Modelling the Magnetic Influence of a Jet Aircraft : A study on the magnetic interference of an aircraft configuration and its effect on a magnetometer

Abstract: Aircraft have been used for the detection of submarines since World War II. The basic concept is to attach a sensor to the back of an aircraft. Since the aircraft is a moving metallic object, it is bound to generate a great deal of interference. Because of this, mathematical models and software have been developed to help filter out this interference and thus make the detection of the submarine easier. Normally, the engines of the aircraft are placed on the wings, quite far away from the sensor. However, for a maritime patrol system in development, the jet engines are placed at the rear of the airframe, generating the necessity to study whether or not they affect the performance of the sensor, which is the purpose of this thesis.   Several models were created, tested and simulated for the airframe and jet engines. One of each of these were then combined to create a simulation model for the complete aircraft. A jet engine model that included rotating machinery -- a possible source of magnetic interference -- was also created, but could not be added to the model for the complete aircraft. The magnetic interference was mathematically compensated for, removing the static interference, but not the interference during manoeuvres. The jet engine part of the complete aircraft model did not seem to generate a significant amount of magnetic interference compared to the airframe. An electric dipole, representing a submarine, was then added to the simulation. The data from that simulation was put through the mathematical model and distortions of a few~nT were noticeable during straight courses. The jet engine model that included rotating machinery yielded different results compared to the jet engine model in the complete aircraft model. They seemed to contain signals of higher frequency, which were however not detected by a frequency domain study or present during straight courses. It was thus concluded that using this particular engine model the submarine could probably still be detected if the course of the aircraft was kept straight, though further research is needed with more advanced models for the engine, in particular with regards to the rotating machinery.