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.
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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).
Note: GPS/SBAS equipment may continue using GEO data and range measurements when outside the GPS/SBAS service provider’s coverage area per the requirements in RTCA/DO-229D (RTCA/DO-229C for TSO revision ‘a’ equipment).
b. GPS/SBAS equipment that complies with the standards implemented by TSO-C145(AR)/C146(AR) does not have an equipment limitation for the aircraft to be equipped with other navigation systems appropriate to the operation. With GPS/SBAS equipment it is also acceptable to flight plan an alternate using an RNAV(GPS) approach to LNAV minimums at the alternate airport rather than a ground-based approach aid (see paragraph 15-7.1). Additionally, GPS/SBAS equipment may be used on RNAV ‘T’ and ‘Q’ routes within the contiguous U.S. and Alaska. AC 90-100 (latest revision) , contains specific information on performance requirements for RNAV routes. These capabilities should be clearly indicated in receiver manufacturer’s operating instructions.
Note: Refer to the appropriate operating rules and operational guidance documents for equipage requirements.
c. Although GPS/SBAS does not have an equipment limitation for other navigation systems onboard the aircraft, the receiver manufacturer’s operating instructions should encourage operators to retain back-up navigation systems to guard against outages or interference events.
d. Class 3 and Class 4 GPS/SBAS equipment that complies with the TSO revision ‘b’ or later has the capability to do LP approaches. TSO-C145a/C146a manufacturers may provide LP capability in their equipment. LP approaches use the horizontal accuracy and integrity values of LPV but do not provide approved vertical guidance deviation indications for operational credit. The intent is to provide LP approaches only at locations where some issue prevents implementing LPV vertical guidance, so LP should be the exception rather than the rule. Therefore, LP is not operationally similar to a localizer-only approach on an ILS because LP and LPV are mutually exclusive. That is, LP and LPV lines of minima will never be on the same approach chart.
e. GPS/SBAS equipment manufacturers need to use caution when implementing LP capability because some LP procedures cannot support a visual descent angle due to obstructions. The FAS datablock glide path angle field coding uses a zero in these instances.
Equipment manufacturers need to ensure a zero in the glide path angle field does not cause unintended software issues; for example, a divide by zero problem.
f. Manufacturers that request a deviation from the LP capability requirement in TSO C145d/C146d for their Class 3 or Class 4 GPS/SBAS equipment must provide an appropriate limitation for the installation instructions (or equivalent installation documentation) as part of their TSO application package. The limitation must be included in the AFM(S)/RFM(S).
5-3.3 Navigation Database - Data Conversion for GPS/SBAS LNAV/VNAV Approaches.
a. For LNAV/VNAV approaches collocated with LPV approaches, GPS/SBAS equipment must use the final approach segment (FAS) data block to define the final approach segment as described in RTCA/DO-229D, Change 1. But, a FAS data block is not provided for stand-alone LNAV/VNAV approaches. The vertical path for such approaches is defined by the threshold location, threshold crossing height, and glidepath angle. However, the altitude of the threshold is published as the height above/below mean sea level (MSL), rather than as the height above/below the WGS-84 ellipsoid. Therefore, the published MSL height (interpreted as a height above/below the WGS-84 geoid) must be converted to height above/below the WGS-84 ellipsoid prior to being used. Actual decision altitude (DA) must be based on the barometric altimeter.
b. The data conversion is not considered alteration of data since it changes the reference system but not the actual vertical location (reference RTCA/DO-200B, Standards for Processing Aeronautical Information, dated June 18, 2015, paragraph 2.4.2)
c. Receiver manufacturers may consider performing the conversion within the GPS/SBAS equipment or using a database process that provides threshold crossing height directly as height above/below the WGS-84 ellipsoid for GPS/SBAS approaches. However, GPS/SBAS integrations with baro-VNAV will need to address the issue of WGS-84 ellipsoid versus MSL height. This can be done through conversion or storing threshold data as both WGS-84 ellipsoid and MSL height to use for GPS/SBAS or baro-VNAV as appropriate.
5-4. GPS/GBAS (TSO-C161a/C162a receivers).
The GPS/GBAS equipment supports Category I precision approach and, optionally, a GPS/GBAS differentially corrected positioning service (DCPS). When the GPS/GBAS avionics supports both levels of service, whether or not the DCPS is available is determined by the GPS/GBAS ground station. All GPS/GBAS ground stations provide precision approach service, but not all ground stations are expected to provide DCPS.
5-4.1 Antennas.
a. TSO-C190 that references RTCA/DO-301, defines an acceptable GPS/GBAS antenna.
b. TSO-C162a GPS/GBAS equipment also requires a VHF antenna to receive the GPS/GBAS ground facility information broadcast. Installed antennas approved for ILS localizer/VOR can be used to receive the VDB signals. Unlike ILS ground antenna arrays, a GBAS VHF data broadcast transmitter may be located anywhere on the airport or in its vicinity.
