U.S. Department of Transportation Federal Aviation Administration
Advisory Circular
Subject: Airworthiness Approval of Positioning and Navigation Systems Date: 9/27/10 Initiated by: AIR-130 AC No: 20-138B
This advisory circular (AC) provides guidance material for the airworthiness approval of installed positioning and navigation equipment. Positioning and navigation equipment may be used for a variety of functions such as navigation, automatic dependent surveillance, and/or terrain awareness and warning systems. This AC addresses the following avionics:
Global positioning system (GPS) equipment including those using GPS augmentations.
Area navigation (RNAV) equipment integrating data from multiple navigation sensors.
RNAV equipment intended for required navigation performance (RNP) operations.
Barometric vertical navigation (baro-VNAV) equipment.
This AC does not address new satellite constellations that are planned or currently under construction. This AC will be updated when sufficient documentation exists to support multiconstellation equipment.
Susan J. M. Cabler Assistant Manager, Aircraft Engineering Division
Table of Contents
Chapter 1. General Inform
ation1
1-1. Purpose1
1-2. Audience2
1-3. Cancellation2
Chapter 2. Technical Standard Order Authorization (TSOA) and Airworthiness Approval
Considerations - General3
2-1. Guidance for TSOA/Letter of De signApproval (LODA) and Airworthiness
Approvals3
2-2. TSOA3
2-3. STC-Approved Model List (AML)4
2-4. Type Certificate4
Chapter 3. TSO Authorization5
3-1. TSO-C129(AR)/C1965
3-2. TSO-C145(AR)/C146(AR)6
3-3. TSO-C161a/C162a9
3-4. RNAV Multi-Sensor Equipment9
3-5. Multiple TSO Authorizations10
Chapter 4. Equipment Performance - Advisory Vertical Guidance11
4-1. Introduction11
4-2. Implementations11
4-3. Limitatations13
Chapter 5. Equipment Performance - GNSS15
5-1. Introduction15
5-2. GPS (TSO-C129(AR) and TSO-C196 receivers)16
5-2.1 Antennas16
5-2.2 Sensors17
5-2.3 Prediction Program17
5-3. GPS/SBAS (TSO-C145/C146(AR) receivers)19
5-3.1 Antenna19
5-3.2 Sensor and Sensor/Navigation Computer Configuration20
5-3.3 Navigation Database - Data Conversion for GPS/SBAS LNAV/VNAV
Approaches21
5-4. GPS/GBAS (TSO-C161a/C162a receivers)21
5-4.1 Antennas21
5-4.2 VHF Data Broadcast Recei ving Equipment (TSO-C162a)22
5-4.3 Sensor/Navigation Computer (TSO-C161a)22
5-5. GNSS Upgrades23
5-5.1 Adding Additional GNSS equipment23
5-5.2 Replacing GNSS Equipment23
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5-5.3 GPS/SBAS
Upgrade24
5-5.4 GNSS Antenna Re-Use/Replacement24
5-5.5 Marking25
5-6. Navigation Database26
5-6.1 Database Installation Instructions26
5-6.2 Database Process26
5-7. GNSS Geometric Altitude26
Chapter 6. Equipment Performance - RNAV Multi-Sensor Equipment27
6-1. Introduction27
6-2. Navigation Database27
6-2.1 Database Installation Instructions27
6-2.2 Database Process27
6-3. GNSS27
6-4. DME/DME28
6-4.1 Reasonableness Checks31
6-4.2 Performance Confirmation32
6-4.3 Multi-Sensor System FMS33
6-5. VOR/DME33
6-6. INS/IRU36
6-7. INS/IRU – GNSS Integration36
6-8. INS/IRU - DME/DME Integration38
Chapter 7. Equipment Performance - RNP (General)40
7-1. Introduction40
7-2. Special Characteristics of RNP Instrument Approaches41
7-3. Special Characteristics of RNP 1 Operations41
Chapter 8. Equipment Performance - RNP Approach43
8-1. Introduction43
8-2. Aircraft and System Requirements43
8-3. Performance and Functional Requirements for RNP Systems44
8-4. System Eligibility and Approval for RNP Operations48
Chapter 9. Equipment Performance - RNP Terminal51
9-1. Introduction51
9-2. Aircraft and System Requirements for RNP Terminal Operations51
9-3. System Performance Monitoring and Alerting52
9-4. System Eligibility and Approval for RNP 1 Operations56
Chapter 10. Equipment Performance - Baro-VNAV58
10-1. General Limitations for Operations under IFR58
10-2. Baro-VNAV Equipment Performa nce for Operations under IFR58
Chapter 11. General Installation Considerations63
