Extending Required Navigation Performance to IncludeTime based operations and the vertical dimension

In this manuscript, we derive a concept for a four dimensional Required Navigation Performance by extending the existing lateral RNP into the vertical and along-track dimensions. Based on the target level of safety desired by ICAO and traffic on a given route, an along track requirement can be formulated for the traffic using the airway. In the vertical, accuracy requirements at the 99.5% level are already specified within the performance based navigation concept, however monitoring and alerting is not foreseen. Here, we suggest a monitoring technology based on satellite navigation that can also be used to ensure vertical separation in RVSM airspace.