Appendix 2 A2-14 how the velocity is output (i.e., in a groundspeed format versus north/east velocity format) and the protocols used.
(5) TSO C145/146 Rev b/c Class 1. Gamma-1 equipment requirements outlined in DO-229D Section 2.2.1.4.10 for the display resolution of ground speed are insufficient to show ADS-B compliance. A recommendation for GNSS manufacturers on label 103 and label 112 can be found in DO-229D, Appendix H. Additional means of compliance for TSO-C145/146 Rev b/c Class 1 requires GNSS manufacturers to provide information in the installation instructions describing how the velocity is output (i.e., in a groundspeed format versus north/east velocity format) and the protocols used.
(6) TSO C145/146 Rev b/c Class 2/3. Gamma-2 and Gamma-3 equipment requirements outlined in DO-229D Section 2.2.1.4.10 for the display resolution of ground speed are insufficient to show ADS-B compliance. A recommendation for GNSS manufacturers on label 103 and label 112 can be found in DO-229D, Appendix H. Additional means of compliance for TSO-C145/146 Rev b/c Class 2/3 requires GNSS manufacturers to provide information in the installation instructions describing how the velocity is output (i.e., in a groundspeed format versus north/east velocity format) and the protocols used.
(7) TSO C196/196a. Means of compliance for this TSO requires GNSS manufacturers to provide information in the installation instructions describing how the velocity is output (i.e., in a groundspeed format versus north/east velocity format) and the protocols used. A recommendation for GNSS manufacturers on label 103 and label 112 can be found in DO-316 Appendix H.
m. Time of Applicability. The GNSS equipment must output a time of applicability.
Note: The intent is to output position, velocity, and HFOM in a consistent manner for time of applicability (refer to DO-229D Section 2.1.2.6 and 2.1.2.6.2).
(1) TSO C129. Means of compliance for this TSO requires GNSS manufacturers to use a manufacturer-defined test and/or analysis to determine the latency between the time satellite measurements are collated for processing and the time the equipment calculates a filtered (impulse response) position solution. The equipment must meet a 500 millisecond time of measurement to time of applicability requirement and account for the impulse response of the position solution.
(2) TSO C129a. Means of compliance for this TSO requires GNSS manufacturers to use a manufacturer-defined test and/or analysis to determine the latency between the time satellite measurements are collated for processing and the time the equipment calculates a filtered (impulse response) position solution. The equipment must meet a 500 millisecond TOM to time of applicability requirement and account for the impulse response of the position solution.
(3) TSO C145/146 Rev a Class 1. Means of compliance for this TSO are defined in DO-229C sections 2.1.2.6 and 2.1.2.6.2.
(4) TSO C145/146 Rev a Class 2/3. Means of compliance for this TSO are defined in DO-229C sections 2.1.2.6, 2.1.2.6.2, and 2.1.5.8.2.
Appendix 2 A2-15
(5) TSO C145/146 Rev b/c Class 1. Means of compliance for this TSO are defined in DO-229D sections 2.1.2.6 and 2.1.2.6.2.
(6) TSO C145/146 Rev b/c Class 2/3. Means of compliance for this TSO are defined in DO-229D sections 2.1.2.6, 2.1.2.6.2, and 2.1.5.8.2.
(7) TSO C196/196a. Means of compliance for this TSO are defined in DO-316 sections 2.1.2.6 and 2.1.2.6.2.
n. Velocity accuracy. The GNSS position source manufacturer must provide design data to assist the installer in setting the NACV. Scaling the reported GNSS position accuracy (HFOM and VFOM) is not an acceptable means to determine NACV.
(1) NACV = 1. For installations intending to support NACV = 1, the GNSS manufacturer must perform the velocity tests in AC 20-138C, appendix 4 paragraph A4-1 through A4-8 associated with NACv = 1. The GNSS manufacturer must indicate that the equipment satisfies the requirements for NACv =1 in the installation instructions for the ADS-B integration.
