Simulation of Aircraft Electromagnetic Environment to Compute EMC Test Conditions

EMI issues are a stark reality confronting avionics equipment. In an aircraft not only a number of electronic systems operate in a confined space but also the external Electromagnetic Environment (EME) has become very harsh, due to presence of high power transmitters and more significantly lightning associated EM fields. Thus EMC testing of aircraft is a complex and costly undertaking where during testing High Intensity Radiated Fields (HIRF) of magnitudes comparable to actual conditions has to be generated. In recent past an innovative approach has been formulated to make this testing easier to perform, namely Low Level Coupling (LLC) tests. Where transfer functions are computed through simulations that can predict the resultant surface currents and EM fields on & inside the fuselage, which grossly lowers test level magnitudes. Therefore, the testing can be done at much lower levels. However, a calculation of these transfer functions requires intricate 3DEM simulations and is time extensive. So far the transfer functions computed by aviation regulatory authorities are generic in nature. This paper elaborates computation of more specific transfer functions, taking into account the effect of additional factors like apertures and orientation of wires, whereas the original transfer function is dependent on fuselage length only. Results are computed through 3D EM simulations and presented and analyzed.