Appendix E E-11 E.9.5.14 Emergency procedures for operations in RNP 2 airspace or on RNP 2 routes are no different than normal oceanic emergency procedures with one exception, crews must be able to recognize and ATC must be advised when the aircraft is no longer able to navigate to its RNP 2 approved capability.
E.9.6 Prior to Commencing the RNP 2 Procedure. In addition to normal operating procedures, prior to commencing the procedure the flightcrew should accomplish the following:
1. For multisensor systems, crew must verify that the correct sensor is being used for position computation; and
2. Where Controller-Pilot Data Link Communication (CPDLC) is used to uplink flight plan changes for routing that is not contained in the navigation database, the flightcrew should confirm the RNP in effect matches the airspace requirement. If not, the flightcrew should manually enter the RNP applicable to the route.
Appendix F F-1 APPENDIX F. QUALIFICATION CRITERIA FOR REQUIRED NAVIGATION PERFORMANCE (RNP) 4 OCEANIC AND REMOTE CONTINENTAL OPERATIONS F.1 Introduction.
F.1.1 Performance and Functional Requirements. This appendix provides guidance on the performance and functional requirements for systems used to conduct RNP 4 over oceanic and remote continental airspace. Previous authorizations in accordance with FAA Order 8400.33, Procedures for Obtaining Authorization for Required Navigation Performance 4 (RNP-4) Oceanic and Remote Area Operations, remain valid. This appendix does not address communications or surveillance requirements that may be specified to operate on a particular route or in a particular area. Those requirements are specified in other documents, such as the Aeronautical Information Publications (AIP) and the International Civil Aviation Organization (ICAO) Doc 7030, Regional Supplementary Procedures (SUPPS) and ICAO Doc 4444 PANS ATM, Procedures for Air Navigation Services, Air Traffic Management.
F.2 Aircraft and System Requirements for RNP 4.
F.2.1 Statement of Compliance (SOC). Aircraft with an SOC with RNP 4 criteria in Advisory Circular (AC) 20-138( ), Airworthiness Approval of Positioning and Navigation Systems, in their Airplane Flight Manual (AFM), Airplane Flight Manual Supplement (AFMS), pilot’s operating handbook (POH), or the operating manual for their avionics meet the performance and functional requirements of this appendix.
F.2.2 Statement from the Manufacturer. Aircraft with a statement from the manufacturer documenting compliance with the RNP 4 criteria in AC 20-138( ) meet the performance and functional requirements of this AC. These statements should include the airworthiness basis for compliance. Compliance with the sensor requirements will have to be determined by the equipment or aircraft manufacturer, while compliance with the functional requirements in this appendix may be determined by the manufacturer or by inspection by the operator.
F.2.3 Navigation Equipment Requirements. Navigation equipage for all RNP 4 operations in oceanic and remote continental areas must have at least dual independent long-range navigation systems (LRNS). Global Navigation Satellite System (GNSS) must be used as either a stand-alone navigation system, as one of the sensors in a multisensor system, or as part of an integrated GNSS/inertial system.
Note: RNP 4 operations are based on Global Positioning System (GPS) positioning. Positioning data from other types of navigation sensors may be integrated with the GPS data provided it does not cause position errors exceeding the Total System Error (TSE) budget. Otherwise, means should be provided to deselect the other navigation sensor types.
Appendix F F-2 F.3 System Performance, Monitoring, and Alerting.
F.3.1 Accuracy. The aircraft must comply with Section 2.1.1 of RTCA/DO-236( ). During operations in airspace or on routes designated as RNP 4, the lateral TSE must be within ±4 nautical miles (NM) for at least 95 percent of the total flight time. The along-track (ATRK) error must also be within ±4 NM for at least 95 percent of the total flight time.
To satisfy the 95 percent accuracy requirement, the Flight Technical Error (FTE) should not exceed 2 NM.
Note: The use of a lateral deviation indicator with 4 NM full-scale deflection has been found to be an acceptable means of compliance (AMC) integrity.
