Appendix I I-1 APPENDIX I. ADDITIONAL CAPABILITIES I.1 Introduction.
I.1.1 Guidance. This appendix provides guidance on the performance, functional and additional operational requirements for Required Navigation Performance (RNP) systems containing additional capabilities.
I.1.2 Applicability. This appendix applies to all operators conducting RNP 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) or offshore airspace areas.
I.2 Radius to Fix (RF).
I.2.1 Description of RF Legs.
I.2.1.1 RF legs are an optional capability for use with:
• Required Navigation Performance Approach (RNP APCH) (Appendix A, Qualification Criteria for Required Navigation Performance Approach (RNP APCH) Operations;
• RNP 1 (Appendix C, Qualification Criteria for Required Navigation Performance (RNP) 1 (Terminal) Operations); and
• RNP 0.3 (Appendix D, Qualification Criteria for Required Navigation Performance (RNP) 0.3 (Rotorcraft) Operations).
I.2.1.2 This functionality can be used in the following:
• Initial and intermediate approach segments;
• Final phase of the missed approach;
• Standard Instrument Departures (SID); and
• Standard Terminal Arrival Routes (STAR).
I.2.1.3 The application of RF legs in the final approach, initial or intermediate phases of the missed approach is prohibited. Such procedure segments wishing to apply RF would have to use the Required Navigation Performance Authorization Required (RNP AR) specification (Refer to Advisory Circular (AC) 20-138( ), Airworthiness Approval of Positioning and Navigation Systems, and AC 90-101( ), Approval Guidance for RNP Procedures with AR).
I.2.2 Path Definition. The RNP lateral accuracy requirement is evaluated around the path defined by the published procedure and RTCA, Inc.’s document, RTCA/DO-236( ).
Appendix I I-2 Note: Industry standards for paths can be found in RTCA/DO-236C( ).
I.2.3 Demonstration of Path Steering Performance. The navigation system must have the capability to execute leg transitions and maintain tracks consistent with an RF leg between two fixes. There is no requirement for the aircraft to include a redundant navigation capability to perform RF legs should a loss of navigation occur during the RF leg. However, type certificate (TC) or Supplemental Type Certificate (STC) applicants for RNP approval that include RF legs are encouraged to provide a redundant navigation capability on the aircraft that can maintain the RF leg track.
I.2.3.1 The Airplane Flight Manual (AFM)/Rotorcraft Flight Manual (RFM) or aircraft qualification guidance should document limitations if:
1. The aircraft cannot proceed “Direct-To” the initial fix defining an RF leg segment.
2. The aircraft cannot accept a radar vector (a heading assigned by air traffic control (ATC)) to the middle of an RF leg segment for intercepting and completing the RF leg segment from that point while sustaining the desired level of performance.
I.2.4 Flight Technical Error (FTE). System documentation should support maintenance of FTE (95 percent of the flying time) during straight and curved path segments, for each phase of flight and each autopilot (AP) and/or flight director (FD) mode requested. If documenting FTE values other than those listed in RTCA/DO-283A, the documentation must show demonstration in accordance with AC 120-29( ), Criteria for Approval of Category I and Category II Weather Minima for Approach, or AC 20-138( ).
I.2.5 Interface to Flight Guidance System (FGS). An acceptable AP and/or FD response to an RNP system failure or loss must be verified in each AP and FD mode, as applicable.
Note: If AP malfunction testing was performed for worst case failures, no further validation is required. In this case, the manufacturer must provide a statement of confirmation.
I.2.6 Failure Modes/Annunciation. System documentation should identify any failure modes potentially affecting RNP system RF leg capability. Failure modes may include loss of electrical power, loss of signal reception, and RNP equipment failure including degradation of navigation performance resulting in a loss of RNP containment integrity.
The applicant should verify that a visible alert occurs within the flightcrew’s primary field of view (FOV) when loss of navigation capability and/or loss of integrity are experienced.
