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 PV T 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 equipm ent 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
14-2.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 Equipm ent.
Compatibility must be established between the existing GNSS equipment and 26
whatever new GNSS equipm ent 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 additional 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 inten ded 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
14-5.
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.a and 14-5. 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-C146c and the appropriate sections of RTCA/DO-229D as a complete 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 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-C145c com pliance.
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 m ay be difficult to upgrade TSO-C129(AR) or TSO-C145a/C146a equipment to TSO-C145c/C146c compliance. Proposed upgrades for this equipment to TSO-C145c/C146c 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). TSO-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-C145b/C146b/C145c/C146c 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-C145b/C146b/C145c/C146c 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 28
accord ing to 14 CFR 21.611 to address the alteration regulatory issues.
TSO-C144(AR) Passive TSO-C144 Active TSO-C190 Antenna Type Receiver Type TSO-C129 TSOA Antenna/Receiver Combination TSO-C145a/C146aAll Classes TSO-C145b/C146b/C145c/C146cOpn’lClass 1 X X X TSO -C145b/C146b/ C145c/C146c Opn’lClass 2,3,4 X X X X X TSO-C129/C129aAll Classes TSO-C196(AR)GPS X X X TSO-C129/C129a Combined Rec/Ant X X X See Note See Note See Note TSO-C144(AR) Passive TSO-C144 Active TSO-C190 Antenna Type Receiver Type TSO-C129 TSOA Antenna/Receiver Combination TSO-C145a/C146aAll Classes TSO-C145b/C146b/C145c/C146cOpn’lClass 1 X X X TSO -C145b/C146b/ C145c/C146c Opn’lClass 2,3,4 X X X X X TSO-C129/C129aAll Classes TSO-C196(AR)GPS X X X TSO-C129/C129a Combined Rec/Ant X X X See Note See Note See Note
Table 2. Acceptable Standard Antennas
Note: An active TSO-C144 antenna may be acceptable for TSO-C145b/C146b/C145c/C146c Operational Class 2, 3, and 4 equipment as a receiver, manufacturer-specified antenna per RTCA/DO-229D, paragraph 2.1.1.10.
5-5.5 Marking.
The m arking must be modified to reflect the new configuration and approval when equipment is upgraded to a new TSO (such as from TSO-C196a to TSO-C145c Operational Class 1). This marking change can be accomplished by a certificated person in accordance with the TSOA/LODA holder’s instructions. A certificated person in this context is defined as one who is authorized under 14 CFR 43.3, persons authorized to perform maintenance, rebuilding, and alterations.
5-6. Navigation Database.
For all com bined sensor/navigator GNSS equipment, the navigation database is an essential component for the equipment to perform its intended function. Guidelines pertaining to the navigation database can be found in AC 20-153 (latest revision). Particular attention should be paid to the specification of the data quality requirements as described in RTCA/DO- 200A, appendix B.
5-6.1 Database Installation Instructions.
The TSOA/ LODA installation instructions/manual must contain a limitation identifying the requirements for the navigation database. This limitation will also be included 29
30 in the AFMS/RFMS.
5-6.2 Database Process.
The RNAV multi-s ensor equipment manufacturer is usually the last link in the aeronautical data processing chain, since the format for the data loaded in the final database is typically proprietary. The applicant for a TSOA/LODA must identify an aeronautical data process accessible to the equipment users. AC 20-153 (latest revision), Acceptance of Data Processes and associated Navigation Databases, provides an acceptable method for this aeronautical data process. The approval of the process is included as part of the TSOA/LODA for GNSS equipment.
5-7. GNSS Geometric Altitude.
GNSS-provided geom etric altitude is not adequate for compliance with air traffic control altitude requirements in the national airspace system (NAS) or internationally. The primary barometric altimeter must be used for compliance with all air traffic control altitude regulations, requirements, instructions, and clearances. GNSS geometric altitude may be used to increase situation awareness, but must be clearly distinguished from a barometric source.
The label GSL may be used to indicate GNSS sea level.
5-8. Terrain Awareness and Warning System (TAWS).
GNSS equipm ent is used to provide positioning inputs to TAWS/helicopter terrain awareness and warning system (HTAWS) equipment. Each type of GNSS equipment described in chapter 5 is acceptable as an input to TAWS/HTAWS equipment.
Chapter 6. Equipment Performa nce - RNAV Multi-Sensor Equipment.
6-1. Introduction.
This chapter provides guidance related to the basic functions and perform ance of a multi-sensor unit. This chapter identifies issues associated with equipment performance that applies to all types of equipment. Each individual sensor must meet the navigation performance and operation criteria contained in the respective TSO and AC applicable to that type sensor.
6-2. Navigation Database.
