Appendix A A-9 A.7.1.5 Manually selecting aircraft bank limiting functions can reduce the aircraft’s ability to maintain the desired track (DTK) and is not recommended.
A.7.1.6 The aircraft RNP APCH capability is dependent on operational aircraft equipment. The flightcrew must be able to assess the impact of equipment failure on the anticipated RNP APCH operation and take appropriate action.
When the dispatch of a flight is predicated on flying an RNP APCH requiring the use of the AP or FD at the destination and/or alternate, the operator must determine that the AP and/or FD is installed and operational.
A.7.1.7 The availability of the navigation infrastructure, required for the intended routes, procedures, or instrument approaches (including any non-RNP contingencies) must be confirmed for the period of intended operations using all available information. Since GPS integrity (e.g., receiver autonomous integrity monitoring (RAIM) or SBAS signal) is required, the availability of these should also be determined, as appropriate (see Chapter 9, Flight Planning, of this AC).
A.7.1.8 The pilot must notify ATC of any loss of the RNP APCH capability, together with the proposed course of action. If unable to comply with the requirements of an RNP APCH procedure, pilots must advise the Air Traffic Service (ATS) as soon as possible. The loss of RNP APCH capability includes any failure or event causing the aircraft to no longer satisfy the RNP APCH requirements of the procedure. The operator should develop contingency procedures in order to react safely following the loss of the RNP APCH capability during the approach.
A.7.2 During the Procedure. Pilots must comply with any instructions or procedures identified by the manufacturer as necessary to comply with the performance requirements in this AC.
A.7.2.1 Pilots must confirm the system has initiated transition from terminal mode to approach mode by 2 NM prior to the FAF.
A.7.2.2 The appropriate displays must be selected so that the following information can be monitored:
1. The RNP APCH computed DTK and
2. Aircraft position relative to the path cross-track (XTK) deviation for FTE monitoring.
A.7.2.3 All pilots are expected to maintain procedure centerline, as depicted by onboard lateral deviation indicators and/or flight guidance during the approach procedure unless authorized to deviate by ATC or under emergency conditions.
Appendix A A-10 A.7.2.4 While operating on RNP APCH segments, pilots are encouraged to use FD and/or AP in LNAV mode and VNAV mode, if available.
A.7.2.5 For aircraft requiring two pilots, crews must verify that each pilot’s altimeter has the current setting before beginning the final approach of an RNP APCH procedure. The crew must also observe any operational limitations associated with the source(s) for the altimeter setting and the latency of checking and setting the altimeters approaching the FAF.
A.7.2.6 Although scaling should change automatically, pilots of aircraft with a lateral deviation indicator (e.g., CDI) must ensure that lateral deviation indicator scaling (full-scale deflection) is suitable for the various segments of the procedure (i.e., ±1.0 NM for the initial and intermediate segments, ±0.3 NM for the FAS, and ±1.0 NM for the missed approach segment).
A.7.2.7 RNP APCH procedures require flightcrew monitoring of lateral and, if installed, vertical track deviations on the pilot’s PFDs to ensure the aircraft remains within the bounds defined by the procedure.
A.7.2.8 The flightcrew must initiate a go-around if either a lateral or vertical deviation is too large unless the visual conditions required to continue the approach exist between the aircraft and the runway of intended landing.
A.7.2.9 For normal operations, XTK/deviation (the difference between the displayed computed path and the displayed aircraft position relative to the path) should be limited to the values specified for the segment of the procedure (i.e., 0.5 NM for the initial and intermediate segments, 0.25 NM for the FAS, and 0.5 NM for the missed approach segment). 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., 1.0 NM for the initial and intermediate segments) are allowable.
A.7.2.10 Flightcrew accomplishing RNP APCH IAPs (RNAV (GPS) or RNAV (GNSS) are required to monitor lateral and, if approved for operational credit, vertical guidance deviations. For baro-VNAV approach operations on an RNP APCH using the LNAV/VNAV minimums, aircraft qualified using AC 20-138( ) must allow the pilot to readily distinguish if the XTK deviation exceeds the RNP value (or a smaller value) or if the vertical deviation exceeds 75 feet (or a smaller value). This information must be published in the AFM, a STC, or verified by the Aircraft Evaluation Division (AED).
Note: Aircraft approved under previous AC guidance using baro-VNAV with LNAV/VNAV minimums, the legacy vertical deviation limits of +100/-50 feet remains valid.
Appendix A A-11 A.8 Go-Around or Missed Approach.
