AC 20-165B: Airworthiness Approval of Automatic Dependent Surveillance

Appendix B B-11 B.4.6.6 TSO-C145/146 Rev b/c/d Class 2/3.

Means of compliance for this TSO are defined in RTCA/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.

B.4.6.7 TSO-C196/196a.

Means of compliance for this TSO are defined in RTCA/DO-316, sections

2.1.1.11 and 2.1.2.2.2.1 through 2.1.2.2.2.4.

B.4.7 Position Integrity Limits.

This 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 nm. Although 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 unaugmented 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:

B.4.7.1 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 0.1 nm, 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.

B.4.7.1.1 TSO-C129.

Means of compliance for this TSO require GNSS manufacturers to present substantiation data whether HPL is limited or not, and provide proper installation instructions for the ADS-B integration.

B.4.7.1.2 TSO-C129a.

Means of compliance for this TSO require GNSS manufacturers to present substantiation data whether HPL is limited or not, and provide proper installation instructions for the ADS-B integration.

Appendix B B-12 B.4.7.1.3 TSO-C196/196a.

Means of compliance for this TSO require GNSS manufacturers to present substantiation data whether HPL is limited or not, and provide proper installation instructions for the ADS-B integration.

B.4.7.2 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.

B.4.7.2.1 TSO-C145/146 Rev a Class 1.

Means of compliance for this TSO require GNSS manufacturers to present substantiation data whether HPL is limited or not, and provide proper installation instructions for the ADS-B integration.

B.4.7.2.2 TSO-C145/146 Rev a Class 2/3.

Means of compliance for this TSO require 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 (RTCA/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 (refer to RTCA/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.

B.4.7.2.3 TSO-C145/146 Rev b/c/d Class 1.

Means of compliance for this TSO require GNSS manufacturers to present substantiation data whether HPL is limited or not, and provide proper installation instructions for the ADS-B integration.

B.4.7.2.4 TSO-C145/146 Rev b/c/d Class 2/3.

Means of compliance for this TSO require 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 (RTCA/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 RTCA/DO-229D appendix J, section 3.1 and appendix U, section 4).

Appendix B B-13 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.

B.4.8 Horizontal Position Accuracy.

GNSS position sources should provide an HFOM output that was demonstrated during the position source’s design approval or during an installation approval. GNSS certified under TSO-C145b/c, TSO-C146b/c/d, or all revisions of TSO-C196 are required to provide the HFOM output. TSO-C129, TSO-C145a, and TSO-C146a do not contain a horizontal position accuracy output requirement; however, all equipment must provide a HFOM output 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 RTCA/DO-229D, sections 2.1.2.6 and 2.1.2.6.2).

B.4.8.1 TSO-C129.

Means of compliance for this TSO require GNSS manufacturers to provide substantiation data showing the equipment computes and outputs HFOM. Refer to the test described in AC 20-138(), appendix 4, section A4-11 for an acceptable HFOM test.

B.4.8.2 TSO-C129a.

Means of compliance for this TSO require GNSS manufacturers to provide substantiation data showing the equipment computes and outputs HFOM. Refer to the test described in AC 20-138(), appendix 4, section A4-11 for an acceptable HFOM test.

B.4.8.3 TSO-C145/146 Rev a Class 1. Means of compliance for this TSO require GNSS manufacturers to provide substantiation data based on the test described in AC 20-138(), appendix 4, section A4-11 for an acceptable HFOM test.

B.4.8.4 TSO-C145/146 Rev a Class 2/3.

Means of compliance for this TSO require GNSS manufacturers to provide substantiation data based on the test described in AC 20-138(), appendix 4, section A4-11 for an acceptable HFOM test.

B.4.8.5 TSO-C145/146 Rev b/c/d Class 1.

Means of compliance for this TSO are defined in RTCA/DO-229D, section 2.1.2.6 (also refer to section 1.7.1 and appendix H of RTCA/DO-229D).

B.4.8.6 TSO-C145/146 Rev b/c/d Class 2/3.

Means of compliance for this TSO are defined in RTCA/DO-229D, section 2.1.2.6 (also refer to section 1.7.1 and appendix H of RTCA/DO-229D).

Appendix B B-14 B.4.8.7 TSO-C196/196a.

Means of compliance for this TSO are defined in RTCA/DO-316, section 2.1.2.6 (also refer to section 1.7.1 and appendix H of RTCA/DO-316).

B.4.9 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 (that is, 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-Geoid (HAG) instead of HAE. The position source manufacturer must provide data on whether the position source outputs HAE or HAG.

