Appendix 2 FIGURE 1. MINIMUM STRAIGHT PATH BEFORE DECISION ALTITUDE Public Required Navigation Performance (RNP) Authorization Required (AR) Procedures Minimum Straight Segments Between Turns and Decision Altitude (DA) RF in final Direction of Flight Min Time = 50s DA - Min Time = 10s LTP Runway RF in miss DER If there is a turn before or after the DA, distance before or after DA computed from Distance(NM) = GS(KT) * T(SEC)/3600 where GS = Category Speed + 15 kt LTP - Landing Threshold Point DER - Departure End of Runway Page 13 (and 14)
Appendix 3 APPENDIX 3. NAVIGATION DATA VALIDATION PROGRAM
1. Introduction. The aircraft’s onboard NDB defines the RNP AR procedure path and associated constraints, allowing for lateral and vertical guidance. In view of the reduced obstacle clearance associated with RNP AR procedures, the associated NDB information warrants special attention and consideration. This appendix provides guidance for validating RNP AR instrument approach data contained in aircraft NDBs. The guidance in this appendix applies in full to aircraft operators performing RNP AR instrument approach procedures (IAP), as well as to any FAA-approved entity with which an operator may contract to provide NDB validation services.
NOTE: An aircraft operator’s application to conduct RNP AR procedures should specifically describe the extent and nature of the services provided by an outside entity contracted to perform NDB validation services.
2. NDB Management Process. The operator must identify in writing the individual responsible for managing the overall onboard NDB process. The operator must also establish the processes and procedures for accepting, verifying, and loading navigation data into the aircraft in writing and maintain those processes and procedures under configuration control (e.g., formal control of revisions and updates to the process). The operator may not delegate this overall management responsibility to a third party.
3. RNP AR Procedure Data Validation. The operator must ensure the validation of an RNP AR IAP contained in its database before flying that approach in instrument meteorological conditions (IMC). The validation process ensures the RNP AR procedure contained in the NDB accurately reflects the intended procedure design parameters. Proper data validation includes the following steps:
a. Accuracy Check. Compare the RNP AR procedure in the NDB with the government source data. The FAA Form 8260 series, specifically the FAA Forms 8260-3, ILS – Standard Instrument Approach Procedures, and 8260-10, Standard Instrument Approach Procedure, defining the procedure, are available at the FAA National Aeronautical Navigation Services (AeroNav Service) Web site at http://aeronav.faa.gov/ndbr.asp. Data for international procedures is available via the respective State’s Aeronautical Information Publication (AIP). Investigate any differences between the database and source data. You can find a list of the specific procedure data parameters, which must be examined during this accuracy check, as well as the allowable differences between source data and that contained in the NDB for each parameter, at the FAA’s Performance Based Flight Systems Branch (AFS-470) Web site located at http://www.faa.gov/about/office_org/headquarters_offices/avs/offices/afs/afs400/afs470/rnp.
b. Flyability Check. An initial flyability check is required for all Title 14 of the Code of Federal Regulations (14 CFR) non-part 97 U.S. RNP AR procedures, as well as all foreign RNP AR procedures the operator is authorized to fly. Using either the actual aircraft in visual meteorological conditions (VMC), a flight simulation training device (FSTD) approved for RNP AR, or appropriately configured desktop/laptop computer, validate the RNP AR procedure contained in the NDB to ensure it matches the published procedure. An FSTD or desktop/laptop computer must utilize software identical to that used by the aircraft (e.g., flight management system (FMS) software) and use an aerodynamic model of the aircraft’s flight characteristics.
Appendix 3 You must use a map display in the aircraft, FSTD, or computer to compare the database procedure with that published. This validation process requires flying the entire procedure and should confirm the path is flyable, does not contain any lateral or vertical discontinuities, and is consistent with the published procedure.
