Appendix 2
(2) Software Problem Reports.
Present clarification on how existing open software problem reports are resolved within the aircraft or other equipment that could directly or indirectly affect the RNP approval.
Open software problems or changes that could affect RNP operations should be addressed.
b. Failure Modes/Annunciation.
Identify any failure modes potentially affecting RNP capability. Verify annunciation of RNP failure modes exists. This verification should be compatible during manual flight and with the aircraft’s FGS to ensure unambiguous flight crew action(s). Verify that following failure modes, any pilot selected entries are retained or their cancellations annunciated (e.g., manual entry of RNP type, blackballed navaid, etc.). Typical failure modes 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 aircraft manufacturer should also verify that a visual alert within the flight crew’s primary field of view occurs with a loss of navigation capability and/or loss of RNP containment integrity.
An aural alert should accompany the visual alert.
c. Aircraft Manufacturer Installation Guidelines.
The aircraft manufacturer should comply with the following installation guidelines. Avionics manufacturers should note the following guidance to ensure their positioning and navigation equipment can support RNP operations.
(1) Each installation of RNP equipment requires an airplane flight manual containing the limitations and operating procedures applicable to the installed equipment. In addition, an RNP capabilities document for the system should be developed and submitted for FAA approval. The RNP capabilities document should be referenced in the airplane flight manual and made available to the operator upon request. The document will provide a description of the system, including assumed operating environment, the interface of the navigation function to the flight crew, the specific navigation capabilities of the system and potential application.
The intended use of the document will be to facilitate operational approval of the navigation capability for RNP operations. The flight manual or referenced capabilities document should contain at least the following information:
(a) A statement indicating the aircraft meets the requirements for RNP and demonstrated the established minimum RNP capabilities. This documentation should include:
the phase of flight (e.g., oceanic, enroute, terminal area, approach), mode of flight (e.g., manual, FD on or off, and/or autopilot on or off, and applicable lateral and vertical modes), minimum demonstrated RNP value, and sensor limitations, if any (e.g., GPS required). The phase of flight description should indicate what procedure design criteria the navigation performance is designed to support, as applicable.
(b) Any conditions or constraints on path steering performance (e.g., autopilot engaged, FD or manual control with CDI or map display, including lateral and vertical modes A2-24
Appendix 2 and/or CDI/map scaling requirements).
(c) The criteria used for the demonstration of the system, acceptable normal and non-normal procedures, the demonstrated configurations, type of facilities used, and any constraints or limitations necessary for safe operation.
(d) Define all the assumptions on systems external to the aircraft (e.g., signal in space performance, coverage, and survey accuracy). This includes GNSS-based limitations in the AFM(S)/RFM(S) for RNP AR APCH availability predictions at the destination, or checking NOTAMs. These predictions are consistent with the equipment performance described in chapter 5.
(i) A pre-departure RAIM prediction (FD or FDE as appropriate) is acceptable for GPS-based RNP AR operations that are limited to RNP AR 0.3 accuracy.
(ii) GPS/SBAS provides improved availability and enhanced accuracy during RNP AR operations. An RNP AR operation that is limited to RNP AR 0.3 accuracy based on GPS/SBAS only needs to confirm via NOTAM that there is no GPS/SBAS outage.
(iii) A pre-departure FDE RAIM prediction is acceptable for RNP AR operations limited to RNP AR 0.3 accuracy when outside of the GPS/SBAS coverage area or during a GPS/SBAS outage.
(iv) A pre-departure RNP prediction must be conducted prior to dispatch for accuracy values below RNP AR 0.3 (i.e., RNP AR < 0.3). If no RNP prediction capability is available (either external to the aircraft or within the navigation system), then the operator must not plan to use RNP AR < 0.3. Instead, the operator must plan to use RNP AR 0.3 if that line of minima exists for the procedure.
Note: The guidance on RNP prediction only applies to RNP AR operations conducted in the U.S. national airspace system. This does not apply to RNP AR operations in other ICAO States. When operating in another State’s airspace, operators must follow the RNP AR operational requirements for that State.
(2) If compliance to the continuity requirements has been shown through a combination of navigation sensors, the AFMS/RFMS should contain a statement that “Continuity of RNP navigation has been demonstrated only where the operational environment supports all of the following types of sensors: <insert type of sensors for which credit is being sought>.
d. Flight Technical Error (FTE).