11-1. Introduction63
11-2. Failure Classification63
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11-3. Software
Considerations64
11-4. Hardware Considerations64
11-5. Installed Equipment Compatibility.......................................................................................6 4
11-6. Installation Instructions64
11-7. Environmental Considerations65
11-8. General Human Factors Considerations65
Chapter 12. General Installation Considerations - Antennas68
12-1. Antenna placement68
12-2. Anti-Ice Protection69
12-3. Antenna Cables69
12-4. Structure69
Chapter 13. General Installation Considerations - Sensors70
13-1. Introduction70
13-2. Positioning and Navigation Configuration Strapping70
13-3. Navigation Source Selection70
13-4. Dual Positioning and Na vigation Installations71
13-5. Intermixing RNAV equipment71
13-6. Interface to FGS72
13-7. Interface to Magnetic/True Switch. ......................................................................................7 3
13-8. Interface to Air Data and Inertial Reference Systems74
13-9. Antenna/Sensor Compatibility74
13-10. Interference - Electromagne tic Compatibility (EMC)75
13-11. Interface Requirements75
Chapter 14. Installation Considerations - GNSS77
14-1. Introduction77
14-2. Navigation Displays77
14-3. Failure Indications78
14-4. Documenting Effects of GNSS Outage79
14-5. GPS Equipment79
14-6. GPS/SBAS Equipment80
14-6.1 Limitations80
14-6.2 LP Approach81
14-6.3 Update Rate81
14-6.4 Performance Monitoring81
14-6.5 System Status82
14-6.6 Annunciations82
14-6.7 Accessibility83
14-6.8 GPWS/TAWS Glideslope Warning83
14-7. GPS/GBAS VDB Receiver...................................................................................................8 3
14-7.1 Interference – EMC83
14-7.2 Compatibility with other systems84
14-7.3 VDB aircraft implementation loss84
14-8. GPS/GBAS Navigation Computer Receiver84
14-8.1 GPS/GBAS equipment in tended for Category I84
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14-8.2 GPS/GBAS
stand-alone or MMR equipment intended for Category I85
14-8.3 Performance and Performance Monitoring86
14-8.4 Integrity86
14-8.5 Continuity of Navigation86
14-8.6 Fault Detection and Annunciation86
14-8.7 System Status87
14-8.8 Annunciation87
14-8.9 Accessibility87
14-8.10 Glidepath Capture88
14-8.11 Equipment Qualification88
14-8.12 Interoperability88
14-8.13 GPS/GBAS GPWS/TAWS Glideslope Warning88
14-9. Special Use Mission Equipm ent - Not for Navigation89
Chapter 15. Installation Considerations - RNAV Multi-Sensor Equipment90
15-1. Introduction90
15-2. Interface to Primary Navigation Display90
15-2.1 Non-numeric Deviation Displays90
15-2.2 Map Displays91
15-3. Interface to Remote Annunciator91
15-4. Unique Software Considerations92
Chapter 16. Installation Considerations - RNP93
16-1. Introduction93
16-2. Flight Technical Error93
16-3. Radius to Fix (RF) Legs93
16-4. Interface to FGS94
Chapter 17. Installation Considerations - Baro-VNAV95
17-1. Failure Protection95
17-2. Manufacturer’s Instructions95
17-3. Annunciations95
17-4. Software Changes95
17-5. Integration with GNSS-Pr ovided Vertical Guidance96
Chapter 18. Installed Performance - Data Submittal98
18-1. Introduction98
18-2. Project Specific Certification Plan98
18-3. TSO Technical Data98
18-4. Review the installation manual99
18-5. Structural Analysis99
18-6. Power Supply100
18-7. Environment100
18-8. Database100
18-9. Operations manual or AFMS/RFMS100
18-10. Stand-Alone Navigation Equipment100
18-11. Ground and Flight Test Plans (f unctional and EMI/EMC testing)101
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Chapter 19. Installed Perform
ance - Test (General)102
19-1. Intended Function102
19-2. Power Supply102
19-3. Accuracy102
19-4. Human Factors102
Chapter 20. Installed Performance - Test (GNSS)103
20-1. Ground Test - GPS, GPS/SBAS, and GPS/GBAS103
20-1.1 Interference103
20-1.2 Antenna to Aircraft Navi gation Reference Offset103
20-1.3 Sensor Installation104
