All public RNAV STARs are RNAV1 and require system performance meeting certain criteria. Which statement is true?

• A. RNAV1 requires aircraft total system error to remain bounded by +1 NM for 95% of total flight time.
• B. RNAV1 allows a maximum error of +/- 2 NM for 95% of flight time on all segments.
• C. RNAV1 applies only to enroute segments with +/- 1 NM bounds.
• D. RNAV1 requires vertical guidance only.

Answer: (A)

RNAV1 is a lateral navigation performance standard used for public RNAV STARs. It requires the total system error to stay within 1 nautical mile for 95% of the total flight time. This tight bound ensures the aircraft remains on the published path with high confidence most of the time, which is crucial for safe sequencing and obstacle clearance in terminal airspace.

The other statements don’t fit because they either describe a different RNAV performance level or misstate where RNAV1 applies. A 2 NM bound corresponds to a less restrictive standard (RNAV2), not RNAV1. Saying RNAV1 applies only to enroute segments ignores that STARs are terminal procedures and need this standard there as well. Finally, RNAV1 is about lateral guidance accuracy, not vertical guidance—vertical guidance is provided by other systems or standards (like LPV/VNAV) and isn’t the defining feature of RNAV1.