Appendix C C-6 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( ).
12. The system must have either automatic or manual capability to fly on a heading to intercept a course or to go direct to another fix after reaching a procedure-specified altitude. The system may use heading to altitude (VA), heading to manual (VM) and heading to intercept (VI) path terminators for automatic capability.
13. The aircraft must have the capability to automatically execute leg transitions consistent with Course to Altitude (CA) and Fix to Manual Termination (FM) ARINC Specification 424 path terminators, or the RNP system must permit the pilot to readily designate a waypoint and select a desired course to or from a designated waypoint.
14. For paths defined by a course (e.g., CF and Fix to an Altitude (FA) path terminators), the navigation system should use the appropriate magnetic variation value of the recommended NAVAID in the navigation database.
15. The capability to load a RNP 1 procedure from the database, by procedure name, into the RNAV system.
16. The capability to display an indication of the RNP 1 system failure, in the pilot’s primary FOV.
17. The system must allow for a means to become established prior to the final approach fix (FAF) on an instrument landing system (ILS) or Ground Based Augmentation System (GBAS) Landing System (GLS) with minimal overshoot or undershoot.
C.3.9 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.
C.3.10 Path Terminators. For RNP procedures, the database supplier should not substitute path terminators in lieu of those specified in the original Aeronautical Information Publication (AIP) data.
C.4 Special Characteristics of RNP 1 Operations.
C.4.1 Operation on RNP ODPs, SIDs, STARs. DME/DME/IRU and/or GNSS are the primary navigation systems supporting RNP 1 operations. Refer to AC 20-138( ), Chapter 6, Sections 6-4, 6-6, and 6-8 for additional aircraft and system qualification criteria when using DME/DME/IRU. Pilots are not required to monitor ground-based navigation facilities used in position updating unless required by the AFM.
C.4.2 Navigation Infrastructure. The FAA will monitor the navigation infrastructure and issue timely warnings of outages and facilities designated out of service (i.e., issue Notices to Airmen (NOTAM)).
Appendix C C-7 C.4.3 Source Data. FAA source data contains the navigation performance needed to fly each RNP procedure and must be clearly designated on all appropriate charts.
C.4.4 DME/DME/IRU. If DME/DME/IRU is used, the available DME navigation infrastructure supporting the design of a procedure will be assessed and validated by the FAA or an FAA-authorized third party service provider.
C.4.4.1 The FAA will ensure all DME signals within reception distance of U.S. airspace meet ICAO standards. These could include non-U.S. DME facilities, or Department of Defense (DOD)-maintained DME facilities excluded from the U.S. National Airspace System (NAS) database. Procedure designs will only use DME facilities listed in the Chart Supplements.
C.4.4.2 DME signals will meet SIS accuracy tolerances everywhere the signals are received in that procedure.
C.4.4.3 For DME-based RNP operations where reliance is placed upon the IRU/inertial reference system (IRS), some aircraft systems revert to very high frequency omni-directional range (VOR)/DME-based navigation before reverting to inertial coasting. When the VOR is within 40 NM from the procedure, and there is insufficient DME/DME navigation infrastructure, the impact of VOR radial accuracy will be evaluated by the FAA to determine the effect on aircraft position accuracy.
C.4.5 DME Facilities. If any critical DME facilities exist for ODPs, SIDs, and STARs, they will be identified within the relevant U.S. Flight Information Publications (FLIP) and comply with applicable ICAO standards.
Note: Procedures with (GPS) in the title or with a GPS required are not evaluated for critical DMEs.
C.5 System Eligibility and Approval for RNP 1 Operations.
C.5.1 Requirements. Systems meeting the requirements in AC 20-138( ) are eligible for RNP 1 operations. Aircraft qualified by AC 90-101( ) are considered qualified for RNP 1 operations without further examination. Additionally, aircraft approved to conduct RNAV 1 procedures using GPS, according to AC 90-100( ), do not require further evaluation (see paragraph C.6.3.2).
1. Stand-Alone Systems. GPS stand-alone systems should be approved in accordance with TSO-C129a Class A1 or TSO-C146( ) Class 1, 2, or 3 and meet the functionality requirements of this appendix. GPS systems must be installed in accordance with AC 20-138( ).
2. Multisensor Systems. Aircraft with a TSO-C129 Class B1, C1, B3, or C3, TSO-C145( ), Class 1, 2, or 3, or TSO-C196 sensors installed in an FMS that meets the requirements of TSO-C115b or later and is installed for instrument flight rules (IFR) use in accordance with AC 20-138( ).
