Abstract: A deployable lightning protection apparatus particularly suited for use with an aircraft radome comprises; a source of electrically conducting fluid (5); a delivery means (3,4,7) for delivering the conducting fluid to the surface of the radome prior to a lightning strike; a control means (1,2) for controlling the delivery means; and means for directing the conducting fluid across the outer surface of the radome thereby providing a conductive channel for the passage of electrical current resulting from a lightning strike and dissipating said current without damage to the radome. The apparatus allows lightning protection to be deployed in response to a change in atmospheric conditions indicative of a high probability of lightning strike and removed when the danger of lightning strike has passed.

Abstract: Spark-resistant structure for use with aircraft, including a sheet-shaped external element made of a composite material with an exterior face bearing an electrically conducting surface layer for dissipating lightning energy. The external element also has an interior face. The structure further includes a sheet-shaped internal element with exterior and interior faces. The interior face of the external element is least partially superimposed on the exterior face of said internal element. Each element has holes which are aligned with each other. The structure also includes a fixing structure for holding the elements together in a fixed position passing through the aligned holes and forming an alignment. The fixing structure electrically contacts the conducting surface layer. Additionally, a first electrically conducting strip is positioned under the conducting surface layer of the external element, and it extends longitudinally in a direction of the alignment of the fixing structure.

Abstract: A structural joint for the transmission and control of high current flows in a carbon fiber or carbon fiber hybrid composite structure, said joint including at least two composite structures comprising a multiplicity of resin bonded carbon fiber plies, an adhesive applied there between and capable of conducting high currents said adhesive comprising a conductive carrier film comprising carbon fibers, wherein the electrical conductivity of the adhesive is comparable with that of the adjacent composite structures.

Abstract: A spacecraft includes a spacecraft base structure having an externally facing, electrically conducting spacecraft surface, with the spacecraft structure including a solar cell array. A grounding structure has an externally facing, electrically conducting plasma grounding surface, and an electrical ground extends between the plasma grounding surface and the spacecraft base structure. In space, the spacecraft is oriented with the plasma grounding surface facing the sun. Electron photoemission from the plasma grounding surface balances electron charging of that portion of the spacecraft surface that does not face the sun, preventing electrical charging of the spacecraft relative to the plasma environment.

Abstract: An aircraft surface for use on composite structure. The detail surface includes a conductive foil, a conductive double pulled expanded screen, and an adhesive for joining the conductive foil and screen to a composite material. The conductive screen is layered between the conductive foil and composite structure, providing electrical contact between the foil and the composite structure.

Abstract: The subject of the invention is an element made of composite material comprising an organic matrix which is reinforced with mineral or organic fibres, as well as at least one assembly with partial superposition of at least two electrically conductive elongate members, which assembly is essentially embedded in the matrix so as to ensure electrical continuity through the element, at least one junction piece, with a conductive coating or made of a conductive metal or alloy, being interposed between superposed portions of said elongate members of each assembly and held in permanent contact with these portions in the composite material by soldering, which links the piece to the elongate members and is preferably carried out during the heat treatment for forming the composite element.

Abstract: A cowling assembly for a vehicle comprises a general external surface having secured to or adjacent thereto, an elongate lightning diverter element which, at least when subjected to a high electric field, is electrically conductive, wherein a portion of the diverter element is arranged to project from the general external surface.

Abstract: The present invention provides a method of fastening an outer composite aircraft skin (12) to an inner substructure (14), which may be the wall of a fuel tank. The method includes the steps of incorporating an electrically conductive layer (26) in an outer surface of the outer composite skin (12), inserting a bolt (11) through the electrically conductive layer (26) and the outer composite skin (12) and through the inner substructure (14), securing the bolt (11) by means of a nut (22) directly or indirectly engaging the inner surface of the inner substructure (14), and applying insulating material (34) over the head (16) of the bolt.

Abstract: A lightning strip particularly for protection of aircraft radomes has an attaching face adapted to be attached to the surface to be protected from lightning and an exposed face. The strip is made of a thermoplastic polymer filled with conducting particles. It has a terminal designed to ensure grounding that is shaped by heating and molding to match the shape of the head of a screw. The greatest height of the strip is greater than the thickness of a layer of water or ice that could cover the surface to be protected in wet weather conditions, namely approximately 2.5 mm or more.

