GNSS and area navigation (RNAV/PBN)
GNSS and area navigation (RNAV/PBN)
This domain tests navigation specification knowledge, GNSS integrity, and what the aircraft is actually allowed to fly.
Specifications. PBN is defined by the navigation specification: RNAV 5, RNAV 2, RNAV 1, RNP 1, RNP 2 and RNP AR APCH. The number is the lateral total system error, in nautical miles, that must be contained 95% of the time. RNP specifications require on-board performance monitoring and alerting; RNAV specifications rely on the navigation infrastructure.
NZ use. NZ has implemented RNP 1 SIDs and STARs at major aerodromes, RNAV(GNSS) non-precision approaches, and RNP AR APCH at terrain-limited aerodromes such as Queenstown. RNP AR requires specific crew authorisation and aircraft capability.
Integrity. GNSS receivers must have fault detection and exclusion (FDE) and a RAIM prediction for the approach; if RAIM is unavailable the approach cannot be flown. Baro-VNAV approaches carry a temperature limit because the vertical path is computed from barometric altitude.
Worked example. An RNP AR approach with RNP 0.3 has lateral obstacle evaluation of 2 × RNP = 0.6 NM in the approach segment, reduced to 0.3 NM where the final segment is designed with the appropriate obstacle clearance. At 5 NM from the threshold the 95% containment is 0.3 NM, so an indicated cross-track error of 0.4 NM is an alert condition.
Traps. Quoting RNP as accuracy instead of containment; using a GPS approach without checking RAIM and NOTAMs; flying a baro-VNAV procedure outside the temperature limit; and assuming an RNP 1 airway clearance permits an RNP AR approach.