I.2.7 Functional Requirements. RNP procedures with RF legs require the use of an AP or FD with at least “roll-steering” capability that is driven by the RNP system. The AP/FD must operate with suitable accuracy to track the lateral and, as appropriate vertical paths required by a specific RNP procedure.
Appendix I I-3 I.2.7.1 The aircraft must have an electronic map display depicting the RNP-computed path of the selected procedure.
I.2.7.2 The flight management computer (FMC), the FD system, and the AP must be capable of commanding a bank angle up to 30 degrees above 400 feet above ground level (AGL).
I.2.7.3 The specified bank angles comply with RTCA/DO-236C and are consistent with a common procedure design criteria that accommodates all aircraft categories; including those with the highest approach speeds. Aircraft with lower approach speeds will typically not achieve these bank angles in normal operations.
I.2.8 Maintaining Lateral Navigation (LNAV) in Missed Approach. If abandoning a procedure while on an RF leg or initiating a go-around or missed approach (through activation of takeoff/go-around (TOGA) or other means), the flight guidance mode should remain in LNAV to enable display of deviation and positive course guidance during an RF leg, including the missed approach segment. If the aircraft does not provide this capability, crew procedures must be used that assure the aircraft will adhere to the specified flightpath during the RF leg segment.
Note: For missed approaches with a RF leg, the flightcrew must be able to couple the AP or FD to the RNP system (engage LNAV) by 500 feet AGL.
I.2.9 Crew Workload Analysis. Analyze the crew workload and determine acceptability when flying and monitoring track adherence in association with RF legs during all phases of flight, including those non-normal procedures that can be evaluated in-flight.
I.2.10 Eligibility Airworthiness Documents. The flight manual or referenced document should contain the following information:
1. A statement indicating the aircraft meets the requirements for RNP operations with RF legs and has demonstrated the established minimum capabilities for these operations. This documentation should include the phase of flight, mode of flight (e.g., FD on or off; and/or AP on or off, and applicable lateral and vertical modes), minimum demonstrated RNP value, and sensor limitations, if any.
2. Any conditions or constraints on path steering performance (e.g., AP-engaged, FD with map display, including lateral and vertical modes, and/or course deviation indicator (CDI)/map scaling requirements) should be identified.
Use of manual control with CDI only is not allowed on RF legs.
3. The criteria used for the demonstration of the system includes:
• Acceptable normal and non-normal procedures,
• Demonstrated configurations,
Appendix I I-4
• Type of facilities used, and
• Any constraints or limitations necessary for safe operation should be identified.
I.3 Parallel Offset.
I.3.1 Description of Parallel Offset. Parallel offsets provide a capability to fly offset from the parent track, as defined by the series of waypoints. Parallel offset capability is required for an A-RNP qualification and mandatory for oceanic/remote continental RNP 2 (Appendix E) and RNP 4 (Appendix F) operations. The turn defined for the parent track (flyby or fixed radius transitions (FRT)) must be applied in the offset track. Parallel offsets are applicable only for en route segments and are not foreseen to be applied on SIDs, STARs, or approach procedures. The activation of an offset must be clearly displayed to the flightcrew with the cross-track (XTK) deviation indication to the offset track.
I.3.2 Usage of Parallel Offset. Parallel offsets can be used on route segments in en route and terminal areas, and are intended to replicate all of the centerline route characteristics at the desired offset to the left or right of the centerline route. Parallel offsets are not intended for approach segments, arrivals, or departures. RTCA/DO-236C, paragraphs 3.2.4.3 and 3.7.2.2.4 provide detailed requirements for implementing parallel offsets in RNP equipment.
I.3.3 Parallel Offset Considerations. The system should be capable of flying tracks offset by up to 20 nautical miles (NM) from the parent track. The presence of an offset should be continuously indicated. Tracks offset from the parent track must be continued for all Air Traffic Service (ATS) route segments and turns until either removed by the crew or automatically cancelled by:
1. Amendment of the active flight plan by executing a “Direct-To,”
2. Commencement of an approach procedure, or
3. Where a course change exceeds 90 degrees. The navigation system can be expected to terminate the offset no later than the fix where the course change occurs. The offset may also be terminated if the route segment ends at a hold fix.
