Definition
A navigation specification requiring an aircraft to maintain its position within 1 nautical mile of the centerline of the intended flight path for at least 95 percent of the total flight time, with onboard performance monitoring and alerting if that accuracy cannot be met. RNP 1 is typically applied to terminal-area procedures such as departures, arrivals, and transitions.
Plain English
RNP 1 is a rule that says the aircraft's navigation system must keep it within one mile of the planned track almost all the time, and must warn the pilot if it can't.
Context Anchor
Seen on instrument departure and arrival procedures that require a specific navigation capability, especially in busy terminal areas.
Derivation
Required Navigation Performance' names what it is: a performance standard the navigation system must meet. The '1' is the accuracy value in nautical miles. So RNP 1 = navigation accurate to within 1 NM, with the system itself confirming that it is meeting that standard.
Why Pilots Care
It lets pilots fly precise curved paths on departures and arrivals without ground-based navigation aids while the monitoring system protects safety.
Intuition Check
RNP 1 does not mean the route is 1 nautical mile long. It means the aircraft must be able to stay within 1 nautical mile of the intended path, with system monitoring and warning if that performance is lost.
Example Sentence 1
The departure procedure requires RNP 1, so the crew confirmed the aircraft was authorized and the navigation system was performing within tolerance before takeoff.
Example Sentence 2
Because the aircraft met RNP 1 standards, it could use the curved RNAV path instead of flying the longer conventional departure.