A.8.1 Visual References. Unless the pilot has in sight the visual references required to continue the approach, the procedure must be discontinued if any of the following conditions occur:
1. The navigation display is flagged invalid,
2. Loss of integrity alerting function,
3. The integrity alerting function is activated before passing the FAF, or
4. Lateral or vertical deviation exceeds the limits in paragraphs A.7.2.6, A.7.2.9, and A.7.2.10.
Appendix B B-1 APPENDIX B. USE OF BAROMETRIC VERTICAL NAVIGATION (BARO-VNAV)
FOR REQUIRED NAVIGATION PERFORMANCE APPROACH (RNP APCH)
OPERATIONS B.1 Introduction. This appendix addresses those systems using barometric altitude and navigation system information in the definition of vertical flightpaths and vertical tracking to a path. Baro-VNAV provides vertical path information defined by vertical angles or altitudes at fixes in the RNP APCH procedure. This specification provides system and operational criteria for the approval of a vertical navigation (VNAV) system using barometric altimetry as a basis for its vertical navigation capability.
B.2 Applicability. This appendix applies to all operators conducting baro-VNAV operations under Title 14 of the Code of Federal Regulations (14 CFR) parts 91, 91 subpart K (part 91K), 121, 125, 129, and 135 within the U.S. National Airspace System (NAS).
This appendix also provides guidance for approval to use baro-VNAV equipment to perform 14 CFR part 97 Area Navigation (RNAV) (Global Positioning System (GPS)) or GPS instrument approach procedures (IAP) published with a lateral navigation (LNAV)/VNAV line of minima with a decision altitude (DA).
B.3 Aircraft Eligibility.
B.3.1 Required Navigation Performance (RNP) System Capability. Eligible aircraft are those which meet the performance and functional requirements outlined in Appendix A, Qualification Criteria for Required Navigation Performance Approach (RNP APCH) Operations, and Appendix C, Qualification Criteria for Required Navigation Performance (RNP) 1 (Terminal) Operations, as appropriate for the RNP operation.
B.3.2 Baro-VNAV Capability. Eligible aircraft are those with an Airplane Flight Manual (AFM)/Rotorcraft Flight Manual (RFM) or Airplane Flight Manual Supplement (AFMS)/Rotorcraft Flight Manual Supplement (RFMS) which explicitly states that the VNAV system is approved for approach operations in accordance with Advisory Circular (AC) 20-138( ), Airworthiness Approval of Positioning and Navigation Systems. Aircraft accomplishing RNP APCH operations (RNAV (GPS) or RNAV (Global Navigation Satellite System (GNSS)) are required to monitor lateral and, if approved for operational credit, vertical guidance deviations. Aircraft qualified using AC 20-138( ) must allow the pilot to readily distinguish if the cross-track (XTK) deviation exceeds the RNP value (or a smaller value) or if the vertical deviation exceeds 75 feet (or a smaller value). Aircraft with an authorization for Required Navigation Performance Authorization Required (RNP AR) operations are considered eligible for baro-VNAV operations conducted in accordance with this AC.
Note: Aircraft approved under previous AC guidance using baro-VNAV with LNAV/VNAV minimums, the legacy vertical deviation limits of +100/-50 feet remains valid.
Appendix B B-2 B.3.2.1 Part 91 operators should review their AFM or AFMS to establish navigation system eligibility as detailed in paragraph B.3. Once the operator establishes system eligibility, the operator should take steps to ensure that baro-VNAV approach operations are conducted in accordance with the guidance in paragraphs B.4 and B.5. After these actions have been completed, the operator may begin to conduct baro-VNAV approach operations to the published LNAV/VNAV line of minima. A Letter of Authorization (LOA) is not required when eligibility is based on the AFM and provisions of this AC.
B.3.3 Documentation. Parts 91K, 121, 125, 129, and 135 operators should present the following documentation to the responsible Flight Standards office:
1. Sections of the AFM or AFMS which document RNAV/RNP airworthiness approval for approach operations in accordance with B.3; and
2. Sections of the training and operations manuals which reflect the operating policies of B.4 and B.5.
B.3.4 Satisfaction. Once the operator has addressed the guidance in these paragraphs to the satisfaction of the responsible Flight Standards office, the operator may begin to conduct baro-VNAV approach operations to the published LNAV/VNAV line of minima.
