--- ---- 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
“advisory” vertical guidance in a “fail-down” mode from LPV or 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 coincident with LNAV/VNAV and display capability can influence the 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.
f. TSO-C146(AR) Operational Class 4 (Functional Class Delta) equipment provides an “ILS look-alike” capability for LPV and LP only. GPS/SBAS Operational Class 4 equipment indicates LP by flagging the vertical guidance indications. It is acceptable for Class Delta equipment to provide advisory vertical guidance during approach procedures to LP minimums. However, it is not acceptable for Operational Class 4 equipment to provide advisory vertical guidance when the equipment “fails-down” from LPV to LNAV minima during the final approach segment due to potential confusion over advisory versus approved vertical guidance and which line of minima applies.
Note: Per RTCA/DO-229D it is not appropriate for GPS/SBAS Operational Class 4 equipment to “fail-down” from LP to LNAV.
g. Advisory vertical guidance may be provided during very high frequency omni-directional range (VOR) and non-directional beacon (NDB) instrument approach operations (including overlays with “or GPS” in the title) and also for older GPS instrument approach operations titled “GPS RWY XX”.
4-3. Limitations.
a. There are no TSO requirements or MOPS standards regarding advisory vertical guidance minimum performance or how advisory vertical guidance is generated (see notes).
Positioning and navigation equipment manufacturers can generally use their discretion when choosing to implement this capability. However, the equipment manufacturers cannot claim any operational or certification credit for advisory vertical guidance. When implementing advisory vertical guidance, the equipment manufacturer must provide an equipment limitation in the installation/instruction manual for inclusion in the airplane flight manual (supplement)/rotorcraft flight manual (supplement) (AFM(S)/RFM(S)) and may also include the information in the operations manual. The limitation should state the following or be equivalent:
“Advisory vertical guidance deviation information is only an aid to help pilots comply with altitude restrictions. When using advisory vertical guidance, the pilot must use the primary barometric altimeter to ensure compliance with all altitude restrictions, particularly during instrument approach operations.”
Note 1: RTCA/DO-229D, referenced by the GPS/SBAS TSOs, does provide some cursory requirements related to GPS/SBAS-provided advisory vertical guidance.
Note 2: The pilot using the primary barometric altimeter to ensure compliance with altitude restrictions is generally considered the mitigation for misleading or erroneous advisory vertical guidance information (i.e., 14 CFR XX.1309 compliance). However, each installation should be individually evaluated.
b. The AFM(S)/RFM(S) and/or installation manual limitation does not preclude positioning and navigation equipment from outputting advisory vertical guidance deviations to an autopilot provided applicable autopilot requirements are satisfied. However, demonstrating autopilot compatibility or compliance is beyond the scope of this AC (see the latest revision of AC 23-17, Systems and Equipment Guide for Certification of Part 23 Airplanes, AC 25.1329-1, Approval of Flight Guidance Systems, AC 27-1, Certification of Normal Category Rotorcraft, or AC 29-2, Certification of Transport Category Rotorcraft, for autopilot guidance information).
c. Positioning and navigation equipment manufacturers should consider providing a method to differentiate advisory vertical guidance indications from those used for approved vertical guidance to reduce potential crew confusion. If practical, the vertical deviation indications for each mode of vertical guidance should be unique and distinct.
Chapter 5. Equipment Performance - GNSS.
5-1. Introduction.
a. There have been questions on whether GNSS is an RNAV or RNP system. The answer is GNSS is both an RNAV and RNP system because RNP is a subset of RNAV that also includes a requirement to provide on-board navigation system accuracy performance monitoring and alerting. Therefore, an RNP system is also capable of RNAV. GNSS equipment provides accuracy performance monitoring and alerting which, by definition, makes it an RNP-capable system. Paragraph 1-4.f contains a frequently asked question and more detailed answer explaining RNAV, RNP and GNSS qualification. Chapters 7 - 10 provide more information about RNP.
b. The TSOs and MOPS for various types of GNSS equipment have been published over a span of several years. Despite efforts to harmonize all the GNSS documents, there are differences among the documents because of this publication time gap; particularly for characterizing the broadband external interference noise environment. The broadband external interference noise is defined in RTCA/DO-235B, Assessment of Radio Frequency Interference Relevant to the GNSS L1 Frequency Band, dated March 1, 2008. Table 1 below summarizes the effective noise density for acquisition, tracking, and re-acquisition that GNSS equipment manufacturers should use when certifying new equipment. Equipment not meeting the effective noise density in Table 1 (e.g., TSO-C129(AR)) may experience performance degradation as more GNSS satellites are launched. Equipment intended for use beyond 2020 in applications such as ADS-B should be qualified using the effective noise density shown in Table 1.
Receiver Function Effective Noise Density (dBm/Hz) Initial Acquisition (GPS Only) -172.2 GPS Tracking and Re acquisition -171.9 SBAS Tracking and Re acquisition -172.8 Table 1. Effective Noise Density for All GNSS Sources
c. It is acceptable to run GPS/SBAS testing separately using a total GNSS noise (IGNSS) of -172.8 dBm/Hz for accuracy verification and/or collection of the GPS/SBAS message loss rate data.
d. TSO-C145b/c and TSO-C146b/c equipment use a slightly earlier broadband external interference noise standard that is very close to the Table 1 effective noise density. This equipment should not experience any difficulty with the increasing noise environment.