B.4.9.1 TSO-C129.

Means of compliance for this TSO require GNSS manufacturers to provide data to substantiate the output of HAE. The data produced to substantiate vertical position accuracy pursuant to the test described in AC 20-138(), appendix 4, section A4-10 is sufficient. For GPS equipment that outputs other altitude measures, the installation instructions must specify a deterministic method to perform conversion to HAE.

B.4.9.2 TSO-C129a.

Means of compliance for this TSO require GNSS manufacturers to provide data to substantiate the output of HAE. The data produced to substantiate vertical position accuracy pursuant to the test described in AC 20-138(), appendix 4, section A4-10 is sufficient. For GPS equipment that outputs other altitude measures, the installation instructions must specify a deterministic method to perform conversion to HAE.

B.4.9.3 TSO-C145/146 Rev a Class 1.

Means of compliance for this TSO require GNSS manufacturers to provide substantiation data showing the equipment outputs HAE. The data produced to substantiate vertical position accuracy pursuant to the test described in AC 20-138(), appendix 4, section A4-10 is sufficient.

B.4.9.4 TSO-C145/146 Rev a Class 2/3.

For Class 2 equipment, the means of compliance for this TSO require GNSS manufacturers to provide substantiation data showing the equipment outputs HAE. The data produced to substantiate vertical position accuracy pursuant to the test described in AC 20-138(), appendix 4, section A4-10 is sufficient. Class 3 equipment complies with the ADS-B geometric altitude requirement pursuant to RTCA/DO-229C, section 2.1.5.8.

Appendix B B-15 B.4.9.5 TSO-C145/146 Rev b/c/d Class 1.

Means of compliance for this TSO require GNSS manufacturers to provide substantiation data showing the equipment outputs HAE. The data produced to substantiate vertical position accuracy pursuant to the test described in AC 20-138(), appendix 4, section A4-10 is sufficient.

B.4.9.6 TSO-C145/146 Rev b/c/d Class 2/3.

Means of compliance for this TSO require GNSS manufacturers to provide substantiation data showing the equipment outputs HAE. The data produced to substantiate vertical position accuracy pursuant to the test described in AC 20-138(), appendix 4, section A4-10 is sufficient.

B.4.9.7 TSO-C196/196a.

Means of compliance for this TSO require GNSS manufacturers to provide substantiation data showing the equipment outputs HAE. The data produced to substantiate vertical position accuracy pursuant to the test described in AC 20-138(), appendix 4, section A4-10 is sufficient.

B.4.10 Update Rate.

The position source must output a new position at a minimum of once per second.

Faster position update rates reduce latency of the transmitted position and are encouraged.

B.4.10.1 TSO-C129.

Means of compliance for TSO-C129 are described in RTCA/DO-208 change 1, section 2.1.11 for displays. This requirement is modified by TSO-C129 section (a)(3)(vi) for navigation data used for display in Class A equipment. Class B and Class C equipment are modified by sections (a)(4)(v) and section (a)(5)(v) respectively.

B.4.10.2 TSO-C129a.

Means of compliance for TSO-C129a are described in RTCA/DO-208 change 1, section 2.1.11 for displays. This requirement is modified by TSO-C129a, section (a)(3)(vi) for navigation data used for display in Class A equipment. Class B and Class C equipment are modified by sections (a)(4)(v) and (a)(5)(v) respectively.

B.4.10.3 TSO-C145/146 Rev a Class 1.

Means of compliance for this TSO are defined in RTCA/DO-229C, section 2.1.2.6.1.

B.4.10.4 TSO-C145/146 Rev a Class 2.

Means of compliance for this TSO are defined in RTCA/DO-229C, sections 2.1.2.6.1 and 2.1.5.8.1.

Appendix B B-16 B.4.10.5 TSO-C145/146 Rev b/c/d Class 1.

Means of compliance for this TSO are defined in RTCA/DO-229D, section 2.1.2.6.1.

B.4.10.6 TSO-C145/146 Rev b/c/d Class 2/3.

Means of compliance for this TSO are defined in RTCA/DO-229D, sections 2.1.2.6.1 and 2.1.5.8.1.

B.4.10.7 TSO-C196/196a.

Means of compliance for this TSO are defined in RTCA/DO-316, section 2.1.2.6.1 B.4.11 Horizontal Velocity.

The position source must output north/south and east/west velocities. It is recommended the position source also output the velocity in a ground speed and track angle format.