Abstract: The installation for removing electrostatic charge and passing lightning current between a conductor of each blade of the rotor and a metallic part of the hub comprises at least one conductive member integral with the member for linking the blade to the hub in its angular deflections, and in electrical continuity with the conductor of the blade and held elastically in permanent contact with a conductive terminal integral with the hub and in electrical continuity therewith.

Abstract: An anti-spark structure includes first and second elements of composite material which are at least partially superimposed and assembled together with a screw and nut. The nut has a recess which defines a storage chamber for storing gases formed at the interface of the screw and the elements. A passage is provided in the structure for allowing gases stored in the chamber to escape from the structure.

Abstract: An electrically conductive bridge is formed over a non conductive joint between two or more adjacent electrically conductive panels. The bridge provides a continuous conductive path between the panels. In an exemplary embodiment, the panels form part of a shield against electromagnetic and/or lightning strike energy. The bridge is formed by taping an expanded conductive mesh over exposed conductive portions of the panels and applying an epoxy adhesive. During a following cure cycle, vacuum compression is applied. The expanded mesh of the bridge has an out-of-plane cross sectional configuration which remains in contact with the panel conductive portions during cure so that when the adhesive has cured, the bridge mesh and the panel conductive portions are held in contact with each other.

Abstract: A laminated window includes at least one rigid external substrate (5) and a sheet made of flexible plastic material (6) which is adjacent to the substrate (5). The window is equipped with an electrostatic protection circuit which is capable of dissipating the charges which have accumulated on the external sheet (7). This circuit includes conducting elements (2) which cross through at least the substrate and at least one part of the sheet made of plastic material (6). The conducting elements (2) are connected to a collector element (3) which is connected to the ground (4) and embedded in the sheet made of flexible plastic material (6).

Abstract: An elongate member is coupled by a socket at one end to the aircraft surface, whilst a tip forms its other end. The electrical resistivity of the elongate member, tip and coupling is equal to or greater than 10.sup.2 ohmmeter; and are preferably molded from a high temperature thermoplastics material having an electrical resistivity equal to or greater than 10.sup.16 ohmmeter. The plastics material is selected from the group comprising polyetherimide, polyethersulphone and polyetheretherketone. The material of the tip is provided with an embedded aligned array of carbon or silicone carbide fibers while the other parts of the discharger are loaded with carbon black or coated with the same thermoplastics material loaded with 4% by weight carbon black. The adhesive used to mount the socket has an electrical resistance between 5 to 10K ohms, while that of the socket is between 5 to 10M ohms, that of the elongate member between 20 to 100M ohms, and that of the tip is between 2 to 5 ohms.

Abstract: Lightning strike protection for an aircraft or part of an aircraft is provided by mounting metal (aluminium) rods adjacent but spaced from the inner surface of the aircraft wall. The rods are provided with ball joints from which extensions through the wall stand proud of the aircraft outer surface and within the material of static dischargers. The rods are coupled to bus bar which run the length of the aircraft in turn are coupled to lightning strike dischargers (again in the form of metal rods carried on but spaced from the wall of an aircraft and having extensions which pass through the aircraft wall). The application of the lightning strike protection system to radomes, antennas, pitot tubes carbon fiber reinforced plastics structures is discussed, in the former two cases metal rods being provided to extend in the null field of a device within the radome or the antenna.

Abstract: A lightning shield comprising a fiber reinforced plastics laminate (13, 14), a fixed leading edge structure (12) and an aircraft wing (1) comprising said laminate shield are provided. The laminate shield comprises a series of laminae (21, 22) of fibre reinforcing material held together by plastics matrix material, the laminate including a layer of electrically conductive material (19) interposed between an outer lamina (21) and its next adjacent lamina (22) for conducting lightning current attaching to the laminate to conducting fasteners (31, 32) passing through the laminate (13, 14).

Abstract: An antisparking structure, in particular for aircraft, comprises two components made of composite electrically conductive material which overlie each other at least in part and which are assembled together by using an electrically conductive screw having a countersunk head. A conduction-improving arrangement is provided for improving the conduction of electricity between the overlying portions of the two components. Electrical insulation is provided for electrically insulating the screw from the second component, at least in the vicinity of the nut. Thus, when lightning strikes the head of the screw, the lightning current flows between the screw and the first component, and then between the first component and the second component through the conduction-improving arrangement, without there being any arc between the nut and the second component.

