Required navigation performance (RNP) is a type of performance-based navigation (PBN) that allows an aircraft to fly a specific path between two 3D-defined points in space.

Navigation precision

Area navigation (RNAV) and RNP systems are fundamentally similar. The key difference between them is the requirement for on-board performance monitoring and alerting. A navigation specification that includes a requirement for on-board navigation performance monitoring and alerting is referred to as an RNP specification. One not having such a requirement is referred to as an RNAV specification. Therefore, if ATC radar monitoring is not provided, safe navigation in respect to terrain shall be self-monitored by the pilot and RNP shall be used instead of RNAV.

RNP also refers to the level of performance required for a specific procedure or a specific block of airspace. An RNP of 10 means that a navigation system must be able to calculate its position to within a circle with a radius of 10 nautical miles. An RNP of 0.3 means the aircraft navigation system must be able to calculate its position to within a circle with a radius of 3/10 of a nautical mile.PBN Learning Center | GE Aviation Systems | GE Aviation The differences in these systems are typically a function of on-board navigational system redundancies.

A related term is ANP which stands for "actual navigation performance." ANP refers to the current performance of a navigation system while "RNP" refers to the accuracy required for a given block of airspace or a specific instrument procedure.

Some oceanic airspace has an RNP capability value of 4 or 10. The level of RNP an aircraft is capable of determines the separation required between aircraft with respect to distance. Improved accuracy of on-board RNP systems represent a significant advantage to traditional non-radar environments, since the number of aircraft that can fit into a volume of airspace at any given altitude is a square of the number of required separation; that is to say, the lower the RNP value, the lower the required distance separation standards, and in general, the more aircraft can fit into a volume of airspace without losing required separation. This is not only a major advantage for air traffic operations, but presents a major cost-savings opportunity for airlines flying over the oceans due to less restrictive routing and better available altitudes.

RNP approaches with RNP values currently down to 0.1 allow aircraft to follow precise three-dimensional curved flight paths through congested airspace, around noise sensitive areas, or through difficult terrain.

History RNP procedures were introduced in the PANS-OPS (ICAO Doc 8168), which became applicable in 1998. These RNP procedures were the predecessor of the current PBN concept, whereby the performance for operation on the route is defined (in lieu of flight elements such as flyover procedures, variability in flight paths, and added airspace buffer), but they resulted in no significant design advantages. As a result, there was a lack of benefits to the user community and little or no implementation.

In 1996, Alaska Airlines became the first airline in the world to utilize an RNP approach with its approach down the Gastineau Channel into Juneau, Alaska. Alaska Airlines Captain Steve Fulton and Captain Hal Anderson developed more than 30 RNP approaches for the airline's Alaska operations. In 2005, Alaska Airlines became the first airline to utilize RNP approaches into Reagan National Airport to avoid congestion.Alaska Airlines Becomes First Carrier Authorized To Conduct RNP Precision Approach Flight Validations In April 2009, Alaska Airlines became the first airline to gain approval from the FAA to validate their own RNP approaches. On 6 April 2010, Southwest Airlines converted to RNP.

Since 2009, regulators in Peru, Chile, and Ecuador have deployed more than 25 RNP AR approach procedures, designed in conjunction with LAN Airlines. Benefits included reduction in greenhouse gases emissions and improved accessibility to airports located on mountainous terrain. The use of RNP AR approaches in Cusco, near Machu Picchu, has reduced cancellations due to foul weather by 60 percent on flights operated by LAN.

In 2011, Boeing, Lion Air, and the Indonesian Directorate General of Civil Aviation performed validation flights to test tailor-made Required Navigation Performance Authorization Required (RNP AR) procedures at two terrain-challenged airports, Ambon and Manado, pioneering the use of RNP precision navigation technology in Southeast Asia.

Established on RNP approaches Inspired by a 2011 white paper written by Sheila Conway, in November 2018 the ICAO published the Established on RNP-Authorization Required (EoR) standard to reduce separation for parallel runways, improving traffic flow while reducing noise, emissions and distance flown. Conservative estimates of CO2 emissions savings due to EoR operations at Denver International Airport exceed 1 billion tons as of 2024. Similar to Denver, it was implemented over three years at Calgary International Airport, lowering the final approach requirement from , before reaching trajectory-based operations. As 40% of aircraft arriving are equipped to fly RNP-AR, 3,000 RNP-AR approaches per month would save , and associated with continuous descent, would reduce greenhouse gases emissions by 2,500 metric tons in the first year.

Description

Capabilities The current specific requirements of an RNP system include: Capability to follow a desired ground track with reliability, repeatability, and predictability, including curved paths; and Where vertical profiles are included for vertical guidance, use of vertical angles or specific altitude constraints to define a desired vertical path.