Note: The intent is to output position, velocity, and quality metrics in a consistent manner for time of applicability (refer to RTCA/DO-229D, sections 2.1.2.6 and

2.1.2.6.2).

B.4.11.1 TSO-C129.

Means of compliance for this TSO require GNSS manufacturers to perform the velocity test in AC 20-138(), appendix 4 and provide information substantiating the data is output.

B.4.11.2 TSO-C129a.

Means of compliance for this TSO require GNSS manufacturers to perform the velocity test in AC 20-138(), appendix 4 and provide information substantiating the data is output.

B.4.11.3 TSO-C145/146 Rev a Class 1.

Means of compliance for this TSO are defined in RTCA/DO-229C, section 2.1.2.6 along with the test defined in AC 20-138(), appendix 4.

B.4.11.4 TSO-C145/146 Rev a Class 2/3.

Means of compliance for this TSO are defined in RTCA/DO-229C, section 2.1.2.6 along with the test defined in AC 20-138(), appendix 4.

B.4.11.5 TSO-C145/146 Rev b/c/d Class 1.

Means of compliance for this TSO are defined in RTCA/DO-229D, section 2.1.2.6. The TSO requirement is only to output velocity, but there is no accuracy requirement. Satisfying this ADS-B requirement means the GNSS manufacturer must also comply with the horizontal velocity accuracy requirements and tests described in AC 20-138(), appendix 4.

Appendix B B-17 B.4.11.6 TSO-C145/146 Rev b/c/d Class 2/3.

Means of compliance for this TSO are defined in RTCA/DO-229D, section 2.1.2.6. The TSO requirement is only to output velocity, but there is no accuracy requirement. Satisfying this ADS-B requirement means the GNSS manufacturer must also comply with the horizontal velocity accuracy requirements and tests described in AC 20-138(), appendix 4.

B.4.11.7 TSO-C196/196a.

Means of compliance for this TSO are defined in RTCA/DO-316, section 2.1.2.6. The TSO requirement is only to output velocity, but there is no accuracy requirement. Satisfying this ADS-B requirement means the GNSS manufacturer must also comply with the horizontal velocity accuracy requirements and tests described in AC 20-138(), appendix 4.

Note: The velocity test found in AC 20-138() is also defined in section

2.3.6.4 of RTCA/DO-316.

B.4.12 Ground Speed.

It is recommended that the position source output ground speed. GNSS manufacturers choosing to output ground speed may show compliance as described below for the appropriate TSO.

B.4.12.1 TSO-C129.

Means of compliance for this TSO require GNSS manufacturers to provide information in the installation instructions describing how the velocity is output (that is, in a ground speed format versus north/east velocity format) and the protocols used.

B.4.12.2 TSO-C129a.

Means of compliance for this TSO require GNSS manufacturers to provide information in the installation instructions describing how the velocity is output (that is, in a ground speed format versus north/east velocity format) and the protocols used.

B.4.12.3 TSO-C145/146 Rev a Class 1.

The Gamma equipment requirements outlined in RTCA/DO-229C, 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 RTCA/DO-229D, appendix H. Additional means of compliance for TSO-C145/146 Rev a Class 1 require GNSS manufacturers to provide information in the installation instructions describing how the velocity is output (that is, in a ground speed format versus north/east velocity format) and the protocols used.

Appendix B B-18 B.4.12.4 TSO-C145/146 Rev a Class 2/3.

The Gamma equipment requirements outlined in RTCA/DO-229C, 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 RTCA/DO-229D, appendix H. Additional means of compliance for TSO-C145/146 Rev a Class 2/3 require GNSS manufacturers to provide information in the installation instructions describing how the velocity is output (that is, in a ground speed format versus north/east velocity format) and the protocols used.

B.4.12.5 TSO-C145/146 Rev b/c/d Class 1.

Gamma-1 equipment requirements outlined in RTCA/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 RTCA/DO-229D, appendix H. Additional means of compliance for TSO-C145/146 Rev b/c/d Class 1 require GNSS manufacturers to provide information in the installation instructions describing how the velocity is output (that is, in a ground speed format versus north/east velocity format) and the protocols used.

B.4.12.6 TSO-C145/146 Rev b/c/d Class 2/3.

Gamma-2 and Gamma-3 equipment requirements outlined in RTCA/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 RTCA/DO-229D, appendix H. Additional means of compliance for TSO-C145/146 Rev b/c/d Class 2/3 require GNSS manufacturers to provide information in the installation instructions describing how the velocity is output (that is, in a ground speed format versus north/east velocity format) and the protocols used.

