Chapter 3. TSO Authorization.
3-1. TSO-C196(AR).
a. TSO-C196(AR), Airborne Supplemental Navigation Sensors for Global Positioning System Equipment Using Aircraft-Based Augmentation, defines an acceptable standard for GPS equipment without ground-based or space-based augmentations. The TSO has been updated to revision ‘b’ for harmonization with TSO-C129a’s cancellation and for TSO-C206 circuit card assemblies. TSO-C196(AR) is intended as the aircraft-based augmentation GPS sensor standard for TSOA/LODA applicants. TSO-C196(AR) equipment has a performance limitation that requires other positioning and navigation systems appropriate to the operation on-board the aircraft.
Note: TSO-C129a has been cancelled, but this does not affect equipment with an existing TSOA/LODA (see paragraph 3-1.c).
b. TSO-C196(AR) defines GPS sensor equipment that incorporates many processing improvements found in the GPS/SBAS equipment MOPS; but, without the GPS/SBAS requirements. Two improvement examples are: a requirement for the receiver to properly account for satellite range error if it is reflected in the User Range Accuracy index (commonly referred to as being “Selective Availability aware”), and requirements to ensure performance is not degraded due to an increasing radio frequency noise environment as other satellite systems become available.
(1) TSOA/LODA applicants may wish to have a previously approved TSO-C145b (or later revision), Airborne Navigation Sensors Using the Global Positioning System (GPS) Augmented by the Wide Area Augmentation System (WAAS), sensor approved as a TSO-C196b sensor. It is acceptable for TSO -C196b applicants to take certification credit by re-using data developed during a previous revision ‘b’ or later TSO-C145 TSOA/LODA approval. RTCA/DO-316, Minimum Operational Performance Standards for Global Positioning System/Aircraft-Based Augmentation System Airborne Equipment, dated April 14, 2009, implemented by TSO-C196(AR) was developed from RTCA/DO-229D, Minimum Operational Performance Standards for Global Positioning System/Wide Area Augmentation System (GPS/WAAS) Airborne Equipment, dated December 3, 2006, implemented by TSO C145b/c (revision ‘d’ implements RTCA/DO-229D, Change 1). Both RTCA/DO-229D and RTCA/DO-229D, Change 1 meets or exceeds the performance requirements for TSO-C196b.
The original RTCA/DO-178B or ‘C’ documentation can be re-used if there are no software changes.
(2) Applicants seeking a TSO-C196b TSOA/LODA based on a previously approved revision ‘b’ or later TSO-C145 sensor must maintain separate part numbers for each unit. It is not acceptable to have both a TSO-C145(AR) and TSO-C196(AR) TSOA/LODA simultaneously on the same article (see paragraph 3-6.b(4)).
Note: Maintaining separate part numbers might only require different software part numbers.
(3) It is acceptable for TSOA/LODA applicants with revision ‘b’ or later TSO-C145 sensors to simply disable the GPS/SBAS tracking loops in their equipment to apply for a TSO-C196b TSOA/LODA. The applicant will need to su pply substantiation that the SBAS tracking loops are permanently disabled along with the data from their revision ‘b’ or later TSO-C145 TSOA/LODA.
(4) TSOA/LODA applicants with TSO-C145a sensors will need to show requirements traceability between RTCA/DO-229C and RTCA/DO-316 along with data applicability to receive appropriate certification credit. In particular, applicants will need to show compliance to all RTCA/DO-316 requirements not addressed in RTCA/DO-229C, and requirements that are more stringent such as enroute/terminal mode accuracy and the broadband external interference noise environment.
c. TSO-C129a was cancelled effective October 21, 2011, but there is no plan to withdraw TSO-C129(AR) authorizations. TSO-C129a cancellation will not affect existing authorizations. Manufacturers can continue production according to their existing TSO-C129(AR) TSOA/LODA. Additionally, the equipment is still eligible for installation according to existing airworthiness approvals and is eligible to receive new airworthiness approvals.
