PBN Concept (ICAO Doc 9613): RNAV, RNP, and Use Cases
The PBN (Performance-Based Navigation) concept specifies that aircraft RNAV system performance requirements be defined in terms of accuracy, integrity, availability, continuity, and functionality, needed for the proposed operations in the context of a particular airspace concept.
PBN Components
PBN is based on three main components:
- NAVAID Infrastructure: Can be ground-based (VOR, DME) or space-based (GNSS).
- Navigation Specification: Defines performance requirements (e.g., RNAV 1, RNP 4).
- Navigation Application: The use of a specification and the infrastructure for specific routes or procedures.
Performance Factors
- Accuracy: The difference between the estimated position and the actual position. Often expressed as the lateral error allowed 95% of the time (e.g., RNP 1 = 1 NM).
- TSE (Total System Error): Sum of PDE (Path Definition Error), FTE (Flight Technical Error), and NSE (Navigation System Error).
- Integrity: The confidence in the correctness of the information and the ability to alert of failures within a reasonable time.
- Continuity: The capability of the system to perform its function without unscheduled interruptions during the operation.
- Availability: The percentage of time the system is usable.
- Functionality: The required functions of the system (e.g., RF legs, Baro-VNAV).
PBN Scope
- Oceanic, En-route, and Terminal Phases: PBN is limited to operations with linear lateral performance requirements.
- Approach Phase: PBN accommodates operations with both linear (LNAV) and angular (LPV, similar to ILS) lateral guidance.
PBN Benefits
- Reduces the need to maintain specific routes and procedures for each sensor.
- Avoids the development of specific operations for each new technology.
- Allows for more efficient use of airspace (more direct routes, fuel savings).
- Facilitates the operational approval process.
Difference between Raw and Computed Data
- Raw Data: Conventional navigation based on direct indications from ground aids (VOR, NDB).
- Computed Data: PBN navigation where the system calculates position by integrating multiple sensors (GNSS, IRS, DME/DME) and validates data consistency.