I.3.4 Lateral Offset Activation. When a lateral offset is activated in the Area Navigation (RNAV) or RNP system, the aircraft will leave the defined route and typically intercept the offset at an angle of 45 degrees or less. When the offset is cancelled, the aircraft returns to the defined route in a similar manner.
I.4 RNAV Holding.
I.4.1 Usage of RNAV Holding. RNAV holding is intended to give aircraft the ability to fly either ATC-defined ad hoc or published holding patterns with the performance, monitoring, and alerting abilities associated with RNP. RTCA/DO-236C,
Appendix I I-5 paragraph 3.2.4.1 defines equipment requirements for RNP holding. RNP holding implemented per RTCA/DO-236C is acceptable for meeting RNAV holding.
I.4.2 Implementation of RNAV Holding. Aircraft implementing RNAV holding capability should have an electronic map display capable of depicting all segments of an RNAV holding procedure. A map display depicting the RNAV holding segments enhances situation awareness.
I.5 FRT. FRTs are waypoint transitions between en route legs using a defined radius. The intent is to define waypoint transitions along airways where separation between parallel routes is required and flyby transitions are not compatible with the separation criteria.
RTCA/DO-236C, Change 1, paragraph 3.2.5.4.2 defines equipment requirements for FRTs.
I.6 Time of Arrival Control (TOAC). This section will be updated at a future revision once system requirements are defined for RTCA/DO-236C.
I.7 Operational and Functional Considerations.
I.7.1 RF Legs. Requirements for RF legs will be indicated on the charts, in the notes section, or at the applicable initial approach fix (IAF) for instrument approaches. When flying an RF leg, flightcrew compliance with the desired path is essential to maintain the intended ground track and to assure obstacle clearance.
I.7.1.1 Pilots must not exceed maximum airspeeds where published, while performing RNP operations containing RF legs.
I.7.1.2 When the dispatch of a flight is predicated on flying a RNP APCH with a RF leg at the destination and/or alternate, the operational control personnel/pilot must determine that the AP/FD is installed and operational.
I.7.1.3 Pilots are not authorized to fly a published RNP procedure unless it is retrievable by the procedure name from the aircraft navigation database and conforms to the charted procedure. The lateral path must not be modified, with the exception of complying with ATC clearances/instructions. However, the aircraft must be on course prior to beginning the RF leg. The only other modification to the loaded procedure is to change altitude and/or airspeed waypoint constraints on the initial, intermediate, or missed approach segments
(e.g., comply with an ATC clearance/instruction).
I.7.2 Parallel Offset. The cross track offset distance should be manually entered into the RNP system to a resolution of 1 NM or better.
I.7.2.1 The lateral track-keeping requirement of RNP must be maintained referenced to the offset track where parallel offsets are applied.
Appendix I I-6 I.7.2.2 Where FRTs are applied, the offset track must be parallel to the parent track
(i.e., a smaller turn radius for offsets to the inside of the turn, and a larger turn radius for offsets to the outside of the turn).
I.7.3 Direct-To Function. The navigation system must have a “Direct-To” function the flightcrew can activate at any time. This function must be available to any fix except initial waypoint of an RF segment.
I.7.3.1 The navigation system must also be capable of generating a geodesic path to the designated “To” fix, without “S-turning” and without undue delay.
Appendix J J-1 APPENDIX J. ADMINISTRATIVE INFORMATION J.1 Terminology.
Aircraft-Based Augmentation System (ABAS). An augmentation system that augments and/or integrates the information obtained from the other Global Positioning System (GPS) elements with information onboard the aircraft. The most common form of ABAS is receiver autonomous integrity monitoring (RAIM).
