GPS, RNAV, RNP, LPV (Performance-Based Navigation)

Performance-Based Navigation is defined in ICAO Doc 9613 (Performance-Based Navigation Manual, 4th Edition) and implemented in the United States through FAA Advisory Circular AC 90-100A (U.S. Terminal and En Route Area Navigation (RNAV) Operations) and AC 90-105A (Approval Guidance for RNP Operations and Barometric Vertical Navigation in the U.S. National Airspace System). EASA implements PBN requirements under AMC1 SPA.PBN.100 and Part-FCL theoretical knowledge standards for IR training. Specific U.S. equipment carriage and navigation accuracy requirements for IFR flight reference 14 CFR §91.205(d), §91.225 (ADS-B, which shares GPS infrastructure), and §91.227 (ADS-B performance requirements referencing WAAS accuracy).

The PBN concept separates navigation specification from hardware, replacing the legacy system in which an approach procedure was tied to a physical NAVAID (VOR, NDB, ILS). Instead, PBN defines two families: RNAV specifications, where accuracy is required but onboard monitoring and alerting is not mandatory, and RNP specifications, where the aircraft must have onboard performance monitoring and alerting (OPMA) that warns the crew when the navigation system cannot meet the required accuracy. This distinction is operationally important: an aircraft approved for RNAV 1 cannot fly an RNP 1 procedure unless it also has OPMA.

RNAV specifications by accuracy value: RNAV 10 (formerly RNP 10, used on oceanic/remote routes beyond radar coverage, 10 NM total system error), RNAV 5 (continental en route, 5 NM), RNAV 2 and RNAV 1 (terminal, SID/STAR use; RNAV 1 requires 1 NM accuracy 95% of flight time). RNP specifications: RNP 4 (oceanic, 4 NM, requires OPMA), RNP 2 (continental en route), RNP 1 (terminal), RNP APCH (non-precision and APV approaches, 0.3 NM accuracy on final), and RNP AR APCH (Authorization Required — curved radius-to-fix segments, RF legs, accuracy as tight as 0.1 NM, specific airline/operator approval required from FAA or EASA, used for approaches into terrain-challenged airports such as Innsbruck LOWI or Kathmandu VNKT). RNAV (GNSS) helicopter approaches are specified at RNAV 0.3.

LPV (Localizer Performance with Vertical guidance) is a specific approach type within the RNP APCH specification that uses SBAS (Satellite-Based Augmentation System) to provide lateral and vertical guidance with an approach procedure design very similar to ILS. In the United States, the SBAS is the FAA's Wide Area Augmentation System (WAAS), which corrects GPS errors in real time via geostationary satellites and provides accuracy of approximately 1–3 m horizontally and 2–4 m vertically at the runway threshold — sufficient to support decision heights as low as 200 ft HAT with ½ SM visibility, identical to ILS CAT I minima. Aircraft must be equipped with a WAAS-certified GPS receiver approved under TSO-C145c or TSO-C146c to fly LPV approaches; TSO-C129 GPS receivers cannot use LPV. The FAA has published over 4,500 LPV approach procedures in the United States, dramatically expanding CAT I-equivalent approach capability to small regional airports that never had — and could not economically justify — ILS ground infrastructure.

Equivalent SBAS systems operate in other ICAO regions: EGNOS (European Geostationary Navigation Overlay Service) covers Europe and supports LPV approaches under EASA certification; MSAS (MTSAT Satellite Augmentation System) covers Japan; GAGAN (GPS Aided Geo Augmented Navigation) covers India; and SDCM (System for Differential Correction and Monitoring) covers Russia. ICAO's future roadmap includes ARAIM (Advanced Receiver Autonomous Integrity Monitoring) as a potential successor to SBAS for CAT I approaches in regions without SBAS ground infrastructure.

For instrument rating training programmes, PBN is not optional knowledge — FAA AC 61-65H (Certification: Pilots and Flight and Ground Instructors) requires that applicants for the instrument rating log training in and demonstrate competency on GPS/RNAV approaches. The ACS requires the applicant to fly at least one GPS approach (RNAV or LPV) during the practical test. Schools conducting instrument training must have aircraft equipped with TSO-C145/146 WAAS GPS receivers to conduct LPV approaches, and CFIIs must be trained and current on PBN procedures including database currency — GPS navigation databases must be current under 14 CFR §91.1015 and Jeppesen/FAA chart subscription cycles.

For Part 141 schools and ATOs conducting EASA integrated or modular IR training, AMC1 FCL.615(b) specifies PBN training requirements including RNAV 1 SID/STAR and RNP APCH operations. Operators seeking ETOPS or oceanic approval must also demonstrate crew PBN competency in the relevant specification (RNAV 10 or RNP 4). The currency and recency requirements for PBN approaches require careful tracking, as a pilot who has not flown an RNAV approach within the preceding six months must receive additional training before serving as PIC on a PBN-dependent operation.

Aviatize tracks PBN approach currency within the training management module at the specification level — distinguishing between LNAV, LNAV/VNAV, LPV, and RNP AR approaches logged in each pilot's record. When a student or pilot-in-command has not flown a GPS/RNAV approach within the ACS-required or operator-required currency window, the system generates an automatic flag visible to the scheduling and chief instructor team, preventing dispatch without remedial currency flight.

For schools managing WAAS GPS aircraft, the maintenance control module tracks GPS database expiry dates — typically 28-day Jeppesen cycles — as a scheduled maintenance item. An expired GPS database renders the aircraft ineligible for IFR approaches under 14 CFR Part 91 and most operators' MEL provisions; Aviatize surfaces database expiry as a hard unavailability block on the aircraft record so that bookings requiring instrument approaches are automatically declined until the database is updated and the discrepancy closed.