Assessment of a coaxial return Direct Drive setup for HIRF testing

The Low Level Direct Drive (LLDD) test technique is applied to aircraft in accordance with ARP5583A in order to determine the transfer function for electromagnetic compatibility stress versus strength assessments of whole system against equipment level test results. The LLDD technique when used to recreate a free space illumination environment for HIRF (High Intensity Radiated Fields) requires considerable post-test analysis to gain equivalence. Eigencurrent analysis has been used to compare three specific modelling setup scenarios for a generic fighter aircraft. Lightning attachment, plane wave illumination and a LLDD current injection were compared; with the results confirming that the direct drive method suits indirect lightning tests but struggles to produce the current distributions required for HIRF environment equivalence.