The Safety Consideration in Civil Aircraft Communication and Navigation System Development

The civil aircraft communication and navigation system primarily provides aircraft position information, navigation, and communication with the outside world for the aircraft. The simultaneous loss of unrecoverable navigation and communication functions is catastrophic, so the aircraft communication and navigation system require high safety. Additional safety measures increase costs, but all development projects are subject to budget and time constraints. Civil aircraft system development must ensure not only safety but also economic efficiency. Achieving this within limited resources and time is a key factor to consider in the development process. This paper outlines the quantitative safety requirements for civil aircraft communication and navigation systems in accordance with civil aviation regulations. It also provides a brief overview of the framework for developing avionics systems in civil aircraft, including the ARP5454A Guidelines for Development of Civil Aircraft and Systems, as well as the safety process involved in development. Next, the functional architecture of the communication system and the navigation system are briefly described, followed by an analysis of the communication and navigation system’s Fault Hazard Analysis (FHA) results. According to the results of the FHA, a system safety assessment is conducted, and the Design Assurance Level (DAL) allocation, probability budget, and bottom-up safety verification are determined using fault tree analysis (FTA). This paper discusses in detail the process and various considerations of DAL allocation, which is closely related to the development cost of communication and navigation systems.