# AC 20-138A: Airworthiness Approval of Global Navigation Satellite System (GNSS) Equipment

- Type: Advisory circular (guidance, not mandatory unless a rule or AD requires it)
- Status: Historical
- Version in force: [AC 20-138D](https://openairdocs.org/ac/20-138), approved March 28, 2014. This is a historical version
- Approved: December 22, 2003
- Last reviewed: February 25, 2011
- Family: AC 20-138
- Cancels: [AC 20-138](https://openairdocs.org/ac/20-138)
- Cancelled by: [AC 20-138B](https://openairdocs.org/ac/20-138B)
- 14 CFR parts: 21, 23, 25, 27, 29, 43, 91, 121, 135
- Pages: 70
- PDF: https://openairdocs.org/files/sha256/df/30/df30d2135cf30c39050dc58e82d6462484db5fe36360c060e5e48411a3227ec6
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/8A2AE2491C85226F86256E35004C638B.0001
- DRS record last changed: November 22, 2025
- Page: https://openairdocs.org/ac/20-138A

## Versions

- [AC 20-138D](https://openairdocs.org/ac/20-138) (Current), approved Mar 28, 2014, 261 pages
- [AC 20-138C](https://openairdocs.org/ac/20-138C) (Historical), approved May 8, 2012, 194 pages
- [AC 20-138B](https://openairdocs.org/ac/20-138B) (Historical), approved Sep 27, 2010, 180 pages
- [AC 20-138A](https://openairdocs.org/ac/20-138A) (Historical), approved Dec 22, 2003, 70 pages
- [AC 20-138](https://openairdocs.org/ac/20-138?v=7EBC0EA8D6A2CFEE862569AF006AB97B) (Historical), approved May 25, 1994, 35 pages

## Text

Each page's text from the PDF; open the PDF at a page with #page=N.

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AC-20-138A

**AIRWORTHINESS APPROVAL OF GLOBAL**

**NAVIGATION SATELLITE SYSTEM (GNSS)**

**EQUIPMENT**

December 22, 2003

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**TABLE OF CONTENTS**

Paragraph Page

1. Purpose … 1

2. Cancellation … 1

3. Related Federal Aviation Regulations … 1

4. How to Use this Document … 1

5. Definitions … 1

6. Related Reading Materials … 3

7. Background … 6

8. Approval Process … 9

9. GNSS Equipment Limited to VFR Use … 12

10. TSO Authorizations … 13

11. Equipment Performance – GPS Antenna … 15

12. Equipment Performance – GNSS Sensor … 17

13. Equipment Performance – Stand Alone Navigation Equipment … 20

14. Equipment Performance – LAAS VDB Receiver … 24

15. Installation Issues – General … 24

16. Installation Issues – GPS Antenna … 25

17. Installation Issues – GNSS Sensor … 26

18. Installation Issues – Stand Alone Navigation Equipment … 28

19. Installation Issues – LPV and GLS Approaches … 33

20. Installation Issues – LAAS VDB Receiver … 34

21. Data Submittal … 35

22. Ground Test … 36

23. Flight Test … 38

APPENDIX 1: GPS Oceanic/Remote Navigation (3 pages) APPENDIX 2: Integration of GLONASS with GPS or GPS/WAAS (4 pages) APPENDIX 3: Example Format for a Quick Reference Guide (8 pages) APPENDIX 4: Sample Airplane/Rotorcraft Flight Manual Supplement (5 pages) APPENDIX 5: Installation of En Route GPS Equipment For VFR Use Only (2 pages) Page i (and ii)

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1. PURPOSE. This ad visory circular (AC) pr ovides guidance m aterial for t he airworthiness approval of Global Na vigation Satellite System (GNSS) equipm ent. Like all AC m aterial, th is AC is not m andatory and does not constitu te a regulation. It is issued for g uidance purposes and to outline a method of com pliance with the ru les. In lieu of following this method without deviation, the applicant m ay elect to follow an alternate m ethod, provided the alternate m ethod is also found by the Federal Aviation Administration (FAA) to be an accep table means of complying with the requirem ents of the federal aviation regulations (Title 14 of the Code of Fe deral Regulations, 14 C FR).

This AC addresses the following equipment:

a. GNSS sensors, including those incorpor ating Wide Area Augm entation System (WAAS), Local Area Aug mentation System (LAAS), or the Russian G lobal Navigation Satellite System (GLONASS).

b. GNSS stand-alone navigation equipm ent that provides deviations (steering commands) for en route, terminal, or approach operations (including Category I precision approach).