Appendix C C-8
3. Multisensor Systems That Rely on Ground-Based NAVAIDs. Multisensor systems that require the use of ground-based NAVAIDs, such as DME/DME, can be used to conduct RNP 1 operations provided that the documentation described in this appendix shows the aircraft is approved for RNP instrument flight operations, the aircraft meets the functional and performance requirements for RNP 1 (e.g., RNP performance monitoring and alerting) and the requirements of AC 90-100( ), Appendix 1, or Appendix 2, as applicable.
Note: Manufacturers should also ensure the equipment in paragraph C.5.1, Items 1, 2, and 3 meet all functional requirements in this AC.
C.5.2 Demonstrations. Demonstration of aircraft performance in accordance with AC 20-138( ) does not constitute operations approval to conduct RNP operations.
C.6 Operational Approval for RNP 1 Operations.
C.6.1 Aircraft Qualification Documentation. The aircraft or avionics manufacturers should develop aircraft qualification documentation that shows compliance with the applicable criteria, as appropriate. This is not required for aircraft with an AFM or AFMS which explicitly states that the RNP system is approved for IFR operations with RNP values at least as low as RNP 1 and the equipment meets the performance and reliability requirements of AC 20-138( ).
C.6.2 Performance Requirements. 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.
C.6.3 FAA Acceptance of Documentation.
C.6.3.1 New Aircraft/Equipment. The aircraft/equipment qualification documentation can be approved as part of an aircraft certification project and reflected in the AFM and related documents.
C.6.3.2 Existing Aircraft/Equipment. Previous approvals to conduct RNAV 1 procedures using GPS, according to AC 90-100( ), do not require further evaluation.
C.6.3.3 Previously Unapproved Installations/Equipment. For installations/equipment not previously approved to conduct RNAV 1 procedures, the aircraft or avionics manufacturer should submit the RNP 1 documentation in accordance with AC 20-138( ). The operator will submit the RNP operational application package (if required) to the FAA.
C.7 Operational Considerations.
C.7.1 Preflight Planning. For systems with receiver autonomous integrity monitoring (RAIM)-based integrity, RAIM prediction must be performed prior to departure. This capability can be a ground service and need not be resident in the aircraft’s avionics
Appendix C C-9 equipment. Preflight integrity checks and the various capabilities that can be utilized to perform them can be found in the Chapter 9, Flight Planning, of this AC.
C.7.2 Multisensor Systems with RNP 1 Approval. For multisensor systems with RNP 1 approval based on DME/DME, pilots must confirm the availability of critical DME for ODPs, SIDs, and STARs.
Note: Procedures with (GPS) in the title and with a GPS required are not evaluated for critical DMEs.
C.7.3 Radius to Fix (RF) Legs. For RNP 1 operations employing RF legs, confirmation of RF leg aircraft eligibility must be confirmed during preflight planning. Refer to Appendix I, Additional Capabilities, for aircraft RF leg eligibility requirements.
C.7.4 General In-Flight Considerations. Pilots must not fly an RNP 1 procedure unless it is retrievable by the procedure name from the onboard navigation database and conforms to the charted procedure. Numeric values for courses and tracks should be automatically loaded from the RNP navigation database for required leg types. However, the procedure may subsequently be modified through the insertion or deletion of specific waypoints in response to ATC clearances. 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. Additionally, pilots must not change any database waypoint type from a flyby to a flyover or vice versa.
C.7.4.1 During RNP 1 operations, pilots must use a navigation system textual display or navigation map display.
C.7.4.2 If the navigation system does not automatically retrieve and set RNP 1 from the onboard navigation database for the entirety of the RNP 1 operation, the flightcrew’s operating procedures must manually set RNP 1.
C.7.4.3 For RNP 1 operations, pilots must use a lateral deviation indicator, FD, or AP in lateral navigation (LNAV) mode. Pilots of aircraft with a lateral deviation display must ensure lateral deviation scaling is suitable for the RNP value associated with the procedure.
Note: If the RNP 1 operation extends beyond 30 NM from the airport and a lateral deviation indicator is used, its full-scale sensitivity must be selected to not greater than 1 NM.
C.7.4.4 Pilots are not required to monitor ground-based navigation facilities used in position updating unless required by the AFM.
C.7.4.5 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 or under emergency conditions. For normal operations, cross-track (XTK) error/deviation (the difference between the displayed path and the displayed
Appendix C C-10 aircraft position relative to the displayed path, (i.e., FTE)) should be limited to half the RNP value associated with the procedure (i.e., 0.5 NM for RNP 1).
