ADS-B Surveillance Separation Error Sensitivity Analysis: Second Edition

The contents of this material reflect the views of the author and/or the Director of the Center for Advanced Aviation System Development (CAASD), and do not necessarily reflect the views of the Federal Aviation Administration (FAA) or the Department of Transportation (DOT). Neither the FAA nor the DOT makes any warranty or guarantee, or promise, expressed or implied, concerning the content or accuracy of the views expressed herein. Abstract Two efforts are currently examining Automatic Dependent Surveillance-Broadcast (ADS-B) separation requirements: a Federal Aviation Administration (FAA) group, titled the Separation Standards Working Group (SSWG); and a joint RTCA/EUROCAE group termed the Requirements Focus Group (RFG). Although coordinated efforts, the SSWG emphasis is on particular issues of concern to the FAA. The different assumptions made by each of these groups are examined, and results are presented in relationship to the different Monopulse Secondary Surveillance Radar (MSSR) reference models used in each comparative assessment. Sensitivity of resulting ADS-B separation requirements to the assumptions and scenarios used in determining these requirements is quantified for both Global Positioning System (GPS) no-fault and fault conditions. A modification to an International Civil Aviation Organization (ICAO) accepted collision risk model was initially used in a comparison to legacy radar surveillance to define requirements for Automatic Dependent Surveillance-Broadcast (ADS-B) support of Air Traffic Control (ATC) separation standards [1]. This model, termed Close Approach Probability (CAP) is the conditional probability that an aircraft pair actually over lap when the apparent distance between them is some given separation. Subsequent experience with this model indicated that a more flexible approach based on the normalized surveillance separation error probability isolated the surveillance requirements from other operational scenario risk factors treated by the usual fault tree risk assessment. When the ADS-B navigation source is in either a fault-free or fault condition, this is termed the Separation Error Probability (SEP) in this document. A weighted combination of these two conditions, termed the Separation Reduction Probability (SRP), is used here to indicate the long term likelihood that a controller will have to deal with a degraded surveillance related problem. Other documents use the term, Surveillance Separation Error (SSE) to refer to both these conditions [2]. The SSE (as well as the equivalent SEP) is defined as the probability that the separation error (apparent separation minus true separation) for two aircraft towards each other is greater than a given value [2]. Two efforts are currently examining ADS-B …