Safety analysis of an automated approach spacing application using ADS-B

This article illustrates new techniques being adopted by RTCA for analysis of the safety of aircraft surveillance applications. The techniques are illustrated using the example flight deck application of approach spacing for instrument approaches (ASIA). The techniques include analysis of the operational procedures, conducting a hazard analysis, and treating identified hazards in a fault-tree analysis. The fault-tree analysis in turn results in requirements on various subsystems that support the operational application. The specific analysis of the approach spacing application results in a requirement that the probability of presenting hazardously misleading information be held to less than 10^-5 per operation. The 10^-5 value represents "major" system criticality, and is a criticality that is considered by avionics vendors to be achievable within reasonable cost constraints. If the benefits of reduced spacing that are offered by the approach spacing concept are significant enough to justify the cost, users may find that it is worthwhile to equip their aircraft with such a capability.