**2. CANCELLATION.**

a. AC 20-138, Airworthiness Approval of Global Positioning System (GPS) Navigation Equipm ent for Use as a VFR and IFR Supplem ental Navigation System , dated May 25, 1994, is canceled.

3. RELATED FEDERAL AVIATION REGULATIONS . 14 CFR Parts 21, 23, 25, 27, 29, 43, 91, 121, and 135.

4. HOW TO USE THIS DOCUME NT. This docum ent is organized into general categories of equipment and installations. Paragraph 8 summarizes the approval process and applies to all projects. Paragraph 9 applie s to GNSS as an aid to visual f light rules (VFR) navigation, while paragraphs 10 through 23 address instrum ent flight rules (IFR) navigation. Guidance concerning the equipm ent performance and functions is provided in paragraphs 11 through 14, and installati on guidance is provided in paragraphs 15 through 20. Paragraphs 21 through 23 provi de additional inform ation on the data submittal, ground test and flight test as they apply to an installation approval.

**5. DEFINITIONS.**

a. Aircraft-Based Augm entation Syste m (ABAS) . An augmentation sys tem that augments and/or integrates the information obtained from the other GNSS elem ents with information available on board the aircraft.

b. Ground-Based Augm entation System (GBAS). An augmentation sys tem in which the user receives augm entation in formation directly from a ground-based transmitter.

c. GLONASS. GLONASS is a Russian satellit e based radio navigation system, which provides a positioning se rvice anywhere in th e worl d. Until th e FAA declares GLONASS fully operational for U.S. aviation, it s use is lim ited to a supplem ent to GPS navigation. The FAA will declare GLONA SS fully operational after the sys tem Par 1 Page 1

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management and maintenance are mature. The following capabilities are expected before the FAA will declare GLONASS operational for U.S. aviation:

(1) Mature maintenance practices;

(2) Commitment to maintain a complete constellation of satellites; and

(3) Issuance of international NOTAMs prior to any scheduled maintenance, and after the onset of any unscheduled outages.

d. Global Navigation Satellite System (GNSS). The GNSS is a generic term for satellite-based navigation, including GPS, SBAS, GBAS , GLONASS, and any other satellite navigation system.

e. GNSS Landing System (GLS). A satellite-based navigation system that provides precision approach (including SBAS/WAAS and GBAS/LAAS).

f. Global Positioning System (GPS). GPS is a U.S. sate llite based radio navigation system that provides a precise positioning se rvice anywhere in the world. The service provided by GPS for ci vil use is defined in the GPS Standard Positioning System Signal Specification.

g. Local Area Augmentation System (LAAS). LAAS is the G BAS provided by the FAA.

h. Navigation. Within the context of this AC, navigation refers to any function used to direct the course of an aircraft. A navi gation system as addressed in this AC provides the functio ns of position estim ation, path definition, p ath steering , and situ ation indications and alerting to the flight crew.

i. Receiver Autonom ous Integrity Monitoring (R AIM). According to T SO-C129 (all rev isions (AR)), an y al gorithm which ve rifies the inte grity of the position output using GPS m easurements, or GPS m easurements and barom etric aiding, is considered a RAIM algor ithm. An algorithm which us es ad ditional inf ormation (e.g ., m ulti-sensor system) to verify the integrity of the position output m ay be acceptable as a RAIM- equivalent. Within this AC, the term RAIM is a synonym for ABAS and is used to refer to both RAIM or RAIM-equivalent algorithms.

j. Satellite-Based Augmentation System (SBAS). A wide coverage augm entation system in which the user rec eives augm entation inf ormation f rom a satellite-ba sed transmitter.

k. Special Category I (SCAT-I). In order to expedite the im plementation of satellite-based navigation, the aeronautical industry and the FAA in 1993 developed RTCA/DO-217, Minimum Aviation System Perfor mance Standards (MASPS) DGNSS Instrument Approach System: Special Category I . The F AA adopted this standard in Order 8400.11, IFR Approval for Differen tial Gl obal Position ing System Special Category I Instrument Approaches Using Private Ground Facilities . The inten t of SCAT-I is the sam e as LAAS, except it is li mited to Ca tegory I p recision approach and does not ensure interoperability between di fferent vendors. SCAT- I allows private facilities to be f ielded bef ore all of the issues associated with a public sys tem are Page 2 Par 5

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resolved. With the adoption of ICAO standards for LAAS in 2001, the SCAT-I standards became obsolete and should no longer be used.

l. Stand-alone. Stand-alone as addressed in this AC refers to navigation equipm ent incorporating the GPS or GPS/ WAAS position se nsor and a navigation function, so that the equipment provides path deviations relative to a selected path.

m. Wide Area Augmentation System (WAAS). WAAS is the SBAS provided by the FAA.

