Appendix 1 A1-7
Table 13. System Design Assurance
SDA Value Supported Failure Condition Note 2 Probability of Failure causing transmission of False or Misleading Information Note 3,4 Software & Hardware Design Assurance Level Note 1,3 3 Hazardous ≤ 1x10-7 Per Hour B 2 Major ≤ 1x10-5 Per Hour C 1 Minor ≤ 1x10-3 Per Hour D 0 Unknown/ No safety effect > 1x10-3 Per Hour or Unknown N/A
Note: 1: Software design assurance per RTCA/DO-178B, Software Considerations in Airborne Systems and Equipment Certification, or equivalent.
Airborne electronic hardware design assurance per RTCA/DO-254, Design Assurance Guidance for Airborne Electronic Hardware, or equivalent.
Note: 2: Supported failure classification defined in AC 25.1309-1, AC 23.1309-1, and AC 29-2.
Note: 3: Because the broadcast position can be used by any other ADS-B equipped aircraft or by ATC, the provisions in AC 23.1309-1() that allow reduction in failure probabilities and design assurance level for aircraft under 6,000 pounds do not apply for the ADS-B system.
Note: 4: Includes probability of transmitting false or misleading latitude, longitude, or associated position accuracy and integrity metrics.
dd. TCAS installed and operational. This parameter indicates whether the aircraft is fitted with a TCAS II and if the TCAS II is turned on and operating in a mode that can generate resolution advisory alerts. The TCAS installed and operational parameter is required to be transmitted by 14 CFR 91.227.
ee. TCAS traffic status. This parameter indicates if a TCAS II equipped aircraft is currently generating a TCAS resolution advisory. The TCAS traffic status parameter is required to be transmitted by 14 CFR 91.227 if the aircraft is TCAS II equipped.
ff. Trajectory change report capability. This information is permanently set to zero in TSO-C166b or TSO-C154c equipment. No installation interface is required. Trajectory change reports are reserved for future use.
gg. Vertical rate. The barometric or geometric rate at which the aircraft is climbing or descending, measured in feet per minute. The vertical rate is typically generated by an air data computer or GNSS position source, or equipment which blends barometric vertical rate with inertial vertical rate and/or GNSS vertical rate.
Appendix 1 A1-8 hh. Version number. The applicable TSO Minimum Operational Performance Standard (MOPS) level is communicated through the version number, which is fixed at the time the ADS-B equipment is manufactured. Version two applies to ADS-B equipment that meets MOPS documents RTCA/DO-260B with Corrigendum 1 or RTCA/DO-282B with corrigendum 1.
ADS-B equipment outputting version two or higher is required by 14 CFR 91.227.
Appendix 2 A2-1 Appendix 2. Identifying and Qualifying ADS-B Position Sources
1. Purpose. This appendix defines the minimum requirements for position sources interfaced to ADS-B systems. The appendix also defines appropriate position source qualification methods when the existing GNSS TSOs do not contain specific requirements or test procedures. The position source manufacturer should provide design data where appropriate, preferably in the GNSS equipment installation manual, so that the installer can properly interface the position source to the ADS-B system. Position source suppliers must ensure that any supplied data is incorporated into the article design, and changes to any documented characteristics result in a change to the part number.
2. Organization. This appendix includes general guidance that applies to all position sources, as well as GNSS specific guidance. The appendix also provides high level requirements for tightly coupled GNSS/IRU position sources and non-GNSS position sources. All references in this AC to TSO-C129, TSO-C145, TSO-C146, and TSO-C196 refer to any revision of the TSO.
3. General Guidance for all Position Sources. All ADS-B position sources should provide the following outputs.
a. Position. The position source must provide a latitude and longitude output.