20-1.4 Stand-Alone Navigation Equipment Installation104
20-2. Flight Test - GPS, GPS/SBAS, and GPS/GBAS104
20-2.1 Equipment Installation104
20-2.2 LPV and Precision Approaches105
20-2.3 GPS/GBAS VDB Receiver Installation106
Chapter 21. Installed Performance - Test (RNAV Mult-Sensor Equipment)107
21-1. Ground Test107
21-2. Flight Test107
21-2.1 Interface to FGS108
21-2.2 GNSS Precision Approach109
Chapter 22. Installed Performance - Test (Baro-VNAV)110
22-1. Introduction110
22-2. Ground Test110
22-2.1 Lab/Bench Tests and Equipment Data Evaluation110
22-2.2 Aircraft Installati on Data Evaluation110
22-3. Flight Test111
22-3.1 Functional Flight Test111
22-3.2 Navigation Error Flight Test. .........................................................................................11 2
22-4. Follow-on Approval113
Appendix 1. GPS Oceanic/Remote NavigationA1-1
A1-1. GPS Oceanic/Remote NavigationA1-1
A1-2. Approval ProcessA1-1
A1-3. Equipment Performance. ................................................................................................. A1 -2
Appendix 2. RNP AR OperationsA2-1
A2-1. IntroductionA2-1
A2-2. Performance Requirements.............................................................................................. A2- 1
A2-3. RNP AR General RequirementsA2-3
A2-4. Requirements for RNP AR Approaches with RF LegsA2-13
A2-5. Requirements for RNP AR Approach values less than 0.3A2-14
A2-6. Requirements for Approaches with a Missed Approach Less Than RNP 1A2-16
A2-7. Navigation Data Va lidation ProgramA2-18
A2-8. Installation Considerations for RNP ARA2-20
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Appendix 3. RNP Advanced Features.
.A3-1
A3-1. IntroductionA3-1
A3-2. Radius to Fix Leg Capability........................................................................................... A3 -1
Appendix 4. GNSS Velocity Tests to Support ADS-BA4-1
A4-1. IntroductionA4-1
A4-2. Velocity Accuracy and Veloc ity Figure of Merit TestsA4-1
A4-3. Horizontal Velocity Ac curacy Test Conditions Commensurate with NACV = 1A4-1
A4-4. Horizontal Accuracy Pa ss/Fail DeterminationA4-3
A4-5. Horizontal Velocity Figure of Merit Pass/Fail DeterminationA4-4
A4-6. Vertical Velocity Accuracy Test Conditions Commensurate with NACV = 1A4-4
A4-7. Vertical Velocity Accuracy Pass/Fail DeterminationA4-6
A4-8. Vertical Velocity Figure of Merit Pass/Fail DeterminationA4-6
A4-9. Additional Tests to Demonstrate Accu racy Commensurate with NACV = 2A4-7
Appendix 5. Sample Airplane/Rotorcraft Flight Manual SupplementA5-8
A5-1. IntroductionA5-8
Appendix 6. Installation of GNSS Equipment for VFR Use OnlyA6-1
A6-1. IntroductionA6-1
A6-2. GeneralA6-1
A6-3. ApplicabilityA6-1
A6-4. Technical InstructionsA6-1
Appendix 7. Definitions and AcronymsA7-1
A7-1. DefinitionsA7-1
A7-2. AcronymsA7-3
Appendix 8. Related DocumentsA8-1
A8-1. FAA Advisory Circulars.................................................................................................. A 8-1
A8-2. FAA Technical Standard OrdersA8-3
A8-3. RTCA, Inc. Documents (RTCA DO) documentsA8-4
A8-4. Other DocumentsA8-5
A8-5. How to Get Related DocumentsA8-6
List of Tables
Table 1. Effective Noise Density for All GNSS Sources15
Table 2. Acceptable Standard Antennas25
Table 3. DME Usable Range29
Table 4. 2D Accuracy Requirements for Equipment Usin g a Single Co-located VOR/DME35
Table 5. Error Elements36
Table 6. Vertical Path Performanc e Limit for Baro-VNAV59
Table 7. Vertical Path Deviations60
Table 8. Typical Hazard Classifications63
Table 9. RNP FTE Performance93
Table 10. INS/IRU Accuracy After Loss of Radio Updating108
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Table 11. Tailwind Component (VKTW) for Turn CalculationsA2-7
Table 12. Platform Dynamics for Horiz ontal Velocity Accuracy TestA4-2
Table 13. Platform Dynamics for Vertical Velocity Accuracy TestA4-5
List of Figures
Figure 1. Minimum Straight Path Before DAA2-17
Chapter 1. General In formation.