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 RNP 1), are allowable.
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 LNAV 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 either fixed radius transition (FRT) or RF procedures.
C.7.4.6 Operational qualification for RNP procedures 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 procedure. The deviation must be monitored, and action taken to minimize errors during all RNP operations.
C.7.4.7 If ATC issues a heading assignment taking the aircraft off a procedure, the pilot should not modify the primary flight plan in the RNP system until a clearance is received to rejoin the route or the controller confirms a new route clearance. The specified accuracy requirement does not apply when the aircraft is not on the published RNP 1 procedure.
C.7.4.8 The flightcrew must be able to assess the impact of equipment failure on the anticipated RNP operation and take appropriate action.
C.7.4.9 Pilots of aircraft with RNP input selection capability should select RNP 1 or smaller values, for RNP 1 operations.
C.7.4.10 Pilots operating aircraft with an approved vertical navigation (VNAV) system based on barometric altimetry and having airworthiness approval for climb functionality may use it when executing RNP 1 ODPs and SIDs. Pilots operating aircraft with an approved VNAV system based on baro altimetry and having airworthiness approval for descent functionality may use it when executing RNP 1 STARs.
C.7.5 Prior to Commencing the RNP 1 Procedure. In addition to normal operating procedures, prior to commencing the procedure the flightcrew should accomplish the following:
1. The flightcrew must confirm that the correct procedure has been selected. This process includes confirmation of the waypoint sequence, reasonableness of track angles, distances, and any other parameters that can be altered by the pilot, such as altitude or speed constraints. A procedure must not be used if validity of the navigation database is in doubt. A navigation system textual display or navigation map display must be used.
Appendix C C-11
2. For multisensor systems, crew must verify that the correct sensor is being used for position computation.
Appendix D D-1 APPENDIX D. QUALIFICATION CRITERIA FOR REQUIRED NAVIGATION PERFORMANCE (RNP) 0.3 (ROTORCRAFT) OPERATIONS D.1 Introduction.
D.1.1 Performance and Functional Requirements. This appendix provides guidance on the performance and functional requirements for rotorcraft systems used to conduct RNP 0.3 for en route and terminal operations. Consult Advisory Circular (AC) 20-138( ), Airworthiness Approval of Positioning and Navigation Systems, for the latest guidance on aircraft and system qualification criteria for rotorcraft en route and terminal RNP 0.3.
This authorization is applicable to operators conducting operations under Title 14 of the Code of Federal Regulations (14 CFR) parts 91, 91 subpart K (part 91K), and 135.
D.1.2 Heliports and Offshore Rig Service. This appendix provides guidance for rotorcraft RNP 0.3 en route and terminal operations servicing offshore rigs and where RNP 0.3 accuracy may be needed to support low level mountainous operations and also in high density airspace.
D.2 Application of RNP 0.3 for Rotorcraft.
D.2.1 Benefits. Operational benefits include:
1. Reduced protected areas, enabling simultaneous fixed-wing and rotorcraft operations in dense terminal airspace.
2. Low level routes in obstacle rich environments reducing exposure to icing environments.
3. Seamless transition from en route to terminal route.
4. More efficient terminal routing in an obstacle rich or noise sensitive terminal environment, specifically in consideration of helicopter air ambulance (HAA) instrument flight rules (IFR) operations between hospitals.
5. Transitions to rotorcraft point in space (PinS) approaches (prior to the final approach fix (FAF) and after the Missed Approach Procedure (MAP)).
D.2.2 Design. RNP 0.3 is designed for operation in en route, on arrival/departure routes, and approaches (prior to the FAF and after the MAP).
Note: A rotorcraft RNP 0.3 qualification is not a qualification for Required Navigation Performance Authorization Required (RNP AR) procedures.
D.2.3 Area Navigation Capability. The area navigation capability required for RNP 0.3 will encompass the lateral aspects of the desired flightpath. The predictability and performance monitoring and alerting for the lateral flightpath will support a number of applications including closely-spaced tracks, RNP departures/arrivals, RNP airways, and missed approach segments.
Appendix D D-2 D.3 System Requirements for Rotorcraft RNP 0.3 Operations.
D.3.1 Qualification Methods. The following qualification methods are:
1. Rotorcraft with a statement of compliance (SOC) with the criteria in AC 20-138( ), in their Rotorcraft Flight Manual (RFM) or Rotorcraft Flight Manual Supplement (RFMS). Rotorcraft conducting RNP 0.3 operations must have an airworthiness approval for Satellite-based Augmentation System (SBAS)-based IFR operations. Any limitations required for IFR operations will also apply to RNP 0.3 operations.