The aircraft manufacturer should verify maintenance of FTE (95% of the flying time) during straight and curved path segments per Table 9. The FTE should be demonstrated in each phase of flight and each autopilot mode.
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Appendix 2
e. Interface to FGS.
Verify acceptable autopilot response to an RNP fault by simulating a representative fault consistent with the equipment architecture (e.g., pulling the circuit breaker) for the RNP equipment. The aircraft manufacturer should complete this test in each of the RNP and autopilot modes, as applicable.
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Appendix 3 Appendix 3. Advanced RNP Functions.
A3-1. Introduction.
a. ICAO document 9613 Performance Based Navigation (PBN) Manual, fourth edition, 2013 lists six advanced RNP functions. The six functions are:
• RF legs
• Parallel offsets
• Scalable RNP
• RNAV holding
• Fixed radius transitions (FRT)
• Time of arrival control (TOAC) Note: The PBN Manual includes Higher Continuity as an advanced RNP function. Higher continuity is not really a function, but a result of the hazard level associated with advance RNP functions affecting aircraft equipage (see paragraph A3-1.e).
b. The equipment must include RF legs, Parallel offsets, Scalable RNP, RNAV holding, and FRTs for advanced RNP recognition. The rationale for including all of these functions is for international harmonization. To include advanced RNP recognition, t he equipment, at a minimum, must meet the performance and functional criteria for RNP 2.0, RNP
1.0 and RNP APCH to LNAV minima.
(1) TSO-C115d implements RTCA/DO-283B which provides acceptable methods of implementing advanced RNP functions in RNP equipment consistent with the aircraft performance requirements found in RTCA/DO-236C, Chg 1.
(2) At present, the U.S. intends to implement only RF legs, Parallel offsets, and Scalable RNP which constitutes the U.S. definition of advanced RNP. RNAV holding, FRT, and TOAC are presently considered optional advanced RNP functions in the U.S.
(3) Other States may choose to implement a different subset of functions, or all six functions for their advanced RNP definition.
(4) At present, TOAC is a function for longer-term implementation and remains optional for all equipment due to uncertain equipment requirements and airspace implementation.
c. Equipment manufacturers may decide to only implement a select set of advanced RNP functions rather than implementing all functions for “advanced RNP” recognition.
Implementing selected functions means the equipment will have limitations for the functions not implemented. That is, aircraft using equipment with a reduced set of functions will not receive “advanced RNP” recognition. These aircraft will be restricted from airspace that requires functions not implemented in the equipment, or that requires “advanced RNP” A3-1
Appendix 3 recognition.
d. This appendix provides the additional equipment guidance unique to implementing advanced RNP functions. Equipment manufacturers that choose to include selected advanced RNP functions or “advanced RNP” recognition should provide an advanced RNP statement of capabilities document in the installation instructions/manual. Airworthiness approval holders must provide an AFM(S)/RFM(S) capabilities statement describing both the advanced RNP functions provided, and the advanced RNP functions not provided (if any).
Note: Advanced RNP functions may have aircraft-level integration dependencies necessary to implement the capability on the aircraft even though the avionics equipment itself includes the functions (see paragraph 12-7).
e. The continuity requirement for advanced RNP implementation is classified as a major failure condition that can be satisfied with dual independent equipage.
f. Manufacturers should refer to RTCA/DO-236C, Chg 1 and RTCA/DO-283B for requirements when implementing RF legs, parallel offsets, scalable RNP, RNAV holding, FRT, and TOAC. Equipment with advanced RNP functions previously approved to RTCA/DO 236B/-283A remains valid for those advanced RNP functions.
A3-2. Radius to Fix Leg Capability.
RF legs are an optional capability rather than a minimum requirement for RNP operations.
This capability can be used in the initial, intermediate, and missed approach segments of instrument approaches, RNP DPs and RNP STARS. Additional information on RF legs may be found in the Aeronautical Information Manual. For RNP systems incorporating RF leg capability, the systems must comply with the criteria in chapter 8 for RNP Approach, and chapter 9 for RNP 1.0 (terminal). Appendix 7 provides information on demonstrating RF leg capability. For RNP AR systems incorporating RF leg capability the RNP value can be less than 1.0., and RNP AR procedures may have RF legs intercept the final approach segment inside the final approach fix. RNP AR systems must comply with the criteria in appendix 2.