Abstract: A structural component exposed to lightning strikes comprises a bonded assembly of a first component part (18) which has a cellular structure and a front face (20) and a second component part (22) extending across the front face (20) of the first component part (18), the second component part (22) comprising an electrically conducting first sheet (23), an electrically non-conductive second sheet (25) at the rear of the first sheet (23) and a fibre reinforced composite third sheet (26) at the rear of the second sheet (25) and positioned between the second sheet (25) and the front face (20) of the first component part (18). In one form, the electrically conducting first sheet (23) is a non-ferrous metal or metal alloy expanded foil, the electrically non-conducting second sheet (25) is a glass fibre fabric, the third sheet (26) is a carbon or graphite fibre reinforced composite sheet and the first component part (18) is an aluminium alloy honeycomb core.

Abstract: A device for dissipating and discharging undesired electric charges, especially from airplanes. The device is formed from nonmetallic conductive material, such as carbon loaded plastic, and comprises a number of regions having varying conductivities. A region at a first end where the device is connected to a mass to be discharged has a lower conductivity than a region at a second end. The device includes a coating comprised of insulating material, which coats the entire surface of the nonmetallic material except for a portion of the nonmetallic material on the second end of the device. A magnetic flux is created which pulls charges from the mass through the device. The charge is in part dissipated in the nonmetallic material and is in part discharged into the air through the exposed portion.

Abstract: Highly conducting lightweight hybrid materials are obtained by weaving strands of carbon or graphite fibers into a 2-dimensional fabric-like structure, depositing a layer of carbon onto the fibers of the fabric-like structure, heating the fabric-like structure to graphitize the carbon layer and intercalating the graphitized carbon layer. Composite materials for use in lightning strike protection are composed of at least one layer of the highly conducting lightweight hybrid material and at least one layer of traditional composite materials.

Abstract: An EMI shield is disclosed for providing EMI protection. The shield is lightweight, and easily moldable into complex shapes, having conductive mating surfaces provided on opposite sides thereof. The clean, highly conductive mating surfaces are part of an embedded aluminum wire mesh sandwiched between at least two face plies which add strength to the shield. By sandwiching the metal mesh alternately with a nonporous tape, and a barrier tape ply, clean conductive areas can be provided on either side of the shield, easing attachment to adjacent structures. During curing, the tapes prevent direct resin inclusion into the metal mesh. After curing, the nonporous tape is removed to expose the clean, highly conductive mating surfaces.

Abstract: Composite assemblies prepared from thermosettable matrix resin-impregnated fiber-reinforced prepregs, conductive metal screens, and film adhesives are provided which do not develop microcracks after extensive thermal cycling. The composite assemblies are particularly useful in the manufacture of vehicles in the transportation industry, especially aircraft.

Abstract: The risk of electrocution by first contact with a hovercraft is eliminated by first establishing an alternate path for electric charge between the hovercraft and earth ground via an electrically conducting liquid stream.

Abstract: A lightning resistant composite structure, particularly for aircraft, in which a composite skin panel, for example of carbon fibre, is attached to an inner composite structure by one or more lightning resistant fastener assemblies. The fastener assembly comprises a nut and bolt, the bolt being in good conductive contact with a conductive sleeve engaging the skin panel and a non-conductive sleeve engaging the inner structure. The nut is contained within a capped nut assembly located to the undersurface of the inner structure.The non-conductive sleeve and the capped nut assembly isolate the inner structure from the effects of lightning strike, the conductive sleeve providing a high quality conductive interface between the bolt and the skin panel. By this means adverse penetration of lightning current into the inner structure is prevented.

Abstract: A lightning eliminating device for reducing the possibility of thunder strokes comprises a supporting base used for fitting semi-conductor rods, and a plural of semi-conductor rods fitted outwardly on the said base and having an elevation-angle or parallel with the ground reference, the two adjacent semi-conductor rods being electrically connected at the ends and separating from each other at the other ends at such a distance as will not cause a break-down voltage greater than the surface-wise flashover voltage generated on a single semi-conductor rod by thunder clouds. The semi-conductor rods may be made of the single variety of resistance material having a proper mechanical strength, or epoxy resin bars coated with semi-conducting materials such as zinc oxide, carbon black and resin. Even when there is a thunder stroke, the lightning eliminator will emasculate a strong stroke and reduce thunder current passing into the ground by 99%.