(2) NACV. = 2. For installations intending to support NACV = 2, the GNSS manufacturer must perform the velocity tests in AC 20-138C, Appendix 4 paragraphs A4-1 through A4-9 associated with NACv = 1 and NACv = 2. The GNSS manufacturer must present substantiation data that the equipment dynamically outputs HFOMV and VFOMV (see AC 20-138() appendix 4, paragraphs A4-5 and A4-8) and that the equipment velocity and accuracy outputs have passed the velocity tests associated with NACv = 1 and NACv = 2. The GNSS manufacturer must indicate that the equipment satisfies the requirements for NACv = 2 in the installation instructions for the ADS-B integration.
(3) NACV. = 3 or 4. No standard for performance has been developed to support NACV = 3 or 4. A NACV = 3 or NACV = 4 should not be set based on GNSS velocity accuracy unless you can demonstrate to the FAA that the error contributions have been adequately modeled to meet those levels of performance.
(4) TSO C129. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data based on the NACv =1 and NACv = 2 test as appropriate and document the NACV in the installation instructions for the ADS-B integration. See AC 20-138() appendix 4, paragraph A4-2.d(3) for additional guidance relative to using the noise environment in DO-235B for the velocity tests.
(5) TSO C129a. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data based on the NACv =1 and NACv = 2 test as appropriate and document the NACV in the installation instructions for the ADS-B integration. See AC 20-138() appendix 4, paragraph A4-2.d(3) for additional guidance relative to using the noise environment in DO-235B for the velocity tests.
Appendix 2 A2-16
(6) TSO C145/146 Rev a Class 1. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data based on the NACv =1 and NACv = 2 test as appropriate and document the NACV in the installation instructions for the ADS-B integration.
(7) TSO C145/146 Rev a Class 2/3. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data based on the NACv =1 and NACv = 2 test as appropriate and document the NACV in the installation instructions for the ADS-B integration.
(8) TSO C145/146 Rev b/c Class 1. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data based on the NACv =1 and NACv = 2 test as appropriate and document the NACV in the installation instructions for the ADS-B integration.
(9) TSO C145/146 Rev b/c Class 2/3. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data based on the NACv =1 and NACv = 2 test as appropriate and document the NACV in the installation instructions for the ADS-B integration.
(10) TSO-C196/196a. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data based on the NACv =1 and NACv = 2 test as appropriate and document the NACV in the installation instructions for the ADS-B integration.
o. Vertical position accuracy. The GNSS should output vertical position accuracy. The vertical accuracy should specify a 95% probability bound on the reported vertical position. No revisions of TSO-C129 or TSO-C196 have vertical accuracy or integrity requirements, and TSO-C145 /146 only has vertical accuracy requirements for certain approach modes. None of the GNSS TSOs have a requirement to continuously output the vertical position accuracy data.
If vertical position accuracy is output, it must have been qualified during design approval of the position source.
(1) TSO C129. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data along with the VFOM output based on the test described in the latest revision of AC 20-138 appendix 4, paragraph A4-10.
(2) TSO C129a. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data along with the VFOM output based on the test described in the latest revision of AC 20-138 appendix 4, paragraph A4-10.
(3) TSO C145/146 Rev a Class 1. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data along with the VFOM output based on the test described in the latest revision of AC 20-138 appendix 4, paragraph A4-10.
(4) TSO C145/146 Rev a Class 2. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data along with the VFOM output based on the test described in the latest revision of AC 20-138 appendix 4, paragraph A4-10.
Appendix 2 A2-17
(5) TSO C145/146 Rev b/c Class 1. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data along with the VFOM output based on the test described in the latest revision of AC 20-138 appendix 4, paragraph A4-10.
(6) TSO C145/146 Rev b/c Class 2/3. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data along with the VFOM output based on the test described in the latest revision of AC 20-138 appendix 4, paragraph A4-10.
(7) TSO C196/196a. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data along with the VFOM output based on the test described in the latest revision of AC 20-138 appendix 4 paragraph A4-10.
p. Mode output. If interpretation of the integrity output of the position source can change due to a change in the position source mode, the position source must have a way of communicating that change of mode to the ADS-B equipment. Additionally, the position source manufacturer should provide a description of the modes and a description of how the position source outputs the mode indication.
(1) TSO C129. Means of compliance for this TSO requires GNSS manufacturers to provide installation instructions describing the modes available (if affecting interpretation of integrity output) and how the position source outputs the mode indication (See Integrity Limit, paragraph 4.g, of this appendix).