B.3.5 Eligibility Not Based on the AFM or AFMS (Special Approval). The operator may not be able to determine baro-VNAV approach eligibility from the AFM or AFMS. In this case, a part 91 operator should request that the assess the equipment for baro-VNAV approach eligibility while parts 91K, 121, 125, 129, and 135 operators should request that the responsible Flight Standards office make the eligibility assessment. The operator should provide the responsible Flight Standards office with the baro-VNAV system make, model, and part number, any evidence of instrument flight rules (IFR) navigation system approval, and pertinent information from crew operating procedures. If the responsible Flight Standards office is unable to determine equipment eligibility, it should forward the request and supporting data to the Aircraft Evaluation Division (AED). The AED will verify that the aircraft and RNP system meet the criteria for baro-VNAV, and that the system can safely fly specified VNAV paths associated with IAPs applying a DA rather than a minimum descent altitude (MDA). The AED will provide written documentation
(i.e., amend Flight Standards Bulletin Report or other official documentation) to verify the eligibility of that equipment. Additionally, the Aircraft Certification Service (AIR) may be consulted.
B.3.5.1 For part 91 operators, if the FAA determines that the navigation equipment is eligible for baro-VNAV instrument approach operations to a published DA, the Flight Standards District Office (FSDO) will provide documentation that the aircraft equipment is approved for these baro-VNAV operations.
B.3.5.2 For parts 91K, 121, 125, 129, and 135 operators, the FAA will attempt to establish system eligibility and ensure that the operator’s training and operations manuals reflect the operating policies of paragraphs B.4 and B.5.
Once these steps are successfully completed, the operator may begin using
Appendix B B-3 this baro-VNAV equipment to fly to the LNAV/VNAV DA as published on the procedure.
B.4 Operating Procedures (General). For baro-VNAV approach operations, the flightcrew should be familiar with the following operating procedures.
B.4.1 Actions at DA. The pilot/crew is expected to fly the aircraft along the published vertical path and execute a Missed Approach Procedure (MAP) upon reaching DA, unless the visual references specified in part 91, § 91.175 for continuing the approach are present.
B.4.2 Temperature Limitation. Because of the pronounced effect of nonstandard temperature on baro-VNAV systems, RNAV (GPS) approaches with an LNAV/VNAV line of minima should contain a low and high temperature limitation. Uncompensated baro-VNAV systems may not operate to the LNAV/VNAV DA when the actual temperature is below or above the temperature limitations. The temperature limitation will be shown as a note on the procedure. If the aircraft contains a temperature compensation capability, manufacturer instructions should be followed for use of the baro-VNAV function.
B.4.3 VNAV Path Mode Selection. Crews should be knowledgeable on selection of the appropriate vertical mode(s) that command VNAV via the published vertical path. Other vertical modes such as Vertical Speed (VS) are not applicable to baro-VNAV approach operations.
B.4.4 Remote Altimeter Setting Restriction. Use of baro-VNAV to a DA is not authorized with a remote altimeter setting. A current altimeter setting for the landing airport is required.
Where remote altimeter minima are shown, the VNAV function may be used but only to the published LNAV MDA.
B.4.5 Altimetry Cross-Check.
B.4.5.1 Pilots must verify the current local altimeter at the airport of intended landing is set not later than the final approach fix (FAF). Remote altimeter settings are not allowed.
B.4.5.2 Where two pilots are required, the flightcrew must complete an altimetry cross-check ensuring both pilots’ altimeters agree within ±100 feet prior to the FAF after receiving the current local altimeter setting at the airport of intended landing. If the altimetry cross-check fails then the procedure should not be conducted or, if in progress, it must not be continued. The flightcrew procedures should also address actions to take if a comparator warning for the pilots’ altimeters occurs while conducting a RNP APCH procedure.
Note: This operational cross-check is not necessary if the aircraft automatically compares the altitudes to within 100 feet.
Appendix B B-4 B.4.6 VNAV System Cross-Check. For baro-VNAV operations to the LNAV/VNAV line of minima, pilots must cross-check the vertical guidance displayed by the navigation system against other available data at the FAF. If the difference between the displayed glidepath and the published altitude at FAF exceeds 75 feet, the LNAV/VNAV line of minima may not be used. Pilots should revert to the LNAV line of minima and comply with any published stepdown fix altitude.
Note 1: This cross-check is not required when GPS/Satellite-based Augmentation System (SBAS) vertical guidance is used with the LNAV/VNAV line of minima.