4. Database Updates.
a. Re-Confirm Data Accuracy. Before using an updated NDB (e.g., 28-day update) the operator must ensure the RNP AR approach data contained in that update remains within the tolerances prescribed in subparagraph 3a when compared to the government source data. If the operator finds a data parameter to exceed prescribed tolerances, he or she should consult with the appropriate navigation data supplier to resolve the discrepancy prior to using the approach procedure. Resolve discrepancies by correcting the error within the current cycle, removal of the procedure from the database, or potentially through operational mitigations approved by the FAA until the procedure data can be corrected.
b. Methodology. The method by which an operator conducts this recurring data comparison is optional, subject to the approval of the principal operations inspector (POI) or Flight Standards District Office (FSDO). One acceptable method is to establish a reference database, sometimes referred to as a “golden database,” containing known, validated approach data, and comparing data from subsequent navigation updates against this reference data. Some FMS suppliers provide automated tools, which enable a quick comparison of data parameters between databases and alert to any changes or differences. Operators may also choose to compare the navigation data contained in the updated database directly against the government source data. Regardless of the method used, operators must assure the integrity of the validated navigation data at each update cycle.
NOTE: An operator should be particularly attentive to discrepancies when updates coincide with a change to the data supplier’s packing software. This software is used to format the navigation data into code readable by aircraft avionics.
5. Data Suppliers. As a minimum, data suppliers must have a Letter of Acceptance for processing navigation data in accordance with AC 20-153( ), Acceptance of Aeronautical Data Processes and Associated Databases. A Letter of Acceptance recognizes the data supplier as one whose data quality, integrity, and quality management practices are consistent with the criteria of RTCA/DO-200( ), Standards for Processing Aeronautical Data. The aircraft operator’s supplier (e.g., FMS company) must have a Type 2 Letter of Acceptance. Those entities providing data to the aircraft operator’s supplier likewise must possess either a Type 1 or Type 2 Letter of Acceptance.
Appendix 3 Page 3 (and 4)
6. Aircraft Modifications. If a manufacturer modifies an aircraft system required for RNP AR operations (e.g., software or hardware change), the operator must, before flying any RNP AR procedures in IMC, confirm the aircraft’s ability to fly RNP AR procedures as published with the modified aircraft system(s). The operator should examine a number of RNP AR procedures in its NDB for this flyability check. Use the criteria described in subparagraph 3b to perform this check.
NOTE: If the manufacturer documents that the modification has no effect on the NDB or path computation, the operator need not perform this additional confirmation.
7. Recurrent Audits. The processes identified in this appendix for validating and updating RNP AR instrument approaches in NDBs are subject to recurrent FAA audits. The operator’s processes, as well as those performed by any outside entity contracted to provide NDB services, are subject to audit by the FAA. Additionally, operators are expected to conduct their own recurrent audits of entities with whom they contract to provide NDB services described in this appendix.
Appendix 4 APPENDIX 4. OPERATIONAL CONSIDERATIONS
1. General. This appendix provides guidance on the conduct of Required Navigation Performance (RNP) Authorization Required (AR) approach operations. In addition to observing the guidance contained herein, the operator must also continue to ensure its flightcrews comply with general Area Navigation (RNAV) operating requirements, check Notices to Airmen (NOTAM), determine availability of Navigational Aids (NAVAID), and confirm airworthiness of aircraft systems.
2. Preflight Considerations.
a. Minimum Equipment List (MEL). Operator’s MELs should address the equipment requirements for RNP AR instrument approaches. Guidance related to these equipment requirements is available from the aircraft manufacturer and Appendix 2 to this advisory circular (AC). The required equipment may depend on the intended RNP value and whether the missed approach requires RNP less than 1.0.
b. Class A Terrain Awareness and Warning System (TAWS). An operable TAWS is required for all RNP AR procedures. The TAWS should use altitude that is compensated for local pressure and temperature effects (e.g., corrected barometric and Global Navigation Satellite System (GNSS) altitude), and include significant terrain and obstacle data.
c. Autopilot and Flight Director (FD). RNP AR procedures with RNP values less than 0.3, or with Radius to Fix (RF) legs, require the use of autopilot or FD driven by the RNAV system in all cases. The autopilot/FD must operate with suitable accuracy to track the lateral and vertical paths required by the RNP AR procedure.
d. RNP Prediction. The operator must have a predictive performance capability, which can forecast if the specified RNP value will be available at the time and location of a desired RNP AR operation. This capability can be a ground service and need not be resident in the aircraft’s avionics equipment. The operator must establish procedures requiring use of this capability as both a preflight dispatch tool and as a flight-following tool in the event of reported failures.