(2) TSO C129a. Means of compliance for this TSO requires GNSS manufacturers to provide installation instructions describing the modes available (if affecting interpretation of integrity output) and how the position source outputs the mode indication (See Integrity Limit, paragraph 4.g, of this appendix).
(3) TSO C145/146 Rev a Class 1. Means of compliance for this TSO requires GNSS manufacturers to provide installation instructions describing the modes available (if affecting interpretation of integrity output) and how the position source outputs the mode indication (See Integrity Limit, paragraph 4.g, of this appendix).
(4) TSO C145/146 Rev a Class 2. Means of compliance for this TSO requires GNSS manufacturers to provide installation instructions describing the modes available (if affecting interpretation of integrity output) and how the position source outputs the mode indication (See Integrity Limit, paragraph 4.g, of this appendix).
(5) TSO C145/146 Rev b/c Class 1. Means of compliance for this TSO requires GNSS manufacturers to provide installation instructions describing the modes available (if affecting interpretation of integrity output) and how the position source outputs the mode indication (See Integrity Limit, paragraph 4.g, of this appendix).
(6) TSO C145/146 Rev b/c Class 2/3. Means of compliance for this TSO requires GNSS manufacturers to provide installation instructions describing the modes available (if affecting
Appendix 2 A2-18 interpretation of integrity output) and how the position source outputs the mode indication (See Integrity Limit, paragraph 4.g, of this appendix).
(7) TSO C196/196a. Means of compliance for this TSO requires GNSS manufacturers to provide installation instructions describing the modes available (if affecting interpretation of integrity output) and how the position source outputs the mode indication (See Integrity Limit, paragraph 4.g, of this appendix).
q. Approach mode integrity. SBAS equipment certified under any revision of TSO-C145 or TSO-C146 is required to have several modes of operation depending on the availability of augmentation. For example, when operating in an augmented mode intended for LPV approach guidance, the position source may determine HPL based on a lateral error versus a horizontal error and an exposure time based on the duration of the approach versus flight hour. Reference RTCA DO- 229D appendix J. If the position source outputs the HPL on lateral error and approach exposure time, it is possible that the ADS-B transmitter would need to inflate the HPL by 3% in approach modes to ensure the integrity is appropriately bounded. GBAS equipment is required to comply with the GNSS or SBAS requirements for the output of position data. This is an integration issue between the GPS and ADS-B transmitter. The position source manufacturer must provide information to the system integrator to determine if the integrity output needs to be scaled (i.e., by applying an inflation factor).
Although we do not address the interface of a GBAS differentially-corrected position source in this AC, it will have similar considerations in approach modes as SBAS.
(1) TSO C129. This is not applicable to this TSO as no HPL scaling is applied.
(2) TSO C129a. This is not applicable to this TSO as no HPL scaling is applied.
(3) TSO C145/146 Rev a Class 1. Means of compliance for this TSO are defined in DO-229C sections 2.1.1.13.1 and 2.1.3.2.2.
(4) TSO C145/146 Rev a Class 2/3. Means of compliance for this TSO are defined in DO-229C sections 2.1.1.13.1, 2.1.3.2.2, 2.1.4.2.2, and 2.1.5.2.2.
(5) TSO C145/146 Rev b/c Class 1. Means of compliance for this TSO are defined in DO-229D sections 2.1.1.13.1 and 2.1.3.2.2.
(6) TSO C145/146 Rev b/c Class 2/3. Means of compliance for this TSO are defined in DO-229D sections 2.1.1.13.1, 2.1.3.2.2, 2.1.4.2.2, and 2.1.5.2.2.
(7) TSO C196/196a. This is not applicable to this TSO as no HPL scaling is applied.
r. Track angle validity. GNSS position sources can provide a track angle, however the GNSS track angle may become invalid below a certain velocity. Optimally, the position source should either invalidate or remove the track angle when it is no longer valid. If the position source does not invalidate the track angle or remove the track angle when it is potentially invalid, then the position source manufacturer must provide information on velocity limitations for GNSS track angle.
Appendix 2 A2-19 Note: 1: The interference levels used to demonstrate velocity accuracy compliance can be used for track angle validity as well.