F.3.2 Integrity. Malfunction of the aircraft navigation equipment that causes the TSE to exceed two times the RNP value is classified as a major failure condition under airworthiness guidance (i.e., 10-5 per hour).
F.3.3 Continuity. For RNP 4, loss of navigation equipment function is a major failure condition. The continuity requirement is satisfied by the carriage of dual independent LRNSs (excluding Signal in Space (SIS)).
Note: Operators and pilots are required to use the specified continuity requirements of the governing state or regional authority before conducting flights outside of the U.S. National Airspace System (NAS).
F.3.4 Performance Monitoring and Alerting. The RNP system, or the RNP system and pilot in combination, must provide an alert if the accuracy requirement is not met, or if the probability that the lateral TSE exceeds 2 x RNP (8 NM) is greater than 10-5 for RNP 4 operations.
F.3.4.1 Onboard performance monitoring and alerting compliance does not imply an automatic monitor of FTE. The onboard monitoring and alerting function should at least consist of a Navigation System Error (NSE) monitoring and alerting algorithm and a lateral deviation display enabling the crew to monitor the FTE.
F.3.4.2 Path Definition Error (PDE) is considered negligible.
F.3.5 SIS. If using GPS, the aircraft navigation equipment must provide an alert if the probability of SIS errors causing a lateral position error greater than 8 NM exceeds 10-7 per hour for RNP 4 operations.
Note: For RNP systems where the architecture is an integrated, multisensor capability and where GNSS integrity is incorporated into a 2 x RNP integrity alert consistent with DO-236( ) where performance cannot be met, a separate GNSS integrity alert is not required.
Appendix F F-3 F.4 Aircraft Eligibility.
F.4.1 Detection Methods. There are two methods to recognize aircraft and system eligibility for RNP 4 operations: 1) RNP certification; and, 2) prior navigation system certification. In both cases, the aircraft must be equipped with at least two independent and serviceable LRNSs; at least one of which must be GNSS.
F.4.2 RNP Certification. RNP certification is typically documented in the AFM/AFMS for aircraft that have been formally certificated and approved for RNP operations and typically is not limited to RNP 4. The AFM/AFMS addresses RNP levels that have been demonstrated to meet the certification criteria and any related provisions applicable to their use (e.g., navigation aid sensor requirements). Operational approval is based upon the performance stated in the AFM/AFMS and pilot qualification. This method also applies in cases where certification is received through a Supplemental Type Certificate (STC) issued to retrofit equipment, such as GNSS receivers, to enable the aircraft to meet RNP 4 performance criteria in oceanic and remote continental area airspace.
F.4.2.1 This method is used to approve aircraft whose level of performance under previous standards equates to the RNP 4 criteria listed in this AC. The AFM/AFMS must indicate the aircraft is equipped with GNSS approved as a LRNS for oceanic and remote continental airspace operations.
F.4.2.2 RNP 4 operations using only GNSS is based upon a predeparture fault detection and exclusion (FDE) availability prediction program. Twenty-five minutes is the maximum allowable time for which FDE capability is projected to be unavailable on any one event. This maximum outage time must be included as a condition of the RNP 4 operational approval. If predictions indicate that the maximum allowable FDE outage will be exceeded, the operation must be rescheduled to a time when FDE is available.
1. Aircraft with Technical Standard Order (TSO)-C129( ) equipment must also document the equipment is approved for oceanic operations according to AC 20-138( ), Appendix 1.
2. TSO-C115b (or later revision) is acceptable for multisensor systems incorporating GNSS sensors.
F.4.2.3 Multisensor systems incorporating an approved inertial navigation system (INS)/(Inertial Reference Unit (IRU) can extend the maximum FDE unavailability time based upon the amount of time the system can maintain RNP 4 coasting performance without a position update. The approval must indicate the maximum GNSS FDE unavailability time.