1-1. Purpose.
This advisory circular (AC) provides guidance m aterial for the airworthiness approval of installed positioning and navigation equipment. Positioning and navigation equipment may be used for a variety of functions such as navigation, automatic dependent surveillance, and/or terrain awareness and warning systems. This AC addresses the following equipment:
a. Global positioning system (GPS) sensors or stand-alone navigation equipment, including those incorporating aircraft-based augmentation system (ABAS), satellite-based augmentation system (SBAS), or ground-based augmentation system (GBAS).
b. Area navigation (RNAV) integrating data from multiple navigation sensors such as global navigation satellite system (GNSS), inertial reference units (IRU), and distance measuring equipment (DME).
c. RNAV intended for required navigation performance (RNP) operations, including advanced functions and RNP authorization required (AR) formerly referred to as special aircraft and aircrew authorization required (SAAAR).
Note: RNP AR was previously named RNP SAAAR. The name has been changed to RNP AR for international harmonization, but might not yet be standardized throughout all documents.
d. Barometric vertical navigation (baro-VNAV) equipment.
e. This AC does not address new satellite constellations that are planned or currently under construction. This AC will be updated when sufficient documentation exists to support multi-constellation equipment.
f. This AC incorporates the airworthiness considerations contained in AC 90-101A, Approval Guidance for RNP Procedures with SAAAR, and AC 90-105, Approval Guidance for RNP Operations and Barometric Vertical Navigation in the U.S. National Airspace System, as a necessary first step to consolidating all the positioning and navigation equipment and RNP airworthiness guidance into one AC. Future AC 90-101 and AC 90-105 revisions will remove the airworthiness guidance. This AC will not replace the operational guidance found in the RNP 90-series ACs. However, this AC does replace the ACs listed in paragraph 1-3 by incorporating and updating the information they contained.
g. This AC is not mandatory and is not a regulation. This AC describes an acceptable means, but not the only means, to comply with applicable regulations.
h. This AC provides guidance information intended for new approvals. This AC is not intended to modify, change or cancel existing equipment design or airworthiness approvals.
2 Equipment with existing approvals can continue to be installed within the provisions of their original design and airworthiness certification.
i. The guidance in this AC cannot ensure compliance with all Title 14 of the Code of Federal Regulations (CFR) parts 23, 25, 27, and 29 airworthiness regulations for every possible installation configuration. The applicant remains responsible for regulatory compliance and should work closely with their geographic aircraft certification office (ACO) to ensure regulatory compliance. Mandatory terms such as “must” used in this AC are only applicable when following the compliance method outlined.
j. In lieu of following this method without deviation, the applicant may elect to follow an alternate method, provided the alternate method is also found by the Federal Aviation Administration (FAA) to be an acceptable means of complying with the requirements of the federal aviation regulations 14 CFR.
1-2. Audience.
