TABLE OF CONTENTS Avionics are electronic equipment designed specifically for mounting in aircraft. In military and commercial aircraft they typically are packaged in modular metal boxes that can easily be disconnected and removed for replacement or maintenance. Avionics equipment includes radio and radar transmitters and receivers and navigational equipment such as GPS receivers, radar beacons, and inertial guidance systems. Aircraft require special antennas that conform to their fuselages or are streamlined to minimize air resistance or drag. Radar antennas typically are mounted behind plastic cones at the nose of the aircraft or in streamlined domes under or on top of the fuselage.
Distance-measuring equipment (DME) is a two-way aircraft ranging system that includes an airborne interrogator and a ground-based transponder. The airborne interrogator transmits 3.5- ?s, 1-kW pulses at the rate of 30 per second on one of 126 channels which are 1 MHz apart in the 1025- to 1150-MHz band. The transponder replies with similar pulses on another channel 63 MHz above or below the interrogating channel. The signal received by the aircraft is compared with its transmitted signal, their time difference is derived, and the distance is computed and displayed. There are about 2000 ground stations worldwide. Tacan is an enhanced military version of DME.
The traffic collision and avoidance system (TCAS) for aircraft is based on secondary surveillance radar (SSR). It consists of microwave-frequency transponders, computers, display screens, and voice alarms on each aircraft...
