Hazard analysis for ADS-B backup performance in Non-Radar and peripheral radar airspace

This paper presents an alternative methodology for deriving ADS-B performance requirements (NIC, NACp, SIL) for backup use in Non-Radar (NRA) and peripheral Radar airspace based on Hazard Analysis methodology proposed by the FAA in recent Safely Management System (SMS) documents. The analysis methodology potentially allows the use of secondary positioning sources such as Flight Management System (FMS) based RNP avionics as well as GPS avionics for primary means ADS-B surveillance. However, for backup ADS-B sources coded as SIL=2 sensors, i.e. with probability of undetected signal-in- space and avionics positioning errors exceeding the position error containment <;= 10^-5 per hour, allowed separation errors between aircraft must satisfy strict criteria to assure Minor hazard severity level. Similarly, separation errors for data sources such as GPS sensors coded as SIL=3, i.e. with probability of position error containment <;= 10^-7 per hour, must satisfy weaker performance criteria to assure Major hazard severity. Specific NIC and NACp performance criteria are derived in this paper for SIL=2 and SIL=3 sensors for 3 nm Terminal area and 5 nm En-Route radar-like separation standards in NRA airspace to illustrate the proposed methodology. For GPS avionics with SIL=3, minimum integrity and accuracy (NIC and NACp) requirements are equivalent to those previously specified in the NRA SPR document [1] (RTCA DO-303). For SIL=2 sensors, this paper provides generic recommendations for minimum backup positioning NIC and NACp performance, and for separation assurance with mixed SIL=2 and SIL=3 ADS-B data sources. Two recommendations for future ADS-B standards are also discussed that could potentially reduce NIC and NACp criteria for backup ADS-B surveillance. The recommended performance criteria may be feasible for backup 3 and 5 nm surveillance with existing FMS avionics such as INS/DME/DME positioning systems.