Requirements and test procedures in TSO-C129/145/146/196 are sufficient and GNSS equipment with Technical Standard Order Authorization (TSOA) for the aforementioned TSOs require no additional qualification for the position output.
b. Horizontal velocity. The position source must output north/south and east/west velocities. We recommend the position source also output the velocity in a ground speed and track angle format.
c. Position accuracy (horizontal). The position source must have a horizontal position accuracy output, and the output must have been qualified during the system’s TSO authorization or design approval. This output must describe the radius of a circle in the horizontal plane, with its center being at the true position which describes the region assured to contain the indicated horizontal position with at least 95% probability under fault-free conditions.
d. Position accuracy (vertical). The position source should output a vertical position accuracy metric. The vertical position accuracy metric must have been qualified during the system’s TSO authorization or design approval. This output must describe the vertical position accuracy with 95% probability under fault-free conditions.
e. Position integrity (horizontal). The position source must have a horizontal position integrity output qualified during the system’s TSO authorization or design approval. This integrity output should describe the radius of a circle in the horizontal plane, with its center being at the true position which describes the region assured to contain the indicated horizontal position with at least 99.99999% probability under fault-free avionics conditions. Position sources which degrade from a 99.99999% probability to a 99.999% probability (e.g., a tightlycoupled inertial/GNSS system after the loss of GNSS) can still be installed, however they won’t meet 14 CFR 91.227 following the degradation. In this case, the position source must have a
Appendix 2 A2-2 way of indicating the change to the ADS-B equipment. Additionally, if the change of probability is due to a change in position source, the new position source must meet all of the requirements in this appendix.
(1) Mode. 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.
(2) Validity limit. If the integrity value of the output cannot be trusted beyond a certain limit, indicate this limitation in the design documentation.
(3) Integrity fault. The position source must be able to identify, and output, an indication of an integrity fault. This indication should occur within 8 seconds of output of an erroneous position. The position source manufacturer must provide information on how this integrity fault is output.
f. Position integrity (probability). The position source manufacturer must provide information describing the basis for the probability of exceeding the horizontal integrity containment radius. This basis must indicate the probability of exceeding the integrity containment radius as well as the sampling duration (per hour or per sample).
g. 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.
h. Velocity accuracy. The position source should have a velocity accuracy output that was qualified in conjunction with the system’s TSO authorization or design approval. In lieu of a dynamic output, the position source manufacturer may demonstrate a worst case velocity accuracy that can be assumed based on testing. A test for GNSS position sources is contained in the latest revision of AC 20-138C, Appendix 4. The position source manufacturer may propose a test method for non GNSS sources or an alternate test for GNSS sources during the TSO authorization or design approval.
i. Design assurance. The position source must support a major or greater failure effect.
This includes software compliant with RTCA/DO-178B, Software Considerations in Airborne Systems and Equipment Certification, Level C, and airborne electronic hardware (AEH) compliant with RTCA/DO-254, Level C. For airborne electronic hardware determined to be simple, RTCA/DO-254, paragraph 1.6 applies. Because the broadcast position can be used by any other ADS-B equipped aircraft or by ATC, the provisions in AC 23.1309-1() that allow reduction in failure probabilities and design assurance level for aircraft under 6,000 pounds do not apply for the ADS-B system. The overall probability of a position source malfunction causing a position to be output which exceeds the output integrity radius must be less than 1x10-5 per hour.
Appendix 2 A2-3
j. Geometric altitude. The position source must have a geometric altitude output. The geometric altitude must be referenced to the WGS-84 ellipsoid.
k. Update rate. The position source must output a new position at least once per second.
Faster position update rates reduce latency of the transmitted position and are encouraged.
l. Position source latency. The position source manufacturer must provide position source latency information. Specifically, the manufacturer must provide the amount of position source total latency and uncompensated latency. Because the latency requirements are based on the entire ADS-B system, and not just the position source, the following position source latency targets are only guidelines. Position source uncompensated latency should be less than 200ms, compensated latency should be less than 500ms, and total latency should be less than 700ms.
Note: 1: System latency requirements are described in paragraph 3-1 of this AC.
