ENG3036: Developing a mathematical model of the lateral dynamics of an aircraft approaching: Simulation Of Engineering Systems Report, UK

Aim
Part 1 of this Simulation of Engineering Systems 3 Assignment involves the modeling, simulation, and validation of an Instrument Landing System (ILS) Lateral Beam Guidance System. This part of the assignment involves developing a mathematical model of the lateral dynamics of an aircraft
approaching using ILS for guidance. This model will be implemented in Matlab code and as a Simulink block diagram.

The responses from the Simulink block diagram will be used to analyze and validate the Matlab model and its associated simulation. This document provides background information about this system, followed by the problem specification for the mathematical model of the system and its simulation. Also, the Assignment Specifications are provided as a step-by-step guide for this part of the assignment.

Introduction
Most major airports have an ILS which can be used for automated or assisted landing of aircraft. Basically, this is a short-range navigational aid that provides azimuth (horizontal) and vertical position information. This assignment involves the development of a simulation of this system for lateral beam guidance as outlined in this document.

Background
The ground-based elements of ILS comprise a localizer transmitter, a glideslope transmitter, and marker beacons. These provide the azimuth, vertical, and distance signals respectively (see Figure 1).

On the aircraft, there is a localizer antenna, a glideslope antenna, an ILS receiver unit, and a marker beacon antenna and receiver. The position of the aircraft relative to the localiser and glideslope is displayed on an indicator in the cockpit and is used to land safely.

The Localiser System
The localiser transmitter is positioned at the far end of the runway which the aircraft is approaching. It transmits on a given frequency in the band 108 MHz to 112MHz. The signals radiate to the left and right of the center line of the runway. The signal to the left is modulated by a 90 Hz component while the corresponding frequency for the signal on the right is 150 Hz. The two signals overlap in the middle. The autopilot uses the stronger overlapping signal region to position the aircraft within the ILS approach corridor.

The Glideslope System
The glideslope transmitter is located near the point of touchdown (threshold) on the runway and transmits on a given frequency in the range 329.3 MHz and 335.0 MHz. The radiated signal pattern is similar to that of the localiser but provides vertical guidance relative to a descent path.

The Marker Beacons
Marker beacon transmitters are located along the approach path and provide 75 MHz signals beamed vertically into the approach corridor. The beacons are located 7.4 km (outer marker) and 1.1 km (inner marker) from the runway threshold. These markers provide distance signals so that the speed of descent can be monitored and adjusted.