**6. RELATED READING MATERIALS.**

a. FAA Orders and Technical Standard Or ders (TSO). The following docum ents may be obtained from the Departm ent of Tr ansportation, FAA, Aircraf t Certif ication Service, Aircraft Engineering Divi sion, AIR-130, 800 Independence Avenue, SW ., Washington, D.C. 20591, or on the FAA Internet at http://av-info.faa.gov/tso/.

(1) TSO-C115b, Airborne Ar ea Navigation Equipm ent Using Multi-Sensor Inputs;

(2) TSO-C129a, Airborne Supplem ental Navigation Equipment Using the Global Positioning System (GPS);

(3) TSO-C144, Airborne Global Positioning System Antenna;

(4) TSO-C145a, Airborne Navigation Sens ors Using the Global Positioning System (GPS) Augmented by the Wide Area Augmentation System (WAAS);

(5) TSO-C146a, Stand-Alone Airborne Navigation Equipment Using the Global Positioning System (GPS) Augm ented by the W ide Area Augm entation System (WAAS);

(6) TSO-C161, Local Area Augm entation Sy stem Position ing and Navigation Equipment;

(7) TSO-C162, Local Area Augm entation Sy stem Very High Frequency Data Broadcast Equipment;

(8) Order 8400.11, IFR Approval of Differential GPS Spec ial Category I Instrument Approaches Using Private Ground Facilities; and

(9) Order 8400.12A, Re quired Navigation Perform ance 10 (RNP-10) Operational Approval.

b. FAA Advisory Circulars. The following documents m ay be obtained from the Department of Transportation, Subseque nt Distribution Office, SVC-121.23, Ardmore East Business Center, 3341 Q 75 th Ave, Landover, MD 20785. The A dvisory Circular Checklist (AC 00-2) is available at http:// www.faa.gov. T he advisory circular checklist contains status and order information for the FAA advisory circulars.

(1) AC 20-115B, Radio Technical Comm ission for Aeronautics, Inc. Document RTCA/DO-178B;

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(2) AC 20-129, Airworthiness Approval of Vertical Navigation (VNAV) Systems for Use in the U.S. National Airspace System (NAS) and Alaska;

(3) AC 20-130A, Airworthiness Approval of Navigation or Flight Managem ent Systems Integrating Multiple Navigation Sensors;

(4) AC 21-40, Application Guide for Obtaining a Supplem ental Type Certificate;

(5) AC 23-17A, System s and Equipm ent Gu ide f or Certif ication of Part 23 Airplanes;

(6) AC 23-1309-1C, Equipm ent, System s, and Installations in Part 23 Airplanes;

(7) AC 23.1419-2A, Certification of Part 23 Aircraft for Flight in Icing Conditions;

(8) AC 25-1309-1A, System Design and Analysis;

(9) AC 25.1329-1A, Automatic Pilot Systems Approval;

(10) AC 25.1419-1, Certification of Part 25 Aircraft for Flight in Icing Conditions;

(11) AC 43.13-1B, Acceptable Method s, Tec hniques and Practices – Aircraft Inspection and Repair;

(12) AC 43-13-2A, Acceptable Method s, Tec hniques and Practices – Aircraft Alterations;

(13) AC 90-79, Recomm ended Practices and Procedures for the Use of Electronic Long-Range Navigation Equipment;

(14) AC 90-94, Guidelines for Using GPS Equipm ent for IFR En Route and Terminal Operations & for Nonprecision Instrument Approaches;

(15) AC 90-96, Approval of U.S. Ope rators and Aircraft to Operate under Instrument Flight Rule s (IFR) in Europ ean Airspace Designa ted f or Basic Area Navigation (BRNAV/RNP-5);

(16) AC 91-49, General Aviation Procedures for Flight in North Atlantic Minimum Navigation Performance Specification Airspace;

(17) AC 120-29A, Criteria for Approving Ca tegory I and Category II Landing Minima for FAR 121 Operators. This AC supplements Appendix 2 of AC 120-29A with respect to the installation of GPS/WAAS Category I equipment;

(18) AC 120-33, Operational Approval of Airborne Long-Range Navigation Systems f or Flight within the North A tlantic Minimu m Navi gation Perfor mance Specification Airspace.