(1) TSO C129. Means of compliance for TSO-C129 requires GNSS manufacturers to use the test environment and guidance defined in the latest revision of AC 20-138, appendix 4 paragraph 4-12.It is recommended that manufacturers use DO-229D, Appendix H for outputting track angle (ARINC 743 all revisions label 103) for those using ARINC 429 characteristics.
(2) TSO C129a. Means of compliance for TSO-C129a requires GNSS manufacturers to use the test environment and guidance defined in the latest revision of AC 20-138, appendix 4 paragraph 4-12. It is recommended that manufacturers use DO-229D, Appendix H for outputting track angle (ARINC 743 all revisions label 103) for those using ARINC 429 characteristics.
(3) TSO C145/146 Rev a Class 1. Means of compliance for TSO-C145/146 Rev a Class 1 requires GNSS manufacturers to use the test environment and guidance defined in the latest revision of AC 20-138, appendix 4 paragraph 4-12. It is recommended that manufacturers use DO-229C, Appendix H for outputting track angle (ARINC 743 all revisions label 103) for those using ARINC 429 characteristics.
(4) TSO C145/146 Rev a Class 2/3. Means of compliance for TSO-C145/146 Rev a Class 2/3 requires GNSS manufacturers to use the test environment and guidance defined in the latest revision of AC 20-138, appendix 4 paragraph 4-12. It is recommended that manufacturers use DO-229C, Appendix H for outputting track angle (ARINC 743 all revisions label 103) for those using ARINC 429 characteristics.
(5) TSO C145/146 Rev b/c Class 1. Means of compliance for TSO-C145/146 Rev b/c Class 1 requires GNSS manufacturers to use the test environment and guidance defined in the latest revision of AC 20-138, appendix 4 paragraph 4-12. It is recommended that manufacturers use DO-229D, Appendix H for outputting track angle (ARINC 743 all revisions label 103) for those using ARINC 429 characteristics.
(6) TSO C145/146 Rev b/c Class 2/3. Means of compliance for this TSO requires GNSS manufacturers to use the test environment and guidance defined in the latest revision of AC 20-138, appendix 4 paragraph 4-12. It is recommended that manufacturers use DO-229D, Appendix H for outputting track angle (ARINC 743 all revisions label 103) for those using ARINC 429 characteristics.
(7) TSO C196/196a. Means of compliance for this TSO requires GNSS manufacturers, using test or analysis to use the test environment and guidance defined in the latest revision of AC 20-138, appendix 4 paragraph 4-12. It is recommended that manufacturers use DO-316, Appendix H for outputting track angle (ARINC 743 all revisions label 103) for those using ARINC 429 characteristics.
s. Time mark. GNSS position sources should output a UTC time mark identifying time of applicability with the successive position output. In modern sensors computing and outputting position multiple times per second, this time mark typically is associated with only one of the
Appendix 2 A2-20 position outputs per second. The time mark can be used by the ADS-B equipment to reduce uncompensated latency. For 1090ES, the time mark output is not required for installations to be rule compliant. When integrating a UAT with an external GPS, the design of the hardware time mark must be interoperable. Some GPS synchronize the leading edge of the time mark to the UTC second. Other GPS let the time mark pulse be asynchronous to the UTC second and then record the time of the leading edge in the digital data along with the position solution. The UAT equipment must support the GPS time mark design. If the UAT equipment and GPS do not share a common time mark design, the UAT equipment will not be properly synchronized with the ground system and other aircraft.
(1) TSO C129. Means of compliance for this TSO requires GNSS manufacturers to provide installation instructions describing how the time mark relates to the position, velocity, FOM, and time of applicability.
(2) TSO C129a. Means of compliance for this TSO requires GNSS manufacturers to provide installation instructions describing how the time mark relates to the position, velocity, FOM, and time of applicability.
(3) TSO C145/146 Rev a Class 1. Means of compliance for this TSO requires GNSS manufacturers to provide installation instructions describing how the time mark relates to the position, velocity, FOM, and time of applicability.
(4) TSO C145/146 Rev a Class 2/3. Means of compliance for this TSO requires GNSS manufacturers to provide installation instructions describing how the time mark relates to the position, velocity, FOM, and time of applicability.
