What is the main difference between RNAV and RNP?

The distinction between RNAV (Area Navigation) and RNP (Required Navigation Performance) primarily hinges on the performance requirements associated with RNP operations. RNP is a more stringent standard that incorporates performance monitoring and alerting capabilities.

Specifically, RNP requires that the aircraft’s navigation capability is not only accurate but also continuously monitored, which ensures that it meets specific accuracy levels throughout the flight. This is where the performance check comes into play; it mandates that an aircraft's navigation system be regularly assessed to ensure it can maintain the required performance levels during operations.

In contrast, while RNAV does include accuracy standards, it does not necessarily stipulate the same level of monitoring and performance checks as RNP. Therefore, in the context of the choices given, stating that only RNP1 has a performance check requirement aligns with the fundamental differences in expectations for these two navigation systems. This focus on ongoing performance checking is essential for the safety and reliability associated with RNP procedures, setting it apart from standard RNAV practices.