RNP APCH supports all leg types and path terminators used in standard RNAV, including TF and RF. RNP AR procedures support only two leg types: TF leg: Track to Fix: a geodesic path between two fixes. RF leg: Radius to Fix. This is a curved path supported by positive course guidance. An RF leg is defined by a radius, arc length, and a fix. Not all RNP capable FMS systems support RF legs. Use of RF legs is allowed prior to the Final Approach Fix. For RNP AR APCH operation see Special Aircraft and Aircrew Authorization Required approach section below.

The performance-monitoring and alerting capabilities may be provided in different forms depending on the system installation, architecture, and configurations, including: display and indication of both the required and the estimated navigation system performance; monitoring of the system performance and alerting the crew when RNP requirements are not met; and cross track deviation displays scaled to RNP, in conjunction with separate monitoring and alerting for navigation integrity.

Error tolerance

An RNP system utilises its navigation sensors, system architecture, and modes of operation to satisfy the RNP navigation specification requirements. It must perform the integrity and reasonableness checks of the sensors and data, and it may provide a means to deselect specific types of navigation aids to prevent reversion to an inadequate sensor.

The RNP type defines the total system error that is allowed in lateral and longitudinal dimensions within a particular airspace. The total system error, which takes account of navigation system errors, computation errors, display errors and flight technical errors, must not exceed the specified RNP value for 95 percent of the flight time on any part of any single flight. RNP requirements may limit the modes of operation of the aircraft, e.g. for low RNP, where flight technical errors is a significant factor, and manual flight by the crew may not be allowed. Dual system/sensor installations may also be required depending on the intended operation or need.

RNP system

An RNAV system capable of achieving the performance requirements of an RNP specification, including monitoring and alerting of Actual Navigation Performance, is referred to as an RNP system. Because specific performance requirements are defined for each navigation specification, an aircraft approved for a RNP specification is not automatically approved for all RNAV specifications. Similarly, an aircraft approved for an RNP or RNAV specification having stringent accuracy requirements is not automatically approved for a navigation specification having a less-stringent accuracy requirement.

Designation For oceanic, remote, enroute and terminal operations, an RNP specification is designated as RNP X, e.g. RNP 4.

Approach navigation specifications cover all segments of the instrument approach. RNP specifications are designated using RNP as a prefix and an abbreviated textual suffix, e.g. RNP APCH (for RNP approach) or RNP AR APCH (for RNP authorisation required approach).

Performance monitoring and alerting requirements The performance monitoring and alerting requirements for RNP 4, Basic-RNP 1 and RNP APCH have common terminology and application. Each of these specifications includes requirements for the following characteristics: Accuracy: The accuracy requirement defines the 95% Total System Error (TSE) for those dimensions where an accuracy requirement is specified. The accuracy requirement is harmonised with the RNAV navigation specifications and is always equal to the accuracy value. A unique aspect of the RNP navigation specifications is that the accuracy is one of the performance characteristics that is monitored. Performance monitoring: The aircraft, or aircraft-and-pilot combination, is required to monitor the TSE and to provide an alert if the accuracy requirement is not met or if the probability that the TSE exceeds two-times the accuracy value is larger than 10−5. To the extent operational procedures are used to satisfy this requirement, the crew procedure, equipment characteristics, and installation are evaluated for their effectiveness and equivalence. Aircraft failures: Failure of the aircraft equipment is considered within airworthiness regulations. Failures are categorised by the severity of the aircraft level effect, and the system must be designed to reduce the likelihood of the failure or mitigate its effects. Both malfunction (equipment operating but not providing appropriate output) and loss of function (equipment ceases to function) are addressed. Dual system requirements are determined based on operational continuity (e.g. oceanic and remote operations). The requirements on aircraft failure characteristics are not unique to RNP navigation specifications. Signal-in-space failures: Signal-in-space characteristics of navigation signals are the responsibility of the ANSP.ICAO. Doc 9613, Performance-based Navigation (PBN) Manual – Annex 10 Aeronautical Telecommunications, 2008.

The net effect of RNP navigation specifications is to provide bounding of the TSE distribution. Since path definition error is assumed to be negligible, the monitoring requirement is reduced to the other two components of TSE, i.e. flight technical error (FTE) and navigation system error (NSE). It is assumed that FTE is an ergodic stochastic process within a given flight control mode. As a result, the FTE distribution is constant over time within a given flight control mode. However, in contrast, the NSE distribution varies over time due to a number of changing characteristics, most notably: Selected navigation sensors: The navigation sensors used to estimate position, such as a Global Navigation Satellite System (GNSS) or DME/DME.