![]() | This article includes a list of general references, but it lacks sufficient corresponding inline citations .(July 2010) |
ICAO performance-based navigation (PBN) specifies that aircraft required navigation performance (RNP) and area navigation (RNAV) systems performance requirements be defined in terms of accuracy, integrity, availability, continuity, and functionality required for the proposed operations in the context of a particular airspace, when supported by the appropriate navigation infrastructure. [1]
Historically, aircraft navigation specifications have been specified directly in terms of sensors (navigation beacons and/or waypoints). A navigation specification that includes an additional requirement for on-board navigation performance monitoring and alerting is referred to as a required navigation performance (RNP) specification. One not having such requirements is referred to as an area navigation (RNAV) specification.
Performance requirements are identified in navigation specifications, which also identify the choice of navigation sensors and equipment that may be used to meet the performance requirements. The navigation specifications provide specific implementation guidance in order to facilitate global harmonisation.
Under PBN, generic navigation requirements are first defined based on the operational requirements. Civil aviation authorities then evaluate options in respect of available technology and navigation services. A chosen solution would be the most cost-effective for the civil aviation authority, as opposed to a solution being established as part of the operational requirements. Technology can evolve over time without requiring the operation itself to be revisited as long as the requisite performance is provided by the RNAV or RNP system.
PBN offers a number of advantages over the sensor-specific method of developing airspace and obstacle clearance criteria:
Within an airspace, PBN requirements will be affected by the communication, surveillance and air traffic control (ATC) environments, the navaid infrastructure and functional and operational capability needed to meet the ATM application. PBN performance requirements also depend on what reversion, non-RNAV means of navigation are available and what degree of redundancy is required to ensure adequate continuity of operations.
To achieve the efficiency and capacity gains partially enabled by RNAV and RNP, the FAA will pursue use of data communications and enhanced surveillance functionality. [2]
Area navigation techniques and specifications started to evolve regionally without overall ICAO guidance. This consequently meant that terms and definitions such as "RNAV" and "RNP" had slightly different meanings in different regions of the world, and even other terms could be used locally. An example of this is the term "P-RNAV" (Precision RNAV) that Europe still uses (2019), which elsewhere is called "RNAV 1".
The terms RNAV and RNP was earlier used with little functional difference. RNP required a certain level of performance but made no attempt to define how it was to be guaranteed.
Performance-based navigation (PBN) is ICAO's initiative to standardise terminology, specifications and meanings. One example is to standardise the terminology used around APVs (Approaches with vertical guidance). All APVs have until recently been designated as RNAV-approaches, while these in fact are RNP-approaches with respect to the PBN implementation. All APVs require on-board performance monitoring and alerting, so the system cannot only be capable of navigation down to the required degree of accuracy, but also needs to continuously monitor the performance and be capable of alerting the pilot if its performance falls below that which is required.
These approaches had some confusing names and designations on charts, and the changeover is currently being conducted across all member states. The two types of RNAV-approaches have traditionally been named RNAV (GNSS) and RNAV (RNP) respectively, where the former is the traditional straight-in approach from the final approach fix, and the latter is a more complex approach that curves in the horizontal plane after the final approach fix which requires authorization for it to be commenced (AR = Authorization Required). The correct naming and designation for these approaches under the PBN implementation are RNP and RNP AR respectively. The images to the right show the naming of the current charts being used, and what they will look like under PBN. [3]
When separation minima and route spacing are determined using a conventional sensor-based approach, the navigation performance data used to determine the separation minima or route spacing depend on the accuracy of the raw data from specific navigation aids such as VOR, DME or NDB. In contrast, PBN requires an RNAV system that integrates raw navigation data to provide a positioning and navigation solution. In determining separation minima and route spacing, this integrated navigation performance "output" is used.
The navigation performance required from the RNAV system is part of the navigation specification. To determine separation minima and route spacing, airspace planners fully exploit that part of the navigation specification which describes the performance required from the RNAV system. Airspace planners also make use of the required performance (accuracy, integrity, availability and continuity) to determine route spacing and separation minima.
In procedurally controlled airspace, separation minima and route spacing on RNP specifications are expected to provide a greater benefit than those based on RNAV specifications. This is because the on-board performance monitoring and alerting function could alleviate the absence of ATS surveillance service by providing an alternative means of risk mitigation.
It is expected that all future RNAV and RNP applications will identify the navigation requirements through the use of performance specifications rather than defining specific navigation sensors.