Note: In the U.S., RF legs will not intercept the final approach segment of an RNP approach inside the final approach fix. However, RF legs may do so for an RNP AR approach.
a. System Criteria.
(1) Path Definition.
Aircraft RNP lateral accuracy performance is evaluated around the path defined by the published procedure. RNP equipment should provide lateral guidance so aircraft remain within the lateral boundaries of the RF leg.
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--- Appendix 3
(2) 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, TC or 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.
Note: The AFM/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 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.
(3) 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 and/or FD mode requested. If using FTE values other than those listed in Table 9, the applicant must complete the demonstration in accordance with paragraph 17-2.
(4) Interface to FGS.
An acceptable autopilot and/or FD response to an RNP system failure or loss must be verified in each autopilot and FD mode, as applicable.
Note: If autopilot malfunction testing was performed for worst case failures, no further validation is required. In this case, the aircraft or equipment manufacturer must provide a statement of confirmation.
(5) 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 navigation performance degradation, resulting in a loss of RNP containment integrity. The applicant should verify that a visible alert occurs within the flight crew’s primary field of view when loss of navigation capability and/or loss of integrity are experienced.
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Appendix 3
b. Functional Criteria.
(1) Autopilot and Flight Director.
Flight Standards requires using an autopilot or FD with at least “roll-steering” capability that is driven by the RNP system during RNP procedures with RF legs (see guidance in AC 90-105A). The autopilot/ FD must operate with suitable accuracy to track the lateral and, as appropriate, vertical paths required by a specific RNP procedure.
(2) Bank Angle.
The flight management computer, the FD system, and the autopilot must be capable of commanding a bank angle up to 30 degrees above 400 feet AGL. Aircraft with lower speeds will typically not achieve these bank angles in normal operations. For these aircraft it may be acceptable for the flight management computer, the FD system, and the autopilot to command bank angles less than 30 degrees consistent with their maximum airspeed provided the airworthiness applicant can demonstrate RF leg performance (see appendix 7).
For RNP AR applications, the flight management computer, FD system and autopilot must be capable of commanding a bank angle up to 8 degrees below 400 feet AGL.
Note: The specified bank angles comply with RTCA/DO-283B and RTCA/DO-236C, Chg 1. These are consistent with a common procedure design criteria that accommodates all aircraft categories; including those with the highest approach speeds.
(3) Electronic Map Display.
The aircraft should have an electronic map display depicting the RNP computed path of the selected procedure including RF legs. The map display should be capable of depicting the curved, RF leg segments without discontinuities on both active and inactive leg segments if a moving map display is included with or interfaced to the positioning and navigation equipment. Positioning and navigation equipment manufacturers should include a list of compatible moving map displays in the installation manual/instructions by part number, model, and/or software version as applicable to support RF leg capability.
(4) Maintaining LNAV in Missed Approach.
If abandoning a procedure while on an RF leg or initiating a go-around or missed approach (through activation of TOGA or other means), the flight guidance mode should remain in LNAV to enable deviation and positive course guidance display during an RF leg. If the aircraft does not provide this capability, crew procedures must be used that assure the aircraft will adhere to the specified flight path during the RF Leg segment.
Note 1: For missed approaches with an RF Leg, the flight crew must be able to couple the autopilot or FD to the RNP system (engage LNAV) by 500 feet AGL.
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Appendix 3 Note 2: For RNP AR, if the flight guidance does not remain in LNAV upon initiation of a go-around or missed approach, then the applicant and/or operator should define flight crew contingency procedures for maintaining compliance with the desired track and re-engaging LNAV as soon as possible. These contingency procedures should clearly address flight crew actions should a go-around or missed approach begin with the aircraft established on or having just completed an RF leg segment.
(5) Crew Workload Analysis.
The installation applicant should 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.
c. System Approval - Eligibility Airworthiness Documents.
The flight manual or referenced document should contain the following information:
(1) A statement indicating the aircraft meets the criteria 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 autopilot 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 should be identified
(e.g., autopilot engaged, FD with map display, including lateral and vertical modes, and/or CDI/map scaling criteria). Use of manual control with CDI only is not allowed on RF legs.
(3) The applicant should identify the criteria used for the system demonstration, acceptable normal and non-normal procedures, the demonstrated configurations, type of facilities used, and any constraints or limitations necessary for safe operation.