This means the VHF broadcast must be received from any direction. The ILS localizer/VOR antennas may, or may not, be included under TSO-C162a. See paragraphs 13-1.1.b, 15-8, and
21-2.3 for installation considerations.
Note: RTCA/DO-253C gives GPS/GBAS equipment manufacturers an option for an antenna/receiver 33
combination or a receiver only. Both can be certified by TSO-C162a.
5-4.2 VHF Data Broadcast Receiving Equipment (TSO-C162a).
The equipment should comply with the RTCA/DO-253C, section 2 requirements as modified by TSO-C162a. The equipment receives the GPS/GBAS VDB and outputs the VDB messages to the sensor/navigation computer (see section 5-4.3). TSO-C162a equipment must be used with TSO-C161a, or equivalent, equipment to provide Category I precision approach guidance or PVT based on GPS/GBAS.
5-4.3 Sensor/Navigation Computer (TSO-C161a).
a. Category I Precision Approach.
(1) The equipment should comply with the RTCA/DO-253C, section 2 requirements as modified by TSO-C161a. The equipment outputs lateral and vertical deviations relative to an approach path defined in the VHF data broadcast. The entire precision approach must be contained within the region defined by the broadcast parameter Dmax.
Outside of Dmax, the avionics may not use the differential corrections and the GPS/GBAS equipment will not provide deviations.
(2) GPS/GBAS approaches will not have LNAV/VNAV or LNAV minimums published with the GBAS landing system (GLS) procedure. There is no fail-down option if guidance is lost during a GPS/GBAS final approach.
b. Position Output.
(1) When the GPS/GBAS ground station does not support positioning service, the GPS/GBAS airborne receiver PVT solution must comply with either TSO-C196(AR) or TSO-C145/C146(AR) receiver outputs.
(2) When the GPS/GBAS ground station supports positioning service and the distance (slant range) between the aircraft and the GPS/GBAS reference point is less than or equal to the maximum GPS/GBAS usable distance, Dmax, the GPS/GBAS airborne receiver PVT solution should comply with either TSO-C161a, TSO-C196(AR) or TSO-C145/C146(AR) receiver outputs (i.e., GPS/GBAS-provided PVT possible).
(3) When the GPS/GBAS ground station supports positioning service and the distance (slant range) between the aircraft and the GPS/GBAS reference point is greater than the maximum GPS/GBAS usable distance, Dmax, the GPS/GBAS airborne receiver PVT solution should comply with either TSO-C196(AR) or TSO-C145/C146(AR) receiver outputs
(i.e., no GPS/GBAS-provided PVT).
Note 1: The GPS/GBAS positioning service coverage region is defined by Dmax for GPS/GBAS ground stations supporting differential positioning service.
Note 2: These paragraphs are consistent with TSO-C161a.
Applicants may use TSO-C129(AR) GPS receivers if the outputs are shown to be equivalent to TSO-C196(AR).
5-5. GNSS Upgrades.
GNSS equipment installations have become very complex due to compatibility issues with the wide range of other installed equipment such as displays, flight guidance systems (FGS), terrain warning systems, etc. GNSS TSOs typically do not include requirements or standards related to installation compatibility or standardized outputs as part of the design and production approval. Therefore, it is recommended that, concurrent with their design and production approvals, equipment manufacturers also pursue an airworthiness approval that includes detailed installation instructions and equipment compatibility lists. See chapter 3 for more information regarding design, production and airworthiness approvals and paragraph
15-2.a for guidance on navigation displays during retrofit installations.
Note: GPS and GPS/SBAS equipment airworthiness approval is not considered novel or unusual per 14 CFR 21.16 and applicants can use designees during the STC process.
5-5.1 Adding Additional GNSS Equipment.
Compatibility must be established between the existing GNSS equipment and whatever new GNSS equipment is added. As an example, some installation applicants may retain existing TSO-C129(AR) equipment and add GPS/SBAS equipment. In this instance, the original TSO-C129(AR) installation should not be re-evaluated, except for modifications made as part of the GPS/SBAS installation. The re-evaluation should be to the affected functions or performance. For example, if the equipment shares a GNSS antenna there will be additi onal signal loss for the original equipment and compliance to the original TSO-C129(AR) installation instructions should be verified.
