Appendix 2
associated constraints, allowing for lateral and vertical guidance. In view of the reduced obstacle clearance associated with RNP AR proc edures, the associated navigation database information warrants special attention and consideration. This paragraph provides guidance for validating RNP AR instrument approach data contained in aircraft navigation databases. The guidance in this paragraph applies in full to aircraft operators performing RNP AR instrument approach procedures, as well as to any other entity with which an operator may contract to provide navigation database validation services.
Note 1: Although an aircraft operator may contract with an outside entity to perform navigation database validation services, the operator is responsible for ensuring the aircraft navigation database contains RNP AR instrument approach procedures validated in accordance with this appendix.
Note 2: An aircraft operator’s application to conduct RNP AR procedures should specifically describe the extent and nature of the services provided by an outside entity contracted to perform navigation database validation services.
a. Database Management Process.
The operator must identify in writing the individual responsible for managing the overall onboard navigation database process. The process and procedures for accepting, verifying and loading navigation data into the aircraft must be established in writing and maintained under configuration control (e.g., formal control of revisions and updates to the process). The operator may not contract out this responsibility to a third party.
b. RNP AR Procedure Data Validation.
The operator must ensure an RNP AR instrument approach procedure contained in its database has been validated before flying that approach procedure in IMC. The validation process ensures the RNP AR procedure contained in the navigation database accurately reflects the intended procedure design parameters. Proper data validation includes the following:
(1) Accuracy Check.
Compare the RNP AR procedure in the navigation database with the government source data. The FAA Form 8260-series, specifically form 8260-10, and other government source data defining the procedure, are available at the FAA Aviation System Standards website. Data for international procedures is available via the respective country’s aeronautical information publication (AIP). Any differences between the database and source data must be investigated. A list of the specific procedure data parameters that must be examined during this accuracy check, as well as the allowable differences between source data and that contained in the navigation database for each parameter can be found at the FAA’s Performance Based Flight Systems Branch (AFS-470) website located at:
A2-18
Appendix 2
http://www.faa.gov/about/office_org/headquarters_offices/avs/offices/af s/afs400/afs470/rnp/
(2) Flyability Check.
An initial flyability check is required for all non-part 97 United States RNP AR procedures, as well as all foreign RNP AR procedures the operator is authorized to fly.
Validate the RNP AR instrument approach procedures in the navigation database to ensure they match the published instrument approach procedures using: the actual aircraft in visual meteorological conditions; a flight simulation training device (FSTD) approved for RNP AR; or an appropriately configured desktop/laptop computer. An FSTD or desktop/laptop computer must use software identical to that used by the aircraft (i.e., FMS software) and use an aerodynamic model of the aircraft's flight characteristics. A map display must be used in the aircraft, FSTD or computer to compare the database procedure with that published. This validation process requires flying the entire procedure and should confirm the path is flyable, does not contain any lateral or vertical discontinuities, and is consistent with the published procedure.
c. Data Updates.
(1) Before using an updated navigation database (e.g., 28 day update), the operator must ensure the RNP AR approach data contained in that update remains within the tolerances prescribed in paragraph A2-7.b(1) of this appendix, when compared to the government source data. If a data parameter is found to exceed prescribed tolerances, the operator should consult with the appropriate navigation data supplier to resolve the discrepancy prior to using the approach procedure. Discrepancies may be resolved by correcting the error within the current cycle, removal of the procedure from the database, or potentially through operational mitigations approved by the FAA until the procedure data can be corrected.
(2) The method by which an operator conducts this recurring data comparison is optional, subject to the approval of the principle operations inspector or flight standards district office. One acceptable method is to establish a reference database, sometimes referred to as a “golden database,” containing known validated approach data, and comparing data from subsequent navigation updates against this reference data. Some FMS suppliers provide automated tools that enable a quick comparison of data parameters between databases and alert to any changes or differences. Operators may also choose to compare the navigation data contained in the updated database directly against the government source data. Regardless of the method used, operators must assure the integrity of the validated navigation data at each update cycle.
Note: An operator should be particularly attentive to potential discrepancies when database updates coincide with a change to the data supplier’s packing software. This packing software is used to format the navigation data into code readable by aircraft avionics.
A2-19
Appendix 2
d. Data Suppliers.