Abstract: A device for shielding composite material surfaces of aircraft from the destructive forces associated with lightning strikes and for protecting avionics from electromagnetic interference (EMI) and radio frequency interference (RFI), is provided, consisting of a thin metallic foil having uniformly spaced polygonal apertures formed therein. The polygonal apertures are so shaped as to provide at least one axis along which the shield material can expand or lengthen, permitting the shield material to better fit the irregular or compound curved surfaces found on aircraft. The foil shield can also be used to protect the filler material used between joints and to repair breaks and openings formed in the aircraft surface. When fashioned out of aluminum and applied to a composite material, such as graphite epoxy, the shield may be plated with nickel to prevent galvanic corrosion caused by the contact between dissimilar materials. When manufactured from copper the shield provides a solderable surface.

Abstract: A sealing tape for sealing the gaps between the edge of an opening in an aircraft fuselage and the lid closing said opening comprising a sealing tape that is a one-piece porous polymeric material having a relatively wide flat portion and a narrower enlarged bulb portion. In addition, the porous polymeric material may be filled or plated with metal powder or filings so that the one-piece sealing tape is rendered conductive.

Abstract: A method and apparatus for grounding multi-layer insulations (MLI) by electric contact, of either of each layer with the other or of all the layers with the underlying structure by means of one or more points of attachment of mechanical type. This makes it possible to simplify the construction procedure and increase the reliability.This method is essentially carried out in the following manner: The layers (FIG. 1) which form the multi-layer insulations (6), (7) (8) are metalized on both faces and have holes (9) which are also metalized. All layers are contacted with each other and with a part of the attachment system (3) which is also electrically conductive.The other part of the attachment system (2) is positioned on the structure (1) in such a manner as to permit the passage of electric charges. By contacting the two parts of the attachment system (2) (3), the multi-layer insulation is grounded with the structure.

Abstract: Two sets of filaments (38, 72) are mounted on opposite sides of a discontinuity (6) between a movable or removable panel (4) and adjacent outer skin portions (2) of an aircraft. The filaments (38, 72) have retracted positions in which they are out of engagement with each other. With the filaments (38, 72) retracted, the panel (4) is moved into its use position flush with the outer surface of the skin (2). The filaments (38, 72) are then extended into the discontinuity (6) by a mechanism, such as a cam-ratchet (44) or an inflatable bladder (68). The extended filaments (38, 72) interdigitate to seal the discontinuity (6) and simulate a solid surface across the discontinuity (6).

Abstract: The invention is a flush head fastener for joining two or more structural elements together. The structural elements have a fasterner hole therein with one of the structural elements being countersunk to accommodate the head of the fastener. The fastener includes head and shank portions and a layer of material joined to the top of the head of the fastener which can readily be deformed to fill any gaps between the head and the countersink. Thereafter, the excess material can be removed leaving an aerodynamically smooth surface. The surface also will have no electrical discontinuities. The procedure for installing the fastener includes the steps of (1) providing two or more structural elements having a countersunk fastener hole therein (2) thereafter the fastener is installed in the hole (3) the layer of material is deformed so as to fill any gaps between the head of the fastener and the countersink, and (4) thereafter, excess material is removed leaving a smooth external surface.

Abstract: A method and apparatus for discharging electric charge accumulated on an object tht expels an electrically conductive gas flow, such as a jet engine, a rocket, or a helicopter or aircraft with an internal combustion engine. The system has an electrical shield surrounding a portion of the gas flow, and an electrode for imposing an electric potential in the shielded gas flow. A servo controller measures the accumulated charge at a point on the object and creates a control signal responsive to the rate at which charge is accumulating. The servo controller imposes an electric potential on the electrode, and hence the gas flow, of an amount and polarity determined by the rate and polarity of charge accumulation. In so doing, the electrode accelerates charges of opposite polarity in the conductive gas away from the object, and deaccelerates like charges towards the object, where they tend to cancel accumulated charges, thus discharging the object.

Abstract: Two composite structures are fastened together using an electrically conductive, threaded fastener. The composite structures have insulating surface regions and inner regions which contain conductive fibers. The threaded fastener is provided with large contact areas through the inner regions to facilitate discharge of high curent densities from the composite materials while minimizing localized heating. This significantly increases the life of the composite material.

