Abstract
Avionics system's function for an air transport mission is analysed. The starting point for designing a Avionics system is a clear understanding of the mission requirements and the requirement allocation by the top level aircraft system. Therefore, the analysis begins by making a top-down analysis to the aircraft missions. The baseline mission is divided into segments, and each segment is subjected to a detailed analysis to establish the requirements for the Avionics system. Special attention is given to capture the key aspects of interfaces, and to incorporate them into the design.