B.4.12.7 TSO-C196/196a.

Means of compliance for this TSO require GNSS manufacturers to provide information in the installation instructions describing how the velocity is output (that is, in a ground speed 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 RTCA/DO-316, appendix H.

B.4.13 Time of Applicability.

The GNSS equipment must output a time of applicability.

Note: The intent is to output position, velocity, and HFOM with a consistent time of applicability (refer to RTCA/DO-229D, sections 2.1.2.6 and 2.1.2.6.2).

Appendix B B-19 B.4.13.1 TSO-C129.

Means of compliance for this TSO require 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. For example; the receiver does not make observations at a single moment in time but instead staggers them, perhaps to reduce throughput.

In that case, the observations would need to be extrapolated to a common moment. There are many extrapolation methods but some use filtering that may induce latency. This would need to be addressed in the latency analysis. Since there are filters involved, measuring the impulse response may be one way of observing this delay. Furthermore, as another example; a receiver uses a Costas filter that has a specific bandwidth as part of the tracking loop. That bandwidth constrains the speed at which a dynamic maneuver will propagate through the tracking loop and thus to the resulting position. Again, measuring the impulse response of the Costas loop would provide insight into delay that would be observed when installed. Bearing this in mind, the equipment must meet a 500- millisecond TOM-to-time-of-applicability requirement and account for the impulse response of the position solution.

B.4.13.2 TSO-C129a.

Means of compliance for this TSO require 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-ofapplicability requirement and account for the impulse response of the position solution.

B.4.13.3 TSO-C145/146 Rev a Class 1.

Means of compliance for this TSO are defined in RTCA/DO-229C sections 2.1.2.6 and 2.1.2.6.2.

B.4.13.4 TSO-C145/146 Rev a Class 2/3.

Means of compliance for this TSO are defined in RTCA/DO-229C, sections 2.1.2.6, 2.1.2.6.2, and 2.1.5.8.2.

B.4.13.5 TSO-C145/146 Rev b/c/d Class 1.

Means of compliance for this TSO are defined in RTCA/DO-229D, sections 2.1.2.6 and 2.1.2.6.2.

B.4.13.6 TSO-C145/146 Rev b/c/d Class 2/3.

Means of compliance for this TSO are defined in RTCA/DO-229D, sections 2.1.2.6, 2.1.2.6.2, and 2.1.5.8.2.

Appendix B B-20 B.4.13.7 TSO-C196/196a.

Means of compliance for this TSO are defined in RTCA/DO-316, sections 2.1.2.6 and 2.1.2.6.2.

B.4.14 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.

B.4.14.1 NACV = 1.

For installations intending to support NACV = 1, the GNSS manufacturer must perform the velocity tests in AC 20-138D, appendix 4, section 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.

B.4.14.2 NACV = 2.

For installations intending to support NACV = 2, the GNSS manufacturer must perform the velocity tests in AC 20-138D, appendix 4, sections 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 (refer to AC 20-138(), appendix 4, sections 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.

B.4.14.3 NACV = 3 or 4.

No standard for performance has been developed to support NACv = 3 or NACV = 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.

B.4.14.4 TSO-C129.

Means of compliance for this TSO require 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. Refer to AC 20-138(), appendix 4, section A4- 2d(3) for additional guidance relative to using the noise environment in RTCA/DO-235B for the velocity tests.

B.4.14.5 TSO-C129a.

Means of compliance for this TSO require GNSS manufacturers to provide substantiation data based on the NACV =1 and NACV = 2 test

Appendix B B-21 as appropriate and document the NACV in the installation instructions for the ADS-B integration. Refer to AC 20-138() appendix 4, section A4- 2d(3) for additional guidance relative to using the noise environment in RTCA/DO-235() for the velocity tests.

B.4.14.6 TSO-C145/146 Rev a Class 1.

Means of compliance for this TSO require 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.

B.4.14.7 TSO-C145/146 Rev a Class 2/3.

Means of compliance for this TSO require 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.

B.4.14.8 TSO-C145/146 Rev b/c/d Class 1.

Means of compliance for this TSO require 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.

B.4.14.9 TSO-C145/146 Rev b/c/d Class 2/3.

Means of compliance for this TSO require 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.

B.4.14.10 TSO-C196/196a.

Means of compliance for this TSO require 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.

B.4.15 Vertical Position Accuracy.

The GNSS should output vertical position accuracy. The vertical accuracy should specify a 95-percent 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.

Appendix B B-22 B.4.15.1 TSO-C129.