(1) This predictive capability must account for known and predicted outages of GNSS satellites or other impacts on the aircraft navigation system. The prediction program should not use a mask angle below 5 degrees, as operational experience indicates that satellite signals at low elevations are not reliable. The prediction must use the actual GNSS constellation, and when equipped, the GNSS augmentations with the algorithm identical to or more conservative than that used in the actual equipment. The RNP prediction must show that the horizontal protection level (HPL) is less than the required RNP value. For RNP AR approaches with high terrain, use a mask angle appropriate to the terrain.
(2) RNP AR procedures require GNSS updating. Therefore, there is no RNP prediction associated with distance measuring equipment (DME)/DME or very high frequency (VHF) omni-directional range station (VOR)/DME updating of the aircraft’s RNAV system.
Appendix 4
e. NAVAID Exclusion. The operator must establish procedures to exclude NAVAID facilities (e.g., DMEs, VORs, localizers) in accordance with NOTAMs. Internal avionics reasonableness checks may not be adequate for RNP AR operations.
f. Navigation System Database (NDB) Currency. During system initialization, pilots must confirm the NDB is current. NDBs are expected to be current for the duration of the flight.
If the Aeronautical Information Regulation and Control (AIRAC) cycle will change during flight, operators must establish procedures to ensure the accuracy of navigation data, including suitability of navigation facilities used to define the routes and procedures for flight.
Traditionally, this has been accomplished by verifying electronic data against paper products.
One acceptable means is to compare aeronautical charts (new and old) to verify navigation fixes prior to dispatch. If an amended chart is published for the procedure, you must not perform the RNP AR approach with the expired NDB.
3. In-Flight Considerations.
a. Modification of Flight Plan. Pilots are not authorized to fly an RNP AR procedure unless it is retrievable by the procedure name from the aircraft NDB and conforms to the charted procedure. You must not modify the lateral path, with the exception of going Direct to Fix (DF), as long as that fix is prior to the final approach fix (FAF) and does not immediately precede an RF leg. For example, referring to Appendix 1 Figure 1, Example of RNP AR Approach Procedures with a Radius to a Fix Leg Segment, or Figure 2, Example of RNP AR Approach Procedures with a Radius to a Fix Leg Segment with a Missed Approach Requiring RNP Less than 1.0, a pilot could not accept a vector to go direct to either DEMGE or SKYKO waypoints, nor to the DMIVZ FAF. The only other authorized modification to the loaded procedure is a change of altitude and/or airspeed waypoint constraints on the initial, intermediate, or Missed Approach Segments (MAS) (e.g., to comply with an air traffic control (ATC) clearance/instruction).
b. Required List of Equipment. The flightcrew must have a readily accessible list of equipment required for conducting RNP AR approaches, as well as methods to address in-flight equipment failures that would prohibit RNP AR approaches (e.g., a quick reference handbook).
c. RNP Management. The flightcrew must ensure that the navigation system uses the appropriate RNP values throughout the approach. If multiple lines of minima associated with different RNP values are shown on the approach chart, the crew must confirm that the desired RNP value is entered in the RNAV system. If the navigation system does not extract and set the RNP value from the onboard NDB for each leg of the procedure, the flightcrew must ensure that the smallest RNP value required to complete the approach or the missed approach is selected before initiating the approach. On approaches with multiple initial approach fixes (IAF), the approach chart may specify an RNP value for each IAF.
d. Sensor Updating.
(1) RNP AR instrument procedures require GNSS performance. If at any time GNSS updating is lost and the navigation system does not have the performance to continue the approach, (i.e., unable to comply with the current RNP value) the flightcrew must abandon the
Appendix 4 RNP AR approach unless visual conditions exist between the aircraft and the runway of intended landing.
(2) Except where specifically designated on a procedure as “Not Authorized,” you may use DME/DME-updating as a reversionary mode during the RNP AR approach or missed approach when:
(a) The navigation system has the performance to continue the procedure, and
(b) An assessment of the DME ground infrastructure has been accomplished.