(5) TSO C145/146 Rev b/c Class 1. Means of compliance for this TSO requires GNSS manufacturers to provide installation instructions describing how the time mark relates to the position, velocity, FOM, and time of applicability.
(6) TSO C145/146 Rev b/c Class 2/3. Means of compliance for this TSO requires GNSS manufacturers to provide installation instructions describing how the time mark relates to the position, velocity, FOM, and time of applicability.
(7) TSO C196/196a. Means of compliance for this TSO requires GNSS manufacturers to provide installation instructions describing how the time mark relates to the position, velocity, FOM, and time of applicability.
t. Signal-in-space error detection. The position source should provide a means to detect a SIS error when the system uses a SIS. The probability of missed detection for a faulty SIS should be less than 1x10-3. GNSS equipment provides the appropriate SIS error detection.
(1) TSO C129. Means of compliance for this TSO is defined in DO-208 change 1 Section 2.2.1.13.1 referring to Table 2-1 (see Table 2-1 Note D). However, TSO-C129 equipment has no requirement for pseudorange step detection. This requires GNSS
Appendix 2 A2-21 manufacturers to provide substantiation data documenting their RAIM algorithm includes pseudorange step detection per TSO-C129a section (a)(3)(xv) 5.
(2) TSO C129a. Means of compliance is defined in DO-208 change 1 section
2.2.1.13.1 referring to Table 2-1 (see Table 2-1 Note D) and TSO-C129a section (a)(3)(xv)5.
(3) TSO C145/146 Rev a Class 1. Means of compliance for this TSO is defined in DO-229C sections 2.1.1.3 and 2.1.1.5 for SBAS, section 2.1.1.2 for GPS health message, and Section 2.1.2.2.2.2.2 for FDE.
Note: The SBAS Signal in Space (SIS) includes health monitoring/fault information which is why these general signal processing requirements are included.
(4) TSO C145/146 Rev a Class 2/3. Means of compliance for this TSO is defined in DO-229C sections 2.1.1.3 and 2.1.1.5 for SBAS, section 2.1.1.2 for GPS health message, and Section 2.1.2.2.2.2.2 for FDE.
Note: The SBAS SIS includes health monitoring/fault information which is why these general signal processing requirements are included.
(5) TSO C145/146 Rev b/c Class 1. Means of compliance for this TSO is defined in DO-229C sections 2.1.1.3 and 2.1.1.5 for SBAS, section 2.1.1.2 for GPS health message, and Section 2.1.2.2.2.2.2 for FDE.
Note: The SBAS SIS includes health monitoring/fault information which is why these general signal processing requirements are included.
(6) TSO C145/146 Rev b/c Class 2/3. Means of compliance for this TSO is defined in DO-229C sections 2.1.1.3 and 2.1.1.5 for SBAS, section 2.1.1.2 for GPS health message, and Section 2.1.2.2.2.2.2 for FDE.
Note: The SBAS SIS includes health monitoring/fault information which is why these general signal processing requirements are included.
(7) TSO C196/196a. Means of compliance for this TSO are defined in DO-316 sections 2.1.1.2, 2.1.1.3, and 2.1.2.2.2.2.
5. Tightly-coupled GNSS/ IRS position sources. This section provides high level guidance on the issues that will need to be addressed to qualify a tightly-coupled Global Navigation Satellite System / Inertial Reference System (GNSS/IRS) for use in an ADS-B system. You must propose to the FAA the method to approve a tightly-coupled GNSS/IRS for use in an ADS-B system.
a. The tightly-coupled GNSS/IRS outputs must meet the requirements, including validation, of either RTCA/DO-229(), appendix R, or RTCA/DO-316, appendix R.
Appendix 2 A2-22
b. Address the horizontal velocity accuracy.
c. The GNSS sensor should meet the minimum performance requirements for any revision of TSO-C129, TSO-C145, TSO-C146, or TSO-C196. Additionally, the GNSS sensor should meet all applicable GNSS requirements of this appendix as applicable.
d. Install the GNSS sensor(s) in accordance with AC 20-138(), Airworthiness Approval of Global Navigation Satellite System (GNSS) Equipment.
e. 14 CFR 91.227 requires a SIL = 3, which means the probability of exceeding the NIC containment radius should be less than 1x10-7 per hour or per sample. The tightly-coupled GNSS/IRS system should transmit the integrity quality metric on a “per-hour” basis. After loss of GNSS or GNSS RAIM, the hybrid system should report the integrity containment radius of 1x10-7 probability on a per sample basis rather than on a per hour basis. Doing so would allow the GNSS/IRS system to transmit at a probability of 1x10-7 for a longer period of time.