For area navigation equipm ent, the navigation database is an essential component for the equipment to perform its intended function. Guidelines pertaining to the navigation database can be found in AC 20-153 (latest revision). Particular attention should be paid to the specification of the data quality requirements as described in RTCA/DO-200A, appendix B.
6-2.1 Database Installation Instructions.
The TSOA/ LODA installation instructions/manual must contain a limitation identifying the requirements for the navigation database. This limitation will also be included in the AFMS/RFMS.
6-2.2 Database Process.
The RNAV multi-s ensor equipment manufacturer is usually the last link in the aeronautical data processing chain, as the format for the data loaded in the final database is typically proprietary. The applicant for a TSOA/LODA must identify an aeronautical data process accessible to the equipment users. AC 20-153 (latest revision), Acceptance of Data Processes and associated Navigation Databases, provides an acceptable method for this aeronautical data process.
6-3. GNSS.
a. When GNSS is integrated in an RNAV m ulti-sensor system, the GNSS position sensor should comply with the acceptable methods as defined by this AC in paragraph 5-2.2 for GPS not augmented by ground- or space-based systems, paragraph 5-3.2 for GPS/SBAS, and paragraph 5-4.2 for GPS/GBAS. The GNSS position sensor should be installed in accordance with guidelines provided in chapters 11 through 15 and 18 through 21.
Note: See paragraphs 14-6.8 and 14-8.16 for GNSS installation considerations regarding GPWS or TAWS alerting functions.
b. See paragraph 3-4 for TSO-C115(AR) compliance guidance on RNAV multi-sensor equipment integrating GPS/SBAS capability. RTCA/DO-229D, section 2, addresses the use of GPS/SBAS vertical position (referenced to WGS-84 ellipsoid) as used on the final approach segment of an LNAV/VNAV or LPV approach procedure or as advisory guidance on an LNAV 31
approach p rocedure. It is acceptable to provide advisory vertical guidance for LP approaches using the method described in RTCA/DO-229D for LNAV (see paragraph 4-2.d).
c. See paragraph 3-3 for TSO compliance guidance on RNAV multi-sensor equipment integrating GPS/GBAS capability.
d. Many RNAV multi-sensor systems have implemented baro-VNAV for use in all phases of flight, and baro-VNAV can be used for vertical guidance on an LNAV/VNAV approach procedure.
(1) The RNAV multi-sensor system manufacturer should address the GPS/SBAS and/or GPS/GBAS integration issues associated with equipment designs that also include baro-VNAV capability. In particular, the RNAV multi-sensor equipment must provide a smooth guidance transition between baro-VNAV and GPS/SBAS and/or GPS/GBAS vertical guidance and a clear mode annunciation to the pilot.
(2) Paragraph 17-5 of this AC provides additional guidance for baro-VNAV, GPS/SBAS, and GPS/GBAS integrations.
6-4. DME/DME.
The FAA is responsib le for evaluating DME/DME coverage and availability against a minimum standard DME/DME RNAV system for each route and procedure. This paragraph defines the minimum performance and functions (baseline) for DME/DME RNAV systems intended to support RNAV 1 and RNAV 2 routes, as well as RNAV 1 departure procedures (DPs) and standard terminal arrival routes (STARs).
a. The DME/DME RNAV system must:
(1) Provide position update within 30 seconds of tuning DME navigation facilities.
(2) Auto-tune multiple DME facilities.
(3) Provide continuous DME/DME position updating.
Note: Given a third DME facility or a second pair has been available for at least the previous 30 seconds, there must be no interruption in DME/DME positioning when the RNAV system switches between DME stations/pairs.
b. The FAA cannot ensure all DME signals within reception distance of United States airspace meet International Civil Aviation Organization (ICAO) standards. These could include non-United States DME facilities, or Department of Defense (DOD) maintained DME facilities excluded from the NAS database. DME/DME RNAV procedure design will only use DME facilities listed in the airport/facility directory (A/FD). Although a procedure design issue, applicants may mitigate this restriction by:
(1) Having the DME/DME RNAV system only use DME f acilities listed in the A/FD.
(2) Requiring exclusion of non-NAS DME facilities from the aircraft’s navigation database when the RNAV routes or procedures are within reception range of these non-NAS DME facilities.
(3) Demonstrating to the FAA that their RNAV system performs reasonableness checks to detect errors from the non-NAS DME facilities and excludes these facilities from the navigation position solution when appropriate (e.g., using the ARINC 424 coding to preclude tuning co-channel DME facilities when the signals-in-space overlap). See paragraph 6-4.1 for guidance on reasonableness check testing.
c. When needed to generate a DME/DME position, the DME/DME RNAV system (also referred to as a FMS) must use, as a minimum, DMEs with a relative angle between 30 and 150. The FMS may use DME pairs outside these angles (for example, 20 to 160).
d. The RNAV system may use any receivable DME facility (listed in the A/FD) regardless of its location. When needed to generate a DME/DME position, as a minimum, the RNAV system must use an available and valid low altitude and/or high altitude DME anywhere within the following region around the DME facility:
(1) Greater than or equal to 3 NM from the facility;
(2) Less than 40 degrees above the horizon when viewed from the DME facility;
and
(3) For facilities with an ARINC 424 figure of merit (FOM), the RNAV system may use the FOM value from Table 3 as the acceptable, usable region.