(1) No new TSO-C129a TSOAs/LODAs will be granted.
(2) Major changes to an existing TSO-C129a equipment design will require a new application according to 14 CFR 21.619(b) for either TSO-C145d, TSO-C146d or TSO C196b.
3-2. TSO-C145(AR)/C146(AR).
a. TSO-C145d, Airborne Navigation Sensors Using the Global Positioning System (GPS) Augmented by the Satellite-Based Augmentation System (SBAS) and TSO-C146d, Stand- Alone Airborne Navigation Equipment Using the Global Positioning System (GPS) Augmented by the Satellite Based Augmentation System (SBAS) define an acceptable standard for GPS/SBAS equipment. There is no equipment performance limitation for GPS/SBAS equipped aircraft to have other positioning and navigation systems on-board.
Note: Refer to the appropriate operating rules and
operational guidance documents for equipage
requirements.
b. RTCA/DO-229D referenced by the GPS/SBAS TSOs will remain as the MOPS for single-frequency GPS/SBAS equipment. Future multi-frequency/multi-constellation equipment will have a separate MOPS and TSO.
c. There is no plan to withdraw authorizations to the earlier TSO revisions, so manufacturers of TSO-C145/C146 revision ‘a’ through ‘c’ equipment can continue production according to their TSOA/LODA; and the equipment is still eligible for installation in accordance with the guidance in this AC.
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d. The difference between revisions ‘b’ and ‘c’ to the GPS/SBAS TSOs is eliminating a 3 decibel (dB) broadband intra-system noise credit for operational Class 1 and Class 2 equipment in RTCA/DO-229D. TSO-C145b/C146b operational Class 3 and Class 4 equipment fully complies with the requirements in TSO-C145c/C146c and is automatically eligible for a revision ‘c’ authorization, i.e., no further evaluation is necessary.
e. The difference between revisions ‘c’ and ‘d’ to the GPS/SBAS TSOs is:
recognizing TSO-C204/C205 circuit card assemblies; and using Change 1 to RTCA/DO-229D.
f. TSO-C145b/C146b operational Class 1 and Class 2 equipment that did not claim the 3dB noise credit is also eligible for a revision ‘c’ authorization. The TSOA/LODA holder only needs to provide substantiation that they did not take the noise credit during the original certification.
g. Displays or navigation computers (such as FMSs) may receive a TSO-C146d Class 1, 2, or 3 (functional Class Gamma) incomplete TSOA/LODA provided they meet the applicable Class Gamma requirements in RTCA/DO-229D and are linked by part number to compatible TSO-C145(AR) sensors in the TSO application documentation. This is an effective method to aid GPS/SBAS installation approvals to make a complete system (sensor, navigation computer, display) at the aircraft level.
Note: See paragraph 3-4 for additional information on FMS incomplete TSO-C146c Class Gamma TSOA/LODAs and Class Delta-4 FMS implementations.
3-3. TSO-C161a/C162a.
a. TSO-C161a, Ground Based Augmentation System Positioning and Navigation Equipment, defines an acceptable standard for GPS/GBAS equipment that provides precision approach capability and position/velocity/time (PVT) information to navigation management equipment. TSO-C162a, Ground Based Augmentation System Very High Frequency Data Broadcast Equipment, defines an acceptable standard for GPS/GBAS equipment designed to receive a very high frequency data broadcast (VDB) and output the VDB messages to GPS/GBAS positioning and navigation equipment.
b. TSO-C161a and TSO-C162a invoke only the requirements in RTCA/DO-253C, Minimum Operational Performance Standards for GPS Local Area Augmentation System Airborne Equipment, dated December 16, 2008, that are needed to support Category I (CAT I) precision approach and, if applicable, the GPS/GBAS positioning service. The equipment may output PVT based on either the GPS/GBAS positioning service, or PVT from GPS or GPS/SBAS. The PVT based on GPS/GBAS is only available when the ground station supports the positioning service. TSO-C161a equipment must also obtain a TSO-C145d, TSO-C146d, or TSO-C196b TSOA. Requirements in RTCA/DO-253C needed to support precision approaches beyond CAT I are not invoked in these TSOs as these requirements have not been validated.
