Definition
A Required Navigation Performance level specifying that an aircraft must be able to maintain its actual position within 1.0 nautical mile 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.
Plain English
A navigation standard that says the aircraft has to stay within 1 nautical mile of the planned track 95 percent of the time, and the system itself has to warn the pilot if it can no longer guarantee that accuracy.
Context Anchor
Seen on instrument charts and route descriptions where a procedure or segment requires a specific navigation accuracy.
Derivation
"Required Navigation Performance" describes a performance standard rather than a specific piece of equipment. The number after RNP is the lateral accuracy requirement in nautical miles. So RNP 1.0 simply means the required performance is one nautical mile of lateral accuracy.
Why Pilots Care
RNP 1.0 capability determines whether an aircraft can legally fly certain RNAV routes and approaches that require tighter navigation accuracy.
Intuition Check
RNP 1.0 does not mean the aircraft is supposed to fly 1 mile away from the route. It means the navigation system must keep the aircraft’s computed position within 1 nautical mile of the intended path most of the time, and alert the pilot if it cannot.
Example Sentence 1
The terminal arrival procedure required RNP 1.0, so the crew confirmed the GPS was operating normally before accepting the clearance.
Example Sentence 2
Because the GPS met RNP 1.0 standards, the crew could continue the approach in low visibility.