Note: 2: This paragraph addresses position latency only.
m. Position, velocity, and accuracy time of applicability. For each position output by the source, a velocity, horizontal position accuracy metric and horizontal velocity accuracy metric must also be output. All measurements and metrics must have the same time of applicability. A horizontal position integrity metric must also be output, but its time of applicability may lag the position. See TSO-C145, TSO-C146, or TSO-C196 for additional information on the integrity time-to-alert.
n. Time mark. position sources should output a time mark identifying the Coordinated Universal Time (UTC) time of applicability of the position. The time mark can be used by the ADS-B equipment to reduce uncompensated latency.
o. Availability. 14 CFR 91.225 and 91.227 do not define an availability requirement, however it is a significant operational factor when selecting the position source, (see table 14, Estimated GNSS availabilities minimum threshold constellation).
4. GNSS position sources. Compliance to the applicable TSOs for GNSS position sources does not guarantee that the unit is suitable as an ADS-B position source. The information in this section describes an acceptable means to demonstrate compliance with ADS-B requirements not addressed by GNSS TSOs when using GNSS position sources for ADS-B.
a. Position. GNSS position sources must provide a latitude and longitude output.
Requirements and test procedures in TSO-C129/145/146/196 are sufficient and GNSS equipment with Technical Standard Order Authorization (TSOA) for the aforementioned TSOs require no additional qualification for the position output.
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).
Appendix 2 A2-4
(1) TSO C129. The requirements outlined for 2D accuracy in paragraph (a)(3)(xvi) of TSO-C129 does not ensure full compliance for the GNSS unit. Additional means of compliance for this TSO requires GNSS manufacturers to substantiate that the latitude/longitude is output and referenced to WGS-84 coordinate system.
(2) TSO C129a. The requirements outlined for 2D accuracy in paragraph (a)(3)(xvi) of TSO-C129a does not ensure full compliance for the GNSS unit. Additional means of compliance for this TSO requires GNSS manufacturers to substantiate that the latitude/longitude is output and referenced to WGS-84 coordinate system.
(3) TSO C145/146 Rev a Class 1. Means of compliance for this TSO are defined in DO-229C, Minimum Operational Performance Standards for Global Positioning System/Wide Area Augmentation System Airborne Equipment, section 2.1.2.6.
(4) TSO C145/146 Rev a Class 2/3. Means of compliance for this TSO are defined in DO-229C sections 2.1.4.8 & 2.1.5.8.
(5) TSO C145/146 Rev b/c Class 1. Means of compliance for this TSO are defined in DO-229 D 2.1.2.6.
(6) TSO C145/146 Rev b/c Class 2/3. Means of compliance for this TSO are defined in DO-229D sections 2.1.4.8 & 2.1.5.8.
(7) TSO C196/196a. Means of compliance for this TSO are defined in DO-316, Minimum Operational Performance Standards (MOPS) for Global Positioning System/Aircraft Based Augmentation System Airborne Equipment, section 2.1.2.6.
b. Position source latency. GNSS position source manufacturer must provide position source latency information.
(1) TSO C129. Means of compliance for this TSO requires GNSS manufacturers to document the position source latency from Time Of Measurement (TOM) to time of position output.
If this latency exceeds 0.9 seconds, it may not support the two second ADS-B transmission latency at the aircraft level.
(2) TSO C129a. Means of compliance for this TSO requires GNSS manufacturers to document the position source latency from TOM to time of position output. If this latency exceeds
0.9 seconds, it may not support the two second ADS-B transmission latency at the aircraft level.
(3) TSO C145/146 Rev a Class 1. Means of compliance for this TSO are defined in DO-229C section 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 and 2.1.5.8.2.
Appendix 2 A2-5
(5) TSO C145/146 Rev b/c Class 1. Means of compliance for this TSO are defined in DO-229 D 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 and 2.1.5.8.2.
(7) TSO C196/196a. Means of compliance for this TSO are defined in DO-316 section
2.1.2.6.2.
c. Availability.