2. Rotorcraft without an RFM or RFMS statement from the manufacturer documenting compliance must meet the following criteria:
• Global Positioning System (GPS) stand-alone systems should be approved in accordance with Technical Standard Order (TSO)-C146a or later operational Class 1, 2, or 3 and must be installed for IFR operations in accordance with AC 20-138( ).
• Rotorcraft with TSO-C145a or later operational Class 1, 2, or 3 sensor installed with a flight management system (FMS) that meets the requirements of TSO-C115b or later and is installed for IFR use in accordance with AC 20-138( ).
D.3.2 Demonstrations. Demonstration of aircraft performance in accordance with AC 20-138( ) does not constitute operations approval to conduct RNP operations.
D.4 System Performance, Monitoring, and Alerting.
D.4.1 Accuracy. The aircraft must comply with Section 2.1.1 of RTCA/DO-236( ). During operations in airspace or on Air Traffic Service (ATS) routes designated as RNP 0.3, the lateral Total System Error (TSE) must be within ±0.3 nautical mile (NM) for at least 95% of the total flight time. The along-track (ATRK) error must also be within ±0.3 NM for at least 95% of the total flight time. To meet this performance requirement, a Flight Technical Error (FTE) of 0.25 NM (95%) may be assumed.
Note: For all RNP 0.3 operations, the use of an autopilot (AP) and/or flight director (FD) is an acceptable means of complying with this FTE assumption (refer to AC 20-138( ), Table 9). Any alternative means of FTE bounding, other than coupled flight guidance system (FGS), may require FTE substantiation through an airworthiness demonstration.
D.4.2 Integrity. Malfunction of the rotorcraft navigation equipment that causes the TSE to exceed 2 times the RNP value without annunciation is classified as a major failure condition under airworthiness regulations (i.e., 1 x 10-5 per hour).
D.4.3 Continuity. For the purpose of this specification, loss of function is a major failure condition for oceanic and remote continental operations. The carriage of dual independent long-range navigation systems (LRNS) may satisfy the continuity requirement. Loss of function is classified as a minor failure condition for other
Appendix D D-3 RNP 0.3 operations if the operator can revert to a different available navigation system and proceed to a suitable airport.
D.4.4 Performance Monitoring and Alerting. The RNP system, or the RNP system and the pilot in combination, is required to monitor TSE and provides an alert if the accuracy requirement is not met, or if the probability that the lateral TSE exceeds 0.6 NM is greater than 10-5.
D.4.5 Path Definition. RNP systems should provide lateral guidance so aircraft remain within the lateral boundaries of the flyby transition area per TSO-C146( ) or as defined in RTCA/DO-236C.
D.4.6 Signal in Space (SIS). The rotorcraft navigation equipment must provide an alert if the probability of SIS errors causing a lateral position error greater than 0.6 NM exceeds 1 x 10-7 per hour.
D.5 Functional Requirements.
D.5.1 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.
D.5.2 Navigation Displays and Functions Requirements. The RNP 0.3 system must have the following navigation displays and functions installed:
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 rotorcraft, for maneuver anticipation and for failure/status/integrity indication.
2. The capability to continuously display to the pilot flying (PF), on the primary flight instruments for navigation of the rotorcraft (primary navigation display), the computed path and rotorcraft position relative to the path. For operations where the required minimum flightcrew is two pilots, the means for the pilot monitoring (PM) to verify the desired path and the rotorcraft position relative to the path must also be provided.
3. The displays must be visible to the pilot and located in the primary field of view (FOV) when looking forward along the flightpath.
4. The lateral deviation display scaling must agree with the RNP 0.3 alerting and annunciation limits.
5. The lateral deviation display must have ±0.3 NM full-scale deflection based on the required total system accuracy.
6. The display scaling may be set automatically by default logic; automatically to a value obtained from a navigation database; or manually by flightcrew
Appendix D D-4 procedures. The full-scale deflection value must be known or must be available for display to the pilot commensurate with the required accuracy.
7. 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 1: This does not apply for installations where an electronic map display contains a graphical display of the flightpath and path deviation.
Note 2: As an alternate means of compliance, a navigation map display may provide equivalent functionality to a lateral deviation display as described in 1 to 7 above, with appropriate map scales and giving equivalent functionality to a lateral deviation display. The map scale may be set manually to a value appropriate for RNP 0.3 operations. To be approved as an alternative means, the navigation map display should meet the TSE criteria and be located in the primary FOV.
