MODELLING OF DIRECT-STRIKE LIGHTNING COUPLING BY A TRANSFER FUNCTION TECHNIQUE

A transfer function approach is applied to the problem of lightning coupling into internal aircraft avionic circuits. This approach allows a systematic procedure for determining transient levels induced on interior aircraft circuits due to exterior inter-ference fields such PS those caused by nearby or direct-striVe lightning. Unique in the approach used here is the use of a tri-angular patch model for the exterior surface of the aircraft with all points of entry (POEs) closed. A moment method procedure is then used to find the("short circuit* * skin current in the frequency domain. This current interacts with all the POEs, described by either measured or theoretically calculated transfer functions, in a secondary interaction problem to create interior penetrating fields. These interior fields are used to derive distributed voltage and current sources which excite a transmission line model of a wire harness or cable bundle. Further levels of coupling are indicated along with their concomitant transfer functions