Once validated, the FAA will either publish TSO revisions or new TSOs.
c. TSO-C161a and TSO-C162a compliant equipment does not address any RNAV capability. A partial missed approach capability is an option in the GPS/GBAS equipment but 14
is not required (see note). RNAV capability for the initial, intermediate, and missed approach segments must be addressed during the aircraft GPS/GBAS integration (see paragraph 15-9.1).
Note: Equipment meeting the RTCA/DO-253C precision and navigation (PAN) requirements can include an optional capability to provide guidance for the initial, straight-out portion of the missed approach segment. However, this capability doesn’t provide guidance for the complete missed approach segment.
3-4. TSO-C115(AR).
a. TSO-C115d, Required Navigation Performance (RNP) Equipment Using Multi- Sensor Inputs defines an acceptable certification standard for obtaining design and production approval for multi-sensor navigation systems or FMSs integrating data from multiple navigation sensors. There is no plan to withdraw TSO authorizations granted under earlier TSO-C115 revisions. Manufacturers of earlier TSO-C115 revisions can continue production according to their TSOA/LODA; and the equipment is still eligible for installation in accordance with the guidance in this AC. However, integrating GNSS into TSO-C115/C115a multi-sensor navigation equipment is considered a major change and requires an application for a TSO-C115dTSOA/LODA.
(1) TSO-C115b only addressed TSO-C129 Class B and C sensors because it was published prior to TSO-C129a, TSO-C145(AR), TSO-C161(AR), and TSO-C196(AR). It is acceptable to integrate any GNSS sensor with TSO-C115b equipment.
Note: The multi-sensor navigation system or FMS must comply with TSO-C115 revision ‘b’ (or a later revision) when integrating GNSS sensors if TSO-C115 is the approval basis. It is not acceptable to use systems certified to earlier TSO-C115 revisions for GNSS sensor integration (see paragraph 3-6.b(1)).
(2) Localizer performance without vertical guidance (LP)/localizer performance with vertical guidance (LPV) is considered a severe major/hazardous failure condition for misleading information (see paragraph 12-2.a). Equipment manufacturers may design FMSs for either a TSO-C146d Class Gamma-3, or Class Delta-4 architecture when integrating LP/LPV capability.
(a) A TSO-C115b (or later revision) FMS designed as a Class Gamma-3 architecture typically has level B software for the LP/LPV processing functions. It is acceptable to have the GPS/SBAS capability and level B software partitioned from other functions in the FMS. See paragraph 3-4.b for additional information on incomplete TSO-C146c Class Gamma TSOA/LODAs.
(b) TSO-C146d Class Delta-4 provides an ILS look-alike for LP/LPV final approach segment-only capability. A TSO-C115b (or later revision) FMS designed for a Class Delta-4 architecture does not process LP/LPV inputs; does not output LP/LPV deviations, path 15
construction, alerts, etc.; and, does not require the FMS to have a TSO-C146d TSOA/LODA.
The aircraft integration must include a GPS/SBAS sensor that has a TSO-C146d Class Delta-4 TSOA/LODA. See paragraph 3-4.c for additional information on Class Delta-4 implementations.
b. FMS manufacturers may add an incomplete TSO-C146d TSOA/LODA to FMSs certified to TSO-C115b (or later revision). An appropriate operational class incomplete TSO-C146d Class Gamma TSOA/LODA provides an established means for the installed FMS to demonstrate navigation computer compliance as a GPS/SBAS system.