Air Traffic Control (ATC) Service:
1. Area Control Service,
2. Approach Control Service, and
3. Airport Control Service.
Air Traffic Service (ATS) − A generic term meaning:
1. Flight Information Services (FIS),
2. Alerting Service, and
3. Air Traffic Advisory Service.
Air Traffic Service (ATS) Routes. The term “ATS Route” is a generic term that includes “VOR Federal airways,” “colored Federal airways,” “jet routes,” and “RNAV routes.” The term “ATS route” does not replace these more familiar route names, but serves only as an overall title when listing the types of routes that comprise the United States route structure.
Area Navigation (RNAV). A method of navigation which permits aircraft operation on any desired flightpath within the coverage of ground or space-based navigation aids or within the limits of the capability of self-contained aids, or a combination of these. RNAV includes Performance-based Navigation (PBN) as well as other operations that do not meet the definition of PBN.
Area Navigation (RNAV) System. A navigation system which permits aircraft operation on any desired flightpath within the coverage of ground or space-based navigation aids or within the limits of the capability of self-contained aids, or a combination of these. A RNAV system may be included as part of a flight management system (FMS).
Barometric Vertical Navigation (baro-VNAV). A function of certain RNAV systems which presents computed vertical guidance to the pilot referenced to a specified vertical path. The computed vertical guidance is based on barometric altitude information and is typically computed as a geometric path between two waypoints or an angle based on a single waypoint.
Airworthiness approval criteria is found in Advisory Circular (AC) 20-138( ), Airworthiness Approval of Positioning and Navigation Systems.
Appendix J J-2 Decision Altitude (DA). In an approach with vertical guidance, DA is a specified altitude expressed in feet above mean sea level at which a missed approach must be initiated if the required visual references to continue the approach have not been established.
Discontinuity. A discontinuity is an interruption in the sequence of waypoints within the active onboard flight plan (primary flight plan loaded into FMS).
Distance Measuring Equipment (DME) DME/DME (D/D) RNAV. Refers to navigation using DME ranging from at least two DME facilities to determine position.
DME/DME/Inertial (D/D/I) RNAV. Refers to navigation using DME ranging from at least two DME facilities to determine position along with use of inertial systems, inertial reference system (IRS) or Inertial Reference Unit (IRU), to provide sufficient position information during limited DME gaps.
Estimate of Position Uncertainty (EPU). A measure based on a defined scale in nautical miles (NM), which conveys the current position estimation performance, also known as Actual Navigation Performance (ANP) or Estimate of Position Error (EPE) in certain aircraft. The EPU is not an estimate of the actual error, but a defined statistical indication of potential error.
Fault Detection and Exclusion (FDE). A RAIM algorithm that can automatically detect and exclude a faulty satellite from the position solution when a sufficient number of redundant satellite measurements are available.
Fixed Radius Transition (FRT). An arc at a constant (specified) radius that is tangent to both the inbound and outbound en route path segments at an en route fix.
Flight Guidance System (FGS). A system primarily intended to assist the flightcrew in the basic control and tactical guidance of the airplane. Typically referred to as an autopilot (AP)/flight director (FD)/autothrust system, it may consist of sensors, computers, power supplies, servo-motors/actuators, and indications and controllers necessary for the pilot to manage and supervise the system. For rotorcraft, it can include a FD with a stability augmentation system and/or AP.
Flight Management System (FMS). An integrated system, consisting of airborne sensor, receiver and computer with both navigation and aircraft performance databases, which provides performance and area navigation guidance to a display and automatic flight control system (AFCS).
Flight Technical Error (FTE) or Path Steering Error (PSE). Accuracy with which an aircraft is controlled, as measured by the indicated aircraft position with respect to the indicated command or desired position. It does not account for procedural blunder errors.
