Statistical Simulation of FM Interference to the Instrument Landing System

Contrary to the popular views, air travel has been the safest compared to other surface transportation (automobile & railroad) in terms of casualty of passengers. This is mainly due to the vigilant pursuit of safety margin in the design of Air Traffic Control and Navigation (ATCN) system. However, the rising demand of air travels requires us to review the safety factor affecting all phases of aircraft operation. In order to determine the operation benefit of any aircraft instrument landing system (ILS), we need to take into consideration of all factor that could jeopardize the successful landing of any aircraft. The concept of "risk" probability, i.e. the probability of an unsuccessful instrument guided aircraft landing, needs to be applied to ILS. This thesis concentrates on the specifics of such uncertainties of a successful landing. We will be mainly concerned with unsuccessful landings due to unwanted electromagnetic interference from nearby Frequency Modulated radio stations. To begin with, we formulate the exact path of electromagnetic wave propagation between the FM transmission towers and the receivers located on the landing aircraft. After obtaining the relationship that guides the course of interference, we then translate each parameter into a random variable with known distribution in order to more accurately model the statistical nature of events. To keep the results consistent, normal algebraic operation were replaced with corresponding statistical operation on the relevant distributions. All calculations were minimized before being implemented for real time analysis in the simulation program. The simulation program, unlike many other programs before that only give a deterministic answer of the interference level compared with a preset threshold, yields instead a measure of the probability of any interference occurring. Running the simulation program with the same inputs, we could get a feel of how the level of interference is related to the probability risk in landing. Thesis Supervisor: Dr. Eric Yang