Abstract: An integral lightning protection system and method for its use with an aircraft graphite epoxy structure. If a repair is to be made to an aircraft composite structure, the hole to be repaired is first cleared of broken composite material and replaced with a bonded adhesive patch. Over the patch and conformal to the surface of the aircraft composite structure, a dielectric layer is placed, and over the dielectric layer, at least one metal-plated graphite fiber fabric ply is placed. Where fasteners are inserted through an aircraft composite panel, the heads of the fasteners are left flush with the outer surface of the composite material, and the composite material and fastener heads are adhesively covered by a dielectric cover. Thereafter, at least one metal-plated graphite fiber fabric ply is placed over the dielectric layer. Subsequently, either structure may be given a primer and paint coating.

Abstract: A volume of gas is enclosed by a cap around a fastener that is through a composite structure on an aircraft. The gas provides spark suppression for arcing that may occur between the composite structure and the metal fastener during a lightning strike. The volume of gas is sufficiently large to absorb the energy of small, very hot particles of graphite, epoxy, etc., that may be present resulting from arcing. High-pressure gas regions between the fastener and composite member vent to the larger volume of gas and are absorbed. This provides effective spark suppression for particular areas in an aircraft, such as a fuel tank, etc.

Abstract: A method for conditioning a composite structure to have an increased sparking current threshold. The method calls for the treatment of the joint in a composite structure by injected currents for predetermined periods of time at a sequence of voltages which are initially less than the present sparking voltage threshold of the structure. The voltage levels can be increased during the treatment to be greater than the sparking voltage threshold of the original structure. If the composite structure contains fasteners, the sparking voltage threshold can be conveniently increased by injecting the current from a timed voltage source through a variety of pairs of the fasteners.

Abstract: A fastener for use with aircraft structures comprising composite materials has improved electrical characteristics designed to reduce damage by lightning strikes. The fastener comprises separate nut and bolt portions and a cage member (4, 1, 6). The nut (4) and the head portion of the bolt 1 both have beveled edges which in use are countersunk in the composite materials to enhance electrical contact between the fastener and aircraft structural members (2, 5). The nut (4) is captively mounted inside the cage member (6) and is moveable, within pre-determined limits, inside the cage (6) so that it may be axially aligned with and the bolt screwed therein, thus compensating for any initial non-aligment of the nut (4) and bolt (1) due to a complex shape of the aircraft structure necessitated by aerodynamic or other considerations.

Abstract: A means for conducting an electrical charge from one nonconducting article having a conductive layer thereon to another article across a joint, wherein the means is displaced from the mechanical interface of the joint. This reduces joint stresses from electrical currents.

Abstract: A charge control apparatus for a flightcraft uses an inherent droplet charging mechanism to remove unwanted charge from the distal portion of a reference body mechanically connected to, and external to the craft, and a driven ion attachment mechanism to adjust the potential of the craft to that of the reference.

Abstract: A method for providing a junction between metal fittings in a composite structure is disclosed which reduces susceptibility of the junction to electrical arcing during a natural lightning strike. A bore is formed in the composite structure which has a diameter approximately equal to a portion of the metal fitting. In a first embodiment, the bore is provided with internal threads. The metal fitting is provided with cooperative threads which engage the bore to form an interference fit. The metal fitting is continuously rotated into the bore to generate substantial heat therebetween until the metal fitting is fully seated. A substantially void-free interface between the metal fitting and the composite structure results which is preconditioned to a lightning strike. The junction is capable of withstanding current flows of up to 30 kA for the particular part described without the occurrence of electrical arcing.

Abstract: An improved composite structure is disclosed for a lightning protective skin member of an aircraft vehicle surface. The skin member includes first and second graphite panels separated by a wire grid. The grid enhances the strength and elasticity of the skin member while also providing a conductive path for lightning current. Each of the graphite panels includes a plurality of graphite plies laminated with an adhesive, preferably epoxy.

Abstract: A device for dissipating static charge collected on the surface of an aircraft window having a plurality of electroconductive film elements on the outboard surface of the aircraft window. The elements are electrically interconnected and grounded such that charges accumulated by the film elements passed there along to the ground. An electrical window heating system may be incorporated into the plies of the window.

Abstract: Lightning protection apparatus for an exterior structural surface includes an electrically insulating protective coating adhered to the exterior surface, and a plurality of conductive particles supported in the coating. The particles are spaced at distances greater than the dimension of the particles in a direction parallel to the surface. The dielectric strength of the coating is thereby weakened by bridging the thickness of the coating with the particles. This enables lightning attachment to occur at a multiplicity of points rather than at one point, thereby reducing interior sparking in an aircraft and minimizing structual damage to the surface of the aircraft.

