An Investigation into the Screening Performance of Aircraft Access Panels and Doors

The work reported in this paper was initiated in order to compare the electromagnetic (E.M.) shielding performance, of hinged, quick release access doors and bolted access panels manufactured in carbon fibre composite (C.F.C) with identical structures manufactured traditionally in aluminium alloy. The experiment was designed such that aperture coupling around the door or panel edge and diffusion coupling through the door or panel material were the only two mechanisms investigated. The experiment was carried out in a shielded room using computer control of the instrumentation and data collection. Results were "smoothed" in order to remove the resonance effects of the shielded enclosure, this made differences between various results clearer. The electric field shielding performance was measured over the frequency band of 50-100MHz The performance of bolted panels was demonstrated to be adequate in the case of metal or C.F.C., with the exception of C.F.C. / honeycomb sandwich panels. Quick release access door performance, however, in the cases of both C.F.C. and metal was inadequate and design changes would be required to improve electrical contact to the surrounding structure around the periphery of the door. In addition, metallisation of the inner or outer surface is required. The magnetic shielding results obtained over a frequency band of 1-250 MHz demonstrated that only metallised C.F.C. and metal bolted panels exhibit sufficient shielding performance. C.F.C./honeycomb/C.F.C sandwich panels with either an aluminium or nomex honeycomb had a particularly poor magnetic shielding performance. Quick release access doors of all types were shown to have very poor magnetic shielding performance due to the electrically insulating weather seal.