A3-3. Parallel Offsets.
a. Parallel offsets can be used on route segments in enroute 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-283B paragraph 2.2.1.2.7 provides detailed requirements for implementing parallel offsets in RNP equipment consistent with the aircraft performance requirements in RTCA/DO-236C Chg 1, paragraph 3.2.4.3.
Note: RTCA/DO-236C and RTCA/DO-283B requirements specify increments of 0.1 nm to support using parallel offsets for both terminal and enroute/oceanic A3-5
Appendix 3 operations. Previous revisions specified 1.0 nm increments consistent with the PBN Manual to support parallel offsets for enroute/oceanic operations only.
b. TSO-C115d Class A equipment requires FRT and parallel offset capability along with the ability to continue a parallel offset through an FRT. FRTs are optional in Class B and earlier TSO-C115 revisions. Equipment including both parallel offset and FRT advanced RNP functions must have the ability to continue parallel offsets through an FRT. Equipment without an FRT function does not need to address FRTs in conjunction with the parallel offset function.
A3-4. RNAV Holding.
a. 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-283B paragraph 2.2.1.2.6 defines RNP equipment requirements for RNP holding consistent with the aircraft performance requirement found in RTCA/DO-236C, Chg 1, paragraph 3.2.4.1. RNP holding implemented per these RTCA documents is acceptable for meeting RNAV holding.
b. 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.
A3-5. Scalable RNP.
a. Scalable RNP is intended for legs on RNP routes or procedures where ATC, terrain, and/or obstacle considerations provide a benefit on selected legs to using RNP values other than RNP 2.0 or RNP 1.0. RTCA/DO-283B paragraph 2.2.1.2.12.1 and 2.2.1.2.12.2 provides RNP equipment requirements for scalable RNP consistent with the aircraft performance requirements found in RTCA/DO-236C, Chg 1, paragraph 3.2.6.
b. The RNP scaling, monitoring and alerting value for scalable legs must be entered into the RNP navigation system automatically from the database. RTCA/DO-283B and RTCA/DO-236C, Chg 1 provides an order of precedence for entering leg RNP values.
Note: State operational implementation may permit manually entering an accuracy values for legs provided the equipment also changes the scaling, monitoring, and alerting consistent with the accuracy value.
(1) The RNP navigation system must provide the ability to enter RNP values in tenths of a nautical mile between 0.3 and 2.0.
(2) It is acceptable to have a smaller RNP value entered in the RNP navigation system than the leg requires. As an example only to illustrate the point, it is acceptable to have the RNP system set to RNP 1.0 for a leg that requires RNP 1.4.
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Appendix 3
(3) The applicant must identify any conditions or constraints on path steering performance (for example, autopilot engaged, FD with map display, and/or CDI/map scaling criteria). This is particularly true for RNP values less than RNP 1.0.
(4) The RNP navigation system must provide an alert prior to the upcoming waypoint when the system cannot support the upcoming RNP value.
(5) The deviation guidance cues must be scaled to the RNP value.
c. The RNP navigation system must provide an alert for any failure mode that potentially affects the navigation performance relative to the selected RNP value. Failure modes may include loss of electrical power, loss of signal reception, and RNP equipment failure, including navigation performance degradation, resulting in a loss of RNP containment integrity. The applicant should verify that a visible alert occurs within the flight crew’s primary field of view when loss of navigation capability and/or loss of integrity are experienced.
A3-6. Fixed Radius Transitions.
FRTs are a waypoint transition between enroute legs using a defined radius. The intent is to define waypoint transitions along airways where separation between parallel routes is required and fly-by transitions are not compatible with the separation criteria. RTCA/DO-283B paragraph 2.2.1.2.9.2 defines equipment requirements for FRTs consistent with the aircraft performance requirements found in RTCA/DO-236C, Chg 1, paragraph 3.2.5.4.2.
A3-7. Time of Arrival Control.
TOAC is an advance RNP function that is not well defined for either equipment requirements or airspace implementation. RTCA/DO-283B paragraph 2.2.4 provides an initial implementation method for RNP equipment that is consistent with RTCA/DO-236C, Chg 1 paragraph 2.2. This section will be updated in the future consistent with TOAC airspace implementation plans.
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Appendix 4 Appendix 4. GNSS Tests to Support ADS-B.