The aircraft’s DME/DME RNAV system must be: If the ARINC 424 FOM is:
Less than or equal to: And less than:
0 40 NM from the facility 12,000 ft above facility elevation 1 70 NM from the facility 18,000 ft above facility elevation 2 130 NM from the facility -- 3 160 NM from the facility -- Table 3. DME Usable Range
Note 1: RNAV systems may use additional DME facilities (for example, a localizer (LOC)/DME facility may be used but is not required to be used for positioning). RNAV systems are not required to use the FOM value.
Note 2: RNAV routes and procedures may include new FOMs with expanded service volumes.
(4) A valid DME f acility:
(a) Broadcasts an accurate facility identifier signal;
(b) Satisfies the minimum field strength requirements; and
(c) Is protected from other interfering DME signals according to the co-channel and adjacent channel requirements.
e. There is no requirement to use VOR, LOC, NDB, IRU or attitude heading reference system (AHRS) during normal operation of the DME/DME RNAV system.
f. When the RNAV system is using a minimum of two DME facilities that satisfy the criteria in paragraph 6-4, and any other valid DME facilities not meeting that criteria, the 95% position estimation error must be better than or equal to 1.75 NM. A flight technical error (FTE) contribution not exceeding 1.0 NM (95%) may be assumed for RNAV 2 operations.
Note 1: This performance requirement is met for any navigation system that uses two DME stations simultaneously, limits the DME inclusion angle to between 30 and 150 and uses DME sensors that meet the accuracy requirements of TSO-C66c. If the RNAV system uses DME facilities outside the range identified above, the DME signal-in-space error can be assumed to be 0.1 NM 95%.
Note 2: When using a minimum of two DME facilities satisfying the criteria above, the 95% position estimation error must be better than or equal to the following equation:
) sin( )2 2( )2 2(22 , 2, 2, 1, 1/ sisairsisairDMEDME
Single facility reference, where:
sis = 0.05 NM
air is MAX {(0.085 NM, (0.125% of distance)}
= inclusion angle (30o to 150o)
g. The RNAV system must ensure co-channel DME facilities do not cause erroneous guidance. This could be accomplished by including VOR reasonableness checking when initially tuning a DME facility, or excluding a DME facility when there is a co-channel DME within line-of-sight. See paragraph 6-4.1 for guidance on testing reasonableness checks.
Note: The DME assessm ent cannot use a DME facility when there is a co-channel DME facility within line-of-sight.
h. The RNAV system must use operational DME facilities. DME facilities listed by NOTAM as unavailable (for example, under test or other maintenance) could still reply to an airborne interrogation. Therefore, non-operational facilities must not be used. An RNAV system may exclude non-operational facilities by checking the identification or inhibiting the use of facilities identified as not operational.
i. Operational mitigations defined to qualify equipment with this AC will not require pilot action during critical phases of flight, pilot monitoring of the RNAV system’s navigation updating source(s), or time intensive programming/blackballing of multiple DME stations prior to executing a procedure.
(1) Blackballing single facilities listed by NOTAM as out-of-service and/or programming route/procedure-defined “critical” DME is acceptable when this mitigation requires no pilot action during a critical phase of flight. A programming requirement also does not imply the pilot should complete manual entry of DME facilities not in the navigation database. Instead, this allows RNAV systems to tune a critical DME, as appropriate to a specific route or procedure.
(2) The critical phase of flight is normally from the final approach fix on an approach procedure through missed approach, or from field elevation to 2,500 ft above airport elevation on a departure.
6-4.1 Reasonableness Checks.
a. Many FMSs perform a reasonableness check to verify valid DME measurements.
Reasonableness checks are very effective against database errors or erroneous system acquisition (such as co-channel facilities), and typically fall into two classes:
(1) Those the FMS uses after it acquires a new DME. The FMS compares the aircraft’s position before using the DME to the aircraft’s range to the DME; and
(2) Those the FMS continuously uses, based on redundant information (for example, extra DME signals or IRU data).
b. The reasonableness checks are intended to prevent navigation aids from being used for navigation update in areas where the data can lead to radio position fixing errors due to co-channel interference, multipath, and direct signal screening. In lieu of using radio navigation aid published service volume, the navigation system should provide checks, which preclude use of duplicate frequency navigation aids (NAVAIDs) within range, over-the-horizon NAVAIDs, and use of NAVAIDs with poor geometry.
c. Under certain conditions, reasonableness checks can be invalid.