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c. RTCA, Inc. docum ents. The following docum ents m ay be purchased from RTCA, Inc., 1828 L Street, NW, Suite 805, Washington, DC 20036, or purchased on-line at http://www.rtca.org/.

(1) RTCA/DO-160D, Environm ental Conditions and Test Procedures for Airborne Equipment;

(2) RTCA/DO-178B, Soft ware Considerat ions in Airborne System s and Equipment Certification;

(3) RTCA/DO-200A, Standards for Processing Aeronautical Data;

(4) RTCA/DO-201A, Standards for Aeronautical Information;

(5) RTCA/DO-208, Minimum Operational Performance Standards for Airborne Supplemental Navigation Equipment Using Global Positioning System (GPS);

(6) RTCA/DO-228 with Change 1, Mi nimum Operational Performance Standards For Global Navigation Satellite System (GNSS) Airborne Antenna Equipment;

(7) RTCA/DO-229C, Minim um Ope rational Perform ance Standards for Airborne GPS/WAAS Equipment;

(8) RTCA/DO-236A, Minim um Avia tion Sy stem Perfor mance Standards:

Required Navigation Performance for Area Navigation;

(9) RTCA/DO-246B, GNSS Based Precisi on Approach Local Area Augmentation System (LAAS) Signal-in-Space Interface Control Document (ICD);

(10) RTCA/DO-253A, Minimum Operational Performance Standards for GPS Local Area Augmentation System Airborne Equipment;

(11) RTCA/DO-257A, Minimum Operational Performance Standards for the Depiction of Navigation Information on Electronic Maps.

d. The FAA and Industry Guide to Avionics Approvals, April 13, 2001. Copies of this docum ent m ay be obtained at http://www1.faa.gov/certification/aircraft/avionics_approvals_guide.htm.

e. GPS Standard Positioning Service Performance Standard, October, 2001. Copies of this docum ent and general infor mation related to GPS may be requested at http://www.navcen.uscg.gov/.

f. Department of Defens e Interface C ontrol Docum ent (ICD) ICD-GPS-200C, Navstar GPS Space Segment/Navigation User Interface. Copies of this document may be requested from the GPS Joint Program O ffice, SSD/CZ, Los A ngeles AFB, CA 90006.

Alternatively, copies of this document may be requested at http://www.navcen.uscg.gov/.

g. National Imagery and Mapping A gency (NIMA) Technical Report NIMA TR 8350.2, W orld Geodetic System 1984, Its Defin ition and Relationships with Lo cal Geodetic Systems. Copies of this document may be requested at http://www.nima.mil/.

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h. FAA National Airspace System Architecture Version 4.0. An electronic version of this docum ent and architecture upd ates is availab le at http://www.faa.gov/nasarchitecture/.

i. FAA Specification W ide Area Augm entation System ( WAAS), FAA- E-2892B.

This docum ent is available on-line at http://www2.faa.gov/asd/international/GUIDANCE_MATL/2892b_c1.pdf.

j. DOD/DOT 2001Federal Radionavigation P lan (FRP). The FRP is published every two years in which copies m ay be ordered through the National Technical Information Service, Springfield, VA 22161; internet: http://www.ntis.gov/.

k. DOD/DOT 2001 Federal Radionavigation Systems (FRS). The FRS is published every two years in which copies m ay be ordered through the National Technical Information Service, Springfield, VA 22161; internet: http://www.ntis.gov/.

**7. BACKGROUND.**

a. Global Positioning System (GPS).

(1) System Descrip tion. The Global Position ing System is a satellite based radio navigation system, which broadcasts a sign al that is used by receivers to determine precise position anywhere in th e world. Th e rec eiver tracks m ultiple sa tellites and determines a pseudorange m easurement that is then used to determ ine the user location.

A m inimum of four satellites are n ecessary to estab lish an accurate th ree-dimensional position. The Department of Defense (DOD) is responsible fo r operating the GPS satellite constellation and m onitors the GPS satellites to ensu re proper operation. Every satellite's orbital parameters (ephem eris da ta) are sent to each sate llite f or broadcas t as part of the data message embedded in the GPS signal. The GPS coordinate system is the Cartesian earth-centered earth-fixed coordi nates as specified in the W orld Geodetic System 1984 (WGS-84).