(1) Analysis has shown the following estimated availability for GPS receivers meeting the minimum TSO performance standards, (see table 14), assuming the minimum threshold GPS satellite constellation. The availability improves when the GPS constellation is full of operational satellites.
(2) The FAA plans to integrate back up surveillance systems with ADS-B, including SSR and Wide Area Multilateration, to mitigate the impact of loss of GNSS performance due to the health of the constellation. Backup surveillance will not be available in all airspace and operators should select an ADS-B positioning source that provides the necessary availability for their route of flight.
The FAA plans to implement a preflight availability determination system to assist operators in determining surveillance availability for ADS-B prior to flight. This tool will consider the GPS constellation that is predicted to be available at the planned flight time. The tool will also consider the status of existing backup surveillance capability and the required performance for the separation standard in use along the route of flight.
Table 14. Estimated GNSS Availabilities (Minimum Threshold Constellation)
Positioning Service (receiver standard) Predicted Availability (ADS-B Compliance) GPS (TSO-C129) (SA On) ≥ 89.0% GPS (TSO-C196) (SA Off) ≥ 99.0% GPS/SBAS (TSO-C145/TSO-C146) ≥ 99.9%
d. Horizontal position integrity. GNSS position sources must have a horizontal position integrity (e.g., HIL or HPL) output qualified during the system’s TSO authorization or design approval to determine NIC.
(1) TSO C129. The requirements outlined for Class A, B, and C equipment provides horizontal integrity through RAIM algorithms under DO-208, Minimum Operational Performance Standards for Airborne Supplemental Navigation Equipment Using Global Positioning System (GPS), change 1 section 2.2.1.13. But there is no requirement to compute or output HPL. To properly comply with the ADS-B requirements, additional means of compliance for this TSO requires GNSS manufacturers to provide substantiation data showing that the equipment outputs a 1x10-7/hr HPL based on the RAIM algorithm at least once per second that meets a 10 second time to alert. This AC recommends an 8 second time to alert. The protection level value is
Appendix 2 A2-6 acceptable as an HPL if the equipment performs the test in DO-208 change 1 section 2.5.2.5 using this protection level value for comparison against the alarm limit. Equipment using the least-squares residual RAIM method recommended in DO-208 change 1 Appendix F provides an acceptable HPL.
(2) TSO C129a. The requirements outlined for Class A, B, and C equipment provides horizontal integrity through RAIM algorithms under DO-208 change 1 section 2.2.1.13. But there is no requirement to compute or output HPL. To properly comply with the ADS-B requirements, additional means of compliance for this TSO requires GNSS manufacturers to provide substantiation data showing that the equipment outputs a 1x10-7/hr HPL based on the RAIM algorithm at least once per second that meets a 10 second time to alert. This Advisory Circular recommends an 8 second time to alert. The protection level value is acceptable as an HPL if the equipment performs the test in DO-208 change 1 section 2.5.2.5 using this protection level value for comparison against the alarm limit. Equipment using the least-squares residual RAIM method recommended in DO-208 change 1 Appendix F provides an acceptable HPL.
(3) TSO C145/146 Rev a Class 1. Means of compliance for this TSO are defined in DO-229C sections 2.1.2.6, 2.1.2.2.2, and 2.1.3.2.2. A summary of the latter requirements can be found in DO-229C section 2.1.1.13.1.
(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, 2.1.2.2.2, 2.1.3.2.2, 2.1.4.2.2, and 2.1.5.2.2. A summary of the latter requirements can be found in DO-229C section 2.1.1.13.1.
(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, 2.1.2.2.2, and 2.1.3.2.2. Related requirements can be found in DO-229D sections 2.1.1.4 and 2.1.4.9.
(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, 2.1.2.2.2, 2.1.3.2.2, 2.1.4.2.2, and 2.1.5.2.2. Related requirements can be found in DO-229D sections 2.1.1.4 and 2.1.4.9.
