What additional function distinguishes Required Navigation Performance (RNP) from the basic Area Navigation (RNAV) description in the material?

### Why this is right RNP is described as RNAV with a system that monitors navigation performance and alerts the crew if the required accuracy limit is exceeded. That monitoring and alerting function is the distinguishing feature asked for. ### The concept Accuracy describes how closely the estimated position or path meets the required tolerance. RNP allows the crew to know the system’s current performance and receive an alert when it no longer meets the required limit. PBN sets the specifications that govern RNAV and RNP operations. Some advanced RNP systems can also fly radius-to-fix paths, but that is not the basic distinction requested here. ### The other options - **B. A requirement to navigate only by visual landmarks**: this describes pilotage, not RNP. - **C. A guarantee that all satellite signals are available everywhere**: RNP monitoring does not guarantee satellite availability. - **D. A replacement of all onboard navigation sensors with ground antennas**: RNAV may combine approved sensors; RNP adds monitoring rather than replacing them with ground antennas. ### Terms - **Required Navigation Performance (RNP)**: RNAV with monitoring and alerting for required navigation performance. - **Area Navigation (RNAV)**: navigation using suitable sensors to determine position and follow a route. - **Performance-Based Navigation (PBN)**: specifications and standards for RNAV and RNP operations. ### Remember RNP’s defining addition is performance monitoring with an alert when requirements are not met.