Definition
A measure of how closely an aircraft's actual position matches the position indicated by its navigation system, expressed as a maximum allowable error (in nautical miles) that the system must stay within for a specified percentage of flight time, typically 95 percent. In RNP operations, the required navigational accuracy is defined by the RNP value for that route or procedure (e.g., RNP 1 means the aircraft must remain within 1 NM of the intended path 95 percent of the time).
Plain English
How close the aircraft really is to where its navigation system says it is. The tighter the required accuracy, the smaller the allowable error between actual position and displayed position.
Context Anchor
Seen in instrument flying, especially when reading about Required Navigation Performance procedures, approach requirements, and whether an aircraft’s navigation equipment is suitable for a route or approach.
Derivation
Navigation comes from older words meaning to travel by ship, and accuracy comes from a word idea of doing something carefully or exactly. Together, the term points to careful guidance along the intended route, not just a general sense of going the right way.
Why Pilots Care
It determines whether the aircraft meets the performance needed to fly a procedure safely and remain clear of terrain and traffic.
Grounding Statement
Picture the cleared course as a narrow path in the sky; navigational accuracy is how tightly the aircraft must stay near the center of that path.
Intuition Check
Accuracy does not mean perfect position here. It means the aircraft must stay within a specified amount of allowable error for the operation being flown.
Example Sentence 1
The approach required RNP 0.3, so the crew confirmed their navigation system could meet that navigational accuracy before commencing.
Example Sentence 2
The pilot checked the displayed navigational accuracy before entering the narrow RNAV airway.