(1) RTCA/DO-229D appendix R, paragraph 2.1 requires tightly-coupled systems to meet two integrity limits. The integrity limit for the faulted satellite case is 1x10-7. The integrity limit for fault free (rare normal) case is 1x10-5. RTCA/DO-229D appendix R, paragraph 2.1.1 acknowledges that in tightly integrated systems that inertial coasting may cause the rare normal limit to be dominant over the limit for the faulted conditions in times of poor satellite coverage. If the HPL output from the tightly-coupled position source changes from the fault detection 1x10-7 basis to the fault free 1x10-5 basis the position source needs to indicate this change to the ADS-B equipment. We recommend the position source use a 1x10-7 integrity basis in all modes.
(2) If the integrity containment probability output of the tightly-coupled GNSS/IRS position source changes from per hour to per sample following a loss of GNSS or a loss of GNSS RAIM, then the position source must indicate this change to the ADS-B equipment (i.e. SIL Supplement).
(3) If the tightly-coupled GNSS/IRS scales the inertial integrity from 1x10-5 to 1x10-7, the scaling must have been demonstrated during design approval of the position source. If the inertial basis is per sample and is scaled to per hour, this scaling must have been demonstrated during the position source design approval.
f. If a tightly coupled GNSS/IRS position source is intended to be used as an ADS-B position source after the loss of GNSS, include integrity coasting performance in the flight manual. Specifically address:
(1) If inertial coasting will meet 14 CFR 91.227 requirements, such as NACP = 8, NIC = 7, SIL = 3, and SDA = 2.
(2) Estimated length of time following a loss of GNSS for which inertial coasting is expected to meet the 14 CFR 91.227 requirements. The estimate should assume the system met minimum 14 CFR 91.227 requirements just prior to the loss of GNSS or GNSS RAIM. This estimate will be helpful to operators in developing a means to assure that the system can meet
Appendix 2 A2-23 14 CFR 91.227 requirements during predicted GNSS degradations.
6. Non-GNSS position sources. The FAA does not know of any currently available non-GNSS position sources that can meet the performance requirements of 14 CFR 91.227. However, you may wish to integrate a backup ADS-B OUT capability in the event of loss of GNSS. Such a backup is not required. We do not expect any ATC operational advantages for systems that provide a non-GNSS backup unless that backup capability meets the performance requirements of 14 CFR 91.227. This section provides high level guidance on the issues that will need to be addressed to qualify a non-GNSS position source for use in an ADS-B system without regard to 14 CFR 91.227 requirements. If you choose to integrate this capability, use the guidance below and propose to the FAA the method to approve a non-GNSS position source for use in an ADS-B system.
a. Distance Measuring Equipment (DME/DME).
(1) The DME/DME RNAV system must meet the minimum performance requirements of TSO-C66c, Distance Measuring Equipment (DME) Operating within the Radio Frequency Range of 960-1215 Megahertz.
(2) There are no industry standards for use of a DME/DME system to determine position integrity or velocity accuracy. You must propose a method to derive these parameters.
(3) The DME/DME system must only use DME facilities listed in the Airport/Facility Directory (A/FD).
(4) The DME/DME system must only use operational DME facilities. The system must exclude non-operational facilities by checking the identification. Operational mitigations, such as manually excluding (blackballing) DME stations or any action that requires pilot action or monitoring of the DME/DME system, are not permissible for ADS-B qualified position sources.
(5) Reasonableness Checks. The DME/DME system must incorporate reasonableness checking. Reference AC 90-100A for additional information on reasonableness checks.
b. VOR/DME. ADS-B position sources may not utilize Very High Frequency Omnidirectional Range (VOR) information. Do not interface any position solution that utilizes VOR information as the performance of the VOR cannot be assumed throughout the region in which the signal is received.
c. Inertial Navigation System/Inertial Reference Unit (INS)/(IRU) Loosely Coupled with DME or GNSS.