F.4.3 GNSS Eligibility. Aircraft fitted with only GNSS for oceanic and remote continental airspace operations must meet the RNP 4 performance requirements. The acceptable technical standards are:
Appendix F F-4
1. Combination GNSS Navigation Computer/Sensor.
• TSO-C129a Class A and
• TSO-C146( ).
2. Flight management system (FMS) (TSO-C115b or later revision) with GNSS sensor.
• TSO-C129a (Class B or C),
• TSO-C145( ), and
• TSO-C196( ).
Note: GNSS equipment approved under TSO-C129a must also meet AC 20-138( ), Appendix 1.
F.4.3.1 For aircraft equipped with GNSS-only, the operator must have an approved GNSS availability prediction program ensuring the requisite availability of the GNSS FDE function. Prior to conducting RNP 4 operations in oceanic or remote continental areas, the operator must use this prediction program prior to dispatch. When using the prediction program, the maximum predicted, allowable time for a loss of FDE is 25 minutes. When the predicted loss of FDE exceeds 25 minutes, then RNP 4 operations are not available, and the operator must reschedule the flight. All RNP 4 operations approvals must document the 25-minute FDE outage limit as a condition of the operational approval.
F.4.4 Integrating Multisensor Systems. Multisensor navigation systems integrating GNSS with INS must be capable of sustaining ±4 NM lateral TSE and ±4 NM ATRK for 95 percent of the total flight time to meet the RNP 4 performance requirements. There is no requirement to use a dispatch FDE availability prediction program when the operator uses an approved multisensor navigation system that includes INS. The INS must be approved in accordance with Title 14 of the Code of Federal Regulations (14 CFR) part 121, Appendix G.
F.4.5 Demonstrations. Demonstration of aircraft performance in accordance with AC 20-138( ) does not constitute operations approval to conduct RNP operations.
F.5 Maintenance Requirements.
F.5.1 LRNS. Aircraft must have established maintenance procedures for all LRNS intended for use in oceanic and remote continental area operations.
F.6 Functional Requirements of Navigation Data Displays.
F.6.1 Installation. The following navigation displays and functions are required and must be installed in accordance with AC 20-138( ) or equivalent airworthiness installation advisory material.
Appendix F F-5 F.6.2 Navigation Data Displays. Navigation data, including a TO/FROM indication and a failure indicator, must be displayed on a lateral deviation display (course deviation indicator (CDI), electronic horizontal-situation indicator (EHSI)) and/or a navigation map display. These must be used as primary flight instruments for the navigation of the aircraft, for maneuver anticipation and for failure/status/integrity indication. A non-numeric lateral deviation display (e.g., CDI, EHSI), with a TO/FROM indication and a failure annunciation, for use as primary flight instruments for navigation of the aircraft, for maneuver anticipation, and for failure/status/integrity indication, should have the following attributes:
1. The displays must be visible to the pilot and located in the primary field of view (FOV).
2. The lateral deviation display scaling must agree with any alerting and annunciation limits.
3. The lateral deviation display must have a full-scale deflection suitable for the current phase of flight.
Note: This does not apply for installations where an electronic map display contains a graphical display of the flightpath and path deviation.
4. The display scaling may be set automatically by default logic; automatically to a value from a navigation database; or manually by flightcrew procedures.
The full-scale deflection value must be known or must be available for display to the pilot commensurate with the required track-keeping accuracy.
5. The lateral deviation display must be automatically slaved to the RNP-computed path. It is recommended that the course selector of the deviation display be automatically slewed to the RNP-computed path.
Note: This does not apply for installations where an electronic map display contains a graphical display of the flightpath and path deviation.
6. As an alternate means, a navigation map display must give equivalent functionality to a lateral deviation display with appropriate map scales (scaling may be set manually by the pilot). To be approved as an alternative means, the navigation map display must be shown to meet the TSE requirements and be located in the primary FOV.
7. It is not necessary for navigation displays, particularly primary flight displays (PFD), to include an Actual Navigation Performance (ANP) or RNP value.
The displays only need to provide an alert if the RNP for the operation cannot be met.