A4-1. Introduction.
a. The information in this appendix describes bench test procedures that GNSS equipment manufacturers can use as an acceptable means to establish the GNSS equipment meets the required outputs described in AC 20-165 (latest revision). This appendix only addresses those ADS-B parameters that require specific tests because the GNSS TSOs do not adequately address the parameter. Other ADS-B parameters simply require coordination among the ADS-B and GNSS equipment manufacturers to properly integrate the equipment. A complete requirements compliance description will be contained in AC 20-165A (or later revision), appendix 2.
b. The tests are only required if the equipment manufacturer chooses to have their equipment provide inputs to ADS-B equipment. Which tests are necessary to qualify as an ADS-B position source is dependent upon which TSO the GNSS equipment has. The tests described below are intended for generating data to prove compliance with the following ADS B parameters if the GNSS TSO requirements are not adequate: velocity accuracy, height above ellipsoid (HAE), horizontal/vertical position accuracy metric, and true track angle/true track angle validity.
A4-2. Velocity Accuracy and Velocity Figure of Merit Tests.
a. All GNSS TSO equipment should use the tests in paragraphs A4-3 through A4-8 to demonstrate both velocity accuracy and velocity figure of merit qualifying as navigation accuracy category - velocity (NACV) = 1. Manufacturers that want their equipment qualified NACV = 2 must also complete the test in paragraph A4-9.
b. AC 20-165 (latest revision), appendix 2 (paragraphs 3h and 4n in revision ‘A’), state that installations with a position source capable of providing velocity accuracy should have the NACV derived from the position source, and the velocity accuracy should be validated during the position source manufacturer’s certification testing. The following procedures, developed by RTCA SC-159, are one means of accomplishing this testing.
c. The purpose of the GNSS velocity accuracy test is to characterize the 95% horizontal and 95% vertical velocity accuracies during normal maneuvers as specified in RTCA/DO-229D, RTCA/DO-253C, and RTCA/DO-316 receiver MOPS for equipment intended to support either NACV =1 or NACV = 2. Test procedures for higher levels are expected to be developed as more demanding ADS-B applications mature.
d. The tests to verify velocity accuracy performance shall be run for each of the scenarios described below for all operating modes of the receiver where a valid position and/or velocity could be output by the receiver.
(1) It is possible that a given receiver may use a different velocity algorithm when computing an un-augmented GPS position solution versus computing a solution augmented with differential corrections. In that case, this test must be repeated for both the augmented and A4-1
Appendix 4 un-augmented modes of operation. Even in the case where the velocity algorithm is the same whether in un-augmented or augmented mode, there are still enough variables like the software path, inputs, outputs etc., that it is required to repeat the test.
(2) It is not required to repeat the test for different sub-modes of an un-augmented or augmented mode where the inputs, velocity algorithm and outputs are the same.
(3) For GNSS equipment that was not required to meet the current environmental noise standard prescribed by DO-235B, the velocity tests in paragraphs A4-3 through A4-8 use environmental noise test conditions that may cause the equipment to stop functioning. That is, the equipment may lose satellite acquisition and tracking capability causing the equipment to stop outputting velocity. This contributes to an ADS-B availability issue for operators, but loss of function will not prevent the equipment from being used as an ADS-B velocity input provided:
• The equipment does not output misleading velocity information at or after the onset of the triggering interference levels.
Note: A method to accomplish this is first running the test at the higher noise level to ensure there is no misleading velocity information at loss of function before running the complete test at the lower noise level.
• The GNSS equipment manufacturer documents the interference levels that cause the equipment to lose function.
• The GNSS equipment manufacturer factors the lower interference levels into an overall ADS-B availability calculation to be included within the installation instructions.
(4) If the conditions in paragraph A4-2.d(3) are met, the velocity tests in AC 20-138D, Appendix 4 can be run using an environmental noise level that does not cause the equipment to lose acquisition and tracking.
A4-3. Horizontal Velocity Accuracy Test Conditions Commensurate with NACV = 1.
a. Ensure the simulator scenario has enough GPS satellites to provide a horizontal dilution of precision (HDOP) of 1.5 or less.
b. One satellite shall be set at maximum power (including maximum combined satellite and aircraft antenna gain), and the other satellites shall be set at minimum power (including minimum antenna gain).
c. Broadband GNSS test noise (IGNSS,Test) of spectral density as defined in RTCA/DO-229D, paragraph 2.5.8, broadband external interference (Iext,test) and thermal noise contribution from the sky and the antenna (Nsky,antenna) shall be simulated.
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