However, manufacturers should use the values listed in Table 1 when conducting the test scenarios described in RTCA/DO-229D.
Note: RTCA/DO-229D, Change 1 contains the latest noise standards and is implemented by TSO-C145d/C146d.
TSO-C196(AR) equipment also incorporates the Table 1 effective noise density.
e. TSO-C145a/C146a equipment complies with RTCA/DO-229C that uses the broadband external interference noise characterized by a previous RTCA/DO-235 revision.
TSO-C145a/C146a equipment may experience performance degradation when other GNSS services are launched because future interference management and prevention will be based on the RTCA/DO-235B-defined broadband external interference noise environment.
f. TSO-C129(AR) equipment has no broadband external interference noise requirements comparable to RTCA/DO-235B. This equipment is more likely to experience performance degradation when other GNSS services are launched because future interference management and prevention will be based on the RTCA/DO-235B-defined environment.
g. Improperly used or installed GNSS re-radiators can present misleading information to GNSS equipment. Equipment manufacturers should consider measures to mitigate against the use of erroneous data for GNSS position and navigation solutions. Possible measures to consider are: implementing or enabling cross-checks of GNSS sensor data against independent position sources and/or other detection monitors using GNSS signal metrics or data.
5-2. GPS (TSO-C129(AR) and TSO-C196(AR) receivers).
a. TSO-C129(AR) and TSO-C196(AR) GPS equipment may be used on RNAV ‘T’ and ‘Q’ routes and for RNAV approaches to LNAV minimums within the contiguous U.S.. AC 90-100 (latest revision) contains specific information on performance requirements for RNAV routes.
Note: TSO-C129a has been cancelled, but this does not affect equipment with an existing TSOA/LODA (see paragraph 3-1.c).
b. Equipment requirements for ‘T’ and ‘Q’ routes in Alaska differ due to infrastructure and other unique characteristics of Alaskan airspace. Special Federal Aviation Regulation (SFAR) 97 provides guidance on flying in Alaska. Alaska Q routes require GNSS (TSO-C129(AR), TSO-C196(AR), TSO-C145(AR) or TSO-C146(AR)) and radar surveillance.
Alaska T routes require TSO-C145(AR) or TSO-C146 (AR). There is an ongoing program to either revise or delete the SFAR 97 requirements. See enroute charts, Notices to Airman Publication (NTAP), and Notice to Airmen (NOTAMs) for latest equipment requirements in Alaska.
5-2.1 Antennas.
a. It is recommended that receiver manufacturers seeking antennas for equipment certified to TSO-C129(AR) and TSO-C196(AR) use antennas compliant with the applicable antenna TSOs described below (see paragraph 5-5.4 for a complete discussion on antenna re-use/replacement). However, combinations where both the antenna and receiver were certified together as a unit under TSO-C129/C129a will need a new certification if antennas meeting the original TSOA are no longer available. Using a diffe rent antenna specification constitutes a major design change that requires a new TSOA/LODA unless the original 27
TSOA/LODA contains part numbers for multiple antennas.
(1) Either passive or active antennas are acceptable for TSO-C129(AR) and TSO-C196(AR) GPS equipment. The current TSOs for passive and active antennas are listed below, but antennas previously certified to TSO-C144 are also acceptable (see Table 2).
(2) TSO-C144a, Passive Airborne Global Navigation Satellite System (GNSS) Antenna, that references RTCA/DO-228, Change 1, paragraph 2.2.1, defines an acceptable passive GPS antenna. A passive antenna is defined as one that does not include a low noise power amplifier as part of the antenna assembly.
(3) TSO-C190, Active Airborne Global Navigation Satellite System (GNSS) Antenna, that references RTCA/DO-301, defines an acceptable active GPS antenna. An active antenna is defined as one that includes a low noise power amplifier as part of the antenna assembly.
b. To aid compatibility findings, antenna manufacturers should identify the antenna minimum DC supply current, and nominal amplifier gain/tolerance for active antennas in the installation instructions. Receiver manufacturers need this information to define installation instructions that integrate the antenna and receiver. Additionally, the antenna manufacturer should identify the antenna minimum radiation pattern gain at 5 degrees and the antenna minimum gain/equivalent input noise temperature (G/T) ratio in the installation instructions so that receiver manufacturers can take advantage of performance better than the minimum MOPS requirement. Documenting the improved performance facilitates the antenna/receiver installation and integration.
5-2.2 Sensors.
a. TSO-C129(AR) and TSO-C196(AR) are positioning and navigation systems with equipment limitations for the aircraft to have other navigation equipment available appropriate to the operation and for alternate airport flight planning (see paragraph 15-6).
Note 1: TSO-C129(AR) Class A equipment is a sensor/navigation computer combination.
Note 2: TSO-C129a has been cancelled, but this does not affect equipment with an existing TSOA/LODA (see paragraph 3-1.c).
b. TSO-C129(AR) systems will not have an equipment limitation for the aircraft to have other navigation equipment in oceanic and remote areas provided additional requirements are met (see appendix 1).
c. TSO-C196(AR) systems will not have an equipment limitation for the aircraft to have other navigation equipment in oceanic and remote areas provided the operator obtains a fault detection and exclusion (FDE) prediction program (see paragraph 5-2.3).