(1) Do not assu me a DME signal remains valid just because it was valid when acquired.
(2) Do not assume extra DME signals are available. The intent of this baseline is to support operations where the infrastructure is minimal (for example, when only two DMEs are available for parts of the procedure).
d. When an FMS manufacturer uses a reasonableness check to satisfy any criteria in this AC, they must test the effectiveness of the check under stressing conditions. An example of this condition is a DME signal that is valid at acquisition and “ramps off” during the test (similar to what a facility under test might do), when there is only one other supporting DME or two signals of equal strength. A “ramp off” rate would be significantly higher or slower than the normal range of groundspeed.
6-4.2 Performance Confirmation.
a. New systems m ay demonstrate compliance with these criteria as part of the airworthiness approval. For existing systems, the applicant should determine compliance with the equipment and aircraft criteria in this chapter.
b. Aircraft manufacturers (TC holders) incorporating FMS and DME/DME positioning should review the available data for the integrated navigation system, and obtain additional data as appropriate, to determine compliance with the criteria in this AC.
c. Equipment manufacturers (typically DME and FMS TSOA/LODA holders) need to consider DME accuracy. DME sensors have been demonstrated to a variety of performance requirements per TSO-C66. TSO-C66 performance standards have evolved as follows:
(1) TSO-C66: (Aug 1960) RTCA/DO-99.
(2) TSO-C66a: (Sep 1965) RTCA/DO-151, accuracy requirement as total error with 0.1 NM attributed to ground facility, airborne equipment accuracy of 0.5 NM or 3% of distance, whichever is greater, with a maximum of 3 NM.
(3) TSO-C66b: (Nov 1978) RTCA/DO-151a, accuracy requirement as total error with 0.1 NM attributed to ground facility, airborne equipment accuracy of 0.5 NM or 1% of distance, whichever is greater, with a maximum of 3 NM.
(4) TSO-C66c: (Sept 1985) RTCA/DO-189, accuracy requirement as total error for the airborne equipment of 0.17 NM or 0.25% of distance, whichever is greater.
d. The accuracy required by TSO-C66c is adequate to support the criteria in this AC.
DME equipment approved under revision ‘c’ does not require further evaluation for RNAV 1 and RNAV 2 operations. Applicants with equipment built to earlier TSO revisions may use the following process to establish more accurate performance than originally credited to support 36
RNAV 1 and RNAV 2 operations.
(1) Rather than relying on original dem onstrated performance, the applicant may elect to review the original TSO or TC/STC test data to determine the demonstrated accuracy and/or make any appropriate changes to qualification tests to determine achieved accuracy.
Note: When conducting accuracy analysis, the DME signal-in-space error can be assumed to be 0.1 NM 95% (both inside and outside the published service volume). If demonstrating accuracy under bench or flight test conditions, the actual accuracy of the bench equipment or ground facility should be considered.
(2) New testing should be performed under the same conditions used to demonstrate compliance with the original TSO-C66 standard.
(3) Applicants who have demonstrated more accurate DME performance should state the demonstrated accuracy in a letter to their customers.
6-4.3 Multi-Sensor System FMS.
a. The FMS or aircraft m anufacturer should review the available data for the integrated navigation system, and obtain additional data as appropriate, to determine compliance with the criteria in paragraph 6-4. Applicants who have determined compliance should state such in the operating instructions or AFMS/RFMS, along with any limitations (for example, if the pilot is expected to manually inhibit the use of facilities that are listed by NOTAM as unavailable).
The applicant’s certification may limit the compliance to specific DME systems, or may reference any DME qualified to the accuracy requirements of TSO-C66c.
b. FMS accuracy is dependent on a number of factors including: latency effects, the selection of DME facilities, the method of combining information from multiple DMEs, and the effects of other sensors used to determine a position. For FMSs using two (or more) DMEs at the same time and limiting the DME include angle to between 30 and 150, the accuracy requirement can be met if the DME sensors meet the accuracy requirements of TSO-C66c. For FMSs without these characteristics, the accuracy should be evaluated under poor DME geometry scenarios and should consider the demonstrated DME sensor accuracy. Poor geometry scenarios may include angles at the limits specified earlier, with or without additional DME facilities available outside those conditions.
c. Identify those conditions that would result in failure to meet the accuracy requirement and the means to preclude those identified conditions.
6-5. VOR/DME.
a. Multi-sensor equipm ent may incorporate VOR/DME updating and must meet the performance for the route to be flown. However, terminal and enroute RNAV implementation in the United States does not require using VOR, so any use of VOR must include reasonableness checking and demonstrate that positional accuracy from an erroneous VOR 37