(7) TSO C196/196a. Means of compliance for this TSO are defined in DO-316 section
2.1.2.6, 2.1.2.2.2, and 2.1.3.2.
e. Position integrity (probability). GNSS position source manufacturer must provide information describing the basis for the probability of exceeding the horizontal integrity containment radius.
(1) TSO C129. Means of compliance for TSO-C129 are defined in DO-208 change 1 section 2.2.1.13.1 referring to Table 2-1.
(2) TSO C129a. Means of compliance for TSO-C129a are defined in DO-208 change 1 section 2.2.1.13.1 referring to Table 2-1.
(3) TSO C145/146 Rev a Class 1. Means of compliance for this TSO are defined in DO-229C section 2.1.2.2.2.1 for SBAS-based integrity. This requirement references Appendix J,
Appendix 2 A2-7 Section J.2.1 defining position integrity (integrity probability is for HPLSBAS only). For additional guidance on an acceptable scaling method, GNSS manufacturers can refer to DO-229D Appendix U Section 4. FDE requirements can be found in 2.1.2.2.2.2.2.
(4) TSO C145/146 Rev a Class 2/3. Means of compliance for this TSO are defined in DO-229C section 2.1.2.2.2.1 for SBAS-based integrity. This requirement references Appendix J, Section J.2.1 defining position integrity (integrity probability is for HPLSBAS only). For additional guidance on an acceptable scaling method, GNSS manufacturers can refer to DO-229D Appendix U Section 4. FDE requirements can be found in section 2.1.2.2.2.2.2.
(5) TSO C145/146 Rev b/c Class 1. Means of compliance for this TSO are defined in DO-229D section 2.1.2.2.2.1 for SBAS-based integrity. This requirement references to Appendix J, Section J.3.1 defining position integrity (integrity probability is for HPLSBAS only). For additional guidance on an acceptable scaling method, GNSS manufacturers can refer to DO-229D Appendix U Section 4. FDE requirements can be found in section 2.1.2.2.2.2.2.
(6) TSO C145/146 Rev b/c Class 2/3. Means of compliance for this TSO are defined in DO-229D Section 2.1.2.2.2.1 for SBAS-based integrity. Appendix J, Section J.3.1 provides a background definition for position integrity (integrity probability is for HPLSBAS only). For additional guidance on an acceptable scaling method, GNSS manufacturers can refer to DO-229D Appendix U Section 4. FDE requirements can be found in section 2.1.2.2.2.2.2.
(7) TSO C196/196a. Means of compliance for this TSO are defined in DO-316 section
2.1.2.2.2.2. For additional guidance on an acceptable scaling method, GNSS manufacturers can refer to DO-316 Appendix U Section 4.
f. Integrity fault alerts. GNSS position source manufacturers must provide design data on the maximum time the position source can take to indicate an integrity fault. If the fault indication is mode specific, data on all modes must be included. It is recommended that the indication of an integrity fault be provided within 8 seconds across all modes. All revisions of TSO-C145, TSO-C146, and TSO-C196 GNSS equipment meet this requirement. No revisions of TSO-C129 GNSS equipment meet this requirement without meeting further qualifications outlined below. ARINC characteristic 743A-5, GNSS Sensor, dated May, 2009, compliant receivers represent the condition where a satellite fault has been detected but the receiver was unable to exclude the faulted satellite by setting bit 11 of label 130. This bit must be interpreted to set the position invalid regardless of the indicated HIL or HPL.
(1) TSO C129. The requirements in DO-208 change 1 section 2.2.1.13.1 cover the time to alarm for different phases of flight. To properly comply with the overall 12 second integrity fault output for ADS-B, additional means of compliance for TSO-C129 requires GNSS manufacturers to provide information in the installation instructions describing the equipment integrity fault latency output with interface instructions and/or limitations for meeting the 12 second allocation set by 14 CFR 91.227.