(3) VOR updating is not authorized on RNP AR approaches.
e. Approach Procedure Confirmation. The flightcrew must confirm that the correct procedure has been selected. This process includes confirmation of the waypoint sequence, reasonableness of track angles and distances, and any other parameters that can be altered by the pilot, such as altitude or speed constraints. Do not use a RNP AR procedure if validity of the NDB is in doubt. You must use a navigation system textual display or map display for this procedure confirmation.
f. Track Deviation Monitoring. Pilots must use a lateral deviation indicator (LDI), FD, and/or autopilot in lateral navigation (LNAV) mode on RNP AR approach procedures. Pilots of aircraft with an LDI must ensure the LDI scaling (full-scale deflection) is suitable for the navigation accuracy associated with the various segments of the RNP AR approach procedure.
Pilots are expected to maintain procedure centerlines (CL), as depicted by onboard LDIs and/or flight guidance, during all RNP AR operations unless authorized to deviate by ATC or under emergency conditions. For normal operations, pilots should limit cross-track error (XTK)/deviation (the difference between the RNP system computed path and the aircraft position relative to the path) to +/- one half the navigation accuracy associated with the procedure segment. Brief lateral deviations from this standard (e.g., overshoots or undershoots) during and immediately after turns, up to a maximum of 1 times the navigation accuracy of the procedure segment, are allowable.
(1) The vertical deviation must be within 75 feet during the Final Approach Segment (FAS). Monitor vertical deviation above and below the glidepath. While being above the glidepath provides margin against obstacles on the final approach, it can result in a go-around decision closer to the runway and reduce the margin against obstacles in the missed approach.
(2) Pilots must execute a missed approach if the lateral deviation exceeds 1xRNP or the vertical deviation exceeds 75 feet, unless the pilot has acquired the visual references required to continue the approach to the intended runway.
(3) Some aircraft navigation displays do not incorporate lateral and vertical deviation indications, scaled for each RNP AR approach operation, in the primary optimum field of view (FOV). Where a moving map, low-resolution vertical deviation indicator (VDI), or numeric display of deviations are to be used, flightcrew training and procedures must ensure the effectiveness of these displays. Typically this involves demonstration of the procedure with a
Appendix 4 number of trained crews and inclusion of this monitoring procedure in the recurrent RNP AR approach training program.
(4) For aircraft that use a course deviation indicator (CDI) for lateral path tracking, the Aircraft Flight Manual (AFM) or aircraft qualification guidance should state which navigation accuracy and operations the aircraft supports and the operational effects on the CDI scale. The flightcrew must know the CDI full-scale deflection value. The avionics may automatically set the CDI scale (dependent on phase of flight) or the flightcrew may manually set the scale. If the flightcrew manually selects the CDI scale, the operator must have procedures and training in place to ensure the selected CDI scale is appropriate for the intended RNP operation. The deviation limit must be readily apparent given the scale (e.g., full-scale deflection).
g. System Crosscheck. For approaches with RNP values less than 0.3, the flightcrew must crosscheck the lateral and vertical guidance provided by the navigation system with other available data and displays provided by an independent means (e.g., TAWS, weather radar, etc.).
NOTE: This crosscheck may not be necessary if the aircraft meets the requirements of Appendix 2, subparagraphs 2d and 3e. Use of Global Positioning System (GPS)/Satellite-based Augmentation System (SBAS) vertical guidance precludes the need for independent monitoring.
h. Procedures with RF Legs. An RNP AR procedure may include an RF leg. As not all aircraft have this capability, flightcrews must know if they can conduct these procedures. When flying an RF leg, flightcrew compliance with the desired path is essential to maintain the intended ground track.
(1) If initiating a go-around during or shortly after the RF leg, the flightcrew must be aware of the importance of maintaining the published path as closely as possible. Operators must develop specific procedures to ensure maintenance of the RNP AR ground track in those aircraft which do not remain in LNAV upon initiation of a go-around.
(2) Pilots must not exceed the maximum airspeeds shown in Table 1, Maximum Airspeeds Throughout the Radius to a Fix Leg Segment, throughout the RF leg segment.