F.6.3 System Capabilities. The following system capabilities are required as a minimum within any RNP 4 equipment:
1. The capability to continuously display to the pilot flying (PF), on the primary flight instruments for navigation of the aircraft (primary navigation display),
Appendix F F-6 the RNP-computed desired path and aircraft position relative to the path. For operations where the required minimum flightcrew is two pilots, a means for the pilot monitoring (PM) to verify the desired path and the aircraft position relative to the path must also be provided.
2. A navigation database, containing current navigation data officially promulgated for civil aviation, which can be updated in accordance with the Aeronautical Information Regulation and Control (AIRAC) cycle. The stored resolution of the data must be sufficient to achieve the required track-keeping accuracy. The database must be protected against pilot modification of the stored data.
3. The means to display the validity period of the navigation data to the pilot.
4. The means to retrieve and display data stored in the navigation database relating to individual waypoints and navigation aids, to enable the pilot to verify the route to be flown.
5. A means for the crew to create, review, and activate a flight plan. The system must incorporate a means for the crew to verify flight plan entries or changes before they are activated. The guidance output must not be affected until the flight plan or flight plan changes are activated.
6. The means to display the following items, either in the pilot’s primary FOV, or on a readily accessible display page:
• The active navigation sensor type,
• The identification of the active (To) waypoint,
• The ground speed or time to the active (To) waypoint, and
• The distance and bearing to the active (To) waypoint.
7. The capability to execute a “direct to” function.
8. The system must have the capability to automatically execute leg transitions and maintain tracks consistent with the following Aeronautical Radio, Inc.
(ARINC) Specification 424 path terminators:
• Course to Fix (CF),
• Direct to Fix (DF), and
• Track to Fix (TF).
Note: Path terminators are defined in ARINC Specification 424, and their application is described in more detail in RTCA documents, DO-236( ) and DO-201( ).
9. When executing a parallel offset (Appendix I, Additional Capabilities), the capability to execute parallel tracks at a selected offset distance. When executing a parallel offset (Appendix I), the RNP value and all performance
Appendix F F-7 criteria of the original route in the active flight plan must be applicable to the offset route.
• The system must provide for entry of offset distances in increments of 1 NM, left or right of course. The system must be capable of offsets of at least 20 NM.
• System offset mode operation must be clearly indicated to the pilot. When in offset mode, the system must provide reference parameters (e.g., cross-track (XTK) deviation, distance-to-go, time-to-go) relative to the offset path and offset reference points.
• An offset must not be propagated through route discontinuities, unreasonable path geometries, or beyond the initial approach fix (IAF).
• The system must provide an annunciation prior to the end of the offset path, with sufficient time to return to the original path.
• Once a parallel offset (Appendix I) is activated, the offset must remain active for all flight plan route segments until removed automatically, until the pilot enters a direct-to routing, or until pilot (manual) cancellation.
• The parallel offset (Appendix I) function must be available for en route TF and the geodesic portion of DF leg types.
Note: Systems compliant with parallel offset (Appendix I) requirements in RTCA/DO-229C (or later revision), DO-236C (or later revision) or DO-283A (or later revision) meet the parallel offset criteria for RNP 4.
10. For RNP 4 tracks in oceanic/remote continental airspace using flexible
(e.g., organized) tracks, a means to enter the unique waypoints required to build a track assigned by the Air Traffic Service (ATS) provider. Manual entry or creation of new waypoints is permitted, by manual entry of latitude and longitude.
11. The capability for automatic leg sequencing with display to the pilots.
12. The capability to automatically sequence fixes.
13. The capability to display an indication of the RNP 4 system failure in the pilot’s primary FOV.
14. The capability to indicate to the crew when the NSE alert limit is exceeded
(i.e., the alert provided by the onboard performance monitoring and alerting function).
15. The system must have the capability to perform flyby transitions:
• Flyby transitions must be the default when a transition type is not specified,
• Navigation systems should be designed to keep aircraft within the theoretical transition area, and
Appendix F F-8
• Flyby theoretical transition areas are based upon the following assumptions:
1. Course changes do not exceed 120 degrees for low altitude transitions (aircraft barometric altitude is less than flight level (FL) 195), and
2. Course changes do not exceed 70 degrees for high altitude transitions (aircraft barometric altitude is equal to or greater than FL 195).
