Required Navigation Performance (RNP) – In-Depth Aviation Glossary

Definition and Overview

Required Navigation Performance (RNP) is an internationally standardized navigation specification that sets performance requirements—specifically, a quantifiable lateral accuracy and continuous performance monitoring—that an aircraft and its operator must meet to fly specific routes or procedures in controlled airspace. RNP falls within the broader Performance-Based Navigation (PBN) framework, as defined by ICAO Doc 9613.

The key feature distinguishing RNP from traditional Area Navigation (RNAV) is the requirement for onboard performance monitoring and alerting. This means that throughout a flight, the aircraft’s navigation system must continuously self-assess its accuracy and alert the crew if it cannot meet the specified standard. RNP is expressed as a numerical value in nautical miles (NM), indicating the maximum permissible deviation from the intended position 95% of the time (for example, RNP 1 = ±1 NM).

RNP is foundational to modernizing airspace worldwide. By leveraging advanced avionics and satellite navigation, RNP enables more direct routing, complex arrivals and departures, and safe, efficient approaches in terrain-challenged or crowded airspace—features central to initiatives like FAA NextGen and ICAO’s Global Air Navigation Plan. This supports increased airspace capacity, safety, and operational flexibility, unlocking access to airports and airspace previously limited by ground-based navigation and terrain constraints.

Background and Context

RNP’s origins trace back to the limitations of ground-based navigation aids like VOR, NDB, and DME, which forced airways and procedures to align with the range or locations of these beacons. This led to inefficiencies—longer routes, less flexible procedures, limited access in remote or mountainous areas, and greater controller workload.

The introduction of RNAV allowed aircraft to fly direct between waypoints using a combination of ground and onboard sensors, but early systems lacked any form of self-validation: there was no way to automatically check or alert if navigation accuracy couldn’t be maintained. The advent of satellite navigation (especially GPS and later SBAS/GBAS augmentation) and advanced avionics made it possible to achieve both higher accuracy and real-time monitoring.

ICAO’s Performance-Based Navigation (PBN) concept formalized these advances, distinguishing between RNAV (no monitoring/alerting) and RNP (monitoring/alerting required). This enabled reduced separation, more efficient airspace design, and access to challenging airports. Today, RNP is standard for oceanic crossings, domestic en route navigation, terminal operations, and precision approaches, including highly specialized RNP AR (Authorization Required) procedures for airports like Innsbruck and Queenstown.

Key Concepts and Terminology

Performance-Based Navigation (PBN)

Performance-Based Navigation is a global ICAO framework that defines navigation requirements based on measurable performance (such as accuracy, integrity, and functionality), not specific equipment. PBN includes both RNAV and RNP specifications and supports flexible, outcome-based navigation.

• Navigation Specifications (NavSpecs): Define required accuracy, monitoring, and functionality (like RNP 1, RNP 4).
• Navigation Applications: Describe where/how NavSpecs are used (e.g., en route, terminal, approach).

PBN enables airspace harmonization, efficient air traffic management, and integration of new navigation technologies.

Area Navigation (RNAV)

RNAV enables aircraft to fly any desired flight path within the coverage of navigation aids or satellites, using onboard systems that integrate multiple sources (e.g., VOR/DME, DME/DME, GNSS, IRS). However, RNAV does not mandate onboard performance monitoring and alerting—a key difference from RNP.

Required Navigation Performance (RNP)

RNP is an RNAV specification that requires continuous onboard monitoring and alerting. The navigation system must ensure it can maintain a lateral navigation accuracy (e.g., RNP 1 = ±1 NM, 95% of the time), and alert the crew if it can’t.

RNP also requires:

• Integrity: High confidence in position information.
• Continuity: Low risk of system interruption during critical phases.
• Functionality: May require additional features (e.g., curved flight paths/RF legs, parallel offsets).