Note 1: FMSs that do not meet the applicable RTCA/DO-229D Class Gamma performance requirements can still receive PVT inputs from a TSO C145(AR) sensor and apply them consistent with their existing approvals. Using a TSO-C145(AR) sensor can remove certain performance limitations associated with a TSO-C129(AR) sensor (see paragraphs 5-5.2.b and
5-5.2.c).
Note 2: There is significant overlap in requirements between TSO-C146d Class Gamma implementation of RTCA/DO-229D and TSO-C115d implementation of RTCA/DO-283B Minimum Operational Performance Standards for Required Navigation Performance for Area Navigation requirements. Where requirements overlap exists it is acceptable to re-use compliance information from RTCA/DO-229D as the method of demonstrating RTCA/DO-283B compliance. However, applicants remain responsible to ensure all RTCA/DO-283B requirements are satisfied.
Note 3: TSO-C146d Class Gamma has alert limits for navigation system error (NSE) at 1 x RNP value and assumes a fixed, manual flight technical error (FTE). The TSO-C146d Class Gamma FTE assumption and NSE alert meets the 2 x RNP TSE alerting requirement for RNP operations. TSO-C115d does not assume a fixed FTE value which allows applicants to trade off FTE and NSE when meeting the 2 x RNP TSE alerting requirement.
(1) TSO-C146d will take precedence when adding an incomplete TSO-C146d Class Gamma TSOA/LODA to an FMS with an existing TSO-C115b or later TSOA/LODA if there are any conflicts between the two TSOs.
(2) TSO-C115d requires the FMS meet the minimum performance standard documentation and qualification requirements for Class A or Class B specified in sections 2.1 and 2.2 of RTCA/DO-283B. Class A includes full VNAV and advanced RNP capability while Class B includes only 2-dimensional RNP navigation functions. Class B applicants that wish to 16
--- ---- include baro-VNAV capability or receive advanced RNP recognition must comply with the appropriate RTCA/DO-283B requirements. See RTCA/DO-283B, Table 2-13 for a complete list of the required Class A and Class B functions. The baro-VNAV guidance in this AC must be used when including baro-VNAV for approach capability. See appendix 3 for guidance on advanced RNP recognition.
(3) FMSs may qualify as TSO-C146d Class Gamma navigation computer systems when receiving inputs from a TSO-C145d Class Beta sensor. An incomplete TSO C146d Class Gamma approval (Gamma-2 or -3 as appropriate) can be added to the TSO-C115b (or later revision) approval, or replace the TSO-C129(AR) approval if one exists, to provide GPS/SBAS-based VNAV approach capability. Class Gamma -1 can be used for FMSs that don’t intend to process GPS/SBAS vertical deviations.
Note: Several issues must be considered for FMSs integrating both baro-VNAV and GPS/SBAS to provide LNAV/VNAV capability. For example; unambiguous navigation source and approach service level annunciation, discontinuities or jumps when switching from baro-VNAV to GPS/SBAS vertical guidance, and prioritizing when to use which source (see paragraphs
6-3.b, 16-2.a, and 18-5).
c. For Class Delta-4 architectures, FMSs in typical federated avionics architectures do not need an incomplete TSO-C146d Class Delta-4 TSOA/LODA for LPV capability since the FMS does not provide or process flight path deviation data or GPS/SBAS alerting functions during the final approach segment. The complete system (sensor with Class Delta-4 TSOA/LODA, level B path, and display) will be confirmed at the time of installation. See paragraph 15-2.a regarding displays and path for legacy aircraft retrofit installations previously certified with ILS.
(1) It is acceptable for the Class Delta-4 sensor to reside within the FMS itself provided the LP/LPV outputs are not processed or altered by the FMS (similar to an ILS).
(2) The FMS may provide an interface for pilot control of the Class Delta-4 equipment (such as selecting the approach) and may host the Final Approach Segment (FAS) database for input to the Class Delta-4 equipment. The Class Delta-4 TSOA/LODA holder must list the specific compatible FMS(s) or provide a detailed interface description to establish FMS compatibility in the installation manual.