The Valley of Mexico will be the first in Mexico where the performance-based navigation system is used, which will allow the new Felipe Ángeles International Airport, the Mexico City International Airport, and the Toluca International Airport to operate simultaneously without the operations of one impeding those of the others. [4]
For legacy reasons associated with the previous RNP concept, PBN is currently limited to operations with linear lateral performance requirements and time constraints. For this reason, operations with angular lateral performance requirements (i.e. approach and landing operations with GNSS vertical guidance—approach procedure with vertical guidance APV-I and APV-II), as well as instrument landing system (ILS) and microwave landing system (MLS) are not considered. Unlike the lateral monitoring and obstacle clearance, for barometric VNAV systems there is neither alerting on vertical error nor is there a two-times relationship between a 95% required total system accuracy and the performance limit. Therefore, barometric VNAV is not considered vertical RNP.
On-board performance monitoring and alerting is the main element that determines whether a navigation system complies with the required safety level associated with an RNP application. It relates to both lateral and longitudinal navigation performance; and it allows the aircrew to detect that the navigation system is not achieving, or cannot guarantee with 10−5 integrity, the navigation performance required for the operation.
RNP systems provide improvements on the integrity of operations. This may permit closer route spacing and can provide sufficient integrity to allow only RNAV systems to be used for navigation in a specific airspace. The use of RNP systems may therefore offer significant safety, operational and efficiency benefits.
On-board performance monitoring and alerting capabilities fulfill two needs, one on board the aircraft and one within the airspace design. The assurance of airborne system performance is implicit for RNAV operations. Based upon existing airworthiness criteria, RNAV systems are only required to demonstrate intended function and performance using explicit requirements that are broadly interpreted. The result is that while the nominal RNAV system performance can be very good, it is characterised by the variability of the system functionality and related flight performance. RNP systems provide a means to minimise variability and assure reliable, repeatable and predictable flight operations.
On-board performance monitoring and alerting allow the air crew to detect whether or not the RNP system satisfies the navigation performance required in the navigation specification. On-board performance monitoring and alerting relate to both lateral and longitudinal navigation performance.
On-board performance monitoring and alerting is concerned with the performance of the area navigation system.
Performance-based flight operations are based on the ability to assure reliable, repeatable and predictable flight paths for improved capacity and efficiency in planned operations. The implementation of performance-based flight operations requires not only the functions traditionally provided by the RNAV system, but also may require specific functions to improve procedures, and airspace and air traffic operations. The system capabilities for established fixed radius paths, RNAV or RNP holding, and lateral offsets fall into this category.
Fixed radius paths (FRP) take two forms:
Fly-by turns are a key characteristic of an RNAV flight path. The RNAV system uses information on aircraft speed, bank angle, wind and track angle change to calculate a flight path turn that smoothly transitions from one path segment to the next. However, because the parameters affecting the turn radius can vary from one plane to another, as well as due to changing conditions in speed and wind, the turn initiation point and turn area can vary.
The RNAV system facilitates the holding pattern specification by allowing the definition of the inbound course to the holding waypoint, turn direction and leg time or distance on the straight segments, as well as the ability to plan the exit from the hold. For RNP systems, further improvement in holding is available. These RNP improvements include fly-by entry into the hold, minimising the necessary protected airspace on the non-holding side of the holding pattern, consistent with the RNP limits provided. Where RNP holding is applied, a maximum of RNP 1 is suggested since less stringent values adversely affect airspace usage and design.
RNAV systems may provide the capability for the flight crew to specify a lateral offset from a defined route. Generally, lateral offsets can be specified in increments of 1 NM up to 20 NM. When a lateral offset is activated in the RNAV system, the RNAV aircraft will depart the defined route and typically intercept the offset at a 45° or less angle. When the offset is cancelled, the aircraft returns to the defined route in a similar manner. Such offsets can be used both strategically i.e. fixed offset for the length of the route, or tactically i.e. temporarily. Most RNAV systems discontinue offsets in the terminal area or at the beginning of an approach procedure, at an RNAV hold, or during course changes of 90° or greater.
