Definition
A statement of the navigation accuracy needed for an aircraft to operate within a defined airspace, route, or procedure, expressed as a number that represents the lateral distance in nautical miles within which the aircraft must remain at least 95 percent of the flight time. RNP also requires that the aircraft's navigation system be capable of monitoring its own performance and alerting the crew if that accuracy cannot be met.
Plain English
A rule that says how accurately the aircraft must be able to follow its intended track, plus a requirement that the aircraft itself can warn the pilot if it loses that accuracy.
Context Anchor
Seen on RNAV and RNP instrument approach charts, aircraft equipment requirements, and procedure notes before flying an instrument approach.
Derivation
From 'required' (what must be met), 'navigational' (relating to determining position and course), and 'performance' (how well a system does its job). The phrase emphasises that the standard is a measured level of accuracy the aircraft must achieve, not just an instruction to fly carefully.
Why Pilots Care
RNP allows aircraft to fly tighter, more efficient paths to runways that lack ground-based navigation aids and supports lower approach minimums in suitable conditions.
Grounding Statement
On an approach requiring RNP 0.3, the aircraft’s navigation system must be able to keep the aircraft very close to the planned path and warn the crew if it cannot.
Intuition Check
RNP does not just mean that navigation is important or that good accuracy is preferred. It is a specific required accuracy standard, tied to onboard monitoring and crew alerting.
Example Sentence 1
The approach required RNP 0.3, meaning the aircraft had to stay within three-tenths of a nautical mile of the centerline at least 95 percent of the time.
Example Sentence 2
ATC cleared the flight for the RNP approach that provided a direct path to the runway without needing traditional ground-based navigation signals.