Global Navigation Satellite System (GNSS). GNSS is a generic term for a worldwide position, velocity, and time determination system, which includes one or more satellite constellations, aircraft receivers, and system integrity monitoring. GNSS includes GPS, Satellite-based Augmentation Systems (SBAS) such as the wide area augmentation system (WAAS), Ground Based Augmentation System (GBAS) such as the Local Area Augmentation System
Appendix J J-3 (LAAS), Global Orbiting Navigation Satellite System (GLONASS), Galileo, and any other satellite navigation system approved for civil use. GNSS can be augmented as necessary to support the Required Navigation Performance (RNP) for the actual phase of operation.
Global Positioning System (GPS). GPS is a U.S. satellite-based radio navigation system that provides a positioning service anywhere in the world. The service provided by GPS for civil use is defined in the GPS Standard Positioning System Signal Specification. GPS is the U.S. core GNSS satellite constellation providing space-based positioning, velocity, and time. GPS is composed of space, control, and user elements.
Lateral Navigation (LNAV). The function of RNAV systems that computes, displays, and provides lateral guidance to a profile or path. Sometimes referred to as managed navigation.
Long-Range Navigation System (LRNS). An electronic navigation unit that is approved for use under instrument flight rules (IFR) as a primary means of navigation, and has at least one source of navigational input, such as inertial navigation system (INS) and/or GPS.
Navigational Aid (NAVAID) Infrastructure. NAVAID infrastructure refers to space-based and or ground-based NAVAIDs available to meet the requirements in the navigation specification (Nav Spec).
Navigation Application. This is defined as the application of a Nav Spec and the supporting NAVAID infrastructure, to routes, procedures, and/or defined airspace volume, in accordance with the intended airspace concept.
Navigation Specification (Nav Spec). A set of aircraft and aircrew requirements needed to support PBN operations within a defined airspace. There are two kinds of Nav Spec:
1. RNAV specification. A Nav Spec based on RNAV that does not include the requirement for onboard performance monitoring and alerting, designated by the prefix RNAV (e.g., RNAV 5, RNAV 1).
2. RNP specification. A Nav Spec based on RNAV that includes the requirement for onboard performance monitoring and alerting, designated by the prefix RNP (e.g., RNP 4, RNP APCH).
Navigation System Error (NSE). NSE or Position Estimation Error (PEE) is the difference between the true position and estimated position.
Oceanic. Oceanic airspace is defined as international airspace over oceans where separation and procedures are in accordance with the International Civil Aviation Organization (ICAO).
Responsibility for the provision of ATC service in this airspace is delegated to various countries.
Offshore. Offshore airspace is defined by Title 14 of the Code of Federal Regulations (14 CFR) part 71, §§ 71.31 and 71.71. It is designated in international airspace within areas of domestic radio navigational signal or ATC radar coverage, and within which domestic ATC procedures are applied.
Appendix J J-4 Path Definition Error (PDE). The difference between defined path and desired path at a specific point.
Path Steering Error (PSE) or Flight Technical Error (FTE). The difference between the estimated position and the abeam point on the system-defined path.
Performance-Based Navigation (PBN). RNAV-based on performance requirements for aircraft operating along an ATS route, on an instrument approach procedure (IAP), or in a designated airspace.
Position Estimation Error (PEE). PEE or NSE is the difference between true position and estimated position.
Primary Flight Display (PFD). A display that provides increased situational awareness to the pilot by replacing the traditional six instruments used for instrument flight with an easy-to-scan display that provides the horizon, airspeed, altitude, Vertical Speed (VS), trend, trim, and rate of turn among other key relevant indications.
Primary Optimum Field of View (FOV). The vertical and horizontal visual fields relative to the design eye reference point that can be viewed with eye rotation only using foveal or central vision. The values for the horizontal (relative to the normal line of sight) are +/-15 degrees optimum, with +/-35 degrees maximum. The values for the vertical (relative to normal line of sight) are +/-15 degrees optimum, with + 40 degrees up and -20 degrees down maximum (Refer to AC 25-11( ), Electronic Flight Displays). The primary FOV definition should be broad enough to include the center radio stack on 14 CFR part 23 airplanes with “classic”, analog basic ‘T’ instrumentation. For rotorcraft, reference the visibility requirements defined in AC 27-1( ), Certification of Normal Category Rotorcraft, and AC 29-2( ), Certification of Transport Category Rotorcraft.