Note: Systems compliant with the flyby transition requirements in RTCA/DO-236C (or later revision), or DO-283A (or later revision) meet the flyby transition criteria for RNP 4.
F.6.4 Database Integrity. The operator must ensure their navigation database supplier possesses a Type 2 Letter of Acceptance (LOA) in accordance with AC 20-153( ), Acceptance of Aeronautical Data Processes and Associated Databases.
F.6.5 Path Terminators. The database supplier should not substitute path terminators in lieu of those specified in the original State AIP data.
F.7 Operational Requirements.
F.7.1 Navigation Equipage. All RNP 4 operations in oceanic and remote continental areas must have at least dual independent LRNSs of integrity such that the navigation system does not provide misleading information.
F.7.2 Aircraft Incorporating GPS. Aircraft equipped with GPS avionics by one of the following three methods is acceptable for receiving an RNP 4 operational approval:
1. Federal Aviation Administration (FAA) responsible Aircraft Certification Service office (or U.S. Military equivalent) letter meeting performance requirements of FAA N 8110.60, GPS as a Primary Means of Navigation for Oceanic/Remote Operations, canceled December 4, 1996.
2. FAA responsible Aircraft Certification Service office (or U.S. Military equivalent) letter meeting performance requirements of AC 20-138( ).
3. GPS avionics marked with TSO-C129( )/TSO-C145( )/TSO-C146( )/ TSO-C196( ) and installed in accordance with AC 20-138( ).
F.7.2.1 The equipment configuration used to demonstrate the required accuracy must be supportable in RNP 4 oceanic and remote continental airspace. For example, the statistical benefit of estimating position using INS position data filtered with distance measuring equipment (DME) data will not be considered.
F.7.2.2 The equipment configuration used to demonstrate the required accuracy must be identical to the configuration, which is specified in the minimum equipment list (MEL).
Appendix F F-9 F.7.3 Aircraft Qualification Documentation. The aircraft or avionics manufacturers should develop aircraft qualification documentation that shows compliance with the applicable criteria, as appropriate. For aircraft without approval to fly RNP 4 operations, the aircraft or avionics manufacturers should develop RNP 4 qualification documentation showing compliance with this appendix provided equipment is properly installed and operated.
The necessary documentation should also define the recommended RNP maintenance procedures. This is not required for aircraft with an AFM or AFMS which explicitly states that the RNP system is approved for instrument flight rules (IFR) operations with RNP values at least as low as RNP 4 and the equipment meets the performance and reliability guidance of AC 20-138( ).
F.7.3.1 Prior to application, operators and manufacturers of their equipment should review all performance requirements. Installation of equipment by itself does not guarantee operational approval or permit operational use.
F.8 Operational Considerations.
F.8.1 Pilot Training and Qualification. Operators should ensure pilots are trained and qualified to operate in RNP 4 airspace.
F.8.2 Preflight. The following actions should be completed during preflight:
1. Review maintenance logs and forms to ascertain the condition of equipment required for flight in RNP 4 airspace or on an RNP 4 route, and
2. Ensure that maintenance action has been taken to correct defects to required equipment.
F.8.2.1 At dispatch or during flight planning, the operator must ensure that adequate navigation capability is available en route to enable the aircraft to navigate to RNP 4 and include the availability of FDE, if appropriate for the operation.
Note: When the predicted loss of FDE exceeds 25 minutes, then RNP 4 operations are not available, and the operator must reschedule the flight.
F.8.3 General In-Flight Considerations. For flexible route structures, manual entry of waypoints (i.e., latitude and longitude) may be permitted provided the potential for entry error by pilots is mitigated by adequate flightcrew procedures. The manual entry or creation of new waypoints, by manual entry of latitude and longitude or rho/theta values for fixed, published routes is not permitted. The pilot may modify the route through the insertion or deletion of specific waypoints in response to air traffic control (ATC) clearances. Pilots must not change any database waypoint type from a flyby to a flyover or vice versa.