Aircraft operating in the North Atlantic airspace are required to meet a minimum navigation performance specification (MNPS). The MNPS specification has intentionally been excluded from PBN because of its mandatory nature and because future MNPS implementations are not envisaged. [5]
It is likely that navigation applications will progress from 2-dimensional to 3-dimensional/4-dimensional applications, although time-scales and operational requirements are currently difficult to determine. Consequently, on-board performance monitoring and alerting is still to be developed in the vertical plane (vertical RNP) and ongoing work is aimed at harmonising longitudinal and linear performance requirements. Angular performance requirements associated with approach and landing will be included in the scope of PBN in the future. Similarly, specifications to support helicopter-specific navigation and holding functional requirements may also be included.
In aviation, the instrument landing system (ILS) is a precision radio navigation system that provides short-range guidance to aircraft to allow them to approach a runway at night or in bad weather. In its original form, it allows an aircraft to approach until it is 200 feet (61 m) over the ground, within a 1⁄2 mile (800 m) of the runway. At that point the runway should be visible to the pilot; if it is not, they perform a missed approach. Bringing the aircraft this close to the runway dramatically increases the range of weather conditions in which a safe landing can be made. Other versions of the system, or "categories", have further reduced the minimum altitudes, runway visual ranges (RVRs), and transmitter and monitoring configurations designed depending on the normal expected weather patterns and airport safety requirements.
The basic principles of air navigation are identical to general navigation, which includes the process of planning, recording, and controlling the movement of a craft from one place to another.
Receiver autonomous integrity monitoring (RAIM) is a technology developed to assess the integrity of global positioning system (GPS) signals in a GPS receiver system. It is of special importance in safety-critical GPS applications, such as in aviation or marine navigation.
In aviation, an instrument approach or instrument approach procedure (IAP) is a series of predetermined maneuvers for the orderly transfer of an aircraft operating under instrument flight rules from the beginning of the initial approach to a landing, or to a point from which a landing may be made visually. These approaches are approved in the European Union by EASA and the respective country authorities and in the United States by the FAA or the United States Department of Defense for the military. The ICAO defines an instrument approach as "a series of predetermined maneuvers by reference to flight instruments with specific protection from obstacles from the initial approach fix, or where applicable, from the beginning of a defined arrival route to a point from which a landing can be completed and thereafter, if landing is not completed, to a position at which holding or en route obstacle clearance criteria apply."
A flight management system (FMS) is a fundamental component of a modern airliner's avionics. An FMS is a specialized computer system that automates a wide variety of in-flight tasks, reducing the workload on the flight crew to the point that modern civilian aircraft no longer carry flight engineers or navigators. A primary function is in-flight management of the flight plan. Using various sensors (such as GPS and INS often backed up by radio navigation) to determine the aircraft's position, the FMS can guide the aircraft along the flight plan. From the cockpit, the FMS is normally controlled through a Control Display Unit (CDU) which incorporates a small screen and keyboard or touchscreen. The FMS sends the flight plan for display to the Electronic Flight Instrument System (EFIS), Navigation Display (ND), or Multifunction Display (MFD). The FMS can be summarised as being a dual system consisting of the Flight Management Computer (FMC), CDU and a cross talk bus.
The local-area augmentation system (LAAS) is an all-weather aircraft landing system based on real-time differential correction of the GPS signal. Local reference receivers located around the airport send data to a central location at the airport. This data is used to formulate a correction message, which is then transmitted to users via a VHF Data Link. A receiver on an aircraft uses this information to correct GPS signals, which then provides a standard instrument landing system (ILS)-style display to use while flying a precision approach. The FAA has stopped using the term LAAS and has transitioned to the International Civil Aviation Organization (ICAO) terminology of ground-based augmentation system (GBAS). While the FAA has indefinitely delayed plans for federal GBAS acquisition, the system can be purchased by airports and installed as a Non-Federal navigation aid.
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.
The Future Air Navigation System (FANS) is an avionics system which provides direct data link communication between the pilot and the air traffic controller. The communications include air traffic control clearances, pilot requests and position reporting. In the FANS-B equipped Airbus A320 family aircraft, an Air Traffic Services Unit (ATSU) and a VHF Data Link radio (VDR3) in the avionics rack and two data link control and display units (DCDUs) in the cockpit enable the flight crew to read and answer the controller–pilot data link communications (CPDLC) messages received from the ground.
Area navigation is a method of instrument flight rules (IFR) navigation that allows an aircraft to choose any course within a network of navigation beacons, rather than navigate directly to and from the beacons. This can conserve flight distance, reduce congestion, and allow flights into airports without beacons. Area navigation used to be called "random navigation", hence the acronym RNAV.
