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
Appendix D D-7 en route and terminal RNP 0.3 operations. If an RNP capability statement is provided, it must include a description of the equipment procedures for pilots to select the rotorcraft en route and terminal RNP 0.3 capability.
D.7.3 Functional and Performance Requirements Review. Manufacturers and commercial operators should review all functional and performance requirements before providing any qualification documentation. Installation of equipment by itself does not guarantee operational approval or permit operational use.
D.8 Federal Aviation Administration (FAA) Acceptance of Documentation.
D.8.1 New Rotorcraft/Equipment. The GPS/SBAS equipment must be installed according to a type certificate (TC), amended TC, or Supplemental Type Certificate (STC) and any rotorcraft limitations required for IFR operations also apply to rotorcraft en route and terminal RNP 0.3 capability. The equipment manufacturer should provide an RNP capability statement (see paragraph D.7.1). It is also acceptable for the TC, air traffic control (ATC), or STC holder to document rotorcraft en route and terminal RNP 0.3 capability in the RFM/RFMS.
D.8.2 Existing Rotorcraft/Equipment. The GPS/SBAS equipment must be installed according to a TC, ATC, or STC and any rotorcraft limitations required for IFR operations also apply to rotorcraft en route and terminal RNP 0.3 capability. The equipment manufacturer should provide an RNP capability statement (see paragraph D.7.1). The operator will submit the RNP operational application package (if required) to the FAA.
D.9 Operational Procedures.
D.9.1 Operational Approval. Airworthiness certification and recognition of RNP 0.3 rotorcraft qualification alone does not authorize RNP 0.3 operations.
D.9.2 Normal and Contingency Procedures. Commercial operations must include normal and contingency RNP 0.3 operational procedures for their particular equipment installation.
D.9.3 Commercial Operators and Approval. Commercial operators must receive approval to fly RNP 0.3 rotorcraft operations via helicopter specification (HSpec).
D.9.3.1 Part 91 operators are not required to have operational approval for RNP 0.3 operations.
D.9.3.2 The operator must have a configuration list and if necessary, a minimum equipment list (MEL) detailing the required aircraft equipment for RNP 0.3 operations.
D.9.4 Preflight Planning. RNP 0.3 is predicated on wide area augmentation system (WAAS) integrity. The availability of WAAS integrity should be confirmed by checking WAAS Notices to Airmen (NOTAM) prior to flight (see Chapter 9, Flight Planning).
Appendix D D-8 D.9.5 General In-Flight Considerations. At system initialization, the pilot must confirm the navigation database is current and check the proper departure entry and correct route depiction. Shortly before takeoff, the pilot must also verify proper entry of their desired ATS route and any ATC changes to that ATS route upon initial clearance and any subsequent change of ATS route. The pilot must ensure the waypoints sequence depicted by their navigation system matches the ATS route depicted on the appropriate chart(s).
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.
D.9.5.1 The pilot must not attempt to fly an RNP 0.3 Instrument Flight Procedure (IFP) unless it is retrievable by name from the onboard navigation database and conforms to the charted procedure. However, the pilot may subsequently modify a procedure by inserting or deleting specific waypoints in response to ATC clearances. The pilot may select the ATS route to be flown for the en route section of the flight from the database or may construct the ATS route by means of selection of individual en route waypoints from the database. 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 Standard Instrument Departure (SID) or Standard Terminal Arrival Route (STAR) database waypoint type from a flyby to a flyover or vice versa.
D.9.5.2 Refer to Appendix H, Advanced Required Navigation Performance (A-RNP) for guidance on scalability and Appendix I, Additional Capabilities, for Radius to Fix (RF).
D.9.5.3 The pilot should cross-check the flight plan clearance by comparing charts or other applicable resources with the navigation system textual display and the rotorcraft map display, if applicable.
D.9.5.4 There is no pilot requirement to cross-check the navigation system’s performance with conventional Navigational Aids (NAVAID) as the absence of an integrity alert is considered sufficient to meet the integrity requirements.
However, the pilot should monitor the reasonableness of the navigation solution and report any loss of RNP 0.3 capability to ATC. In addition, the pilot must continuously monitor the lateral deviation indicator (or equivalent navigation map display) during all RNP 0.3 operations.
D.9.5.5 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 appendix 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 rotorcraft position relative to the displayed path, (i.e., FTE)) should be limited
Appendix D D-9 to half the RNP value associated with the procedure (i.e., 0.15 NM for RNP
0.3). 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., 0.3 NM for RNP 0.3), are allowable.