(3) At the aircraft level, Class Delta-4 implementations depend upon the entire path for the guidance deviations complying with a severe major/hazardous failure condition in modern aircraft with digital data busses. See paragraph 15-2.a regarding displays and path for legacy aircraft retrofit installations previously certified with ILS.
(4) Non-federated FMS architectures, such as integrated modular avionics, may have the Class Delta-4 LP/LPV final approach segment capability residing within the FMS functions or components. The applicable modules for these FMSs will need a TSO-C146d Class Delta-4 TSOA/LODA and appropriate software level for the Class Delta-4 performance 17
requirements listed in RTCA/DO-229D that they provide.
Note: It is also acceptable for applicants with non-federated FMS architectures to consider pursuing incomplete TSO-C146d Class Gamma approval for the navigation computer functions/components.
(5) An FMS that is part of an aircraft-level TSO-C146d Class Delta-4 integration normally provides the RNP capability for the initial and intermediate approach segments to place the aircraft in proper position for the Class Delta-4 GPS/SBAS equipment to conduct the LP/LPV final approach segment. The FMS also provides the RNP capability for the missed approach segment.
Note: RNP capability for the initial, intermediate, and missed approach segments can be accomplished by the FMS according to its TSO-C115b (or later revision) or other GNSS TSO approval. However, the FMS will be limited to its approved functions per those TSOs or as modified if receiving PVT inputs from a TSO-C145(AR) sensor (see paragraphs 5-5.2.b and 5-5.2.c).
d. Multi-sensor systems must also comply with the appropriate TSO requirements for the individual sensors that are integrated. For example, if distance measuring equipment (DME) is integrated, then the system must also comply with TSO-C66c, Distance Measuring Equipment (DME) Operating Within the Radio Frequency Range of 960 to 1215 Megahertz, for DME equipment. Refer to AC 90-100 (latest revision) , U.S. Terminal and Enroute Area Navigation (RNAV) Operations, for operational approval of terminal and enroute area navigation systems for use in the U.S. national airspace system.
3-5. TSO-C204/C205/C206.
a. The FAA created three new TSOs to recognize the functional capability of GNSS sensor circuit card assemblies and enable end-use manufacturers to incorporate these devices for navigation and non-navigation uses. The intent is to ease the GNSS sensor TSO burden for end-use equipment manufacturers; particularly for non-navigation equipment such as ADS-B or TAWS. But FMS, multi-mode receiver, or other navigation equipment manufacturers could also benefit from these TSOs.
b. The three circuit card assembly TSOs are matched to the three existing GNSS sensor TSOs as follows:
• TSO-C204 to TSO-C145d
• TSO-C205 to TSO-C146d Class Delta-4
• TSO-C206 to TSO-C196b 18
--- Note: TSO-C205 is not appropriate for TSO-C146d Class Gamma functionality since Class Gamma is a combined sensor/navigation computer/display. However, TSO-C204 can be used for the sensor portion of a Class Gamma unit similar to using TSO-C204 in an FMS or multi-mode receiver.
c. Appendix 1 in TSO-C145d/C146d/C196b contains information on the MOPS performance tests the end-use manufacturer must re-accomplish to receive the appropriate TSOA. The end-use manufacturer must mark their equipment with the appropriate GNSS sensor TSO and assumes full responsibility for the GNSS sensor TSOA per the 14 CFR Part 21 Subpart O regulations.
d. The purpose of the new TSOs is to provide certification credit to the end-use equipment manufacturer for the following items performed by the circuit card assembly manufacturer:
• compliance with the requisite MOPS section 2 requirements,
• hardware/software development,
• failure condition classification, and;
• partial MOPS performance testing.