For example, a Category (CAT) C aircraft must slow to 140 knots indicated airspeed (KIAS) at the FAF or may fly as fast as 165 KIAS if using CAT D minima. A missed approach prior to decision altitude (DA) requires maintaining the segment speed to the DA and then observing any speed limitations specified for the MAS.
Appendix 4 TABLE 1. MAXIMUM AIRSPEEDS THROUGHOUT THE RADIUS TO A FIX
LEG SEGMENT Indicated Airspeed (Knots) Segment Indicated Airspeed by Aircraft CAT Cat A Cat B Cat C Cat D Cat E Initial & Intermediate (IAF to FAF) 150 150 250 250 250 Final (FAF to DA) 90 120 140 165 As Specified Missed Approach (DA to missed approach holding point) 110 150 250 265 As Specified
i. Temperature Compensation. For aircraft equipped with temperature compensation in accordance with Appendix 2, subparagraph 3a(7), flightcrews may disregard the temperature limits on RNP AR procedures if the operator provides pilot training on the use of the temperature compensation function.
NOTE: Since the charted temperature limits ensure obstacle clearance solely in the FAS, and since temperature compensation only affects the vertical guidance, the pilot may need to manually adjust the minimum altitude on the initial and intermediate approach segments and the DA. Pilots must coordinate with ATC prior to use of temperature compensation in order to prevent loss of aircraft separation.
j. Altimeter Crosscheck. The flightcrew must complete an altimetry crosscheck ensuring that both pilots’ altimeters agree within ±100 feet not later than the FAF after receiving the current local altimeter setting at the airport of intended landing. Do not continue the procedure if the altimetry crosscheck fails.
NOTE: This operational crosscheck is not necessary if the aircraft automatically compares the altitudes to within 100 feet (see Appendix 2, subparagraph 3d(14)).
k. Altimeter Setting. Due to the reduced obstruction clearance inherent in RNP AR instrument procedures, the flightcrew must verify the current local altimeter at the airport of intended landing is set not later than the FAF. Remote altimeter settings are not allowed.
l. Non-Standard Climb Gradient. When planning to use the DA associated with a non-standard missed approach climb gradient, the operator must ensure the aircraft will be able to comply with the published climb gradient for the planned aircraft loading, atmospheric conditions, and operating procedures.
Appendix 4
m. Engine-Out Procedures. RNP AR procedures are based on normal operations. However, you can find guidance for developing engine-out extraction procedures in AC 120-91( ), Airport Obstacle Analysis.
n. Go-Around or Missed Approach. There are two types of Missed Approach Procedures (MAP): RNP 1.0 and RNP less than 1.0.
(1) RNP AR missed approaches are typically designed to require RNP 1.0 and no additional actions on the part of the flightcrew. The missed approach portion of these procedures is similar to a missed approach on an RNAV GPS approach.
(2) If the Missed Approach Segment (MAS) requires an RNP value less than 1.0, the approach chart will include the following note: “Missed approach requires RNP less than 1.0.”
In order to fly such an RNP AR procedure, aircraft equipage and operating procedures must meet the criteria of Appendix 2, paragraph 6.
(3) In many aircraft, activating takeoff/go-around (TOGA) causes a change in LNAV.
Activating TOGA may also disengage the autopilot and FD from LNAV guidance, with the FD reverting to track-hold derived from the inertial system. LNAV guidance to the autopilot and FD should be re-engaged as quickly as possible.
(4) Flightcrew procedures and training must address the impact on navigation capability and flight guidance if the pilot initiates a go-around while the aircraft is in a turn (e.g., on an RF leg).
o. Contingency Procedures.
(1) Provide guidance to the flightcrew on how to assess and react to en route failures of RNP AR approach required equipment.
(2) The operator’s contingency procedures must also address at least the following conditions occurring during the RNP AR approach:
(a) Failure of RNP system components, including those affecting lateral and vertical path tracking performance (e.g., failures of a GPS sensor, the FD, or automatic pilot); and
(b) Loss of navigation signal-in-space (loss or degradation of external signal).