Phase II Demonstration Test of the Electromagnetic Reverberation Characteristics of a Large Transport Aircraft

This report describes the second phase of an investigation into the electromagnetic characterization of a typical large commercial aircraft. The test aircraft, the same one used for the Phase I test, was a decommissioned Boeing 707-720B. A major objective was a comparison of data obtained with band-limited white Gaussian noise (BLWGN) excitation and data obtained with continuous wave (CW) excitation and mechanical mode-mixing. Five aircraft areas were instrumented with probes. A common test article (CTA), developed by Naval Surface Warfare Center, Dahlgren Division, was tested in several locations in the cockpit and avionics bay. Test areas were excited from 100 MHz to 6 GHz using discrete or swept-frequency CW signals. Aluminum foil tuners provided mode-mixing. Normalized cavity power density was the ratio of received power to input power. Stirring ratios in several areas were determined and limited cavity-to-cavity coupling was measured. Power received by instrumented boxes and the CTA was measured using discrete and swept-frequency CW. Mode-mixing for the areas excited with BLWGN was in 2-, 10-, and 50-MHz bandwidths; four measurements were obtained for each cavity, frequency span, and bandwidth combination. Pulse decay measurements provided a direct measurement of the cavity quality factor (Q). External excitation from three aspect angles provided external-to-internal shielding effectiveness (SE) measurements. Limited narrow pulsewidth external and internal excitation of two areas was performed. Time domain analysis of received power yielded external-to-internal SE and cavity Q.