However, the circuit card assembly TSOs have limitations requiring the end-use manufacturer to apply for the latest revision of TSO-C145, TSO-C146 Class Delta-4, or TSO-C196, consistent with the circuit card assembly TSO.
e. The end-use equipment manufacturer receives credit for the items in paragraph 3-5.d by virtue of the circuit card assembly TSO. To receive a GNSS sensor TSOA the end-use equipment manufacturer data submittal is:
(1) The TSO on the circuit card assembly;
(2) The repeated MOPS performance testing according to the GNSS TSO appendix 1;
(3) All other documentation associated with the GNSS sensor TSO, including environmental testing.
3-6. Multiple TSO Authorizations.
a. Multiple TSO authorizations may be granted for equipment that accomplishes multiple functions. However, the number of TSO markings on positioning and navigation equipment should be minimized to avoid confusion during installation and approval.
b. The following combinations of TSO authorizations must not be granted, as the TSOs either contradict each other or are superfluous to a TSO with broader scope:
(1) TSO-C115/C115a with TSO-C129(AR), TSO-C145(AR)/C146(AR), TSO-C196(AR), or TSO-C161a/C162a).
(2) TSO-C129(AR) Class A with TSO-C146(AR) Class Gamma.
(3) TSO-C129(AR) Class B or Class C with TSO-C145(AR), TSO-C146(AR) or TSO-C196(AR).
(4) TSO-C196(AR) with TSO-C145(AR) or TSO-C146(AR).
Note: The intent is that combinations not specifically prohibited by paragraphs 3-5.b(1) through 3-5.b(4) are acceptable.
Chapter 4. Equipment Performance - Advisory Vertical Guidance.
4-1. Introduction.
Positioning and navigation equipment may provide vertical path deviation guidance indications on a non-essential, not-required basis as an aid to help pilots meet barometric altitude restrictions. Equipment that has this capability typically uses GNSS or baro-VNAV, but may use any method to generate the vertical path information. Advisory vertical guidance does not provide approved vertical guidance deviation indications for operational credit. Only vertical guidance deviation indications for LNAV/VNAV or LPV approach procedures are approved for operational credit.
Note 1: Advisory vertical guidance is an optional capability implemented at the equipment manufacturer’s discretion for enroute, terminal, and/or approach operations; not a requirement for positioning and navigation equipment.
Note 2: Paragraph 4-1 does not apply to ILS.
Note 3: We recommend that equipment manufacturers provide a means for pilots to inhibit advisory vertical guidance to support non-precision approach training requirements.
4-2. Implementations.
a. It is acceptable to provide advisory vertical guidance as a descent aid during oceanic/remote, enroute, and terminal operations.
b. GPS equipment without GPS-provided approved vertical capability (TSO-C129(AR), TSO-C196(AR), TSO-C145/C146(AR) Operational Class 1) and no baro- VNAV integration in the aircraft may provide advisory vertical guidance deviation indications on any approach using the LNAV line of minima.
c. Some aircraft integrations may use GPS equipment without GPS-provided approved vertical capability (TSO-C129(AR), TSO-C196(AR), TSO-C145/C146(AR) Operational Class
1) to provide lateral path deviation indications and an approved baro-VNAV installation to provide vertical path deviation indications for an approach to the LNAV/VNAV line of minima.
(1) This integration constitutes approved vertical guidance to conduct a charted instrument approach procedure to the LNAV/VNAV line of minima and should not be confused with advisory vertical guidance applications.
(2) There may be occasions where it is operationally advantageous to use the LNAV line of minima rather than the LNAV/VNAV minima during an instrument approach procedure. It is acceptable for approved baro-VNAV installations to provide advisory vertical guidance when using the LNAV line of minima. However, during these operations, the 21
flight crew must use the primary barometric altimeter as the primary reference for compliance with all altitude restrictions associated with the instrument approach procedure; including compliance with all associated step-down fixes (see paragraphs 12-8 and 18-2.b).