Technical Requirements

RNP Levels and Navigation Specifications (NavSpecs)

RNP operations are defined by NavSpecs, each specifying:

• Required accuracy (in NM)
• System monitoring/alerting
• Functionality requirements

Common RNP NavSpecs:

Onboard Performance Monitoring and Alerting (OBPMA)

The defining feature of RNP is continuous onboard performance monitoring and alerting. The navigation system must:

• Continuously compare actual navigation performance (ANP or EPU) to the required RNP value.
• Immediately alert the crew if it cannot maintain the required performance.
• Provide clear visual and/or aural alerts for any exceedance or loss of integrity.

This enables reduced separation minima, flexible routing, and safer operations in complex or high-risk environments.

Equipment & System Requirements

• Flight Management System (FMS): Integrates multiple navigation sensors.
• Certified GNSS Receiver: Often SBAS (WAAS/EGNOS) or GBAS, TSO-C145/146.
• Inertial Reference System (IRS): For short GPS outages or increased redundancy.
• Automatic Alerting: For loss of performance, loss of signal, or system failure.
• Additional Equipment (as required): TAWS for RNP AR, dual GNSS for RNP 4, redundant power.

All equipment must be certified to applicable standards, with explicit RNP eligibility noted in the AFM or avionics documentation.

Navigation Database

• Must be current/valid.
• Only authorized procedures may be loaded.
• Procedures must be selectable by published name.
• Database must match published chart data.
• For RNP AR, every procedure must be validated for each database cycle.

Operational Use and Procedures

Flight Crew and Operator Responsibilities

• Only fly RNP procedures for which crew, aircraft, and operator are authorized.
• Pre-flight: Check database currency, procedure availability, and eligibility.
• FMS Setup: Load and activate procedures correctly, match published data.
• Continuous monitoring: Watch ANP/RNP, alerts, and system integrity.
• If navigation performance degrades, follow contingency procedures and notify ATC.
• Operators must maintain documentation, training, and recurrent proficiency for RNP operations.

RNP in Airspace and Flight Phases

RNP Approaches

RNP APCH (RNAV (GPS))

• Multiple minima lines: LNAV, LNAV/VNAV, LPV, LP.
• Available to most SBAS-equipped aircraft.
• May include curved paths (RF legs), requiring additional authorization.

RNP AR APCH (Authorization Required)

• For airports with challenging terrain, airspace constraints, or complex procedures.
• Tighter accuracy (as low as 0.1 NM), curved legs, and special minima.
• Requires explicit operator/crew authorization, database validation, and advanced crew training (as per FAA AC 90-101A, ICAO Doc 9905).

Benefits of RNP

• Increased airspace capacity and efficiency: Tighter separation, direct routes, optimized flows.
• Access to challenging airports: Safe operations in terrain/obstacle-constrained environments.
• Environmental benefits: Reduced track miles, lower fuel burn, and noise abatement.
• Enhanced safety: Continuous monitoring, rapid crew awareness of performance loss.
• Integration with advanced airspace concepts: Supports NextGen, SESAR, and future trajectory-based operations.

Regulatory and Global Harmonization

• RNP is standardized in ICAO Doc 9613 and adopted worldwide.
• National authorities (FAA, EASA, etc.) publish guidance and authorize operators/aircraft.
• Harmonized standards support seamless international operations.

The Future of RNP

RNP continues to evolve, supporting concepts like time-based separation, 4D trajectories, and dynamic sectorization. Advancements in GNSS augmentation and avionics will enable even greater accuracy, integrity, and flexibility—key to meeting the growing demands of global air traffic and new entrants such as UAVs and urban air mobility.

Summary

Required Navigation Performance (RNP) is a cornerstone of modern aviation navigation, combining advanced avionics, satellite navigation, and rigorous performance monitoring to enable safer, more efficient, and more flexible airspace operations. It unlocks new operational possibilities, improves safety, and is central to the ongoing transformation of global airspace.

For operators and crews, mastering RNP is essential for accessing future airspace, leveraging new technologies, and maintaining the highest standards of flight safety and efficiency.