Radius to Fix (RF) Leg. An RF leg is defined as a constant radius circular path around a defined turn center that starts and terminates at a fix.
Receiver Autonomous Integrity Monitoring (RAIM). An algorithm that verifies the integrity of the position output using GPS measurements, or GPS measurements and barometric aiding.
Remote Continental. Remote continental airspace is defined as airspace above terrain where line-of-sight communications, independent surveillance and reliable ground-based NAVAIDs is not available. Controllers provide ATSs utilizing procedural control and procedural separation.
Required Navigation Performance (RNP). RNP is a statement of the 95 percent navigation accuracy performance that meets a specified value for a particular phase of flight or flight segment and incorporates associated onboard performance monitoring and alerting features to notify the pilot when the RNP for a particular phase or segment of a flight is not being met.
RNAV. See Area Navigation (RNAV) above.
RNP/RNAV Procedure. An RNP/RNAV Procedure includes instrument departure procedures (DP), Standard Terminal Arrivals (STAR), and instrument approaches based on PBN.
Appendix J J-5 RNP Value. The RNP value designates the 95 percent LNAV performance (in NM) and the related monitoring and alerting requirements associated with an RNP instrument flight operation or a particular segment of that instrument flight.
RNP System. An RNAV system which supports onboard performance monitoring and alerting.
For the purposes of this AC, RNP systems comply with Appendices A through I, as appropriate.
Total System Error (TSE). The difference between the true position and the desired position and is equal to the vector sum of the FTE, PDE, and NSE.
Waypoints. A waypoint is a predetermined geographical position that is defined in terms of latitude/longitude coordinates. Waypoints may be a simple named point in space or associated with existing NAVAIDs, intersections, or fixes. A waypoint is most often used to indicate a change in direction, speed, or altitude along the desired path. RNAV procedures make use of both flyover and flyby waypoints.
1. Flyby Waypoints. Flyby waypoints are used when an aircraft should begin a turn to the next course prior to reaching the waypoint separating the two route segments. This is known as turn anticipation.
2. Flyover Waypoints. Flyover waypoints are used when the aircraft must fly over the point prior to starting a turn.
Appendix J J-6 J.2 Acronyms.
Table J-1. Acronyms Acronym Meaning 14 CFR Title 14 of the Code of Federal Regulations ABAS Aircraft-Based Augmentation System AC Advisory Circular AED Aircraft Evaluation Division AFCS Automatic Flight Control System AFM Airplane Flight Manual AFMS Airplane Flight Manual Supplement AGL Above Ground Level AIP Aeronautical Information Publication AIR Aircraft Certification Service AIRAC Aeronautical Information Regulation and Control AMC Acceptable Means of Compliance ANP Actual Navigation Performance ANSP Air Navigation Service Provider AP Autopilot ARINC Aeronautical Radio Incorporated A-RNP Advanced Required Navigation Performance ATC Air Traffic Control ATRK Along-Track ATS Air Traffic Service baro-VNAV Barometric Vertical Navigation CA Course to Altitude (path terminator per ARINC Specification 424) CDI Course Deviation Indicator CF Course to Fix (path terminator per ARINC Specification 424) CPDLC Controller-Pilot Data Link Communications CTA Control Area CTA/FIR Control Area/Flight Information Region
D/D DME/DME D/D/I DME/DME/Inertial DA Decision Altitude DF Direct to Fix DME Distance Measuring Equipment DOD Department of Defense DP Departure Procedure DTK Desired Track EFB Electronic Flight Bag EHSI Electronic Horizontal Situation Indicator EPE Estimate of Position Error EPU Estimate of Position Uncertainty ETA Estimated Time of Arrival EUROCAE European Organization for Civil Aviation Equipment FA Fix to an Altitude (path terminator per ARINC Specification 424)