(2) TSO C129a. The requirements in DO-208 change 1 section 2.2.1.13.1 cover the time to alarm for different phases of flight. To properly comply with the overall 12 second
Appendix 2 A2-8 integrity fault output for ADS-B, additional means of compliance for TSO-C129a requires GNSS manufacturers to provide information in the installation instructions describing the equipment integrity fault latency output with interface instructions and/or limitations for meeting the 12 second allocation set by this Advisory Circular.
(3) TSO C145/146 Rev a Class 1. Means of compliance for this TSO are defined in DO-229C sections 2.1.1.13, and 2.1.2.2.2.2.1 through 2.1.2.2.2.2.4.
(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, 2.1.2.2.2.2.1 through 2.1.2.2.2.2.4, and 2.1.4.2.2.2.1 through
2.1.4.2.2.2.3.
(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, and 2.1.2.2.2.2.1 through 2.1.2.2.2.2.4.
(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, 2.1.2.2.2.2.1 through 2.1.2.2.2.2.4, and 2.1.4.2.2.2.1 through
2.1.4.2.2.2.3.
(7) TSO C196/196a. Means of compliance for this TSO are defined in DO-316 sections 2.1.1.11, and 2.1.2.2.2.1 through 2.1.2.2.2.4.
g. Position integrity limits. The requirement was previously called Integrity Validity Limit. Single frequency RAIM-based HPL computations have been designed to support navigation applications and provide an appropriate error bound down to approximately 0.1 nautical mile (nm). While HPL values significantly smaller than 0.1 nm can be output from single frequency GNSS sources, if the HPL value was computed using RAIM, it may not actually achieve the reported level of protection as there are error contributions that are no longer negligible and should be taken into consideration. Such error sources specifically include correlation of ionospheric errors across satellites, tropospheric delay compensation errors, multipath, and receiver noise errors. This issue is not unique to un-augmented GPS position sources, as all revisions of TSO-C145 and TSO-C146 GNSS position sources also calculate integrity based on RAIM when Satellite-Based Augmentation System (SBAS) integrity is not used. Even when using SBAS augmentation, the integrity calculation is not required to account for these error sources except when in LNAV/VNAV or LPV/LP approach modes. ADS-B capable position sources must provide design information to the installer that identifies the following:
(1) Whether a TSO-C129 or TSO-C196 position source limits the HPL output to greater than 75 meters. If the position source does not limit its HPL output, the position source manufacturer should provide guidance to the ADS-B system installer to ensure the ADS-B equipment limits the NIC to ≤ 8. Although single frequency RAIM-based HPL values are only accurate down to approximately 0.1nm, for ADS-B purposes, the position source only need limit the HPL to greater than 75 meters, because an HPL greater than 75 meters ensures the ADS-B equipment will only set a NIC of ≤ 8.
Appendix 2 A2-9
(a) TSO C129. Means of compliance for this TSO requires GNSS manufacturers to present substantiation data whether HPL is limited or not, and provide proper installation instructions for the ADS-B integration.
(b) TSO C129a. Means of compliance for this TSO requires GNSS manufacturers to present substantiation data whether HPL is limited or not, and provide proper installation instructions for the ADS-B integration.
(c) TSO C196/196a. Means of compliance for this TSO requires GNSS manufacturers to present substantiation data whether HPL is limited or not, and provide proper installation instructions for the ADS-B integration.
(2) Whether a TSO-C145 or TSO-C146 position source limits the HPL in non-SBAS augmented modes to greater than 75 meters. If the position source does not limit the HPL output in non-augmented modes, the position source manufacturer should provide guidance to the ADS-B system installer to ensure the ADS-B equipment limits the NIC to ≤ 8 in non-augmented modes. The position source manufacturer should also provide instructions on how to determine the position source mode if appropriate.
(a) TSO C145/146 Rev a Class 1. Means of compliance for this TSO requires GNSS manufacturers to present substantiation data whether HPL is limited or not, and provide proper installation instructions for the ADS-B integration.
