Definition
A measurable standard of how accurately, reliably, and consistently an aircraft's navigation system can determine and maintain its position along an intended flight path. In modern airspace, navigational performance is expressed as a required level of accuracy (for example, RNP 1 means the aircraft must stay within 1 nautical mile of the intended track 95% of the time) along with associated requirements for integrity, continuity, and onboard monitoring.
Plain English
How well the aircraft can know where it is and stay on the path it's supposed to fly. It's a stated standard the airplane and its equipment must meet — not just a vague idea of being on course.
Context Anchor
Seen in instrument procedure discussions, especially when deciding whether an aircraft can safely and legally fly a published arrival or approach.
Derivation
Navigation comes from older words meaning to travel by ship. Performance means how well something carries out a required job. Together, navigational performance means how well the aircraft carries out the job of navigating, not how fast or powerful the aircraft is.
Why Pilots Care
It determines whether the aircraft can safely use a procedure without violating protected airspace or obstacle clearance limits.
Intuition Check
Do not read performance here as engine power, climb ability, or speed. Here it means the accuracy and reliability of the aircraft’s navigation for the procedure being flown.
Example Sentence 1
Before flying the RNAV arrival, the crew confirmed the aircraft met the navigational performance required for the procedure.
Example Sentence 2
ATC cleared the flight for the procedure after confirming its navigational performance.