Note 2: For systems that provide temperature compensation capability, the displayed temperature compensated glidepath should be compared to the temperature compensated altitude computed by system when crossing the FAF.
Note 3: This cross-check may be accomplished by ensuring that the glidepath displacement from center does not exceed 75 feet when crossing the FAF at the published crossing altitude, or if descending on a centered glidepath, ensuring that the aircraft’s altitude crossing the FAF is within 75 feet of the altitude published at the FAF.
Note 4: Aircraft approved under previous AC guidance using baro-VNAV with LNAV/VNAV minimums, the legacy vertical deviation limits of +100/-50 feet remains valid.
B.5 Pilot Knowledge. Pilot knowledge should include the following:
1. The aeronautical instrument approach chart that will promulgate LNAV/VNAV procedures including, but not limited to, temperature and altimeter source limitations for baro-VNAV operations.
2. Barometric altimeters are calibrated to indicate true altitude under International Standard Atmosphere (ISA) conditions.
3. The effect of temperature on true altitude vs. indicated altitude (i.e., warmer than ISA, the true altitude will be higher than indicated altitude and colder than ISA, the true altitude will be lower than indicated altitude).
4. Understanding the VNAV system capabilities relating to geometric or performance-based VNAV paths.
5. Understanding the use of VNAV angles and altitude restrictions during arrival.
6. Interpretation of electronic displays and symbols.
7. Levels of automation, mode annunciations, changes, alerts, interactions, reversions, degradation.
8. Turn anticipation with consideration to speed and altitude effects.
9. Functional integration with other aircraft systems.
Appendix B B-5
10. The meaning of vertical path discontinuities as well as related flightcrew procedures.
11. VNAV equipment operating procedures, including how to determine vertical-track error/deviation.
12. Procedures for change in arrival/runway assignment.
13. Understanding of possible conflicts between aircraft performance and flight management system (FMS) functions (e.g., airspeed and descent angles).
14. Failures and mode reversions, which adversely impact the aircraft’s ability to conduct baro-VNAV approach operations.
15. Contingency downgrade actions (i.e., reverting to LNAV MDA following VNAV failures).
16. Contingency abort actions (i.e., understand which failures and performance parameters require discontinuing the approach and executing an early missed approach).
17. Altimeter cross-check procedures.
18. VNAV system-specific information, including VNAV vertical deviation scaling provided in the Final Approach Segment (FAS). Pilot and flightcrews should be knowledgeable in applying this scaling to the baro-VNAV display cross-check required at the FAF when conducting an approach to the LNAV/VNAV line of minima.
Appendix C C-1 APPENDIX C. QUALIFICATION CRITERIA FOR REQUIRED NAVIGATION PERFORMANCE (RNP) 1 (TERMINAL) OPERATIONS C.1 Introduction. This appendix provides guidance on the performance and functional requirements for systems used to conduct RNP in terminal operations. This appendix includes:
1. Instrument departure procedures (DP) RNP Obstacle Departure Procedures (ODP),
2. RNP Standard Instrument Departures (SID), and
3. RNP Standard Terminal Arrival Routes (STAR).
C.2 Aircraft and System Requirements for RNP Terminal Operations.
C.2.1 Performance and Airworthiness Guidance. Refer to Advisory Circular (AC) 20-138( ), Airworthiness Approval of Positioning and Navigation Systems, for performance and airworthiness guidance on aircraft and system criteria.
C.2.2 Statement of Compliance (SOC). Aircraft with an SOC with the criteria in this AC or AC 20-138( ) 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 AC.
C.2.3 Qualified Avionics Equipment and Airworthiness Approval. Aircraft with the following avionics equipment and an appropriate airworthiness approval automatically qualify for RNP 1 capability without further documentation by virtue of the avionics Technical Standard Order (TSO) and airworthiness approval:
1. Global Positioning System (GPS) stand-alone systems approved in accordance with TSO-C146( ) operational Class 1, 2, or 3.
2. A TSO-C115c light management system (FMS) (or later revision) with a TSO-C129( ) Class B1 or C1, TSO-C145( ), or TSO-C196( ) sensor.
Note: TSO-C129a has been cancelled, but equipment with an existing TSO-C129a Technical Standard Order Authorization (TSOA) may still be installed.
3. A TSO-C115b FMS using a TSO-C129( ) Class B1 or C1, TSO-C145( ), or TSO-C196( ) sensor with documented compliance to the RNP requirements in RTCA, Inc.’s document, RTCA/DO-236 (revision ‘B’ or later) or RTCA/DO-283A.
