Some Electromagnetic Compatibility Grounding and Shielding Considerations in Titanium Aircraft Structures

Abstract

High resistivity of titanium alloys (in the vicinity of 200 microohm-cm) requires special consideration of the role of airplane structure as a current return and as an electromagnetic shield. Experimental data and supporting analysis are presented. Voltage drops due to structure currents are larger in titanium than in aluminum airplanes. Return currents in structure are distributed widely instead of being relatively concentrated. For representative skin thicknesses, magnetic field shielding effectiveness is rather insignificant even at frequencies in the ADF range. Achieving electromagnetic compatibility in titanium airplanes will require greater than previous use of wire rather than of structure returns for susceptible circuits. To obtain a given magnetic field, isolation between a source and a receptor will require greater reliance on physical separation than on intrinsic magnetic field shielding of the structural material.