F.8.3.1 The pilot must confirm the correct route is loaded. 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
Appendix F F-10 altitude or speed constraints. A navigation system textual display or navigation map display must be used.
Note: Flightcrew may notice a slight difference between the navigation information portrayed on the chart and their primary navigation display. Differences of 3 degrees or less may result from equipment manufacturer’s application of magnetic variation and are operationally acceptable.
F.8.3.2 For RNP 4 operations, pilots must use a lateral deviation indicator, flight director (FD), or autopilot (AP) in lateral navigation (LNAV) mode. Pilots of aircraft with a lateral deviation display must ensure lateral deviation scaling is suitable for RNP 4 operations.
F.8.3.3 At least two independent LRNS capable of navigating to the RNP should be operational at the oceanic entry point. If this is not the case, the pilot should consider an alternate routing or divert for repairs.
F.8.3.4 If the navigation system does not automatically retrieve and set RNP 4 from the onboard navigation database for the entirety of the RNP 4 operation, the flightcrew’s operating procedures must manually set RNP 4. This ensures proper RNP system monitoring and alerting is available for the RNP 4 operation.
F.8.3.5 Operator in-flight procedures must include verifying the RNP value set in the FMS matches the equipment capability and authorizations as annotated in the flight plan prior to entering oceanic and remote continental airspace.
F.8.3.6 Operator in-flight operating procedures must include mandatory cross-checking procedures to identify navigation errors in sufficient time to prevent aircraft from an inadvertent deviation from ATC-cleared routes.
F.8.3.7 Crews must advise ATC of any deterioration or failure of the navigation equipment below the navigation performance requirements or of any deviations required for a contingency procedure.
F.8.3.8 All pilots are expected to maintain centerline, as depicted by onboard lateral deviation indicators and/or flight guidance during all RNP operations described in this AC unless authorized to deviate by ATC (such as Strategic Lateral Offset Procedure (SLOP)) or under emergency conditions.
For normal operations, XTK error/deviation (the difference between the displayed path and the displayed aircraft position relative to the displayed path, (i.e., FTE)) should be limited to half the RNP value associated with the procedure (i.e., 2 NM for RNP 4). Brief deviations from this standard
(e.g., overshoots or undershoots) during and immediately after turns, up to a maximum of one times the RNP value (i.e., 4 NM for RNP 4), are allowable.
Appendix F F-11 Note: Some aircraft do not display or compute a path during flyby turns. As such, pilots of these aircraft may not be able to adhere to half the lateral navigation accuracy during turns but are still expected to satisfy the standard during intercepts following turns and on straight segments. This does not apply to the execution of fixed radius transition (FRT) procedures.
F.8.3.9 Operational qualification for RNP routes requires flightcrew monitoring of lateral and, if installed, vertical deviations on the pilot’s PFDs to ensure the aircraft remains within the bounds defined by the route. The deviation must be monitored, and action taken to minimize errors during all RNP operations.
F.8.3.10 The flightcrew must be able to assess the impact of equipment failure on the anticipated RNP operation and take appropriate action.
F.8.3.11 In addition to normal operating procedures, prior to commencing the procedure the flightcrew should accomplish the following:
1. For multisensor systems, crews must verify that the correct sensor is being used for position computation; and
2. Where Controller-Pilot Data Link Communication (CPDLC) is used to uplink flight plan changes for routing that is not contained in the navigation database, the flightcrew should confirm the RNP in effect matches the airspace requirement. If not, the flightcrew should manually enter the RNP applicable to the route.
F.8.3.12 Emergency procedures for operations in RNP 4 airspace or on RNP 4 routes are no different than normal oceanic emergency procedures with one exception, crews must be able to recognize and ATC must be advised when the aircraft is no longer able to navigate to its RNP 4 approved capability.