As a m inimum, data suppliers must have an LOA for processing navigation data in accordance with AC 20-153. An LOA recognizes the data supplier as one whose data quality, integrity, and quality management practices are consistent with the criteria of DO-200A. The aircraft operator’s supplier (e.g., FMS manufacturer) must have a Type 2 LOA. Those entities providing data to the aircraft operator’s supplier likewise must possess either a Type 1 or Type 2 LOA.
e. Aircraft Modifications.
If a manufacturer modifies an aircraft system required for RNP AR operations
(e.g., software or hardware change), the operator must, before flying any RNP AR procedures in IMC, confirm the aircraft’s ability to fly RNP AR procedures as published, with the modified aircraft system(s). The operator should examine a number of RNP AR procedures in its navigation database for this flyability check. The criteria described in paragraph A2-7.b(2) of this appendix should be used to perform this check.
Note: The operator does not need to perform this additional confirmation if the manufacturer documents the modification has no effect on the navigation database, or path computation.
f. Recurrent Audits.
The processes identified in this paragraph for validating and updating RNP AR instrument approaches in navigation databases are subject to recurrent FAA audits. The operator’s processes, as well as those performed by any outside entity contracted to provide navigation database services, are subject to audit by the FAA. Additionally, operators are expected to conduct their own recurrent audits of entities with whom they contract to provide navigation database services described in this appendix.
A2-8. Installation Considerations for RNP AR.
a. Detailed Rationale.
The applicant should provide:
(1) RNP Certification Plan.
Provide detailed rationale in the RNP certification plan (or project specific certification plan) for the use of RNP. This rationale should include a detailed explanation as to how the assigned levels support the system safety assessment, as well as a detailed explanation of the system architecture, including any means used to mitigate hazards and failure conditions resulting from the use of RNP. Additionally, include a detailed explanation of the interfaces between the FD, the autopilot and other sensors, and avionics hardware/software required, as it relates to the computed commands used for RNP.
A2-20
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 effect 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 A2-21
Appendix 2
A2-22 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).
(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 2-6 in RTCA/DO-283A. The FTE should be demonstrated in each phase of flight and each autopilot mode.
e. Interface to FGS.
Verify acceptable autopilot response to an RNP fault by 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.
Appendix 3
Appendix 3. RNP Advanced Features.
A3-1. Introductio
n.
This appendix provides guidance on the performance and functional requirements for RNP systems containing radius to fix capability. This appendix does not apply to RNP AR; see appendix 2 for all RNP AR guidance.
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 (terminal).
Note: RF legs will not be used in the final approach segment of an RNP approach.
a. System Requirements.
(1) Path Definition.
The RNP lateral accuracy requirement is evaluated around the path defined by the published procedure and RTCA/DO-236B, paragraph 3.2.3.3.
Note 1: Industry standards for paths can be found in RTCA/DO-236B.
Note 2: The guidance in this paragraph clarifies the intent in AC 90-105 for RNP Advanced Features. AC 90-105 mistakenly references RTCA/DO-236B paragraphs
3.2.5.4.1, Fly-By Transitions, and 3.2.5.4.2, Fixed-Radius Transitions, rather than paragraph 3.2.3.3, RF legs.
(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 A3-1
Appendix 3
proceed “Direct-To” the initial fix defining an RF leg segm ent, 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 RTCA/DO-283A, the applicant must complete the demonstration in accordance with AC 120-29A, paragraphs 5.19.2.2 and 5.19.3.1.
Note: The applicant may use AC 120-29A, paragraphs
5.19.2.2 and 5.19.3.1 to compute accepted FTE values.
(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 flightcrew’s primary field of view when loss of navigation capability and/or loss of integrity are experienced.
b. Functional Requirements.
(1) Autopilot and Flight Director.
RNP procedures with RF legs require using an autopilot or FD with at least “roll-steering” capability that is driven by the RNP system. The autopilot/FD must operate with suitable accuracy to track the lateral and, as appropriate, vertical paths required by a specific RNP procedure.
A3-2
Appendix 3
A3-3
(2) Bank Angle.
The flight management computer, the FD system, and the autopilot must be capable of commanding a bank angle up to 25 degrees above 400 feet AGL.
(3) Electronic Map Display.
The aircraft must have an electronic map display depicting the RNP computed path of the selected procedure including RF legs.