(b) TSO C145/146 Rev a Class 2/3. Means of compliance for this TSO requires GNSS manufacturers to present substantiation data whether HPL is limited or not, and provide proper installation instructions for the ADS-B integration. Installations intending to support NIC = 9 must use LNAV/VNAV or LPV/LP approach requirements (DO-229C section 2.1) at the time of HPL output, in accordance with TSO-C145/C146 rev a, but the enroute through LNAV K-Factor (6.18 vs.
6) must be applied (reference DO-229C Appendix J Section 2.1 and Appendix U Section 4). Either the GNSS source equipment sets the K-Factor for HPL, or the ADS-B equipment applies proper scaling. The GNSS manufacturer must present substantiation data on which K-Factor is used and provide proper installation instructions for the ADS-B integration.
(c) TSO C145/146 Rev b/c Class 1. Means of compliance for this TSO requires GNSS manufacturers to present substantiation data whether HPL is limited or not, and provide proper installation instructions for the ADS-B integration.
(d) TSO C145/146 Rev b/c Class 2/3. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data whether HPL is limited or not, and provide proper installation instructions for the ADS-B integration. Installations intending to support NIC = 9 must use LNAV/VNAV or LPV/LP approach requirements (DO-229D Section 2.1) at the time of HPL output, in accordance with TSO-C145/C146 rev b/c, but the enroute through LNAV K-Factor (6.18 vs. 6) must be applied (refer to DO-229D Appendix J Section 3.1 and Appendix U Section 4). Either the GNSS source equipment sets the K-Factor for HPL, or the ADS-B equipment applies proper scaling. The GNSS manufacturer must present substantiation data on which K-Factor is used and provide proper installation instructions for the ADS-B integration.
Appendix 2 A2-10
h. Horizontal Position accuracy. GNSS position sources should provide a HFOM output which was demonstrated during the position source’s design approval or during an installation approval. GNSS certified under TSO-C145b/c, C146b/c, or all revisions of TSO-C196 are required to provide the HFOM output. TSO-C129, TSO-C145a, and TSO-C146a does not contain a horizontal position accuracy output requirement, however all equipment must provide a HFOM output in order to be considered an ADS-B compliant position source.
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 provide substantiation data showing the equipment computes and outputs HFOM. See the test described in the latest revision of AC 20-138 appendix 4, paragraph A4-11 for an acceptable HFOM test.
(2) TSO C129a. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data showing the equipment computes and outputs HFOM. See the test described in the latest revision of AC 20-138 appendix 4, paragraph A4-11 for an acceptable HFOM test.
(3) TSO C145/146 Rev a Class 1. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data based on the test described in the latest revision of AC 20-138 appendix 4, paragraph A4-11 for an acceptable HFOM test.
(4) TSO C145/146 Rev a Class 2/3. Means of compliance for this TSO requires GNSS manufacturers to provide substantiation data based on the test described in the latest revision of AC 20-138 appendix 4, paragraph A4-11 for an acceptable HFOM test.
(5) TSO C145/146 Rev b/c Class 1. Means of compliance for this TSO are defined in DO-229D section 2.1.2.6 (also see section 1.7.1 and Appendix H of DO-229D).
(6) TSO C145/146 Rev b/c Class 2/3. Means of compliance for this TSO are defined in DO-229D section 2.1.2.6 (also see section 1.7.1 and Appendix H of DO-229D).
(7) TSO C196/196a. Means of compliance for this TSO are defined in DO-316 section
2.1.2.6 (also see section 1.7.1 and Appendix H of DO-316).
i. Geometric altitude. All GNSS position sources must output a geometric altitude.
Geometric Altitude for ADS-B purposes is the height above the WGS-84 ellipsoid (i.e. it is not MSL).
We recommend that the GNSS position source output geometric altitude as height-above-ellipsoid (HAE). Some GNSS position sources provide height above the geoid (HAG) instead of height above the ellipsoid (HAE). The position source manufacturer must provide data on whether the position source outputs HAE or HAG.