(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).
d. The intent for TSO-C196(AR) equipment is to take advantage of signal processing improvements found in RTCA/DO-229D without including the GPS/SBAS requirements.
TSO-C196(AR) equipment is intended as a direct replacement for Class B & C sensors certified to TSO-C129(AR). Additionally, TSO-C145(AR) equipment can also replace TSO-C129(AR) Class B & C sensors.
Note 1: Applicants will have to establish sensor/antenna compatibility when replacing TSO-C129(AR) sensors with either TSO-C196(AR) or TSO-C145(AR) sensors.
Note 2: GPS/SBAS TSO-C146(AR) Class Gamma equipment is considered the direct replacement for a Class A sensor/navigation computer combination certified to TSO-C129(AR).
5-2.3 Prediction Program.
a. GPS satellite failures have a non-intuitive impact on operational capability unlike conventional ground-based navigation aids that have a direct correlation between a facility outage (VOR fails) and the loss of an operational capability (VOR approach is unavailable).
The operator is responsible for considering the effects of satellite outages during flight planning. Flight Standards defines the operational requirements to review NOTAMs, review published aeronautical information, and perform pre-departure receiver autonomous integrity monitoring (RAIM) or FDE availability checks. Prediction programs and availability assessments are essential to enabling the operator to fulfill this responsibility. The FAA currently provides availability service through NOTAMs for GPS/SBAS equipment for domestic navigation operations, and plans to provide prediction services through the aeronautical information system. Either the FAA (through NOTAM or aeronautical information system) or the service provider provides these services for GPS/GBAS equipment for domestic navigation operations depending upon the specific ground facility status; Federal or non-Federal. Paragraph 5 -2.3 applies to operations that require a prediction program.
b. The following guidelines apply to any prediction program applicable to a particular model TSO-C129(AR) or TSO-C196(AR) receiver that is intended to assess the operational impact of satellite outages for flight planning purposes. Some operators are required to have an approved prediction program. A prediction program with the characteristics described below is acceptable.
Note: The guidelines also apply to prediction programs for TSO-C145/C146(AR) if the equipment is intended for oceanic/remote operations without limitations (see appendix 1 and paragraph 5-3.2.a.
c. TSO-C129(AR) equipment may have either a fault detection-only algorithm or an FDE algorithm. TSO-C196(AR) equipment is required by RTCA/DO-316 to have an FDE algorithm. The prediction program must include the appropriate capability for the intended receiver.
-
d. Operational guidance on predictive RAIM requirements may be found in the Aeronautical Information Manual (or other FAA guidance). The best performance model most likely comes from the original GPS equipment manufacturer.
Note: The FAA has transitioned to the service availability prediction tool (SAPT) for RAIM predictions which is available at www.sapt.faa.gov. However, SAPT does not provide FDE predictions for oceanic operations.
e. The prediction program can be provided on any processing platform (in the GPS equipment or elsewhere).
f. The prediction program software should be developed in accordance with at least RTCA/DO-178B or ‘C’ level D guidelines or equivalent.
g. The program should use either an algorithm identical to that used in the airborne equipment, or an algorithm based on assumptions for RAIM or FDE prediction that give a more conservative result.
h. The program should calculate RAIM or FDE availability based on the same satellite mask angle used in the equipment, but not less than 2 degrees for enroute/terminal operations or 5 degrees for approach.
i. The program should have the capability to manually or automatically designate GPS satellites which are expected to be out-of-service for the intended flight.
j. The program should allow the user to select the intended route (including declared alternates) and the time and duration of the flight. The program should identify the maximum RAIM or FDE outage time, and any predicted navigation capability outages.
(1) For approach operations, the maximum RAIM or FDE outage duration cannot exceed 5 minutes.
(2) For RNAV 1 and 2 operations, the maximum RAIM or FDE outage duration cannot exceed 5 minutes when TSO-C129(AR) or TSO-C196(AR) receivers are used as the only means of RNAV 1 and 2 compliance.
(3) For oceanic/remote operations, the maximum FDE outage duration cannot exceed 25 minutes for RNP 4.0 operation, 34 minutes for RNP 10 operation, and 51 minutes for minimum navigation performance standards (MNPS) operation.
Note: Prediction programs must use FDE for oceanic/remote operations (See appendix 1). SAPT does not provide FDE predictions for oceanic operations.
k. For approach predictions, the program should allow the user to select the destination and expected time of arrival, and provide a RAIM or FDE availability prediction over an interval of at least +15 minutes computed in intervals of 5 minutes or less about the estimated 30
--- time of arrival.
l. Prediction programs supporting ADS-B out should meet the requirements in 14 CFR
91.227(c)(1)(i) and 14 CFR 91.227(c)(1)(iii). The program should identify the maximum RAIM or FDE outage time, and any predicted surveillance capability outages.
5-3. GPS/SBAS (TSO-C145/C146(AR) receivers).
5-3.1 Antenna.
a. This paragraph provides guidance on acceptable GPS/SBAS antennas. See Table 2 for a list of acceptable standard antenna TSOs matched with GPS/SBAS receiver TSO revision and operational class.
b.
antenna.
TSO-C190, that references RTCA/DO-301, defines an acceptable GPS/SBAS Note: RTCA/DO-229D, paragraph 2.1.1.10 allows receiver manufacturers to designate manufacturer-specified antennas to take advantage of unique antenna performance rather than using the “minimum standard” antenna defined by TSO-C190.
c. A number of “passive” and “active” antennas were authorized under TSO-C144 for TSO-C145a/C146a compliant GPS/SBAS receivers. These antennas remain acceptable for those receiver installations according to their original TSOA/LODA. Receiver manufacturers are encouraged to use a TSO-C190 antenna whenever a replacement becomes necessary for a TSO-C144 antenna.
d. Major modifications to TSO-C145a/146a receivers that require a new TSOA/LODA upgrade to the latest TSO revision (for operational class 2, 3, and 4) must use either a TSO C190 or a receiver manufacturer-specified antenna that meets current requirements in RTCA/DO-229D (such as, sensitivity and dynamic range, geostationary orbit satellite (GEO) bias, broadband interference, and group delay).
5-3.2 Sensor and Sensor/Navigation Computer Configuration.
a. GPS/SBAS equipment has two different TSOs depending on whether the equipment is designed as a position sensor only, or a sensor/navigation computer combination.
TSO-C145d defines an acceptable standard for GPS/SBAS sensors (Class Beta) while TSO-C146d defines two configurations; a complete sensor/navigation computer (Class Gamma) and an “ILS look-alike” (Class Delta). Both TSOs reference RTCA/DO -229D, Change 1 for operations within and outside of the GPS/SBAS service provider coverage area.
When outside of a GPS/SBAS service provider’s coverage area the receivers can revert to using FDE for integrity. The receiver will use GPS/SBAS integrity or FDE; whichever provides the best protection level. GPS/SBAS equipment will not have any limitations in oceanic and remote areas provided the operator obtains an FDE prediction program (see paragraph 5-2.3).