In aviation, lateral navigation is azimuth navigation, without vertical navigation (VNAV). Area navigation (RNAV) approach plates include LNAV as a non-precision instrument approach (NPA). When combined with VNAV, the resulting instrument approach, LNAV/VNAV, is referred to as an Approach with Vertical Guidance (APV).
An equipment code describes the communication (COM), navigation (NAV), approach aids and surveillance transponder equipment on board an aircraft. These alphabetic codes are used on FAA and ICAO flight plan forms to aid Flight service station (FSS) personnel in their handling of aircraft.
The GPS-aided GEO augmented navigation (GAGAN) is an implementation of a regional satellite-based augmentation system (SBAS) by the Government of India. It is a system to improve the accuracy of a GNSS receiver by providing reference signals. The Airports Authority of India (AAI)'s efforts towards implementation of operational SBAS can be viewed as the first step towards introduction of modern communication, navigation and surveillance / air traffic management system over the Indian airspace.
In aviation, an air traffic service (ATS) is a service which regulates and assists aircraft in real-time to ensure their safe operations. In particular, ATS is to:
The Aeronautical Information Service, or AIS is a service established in support of international civil aviation, whose objective is to ensure the flow of information necessary for the safety, regularity, and efficiency of international air navigation.
The Next Generation Air Transportation System (NextGen) is an ongoing United States Federal Aviation Administration (FAA) project to modernize the National Airspace System (NAS). The FAA began work on NextGen improvements in 2007 and plans to finish the final implementation segment by 2030. The goals of the modernization include using new technologies and procedures to increase the safety, efficiency, capacity, access, flexibility, predictability, and resilience of the NAS while reducing the environmental impact of aviation.
Strategic lateral offset procedure (SLOP) is a solution to a byproduct of increased navigation accuracy in aircraft. Because most now use GPS, aircraft track flight routes with extremely high accuracy. As a result, if an error in height occurs, there is a much higher chance of collision. SLOP allows aircraft to offset the centreline of an airway or flight route by a small amount, normally to the right, so that collision with opposite direction aircraft becomes unlikely.
Automatic Dependent Surveillance–Broadcast (ADS-B) is an aviation surveillance technology and form of Electronic Conspicuity in which an aircraft determines its position via satellite navigation or other sensors and periodically broadcasts its position and other related data, enabling it to be tracked. The information can be received by air traffic control ground-based or satellite-based receivers as a replacement for secondary surveillance radar (SSR). Unlike SSR ADS-B does not require an interrogation signal from the ground or other aircraft to activate its transmissions. ADS-B can also received point-to-point by other nearby equipped "ADS-B In" equipped aircraft to provide traffic situational awareness and support self-separation. ADS-B is "automatic" in that it requires no pilot or external input to trigger its transmissions. It is "dependent" in that it depends on data from the aircraft's navigation system to provide the transmitted data.
Localizer performance with vertical guidance (LPV) are the highest precision GPS aviation instrument approach procedures currently available without specialized aircrew training requirements, such as required navigation performance (RNP). Landing minima are usually similar to those of a Cat I instrument landing system (ILS), that is, a decision height of 200 feet (61 m) and visibility of 800 m. Lateral guidance is equivalent to a localizer, and uses a ground-independent electronic glide path. Thus, the decision altitude, DA, can be as low as 200 feet. An LPV approach is an approach with vertical guidance, APV, to distinguish it from a precision approach, PA, or a non-precision approach, NPA. WAAS criteria includes a vertical alarm limit more than 12 m, but less than 50 m, yet an LPV does not meet the ICAO Annex 10 precision approach standard.
Anchorage Air Route Traffic Control Center (PAZA/ZAN) is located just outside the main gate of Joint Base Elmendorf-Richardson at 700 North Boniface Parkway in Anchorage, Alaska, United States. The Anchorage ARTCC is one of 22 Air Route Traffic Control Centers in the United States.
Airbus ProSky was an Airbus subsidiary dedicated to improving the performance of global air traffic management (ATM) prior to Airbus merging it with Airbus LUCEM and NAVTECH to form Navblue. Composed of ATM experts and offering various solutions to enhance air traffic capacity, efficiency and safety, Airbus ProSky works with air navigation service providers (ANSP), aircraft operators, airport authorities and Civil Aviation Authorities.
This article incorporates public domain material from websites or documents of the Federal Aviation Administration .