Abstract: An apparatus for detecting the onset of a potential lightning discharge condition monitors the odd harmonics of an RF signal radiated from a conductive probe (antenna) for fluctuations that are representative of an electrostatic condition-induced corona. In response to the such fluctuations, an output signal representative of the onset of said condition is generated. This output signal may be employed to decouple communication equipment from its antenna until the lightning condition has subsided. In accordance with a further aspect of the present invention, there is provided a device for discharging static charge accumulation from a moving body (e.g. an aircraft) which is comprised of at least one discharging conductive wick arranged to be affixed to the trailing edge of a wing, so that charges may flow from the aircraft into the wick and be discharged therefrom.

Abstract: This invention relates to a seal for an aircraft canopy having a compressible, resilient core and is encapsulated by a low-density, electrically conductive polymeric tape and to a method for making the seal.

Abstract: An apparatus provides lightning protection for the radome of an aircraft, or the like, by providing an electrically discontinuous path having a plurality of separated electrically conductive segments that upon exposure to a high voltage field, form an inonization channel in the air above the segments. The conductive segments are so formed that the gap separating adjacent segments is narrower along the outer, exposed surfaces of the segments than is the case between surfaces of the adjacent segments anchored to a dielectric material. Such a design ensures the electrical separation of adjoining segments while permitting the breakdown voltage between adjacent exposed surfaces to be minimized.

Abstract: A lightning protection repair system for graphite epoxy structures. An aircraft graphite epoxy structure is repaired by fastening a repair plate over the hole to be covered, followed by a dielectric sheet covering the outer surface of the metal repair plate. An electrically conducting lightning diversion sheet, conforming to the outer surface of the repair plate, is fastened to the repair plate through the dielectric sheet. The edges of the lightning diversion sheet are bent toward the outer surface of the aircraft graphite epoxy structure to be adjacent or touching its outer surface. Sealing compounds can be used around the repair plate to prevent moisture intrusion, and the repair can be faired into the aircraft graphite epoxy structure by means of a fairing compound.

Abstract: Apparatus and method for efficiently and economically reducing and removing static charge from a surface of a dielectric material. One device is a window assembly comprising a window having an outer surface and a perimeter. The outer surface comprises a dielectric material. A frame is around the window and houses the perimeter. The frame has an outer surface which terminates along the outer surface of the window at a border. At least one corona point is attached to the window assembly proximate the border. Means for grounding the corona point is in electrical communication with the corona point. The number of corona points required to dissipate the static charge is minimized by a method that locates arc attracting regions and installs the corona points proximate these regions. Also provided are a corona point assembly and a kit comprising (1) the corona point assembly and (2) means for attaching the corona point assembly to the frame.

Abstract: The conductivity of the outer surface of skin (2) is enhanced by providing an outer layer of conductive material. The outer surfaces of each external metal fastener (8) and the skin around it are covered with a patch (6) of a strongly dielectric material. Patch (6) is dimensioned to cause current flow from lightning strikes to diffuse to a current density below an arcing threshold before reaching fastener (8). Preferably, further protection against arcing between the outer surface of skin (2) and metallic fasteners and fittings is provided by coating with a dielectric any surface portions of such fasteners and fittings that contact the skin (2) or an integral continuation thereof. When load requirements permit, fasteners made from dielectric materials are used instead of dielectric coated fasteners.

Abstract: A multilayered electronics protection system includes a first ablator layer providing thermal protection that is sprayed on to a non-metallic surface of an electronics enclosure. A second ablator layer comprised of highly conductive material is sprayed on to the first ablator layer and provides protection against strategic environmental threats.

Abstract: A composite material skin (42) is attached to a composite material support structure (26) by a plurality of metal lock bolts (64). A foraminous metal material (44) is embedded in the matrix of the outer layer of the skin (42) and positioned outwardly of reinforcing graphite fibers. The metal (44) is preferably copper in a knitted, woven, or expanded metal configuration. The metal (44) is in direct electrical contact with the graphite fibers to disperse current throughout the skin (42) and is sufficiently proximate to the lock bolts (64) to divert current away from the bolts (64). Each bolt (64) is surrounded by an expanded sleeve (74) and fits tightly within the sleeve (74) to provide good electrical contact between the bolt (64) and the skin (42). The inner end (70) of the bolt (64) has parallel grooves (72) thereon, and a collar (76) is swaged onto the end (70) to prevent arc plasma from escaping into the interior of the aircraft.