Note 1: Baro-VNAV integrations may use non-GPS RNAV position sources to generate lateral path deviations for approaches that do not require GPS.
Note 2: Baro-VNAV is subject to performance limitations that could potentially cause advisory vertical path guidance to fall below step-down fixes on LNAV approaches.
d. During RNAV (GPS) instrument approach operations, TSO-C145/C146(AR) Operational Class 2 equipment may provide advisory vertical guidance when the procedure defines only the LNAV line of minima (i.e., procedures without a charted LNAV/VNAV and/or LPV line of minima). GPS/SBAS Operational Class 2 equipment is not capable of performing LP approaches, but may provide advisory vertical guidance for the LNAV line of minima on instrument approach procedures that define both an LNAV and LP line of minima.
(1) It is possible for GPS/SBAS Operational Class 2 equipment to also provide advisory vertical guidance for LNAV minima on instrument approach procedures that also contain LNAV/VNAV or LPV lines of minima as published, but with the additional considerations listed below. The reason is due to the wide range of displays, cockpit configurations, and potential confusion over “advisory” versus “approved” vertical guidance and which line of minima applies.
(a) LNAV with “advisory” vertical guidance must only be selectable prior to the FAF.
(b) The “advisory” vertical guidance indication must be unambiguous and easily distinguishable from the “approved” vertical guidance indication.
(c) The installation instructions/manual (or equivalent documents) must define the minimum display capability and cockpit configuration.
(d) The equipment must have an installation limitation or method to inhibit the function for non-qualifying installations.
(2) It is not acceptable for GPS/SBAS Operational Class 2 equipment to provide “advisory” vertical guidance in a “fail-down” mode from LNAV/VNAV to LNAV minima during the final approach segment.
Note 1: GPS/SBAS equipment manufacturers should exercise care when implementing “advisory” vertical guidance for LNAV minima collocated with LNAV/VNAV or LPV minima as published. The cockpit configuration and display capability can influence the 22
ability to provide an unambiguous, easily distinguishable vertical guidance indication during the airworthiness approval.
Note 2: Both the design approval applicant and airworthiness approval applicant have a responsibility to ensure the implementation is properly configured.
Airworthiness approval applicants should contact their ACO early for concurrence on the proposed implementation.
e. During RNAV (GPS) instrument approach operations, TSO-C145/C146(AR) Operational Class 3 equipment may provide advisory vertical guidance when the procedure defines only the LNAV and/or LP line of minima (i.e., procedures without a charted LNAV/VNAV and/or LPV line of minima).
Note 1: LP approach procedures will never be published with other lines of minima that contain approved vertical guidance (i.e., LNAV/VNAV or LPV). LNAV and LP lines of minima can be published on the same approach chart; and, it is acceptable to provide advisory vertical guidance, either GPS/SBAS or baro-VNAV, during approach operations using these lines of minima.
Note 2: Per RTCA/DO-229D it is not appropriate for GPS/SBAS Operational Class 3 equipment to “fail-down” from LP to LNAV.
(1) It is possible for GPS/SBAS Operational Class 3 equipment to also provide advisory vertical guidance for LNAV minima on instrument approach procedures that also contain LNAV/VNAV or LPV lines of minima as published, but with the additional considerations listed below. The reason is due to the wide range of displays, cockpit configurations, and potential confusion over “advisory” versus “approved” vertical guidance and which line of minima applies.
(a) LNAV with “advisory” vertical guidance must only be selectable prior to the FAF.
(b) The “advisory” vertical guidance indication must be unambiguous and easily distinguishable from the “approved” vertical guidance indication.
(c) The installation instructions/manual (or equivalent documents) must define the minimum display capability and cockpit configuration.
(d) The equipment must have an installation limitation or method to inhibit the function for non-qualifying installations.
(2) It is not acceptable for GPS/SBAS Operational Class 3 equipment to provide 23