4. Aircraft with a Required Navigation Performance Authorization Required (RNP AR) approval per AC 90-101( ), Approval Guidance for RNP Procedures with AR, or AC 20-138( ).
Appendix C C-2 C.2.3.1 Aircraft/equipment with approval under AC 90-100( ), U.S. Terminal and En Route Area Navigation (RNAV) Operations, for use of GPS are approved under this AC for RNP 1 operations.
C.2.3.2 GPS stand-alone systems approved in accordance with TSO-C129( ) Class A1 typically supports RNP 1 operations associated with instrument approach and DPs, but might not support other operations requiring RNP 1. TSO-C129( ) avionics manufacturers should provide an RNP capabilities document stating compliance with the criteria in AC 20-138( ) for RNP 1 capability. Avionics or aircraft manufacturers may provide a Service Bulletin (SB) for a pilot or equipment operating handbook entry or other notification stating aircraft with this equipment has RNP 1 capability based on the avionics manufacturer’s SOC.
C.2.3.3 RNP 1 aircraft with European Precision Area Navigation (P-RNAV) approval based on GPS capability meet the functional requirements of this AC for RNP 1 operations, such as RNP DPs, RNP SIDs, and RNP STARs. GPS equipment approved in accordance with TSO-C129a and satisfying the step-detection and health word checking contained in TSO-C129a meet P-RNAV performance requirements.
Note 1. RNP 1 operations are based on GPS positioning and, if adequate coverage is available, distance measuring equipment (DME)/DME/Inertial Reference Unit (IRU). 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.
Note 2. TSO-C145 or TSO-C146 equipment may also be authorized, in accordance with this AC, for use as the only means of navigation for conducting RNP 1 operations in the U.S. airspace where domestic air traffic control (ATC) procedures are applied. This includes RNP operations outside the navigational service volume of the Federal Aviation Administration (FAA) or the International Civil Aviation Organization (ICAO) standard ground-based Navigational Aids (NAVAID).
Note 3: Operators are encouraged to retain back-up navigation systems to guard against outages and interference events.
C.3 System Performance, Monitoring, and Alerting.
C.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 1, the lateral TSE must be within ±1 nautical mile (NM) for at least 95 percent of the total flight time. The along-track (ATRK) error must also be within ±1 NM for at least 95 percent of the total flight time.
Appendix C C-3 To satisfy the 95 percent accuracy requirement, Flight Technical Error (FTE) should not exceed 0.5 NM for autopilot (AP) or flight director (FD) or 0.8 NM for manual control.
Note: The use of a lateral deviation indicator with 1 NM full-scale deflection has been found to be an acceptable means of compliance (AMC). An AP or FD may also be used for maintaining TSE, but roll stabilization systems do not qualify.
C.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).
C.3.3 Continuity. Loss of function is classified as a minor failure condition if the operator can revert to a different navigation system and proceed to a suitable airport.
C.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 NM is greater than 10-5 for RNP 1 operations.
C.3.5 Path Definition. Aircraft performance is evaluated around the path defined by the published procedure and RTCA/DO-236C.
C.3.6 Signal in Space (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 2 NM exceeds 10-7 per hour for RNP 1 operations.
Note: Aircraft with an approved multisensor RNP system where Global Navigation Satellite System (GNSS) integrity is incorporated into a 2 x RNP integrity alert consistent with DO-236( ) do not require a separate GNSS integrity alert when performance cannot be met.
C.3.7 Functional Requirements of Navigation Data Displays. The following navigation displays and functions are required and must be installed in accordance with AC 20-138( ) or equivalent airworthiness installation advisory material.
C.3.7.1 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:
Appendix C C-4
1. The displays must be visible to the pilot and located in the primary field of view (FOV) when looking forward along the flightpath.
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 and must be based on the required total system accuracy; ±1 NM for RNP 1. It is also acceptable for the scaling to be more conservative (e.g., ±0.5 NM for an RNP 1 route).
4. The display scaling may be set automatically by default logic or set to a value obtained from a navigation database. The full-scale deflection value must be known or must be available for display to the pilot commensurate with terminal area values.
5. The lateral deviation display must be automatically slaved to the RNP 1 computed path. It is recommended that the course selector of the deviation display be automatically slewed to the RNP-computed path.
C.3.7.2 As an alternative 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.
C.3.7.3 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.
C.3.8 System Capabilities. The following system capabilities are required as a minimum within any RNP 1 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), 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.