An airliner is cleared for an RNP AR approach that requires RNP 0.30. What does this RNP value represent regarding the aircraft's required navigation performance?
- AObstacle clearance areas extend 0.30 NM on either side of the final approach course regardless of aircraft capability
- BThe aircraft's navigation system must keep it within 0.30 NM of the course centerline 95% of the flight time, with onboard performance monitoring and alerting
- CThe aircraft's vertical guidance must be accurate to within 0.30 NM of the glidepath
- DThe runway must have a minimum visual range of 0.30 statute miles for the approach to be flown
Show answer & explanationAnswer & explanation
Correct answer: B. The aircraft's navigation system must keep it within 0.30 NM of the course centerline 95% of the flight time, with onboard performance monitoring and alerting
RNP specifies a required lateral navigation accuracy (in nautical miles) that the aircraft's system must maintain for 95% of the flight time along the route or approach, combined with onboard monitoring and alerting if that performance cannot be assured. RNP 0.30 means 0.30 NM lateral containment with monitoring, not a visibility, obstacle clearance, or vertical accuracy value directly.
Why the other options are wrong
- A. Obstacle clearance surfaces are derived from RNP but RNP itself is an aircraft performance/containment value, not a fixed protected-area statement independent of capability.
- C. RNP values as commonly specified (e.g., RNP 0.30) describe lateral, not vertical, navigation performance.
- D. RNP is unrelated to runway visual range values.
Required Navigation Performance (RNP)
A statement of the lateral navigation accuracy (in NM) an aircraft's system must maintain for 95% of flight time, combined with onboard monitoring and alerting of that performance.
- Lower RNP values (e.g., RNP 0.30) mean tighter accuracy requirements
- Includes onboard performance monitoring and alerting (unlike basic RNAV)
- RNP AR approaches may require RNP as low as 0.10 to 0.30
- RNP defines a total system error budget, not just GPS signal accuracy
Memory trick: 'RNP = Really Narrow Path, with a Watchdog' (monitoring/alerting)