RNP approaches are enabled by GNSS. Modern avionics can provide both lateral and vertical guidance along a defined path when it is published as an RNP approach. These approaches are described by a series of waypoints, legs that connect the waypoints and any speed and altitude constraints required on that procedure. This information is held in the aircraft’s navigation database.
RNP Approaches improve flight safety by reducing the risk of controlled flight into terrain (CFIT). They can also provide better access and lower minima to runways that are not equipped with precision approach and landing systems such as ILS.
A RNP APCH is designed to support most approach operations and any aircraft certified for RNP APCH with approved flight crews can fly any published RNP approach.
A RNP AR APCH is designed for more demanding procedures that require specific authorisation. These procedures require a specific approval for the aircraft, specific crew training and, usually, a Flight Operational Safety Assessment (FOSA).
See the Implementation section, Upcoming Changes or click here for more information on Instrument Approach Chart title changes
Historical Non-Precision Approaches (NPA) were based on conventional navigation aids such as NDB, VOR and DME and were designed with a lateral path to guide the aircraft to a point where the runway is in view and a visual landing can be performed. Although NPA procedures do not include vertical guidance ICAO and EASA expect that the vertical profiles are flown as Constant Descent Final Approaches (CDFA). Therefore, NPA operations are either 2D operations when they are flown with step down or 3D operations when flown with CDFA.
RNP APCH introduced new types of 3D operations, making use of certified Baro-VNAV systems or the SBAS geometric positioning (RNP APCH to LNAV/VNAV and to LPV respectively).
RNP APCH to LNAV/VNAV is a vertically guided approach that can be flown by modern aircraft with VNAV functionality using barometric inputs. Most Boeing and Airbus aircraft have this capability meaning that a large part of the commercial air transport (CAT) fleet is equipped.
RNP APCH to LPV is supported by Satellite Based Augmentation Systems (SBAS) such as EGNOS in Europe and WAAS in the US to provide lateral and vertical guidance. The lateral guidance is equivalent to an ILS localizer and the vertical guidance is provided against a geometrical path in space rather than a barometric altitude. RNP APCH to LP, which would be published if the geometric vertical positioning from SBAS could not be assured. This minima will rarely be seen on approach charts.
Two sets of procedure design criteria exist for APV SBAS procedures: APV 1 and SBAS Cat I; the EGNOS LPV200 service level supports SBAS Cat I operations.
RNP APCH charts can have several minima depending on the kind of RNP approach to be flown:
- LNAV and LP minima (MDA/H) for 2D operations.
- LNAV/VNAV minima (DA/H) for 3D operation using barometric vertical guidance.
- LPV minima (DA/H) for a 3D approach with geometric vertical guidance based on SBAS.
The RNP specification for operations with authorization required (RNP AR operations) is the ICAO standard for instrument approach and departure procedures at airports with limiting terrain and obstacle environments, or other operational challenges.
These specifications are not intended for application at every airport, nor are they intended for every operator.
RNP AR operations can offer efficiency and/or access in challenging environments where no other navigation specification can offer benefits.
RNP AR operations will have unique instrument procedures requiring additional levels of scrutiny, control and authorization. These RNP AR procedures increase risk and complexity; however, stringent performance and eligibility criteria mitigate the risks and enable safe operations by taking advantage of advanced aircraft capabilities and additional training and procedures for the operator and the operator’s flight crews.
The State AIP should clearly indicate when a published RNP AR operation is a RNP AR APCH or a RNP AR DP procedure. The AIP and the associated charts should also clearly indicate the procedures require specific authorization (e.g. “AUTHORIZATION REQUIRED”). In addition, when the State requires distinct approvals for specific RNP AR operations the State should clearly document this requirement(s) in their AIP.
The State should clearly publish the minimum RNP value any RNP AR procedure requires during any segment or part of the procedure. The minimum will allow the flight crew to identify the operational suitability of each individual RNP AR procedure. In addition, if the maximum deviation for the procedure is allowed to be manually set, this can be done prior to the beginning of that procedure.