(1) The GNSS equipment or DME equipment must meet the requirements in this appendix.
(2) Loosely coupled INS/IRU equipment must meet 14 CFR part 121, appendix G.
Appendix 2 A2-24
(3) The loosely coupled INS/IRU position source must provide all of the required position source outputs listed in this appendix. Qualify the outputs during installation approval of the ADS-B system, see paragraph 3 of this appendix. Velocity accuracy may be qualified and set statically. Update the position accuracy and position integrity metrics dynamically.
(4) 14 CFR 91.227 requires a SIL = 3, which means the probability of exceeding the NIC containment radius should be less than 1x10-7 per hour or per sample. A GNSS/IRS that continues to provide the integrity containment radius based on a 1x10-7 probability after loss of GNSS or GNSS RAIM is preferred. Potential errors, caused by GNSS updating prior to the loss of GNSS, must continue to be bounded.
(a) If the integrity containment probability output of a loosely coupled GNSS/IRS position source changes from 1x10-7 to 1x10-5 following a loss of GNSS or a loss of GNSS RAIM, then the position source must relay this change to the ADS-B equipment. The overall system time to transmit a change in SIL must be 10 seconds or less.
(b) If the integrity containment probability output of a loosely coupled GNSS/IRS position source changes from per hour to per sample following a loss of GNSS or a loss of GNSS RAIM, then the position source must relay this change to the ADS-B equipment.
7. Future position sources. It is expected that future position sources such as dual frequency GPS and GPS/Galileo sources will be acceptable position sources for ADS-B and meet the performance requirements of 14 CFR 91.227. Future revisions of this AC will address new position source technology when it becomes available.
Appendix 3 A3-1 Appendix 3. Latency Analysis
1. Purpose. The purpose of this appendix is to provide guidelines on accomplishing a latency analysis on your ADS-B system.
2. Analysis. Accomplish the analysis by determining the applicable latencies for each component and totaling all of the individual component latencies. You must include all sources of position latency, including, but not limited to the position source, intermediary devices between the position source and ADS-B equipment, and the ADS-B equipment. Use the following guidelines to determine latency for each component:
a. Position source latency considerations. In general, the latency information should be generated by the position source manufacturer and presented as part of the latency analysis. The latency measurement should begin at the Time-Of-Measurement (TOM) and end when the position is output from the position source.
(1) TSO-C145, TSO-C146, and TSO-C196 GNSS. Use the TSO latency standards in the latency analysis or use actual latency information generated by the GNSS manufacturer to determine the position source maximum total latency and uncompensated latency. If the GNSS equipment is classified as Class 3 per any revision of TSO-C145, there are tighter latency standards for the LPV modes. If the Class 3 standard is implemented across all modes, the tighter latency numbers may be used, however if the tighter latency standards are only met when in approach mode, use the worst-case latency across all modes.
(2) TSO-C129 GNSS. There are no latency standards for any revision of TSO-C129 GNSS equipment. Latency information must be generated by the GNSS manufacturer and included as part of the latency analysis.
(3) Tightly-coupled GNSS/inertial. There are no latency standards for tightly-coupled GNSS/Inertial equipment. Total and uncompensated latency information should be generated by the position source manufacturer and presented as part of the latency analysis. Base the latency analysis on the update rate of the inertial sensor, as 10 or 20 second GNSS updates to the inertial sensor are not impacting the latency of the position output. However, the GNSS update latency does affect the position accuracy and should be appropriately reflected in the position source accuracy output.
(4) Other position sources. Total and uncompensated latency information should be generated by the position source manufacturer and included as part of the latency analysis.
b. Intermediary device. Intermediary devices are typically data concentrators. The latency information should be generated by the intermediary device manufacturer and presented as part of the latency analysis. If the intermediary device latency is variable, use the worst-case latency.
c. ADS-B equipment. Use the TSO-C166b and TSO-C154c latency standards for the latency analysis or use the actual latency information generated by the ADS-B equipment manufacturer.
TSO-C166b and TSO-C154c require the uncompensated latency of the ADS-B equipment to be less than 100ms.