(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: For missed approaches with an RF Leg, the flightcrew must be able to couple the autopilot or FD to the RNP system (engage LNAV) by 500 feet AGL.
(5) 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.
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 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 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 requirements). 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.
Appendix 4
Appendix 4. GNSS Tests to Support ADS-B.
A4-1. Introductio
n.
a. The information in this appendix describes bench test procedures that can be used 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, paragraph 7d, states 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 un-augmented modes of operation. Even in the case where the velocity algorithm is the same A4-1
Appendix 4
whether in un-augm ented 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- 138C, 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.
A4-2
Appendix 4
Note: In R TCA/DO-229D, paragraph 2.5.8.2 step 2, replace -173.0 dBm/Hz with -172.8 dBm/Hz for total GNSS noise (IGNSS) when running separate GPS/SBAS testing for accuracy verification and/or GPS/SBAS message loss rate data.
d. The airborne equipment shall be initialized with the appropriate position and time. It is assumed that the receiver has obtained a valid almanac for the simulator scenario to be tested prior to conducting the test.
e. Platform dynamics for the horizontal velocity accuracy test shall be as defined in Table 12 below.
Time (s) Start Jerk (g/s) End Jerk (g/s) From To Dynamics North East Down Total North East Down Total 0 T Static 0 0 0 0 0 0 0 0 T+1 T+71 0.58g longitudinal acceleration to 411 m/s
0.xx Note 1
0.xx Note 1 0 0.25 0.xx Note 1
0.xx Note 1 0 0.25 T+72 T+129 Straight un-accelerated flight 0 0 0 0 0 0 0 0 T+130 T+194 -0.45g longitudinal acceleration to 125 m/s
0.xx Note 1
0.xx Note 1 0 0.2 0.xx Note 1
0.xx Note 1 0 0.2 T+195 T+254 Straight un-accelerated flight 0 0 0 0 0 0 0 0 T+255 T+325 turn 180° with 0.58g lateral acceleration
0.xx Note 1
0.xx Note 1 0 0.25 0.xx Note 1
0.xx Note 1 0 0.25 T+326 T+420 Straight un-accelerated flight 0 0 0 0 0 0 0 0 Table 12. Platform Dynamics for Horizontal Velocity Accuracy Test
Note 1: The components of the jerk in the north and east direction depends on the heading chosen in the scenario.
The total jerk is not to exceed the vector combination of north, east, and down jerk components. The maximum total jerk to quickly achieve the desired dynamics should be used, but the jerk should not exceed the normal maneuver total jerk requirement of 0.25 g/s.
Note 2: The actual times may vary based on the simulator scenario control settings.
A4-3
Appendix 4
f. Signal and radio frequency interference (RFI) conditions can be m odified during static period to aid acquisition. Ensure the receiver enters the desired operation mode before dynamics and appropriate signal and interference conditions are applied.
g. Use the simulator velocity truth data ( trutheast iV _ , truthnorthiV _ ) and the GNSS receiver velocity data ( east iV , northiV ) to determine the horizontal velocity error ih after the GNSS receiver has entered the desired navigation mode with the specified signal and RFI conditions:
2_2_ )()( northitruthnorthieastitrutheastii VVVVh
A4-4. Horizontal Accuracy Pass/Fail Determination.
a. The 95% horizontal velocity accuracy statistic shall be computed using the formula given below. The equipment shall pass if the statistic is less than or equal to 10-LSB m/s.
Note: The notation “10-LSB m/s” specifies that the pass threshold is 10 m/s minus the magnitude of the least significant bit of the output data fields representing the horizontal velocity components. The intent is to ensure that quantization error in the velocity output does not degrade the accuracy below the threshold.
N i i N i HDOP h 1 2
5.1 *2
Where:
hi = horizontal velocity error (m/sec).
HDOPi = horizontal dilution of precision at epoch i.
N = number of sample points used.
b. For this test, the number of samples shall include all samples where the receiver is in the desired navigation mode and when in motion.
Note: The minimum number of samples is 420 for a 1 Hz solution and 2100 for a 5 Hz solution (i.e., 5* 420).
A4-5. Horizontal Velocity Figure of Merit Pass/Fail Determination.
The receiver velocity data and the horizontal figure of merit - velocity (HFOMV) data shall be used to determine the percentage of samples bounded by the HFOMV as shown below. The test passes if TSh,b is greater than or equal to 0.95.
A4-4