5-5.2 Replacing GNSS Equipment.
a. The TSO-C196(AR) sensor is intended as a direct replacement for a TSO-C129(AR) Class B or C sensor provided the installation applicant or TSOA/LODA holder ensures compatibility with the display and navigation computer. The complete sensor/navigation computer/display system will continue to have the limitations noted in paragraphs 5-2.2.a and
15-6.
b. It is also possible to use either a TSO-C145(AR) sensor or a combined TSO-C145(AR)/C146(AR) Class Delta-4 sensor to replace a TSO-C129(AR) Class B or Class C sensor provided the installation applicant or TSOA/LODA holder ensures compatibility with the display and navigation computer. In such a sensor replacement, the aircraft operator can derive additional benefits and navigation capability such as removing the limitations noted in paragraphs 5-2.2 and 15-6. However, the benefits do not automatically extend to enabling GPS/SBAS-provided LNAV/VNAV or LP/LPV capability. See paragraph 3-2 for compliance to TSO-C146d and the appropriate sections of RTCA/DO-229D, Change 1 as a complete 35
-- system in the aircraft.
c. Using a TSO-C145(AR) or TSO-C196(AR) sensor as a direct replacement for a TSO-C129(AR) sensor may be advantageous to remove performance or operational limitations other than those associated with redundant navigation sources onboard the aircraft even though the complete system retains its original TSO-C129(AR) certification basis. For example, the sensor processing improvements obviate the need to perform a RAIM prediction check 2 NM (nautical miles) prior to the final approach fix (FAF) as required by the original TSO-C129(AR) TSOA.
Note: RTCA/DO-229D, Change 1 and RTCA/DO-316 both have a fault detection prediction requirement that applicants can use to perform the prediction check if needed for integration compatibility. But, the equipment requirement is there primarily to support an operational requirement for pre-departure fault detection checks for TSO-C196(AR) equipment or when flying outside of the GPS/SBAS service provider’s coverage area for TSO-C145(AR) equipment.
5-5.3 GPS/SBAS Upgrade.
It is possible to upgrade TSO-C196(AR) equipment to TSO-C145d compliance.
Receiver manufacturers who provide an upgrade path are encouraged to use an STC-AML to streamline the installation approvals (see paragraph 2-3).
Note: It may be difficult to upgrade TSO-C129(AR) or TSO-C145a/C146a equipment to TSO-C145d/C146d compliance. Proposed upgrades for this equipment to TSO-C145d/C146d will have to be carefully evaluated.
5-5.4 GNSS Antenna Re-Use/Replacement.
a. There are no re-use or replacement possibilities for antennas certified under TSO-C129/C129a as part of the receiver TSOA/LODA. For receiver/antenna combinations certified by this method to use a different antenna design or specification is a major design change that invalidates the original TSOA/LODA.
b. For a TSO-C129/C129a receiver, it is possible to replace the original antenna if the antenna was certified to a separate antenna TSO. In this case, a TSO -C190 antenna, or antennas approved under TSO-C144(AR), can be used as replacements for any class of TSO-C129/C129a receiver.
c. For TSO-C196(AR) receivers it is possible to re-use or replace both “active” and “passive” antennas approved under TSO-C144(AR). TSO-C190 “active” antennas can be used as well.
d. For TSO-C145/C146(AR) operational Class 1 receivers and all classes of TSO-C145a/C146a receivers (see note below), it is possible to re-use both “passive” and “active” antennas approved under TSO-C144(AR). T SO-C145/C146(AR) operational Class 1 receivers are limited to enroute through LNAV approaches.
(1) The standards for equipment previously certified to TSO-C145a/C146a do permit using either TSO-C144 “passive” or “active” antennas for all receiver operational classes. However, receiver manufacturers are encouraged to use a TSO-C190 antenna when replacing the original antenna.
(2) If the receiver manufacturer chooses to not use a TSO-C190 antenna, they should use a TSO-C144 “active” antenna that complies with the intra-system noise environment, test procedures/methodologies, and 25 nanosecond differential group delay requirements found in RTCA/DO-301. Failure to do so may cause performance degradation due to GEO bias and an increasing broadband interference noise environment.
e. For TSO-C145/C146 revision ‘b’ or later operational Class 2, 3, or 4 receivers, “passive” TSO-C144(AR) antennas cannot be re-used. TSO-C190 describes the standard “active” antenna for TSO-C145/C146 revision ‘b’ or later operational Class 2, 3, or 4 receivers.
It may be possible to re-use an “active” TSO-C144 antenna for these receivers as a manufacturer-specified antenna per RTCA/DO-229D, paragraph 2.1.1.10.
f. In all cases, a TSO approval does not guarantee antenna/receiver installation compatibility. Installation compatibility must be established by the antenna or receiver manufacturer and documented in the approved installation instructions. Also, there can be 14 CFR 21.611 issues related to major versus minor alterations. Each project must be evaluated according to 14 CFR 21.611 to address the alteration regulatory issues.
TSO-C144(AR) Passive TSO-C144 Active TSO-C190 Antenna Type TSO-C129 TSOA Antenna/Receiver Combination X X X X X X X X X X X X X X See Note See Note See Note Table 2. Acceptable Standard Antennas 37