Note: Some rotorcraft avionics do not display or compute a path during turns. As such, pilots of rotorcraft 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.
D.9.5.6 Operational qualification for RNP procedures requires flightcrew monitoring of lateral and, if installed, vertical deviations on the pilot’s primary flight displays (PFD) to ensure the rotorcraft remains within the bounds defined by the procedure. The deviation must be monitored, and action taken to minimize errors during all RNP operations.
D.9.5.7 If ATC issues a heading assignment taking the rotorcraft 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 rotorcraft is not on a published RNP 0.3 procedure.
D.9.5.8 The flightcrew must be able to assess the impact of equipment failure on the anticipated RNP operation and take appropriate action.
D.9.5.9 Whenever possible, RNP en route and terminal segments should be extracted from the database in their entirety, rather than loading RNP route waypoints from the database into the flight plan individually. Selecting and inserting individual, named fixes from the database is permitted, provided all fixes along the published route to be flown are inserted.
D.9.5.10 Manually selecting rotorcraft bank limiting functions may reduce the rotorcraft’s ability to maintain its desired track (DTK) and is not recommended. The pilot should recognize manually selectable rotorcraft bank-limiting functions might reduce the ability to satisfy path requirements of the procedure, especially when executing large angle turns. This should not be construed as a requirement to deviate from RFM procedures; rather, pilots should be encouraged to avoid the selection of such functions except where needed for flight safety reasons.
D.9.5.11 Any limitations required for normal IFR operation will also apply to rotorcraft en route and terminal RNP 0.3.
D.9.6 Manual Entry of RNP. If the navigation system does not automatically retrieve and set RNP 0.3 from the onboard navigation database for each leg segment of the RNP 0.3 operation, the flightcrew’s operating procedures must verify manually setting RNP 0.3 into the RNP system.
Appendix D D-10 D.9.7 Engagement of FGS after Takeoff. When required, the pilot must be able to engage
(i.e., couple) the FGS prior to reaching the first waypoint defining a procedure requiring RNP 0.3 in accordance with this specification.
D.9.8 RNP 0.3 SID Specific Requirements. Prior to commencing takeoff, the pilot must verify the rotorcraft RNP system is available, operating correctly, and the correct airport/heliport and departure data are loaded and properly depicted (including the rotorcraft’s initial position). A pilot assigned an RNP 0.3 departure procedure (DP) and subsequently issued a change to the procedure or a transition from the procedure must verify that the appropriate changes are entered and available for navigation prior to takeoff. This includes confirmation of the waypoint sequence, reasonableness of track angles and distances, any altitude or speed constraints, and, where possible, identification of which waypoints are flyby and which are flyover or which represent the beginning or end of a RF leg segment. An ATS route must not be used if the pilot has any reason to doubt the validity of the ATS route in the navigation database.
Note: As a minimum, the departure checks can be a simple inspection of a suitable map display that achieves the objectives of this paragraph.
D.9.9 RNP 0.3 STAR Specific Requirements. Prior to the arrival phase, the pilot should verify loading of the correct terminal route. The active flight plan should be checked by comparing the charts (paper or electronic) with the map display (if applicable) and the multipurpose control and display unit (MCDU). This includes confirmation of the waypoint sequence, reasonableness of track angles and distances, any altitude or speed constraints, and, where possible, identification of which waypoints are flyby and which are flyover or which represent the beginning or end of a RF leg segment. An ATS route must not be used if the pilot has any reason to doubt the validity of the ATS route in the navigation database.
Note: As a minimum, the arrival checks can be a simple inspection of a suitable map display that achieves the objectives of this paragraph.
D.9.10 Contingency Procedures. The pilot must notify ATC of any loss of the RNP capability (integrity alerts or loss of navigation), together with the proposed course of action. If unable to comply with the requirements of an RNP procedure, pilots must advise ATS as soon as possible. The loss of RNP capability includes any failure or event causing the rotorcraft to no longer satisfy the RNP 0.3 requirements of the route.
D.10 Pilot Knowledge and Training.
D.10.1 Training Program. Operators with an approved training program should address the elements listed below. Part 91 operators should be familiar with the practices and procedures identified in this section.
D.10.2 Knowledge. The training program should provide sufficient training (e.g., simulator, training device, or rotorcraft) to the extent that the pilot is familiar with the following as applicable to the rotorcraft RNP system: