwave source is operated while the others are shut down such that, between two operative microwave sources, there is another one which is shut down, and operating each microwave source which is in operation selectively continuously or in a pulsed manner for controlling the heat input into the respective surface segment.