D.5.3 System Capabilities. The following system capabilities and functions are required as a minimum within any RNP 0.3 equipment:
1. The capability to continuously display to the PF, on the primary flight instruments for navigation of the rotorcraft (primary navigation display), the RNP-computed desired path and rotorcraft position relative to the path. For operations where the required minimum flightcrew is two pilots, a means for the PM to verify the desired path and the rotorcraft 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 negligible Path Definition Error (PDE). 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. The capability to load from the database into the RNP system the RNP 0.3 procedure and/or route to be flown.
Note 1: It is acceptable to manually load en route and terminal waypoints from the database into a flight plan page and manually set the scaling and alerting.
Note 2: Due to variability in systems, this document defines the segment from the first occurrence of a named waypoint, track, or course to the last occurrence of
Appendix D D-5 a named waypoint, track, or course. Heading legs prior to the first named waypoint or after the last named waypoint do not have to be loaded from the database.
6. The capability to automatically set RNP 0.3 from the onboard navigation database for each leg segment of a RNP 0.3 route or procedure.
7. The means to display the following items, either in the pilot’s primary FOV, or on a readily accessible display page:
• Along track distances between waypoints,
• 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.
8. The capability to execute a “Direct to” function.
9. The capability for automatic leg sequencing with display of sequencing to the pilot.
10. The capability to execute RNP 0.3 terminal procedures extracted from the onboard database, including the capability to execute flyby turns.
11. The capability to automatically execute leg transitions and maintain tracks consistent with the following Aeronautical Radio, Inc. (ARINC) Specification 424 path terminators, or their equivalent:
• Initial Fix (IF),
• Track to Fix (TF),
• Course to Altitude (CA),
• Direct to Fix (DF), and
• Course to Fix (CF).
Note 1: Path terminators are defined in ARINC Specification 424, and their application is described in more detail in RTCA, Inc.’s documents, DO-236( ) and DO-201( ).
Note 2: The system must be capable of loading numeric values for courses and tracks from the onboard navigation database.
12. The capability to automatically or manually fly on a heading to intercept (VI) a course or to go direct to another fix after reaching a procedure-specified altitude. The system may use heading to altitude (VA), heading to manual (VM) and VI path terminators for automatic capability.
Appendix D D-6
13. The capability to automatically or manually permit the pilot to readily designate a waypoint and select a desired course to or from a designated waypoint. The system may use CA and Fix to Manual Termination (FM) path terminators for automatic capability.
14. The capability for the flightcrew to build an en route or offshore segment in the equipment flight plan function using individual waypoints from the database. This is similar to existing en route capability.
Note: It is also acceptable for the navigation system to automatically load all route waypoints from the database by selecting the route name.
15. The capability to load numeric values for courses and tracks from the onboard navigation database.
16. The capability to display an indication of the RNP 0.3 system failure, in the pilot’s primary FOV.
17. The capability to indicate to the crew when the Navigation System Error (NSE) alert limit is exceeded (alert provided by the onboard performance monitoring and alerting function).
D.5.4 FD/AP. For all rotorcraft RNP 0.3 operations, the use of an AP and/or FD is an acceptable means of complying with FTE assumption in Chapter 4, General Information, of this AC. Any alternate means of FTE bounding will require a demonstration.
D.6 Navigation Database Integrity.
D.6.1 Type 2 Letter of Acceptance (LOA). The operator must ensure their navigation database supplier possesses a Type 2 LOA in accordance with AC 20-153( ), Acceptance of Aeronautical Data Processes and Associated Databases.
D.6.2 Path Terminators. The database supplier should not substitute path terminators in lieu of those specified in the original State Aeronautical Information Publication (AIP) data.
D.7 Operational Approval for RNP 0.3 Operations.
D.7.1 Rotorcraft Qualification Documentation. The rotorcraft and avionics manufacturers should develop rotorcraft qualification documentation that shows compliance. For rotorcraft without RFM approval for RNP 0.3 operations, the rotorcraft and avionics manufacturers should develop RNP 0.3 qualification documentation showing compliance with this appendix. The necessary documentation should also define the recommended operations and maintenance procedures. This is not required for rotorcraft with an RFM or RFMS which explicitly states that the RNP system is approved for IFR operations with RNP values as low as RNP 0.3.
D.7.2 RNP Capability Statement. The GPS/SBAS-enabled navigation system equipment manufacturer should provide an RNP capability statement that the equipment meets the performance and functional criteria in AC 20-138( ), Chapter 9, Section 9-5 for rotorcraft