This AC is for aircraft m anufacturers, avionics manufacturers, installation shops, or other applicants seeking design and/or airworthiness approval for the positioning and navigation systems described in this document.
1-3. Cancellation.
This AC supersedes the ACs listed b elow. Equipment previously approved per the guidance in the superseded ACs is still valid for the operations and conditions stated in their approvals. The following documents are cancelled:
a. AC 20-129, Airworthiness Approval of Vertical Navigation (VNAV) Systems for use in the U.S. National Airspace System (NAS) and Alaska.
b. AC 20-130A, Airworthiness Approval of Navigation or Flight Management Systems Integrating Multiple Navigation Sensors.
c. AC 20-138A, Airworthiness Approval of Global Navigation Satellite System (GNSS) Equipment.
d. AC 25-4, Inertial Navigation Systems.
Chapter 2. T echnical Standard Order Authorization (TSOA) and Airworthiness Approval Considerations - General.
2-1. Guidance for TSOA/Letter of DesignApproval (LODA) and Air worthiness Approvals.
Title 14 CFR part 21; subparts D, E, and O provide the regulatory basis defining changes to type certificates (TC) (major/minor changes to aircraft type design), supplemental type certificates (STC), and TSOAs. The regulations and technical standard orders (TSOs) can be found at: http://rgl.faa.gov. This chapter provides general guidance on TSOA/LODA and airworthiness approval considerations specific to positioning and navigation equipment.
2-2. TSOA.
a. Several TS Os have been written for positioning and navigation-related equipment and components (see appendix 8 of this AC). New TSO’s will be written to address modernized GPS and other GNSSs once appropriate equipment standards are in place. It is beneficial to involve the ACO (both engineers and flight test pilots) in equipment evaluations as early as possible for four primary reasons:
(1) Obtaining a TSOA/LODA does not ensure that the equipment will satisfy all of the applicable operational requirements and/or airworthiness regulations when it is installed.
(2) The design of positioning and navigation equipment has become increasingly more complex and workload intensive with no standardized interface with the pilot. The human factors evaluation of the equipment is subjective.
(3) There is not one, single standard for interfacing positioning and navigation equipment to other equipment on-board the aircraft such as displays, autopilots, and terrain warning systems. Positioning and navigation equipment manufacturers should develop compatibility data relative to other equipment for inclusion within the installation manual.
(4) The installed intended function for the equipment needs to be compatible with the original design for the system, including software and hardware design assurance levels.
For example, a decision by the positioning and navigation equipment manufacturer to develop system software to RTCA, Inc. document (RTCA)/(DO)-178B, Software Considerations in Airborne Systems and Equipment Certification, dated December 1, 1992, Level C, may limit installation eligibility if that equipment contributes to failure conditions of other systems that perform critical functions to a higher software level.
b. It is recommended that the positioning and navigation equipment manufacturer elect to obtain an STC for equipment installation concurrent with obtaining the TSOA/LODA. This has proven to be an effective method to aid installations.
Note: Any applicant may apply for an equipment installation STC. It is not this paragraph’s intent to limit positioning and navigation STCs for installation solely to avionics manufacturers.
c. The installation manual and other data accepted during the TSO process can be used as a source of acceptable data to support an installation airworthiness compliance finding.
2-3. STC-Approved Model List (AML).
a. All STC applican ts are encouraged to use an AML for aircraft makes/models (including 14 CFR parts 23, 25, 27, and 29 aircraft) with similar characteristics and compatible equipment configurations to streamline the approval of subsequent installations. Applicants and ACOs need to contact the applicable directorate for specific policy and guidance information on obtaining an STC-AML.
b. Using the STC-AML method can simplify follow-on installations for makes/models on the AML. The installer needs access to the STC approved data; apply the approved data;
and comply with the detailed installation instructions. The installer then needs only complete FAA Form 337, Major Repair and Alteration (Airframe, Powerplant, Propeller, Appliance), identifying the nature of the change to return the aircraft to service (see AC 43.9-1 (latest revision), Instructions for Completion of FAA Form 337).
c. 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.
2-4. Type Certificate.
Position ing and navigation equipment manufacturers are also encouraged to work with TC holders. This has also proven to be an effective method to aid installations.