(2) System Availability and Reliability.

(i) The status of GPS satellites is bro adcast as part of the data m essage transmitted by the GPS sate llites. GPS status information is also available by means of the U.S. Coast Guard navigation infor mation service: (703) 313-5907, Internet:

http://www.navcen.uscg.mil/gpsnotices/. Add itionally, s atellite s tatus is available through the Notice to Airmen (NOTAM) system.

(ii) The operational status of GNSS opera tions depends upon the type of equipment being used. For GPS-only equipm ent TSO-C129(AR), the operational status of nonprecision approach capability for flight planning purposes is provided through a prediction program that is embedded in the receiver or provided separately.

(3) Receiver Autonom ous Integ rity Mon itoring (RAIM). W hen GNSS equipment is not using integrity inform ation from WAAS or LAAS, the GPS navigation receiver using RAIM provides GPS signal integrity monitoring. RAIM is necessary since delays of up to two hours ca n occur before an erroneous satellite transm ission can be detected an d corrected by the satellite con trol segm ent. The RAIM function is also referred to as fault detection. Another capabili ty, fault exclusion, refers to the ability of Page 6 Par 6

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the receiver to exclude a failed satellite from the position s olution. Fault detection and exclusion (FDE) is provided in ocea nic/remote GPS e quipment (Appendix 1, paragraph 2b of this AC) and in all GPS/WAAS equipment.

(4) Selective Availability. Selective Availability (SA) is a method by which the accuracy of GPS is intentionally degraded. This feature is designed to deny hostile use of precise GPS positioning data. SA wa s discontinued on May 1, 2000, but m any GPS receivers are designed to assum e that SA is still active. New receivers m ay take advantage of the discontinuance of SA base d on the performance values in ICAO Annex 10, and do not need to be designed to operate outside of that performance.

(5) GPS Modernization. Initiatives to modernize the Global Positioning System include two new civilian signals. One of the new signals will be cen tered at 117 6.45 MHz, and will prov ide an im proved serv ice that supports safety-of-life applications, including aeronautical app lications. The other new si gnal will be centered at 122 7.60 MHz, and will be available for general use in non-safety cr itical applications. Depending on the rate of GPS satellite launches, initial operating capability will be available between the years 2012 and 2015.

(6) System Performance. The GPS perform ance specifications contained in this AC are based upon unaugm ented perform ance ach ieved w ith the Standard Positioning Service (SPS). GPS perform ance for a repr esentative single-frequency receiver, as defined in the GPS SPS Performance Standard, is summarized in the following table.

Table 1. Summary of GPS Performance Availability Unspecified Horizontal Navigation System Accuracy (95%) 33 m Vertical Navigation System Accuracy (95%) 73 m SIS Integrity Unspecified Service Volume Global

(7) General Operational Limitations.

(i) TSO-C129(AR) equipm ent: the requirements defined in TSO-C129(AR) were developed for GPS to be used in addition to other navigation equipment.

(ii) GPS Oceanic/Remote operation: the requirements specified in appendix 1 of this AC were developed for GPS to be used for lim ited operations (e.g.

oceanic/remote operations as discussed in AC 90-94) without th e need for other navigation equipment appropriate to the route to be flown.

(8) Equipment Classes. TSO-C129(AR) defi nes different classes of equipment to support different equipm ent configurations . These classes are defined in paragraph

(a)(2) of TSO-C129(AR).

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b. Satellite-Based Augm entation Syste m (SBAS) . To i mprove the accuracy, integrity and availability of GPS signals, ICAO has defined Standards and Recommended Practices (SARPs) for satellite-based augmentation system s (SBAS). The FAA developed the W ide Area Augm entation Syst em ( WAAS) to provide SBAS service throughout U.S. airspace. In addition, the FA A is working with civil aviation authorities in Europe and Japan to coordinate the de velopment of their SB AS, (the European Geostationary Navigation Ov erlay System , or EGNOS, a nd the Japan Multifunctional Transport Satellite (MTSAT) Satellite-based Augmentation System, or MSAS).

(1) WAAS Description.

(i) The WAAS uses measurements from a wide area network of reference stations to determ ine satellite cloc k a nd ephem eris corrections and to m odel the propagation effects of the ionosphere. A m onitoring system ensures that the SBAS i s operating c orrectly and that the co rrection inf ormation is corre ct. This inf ormation is broadcast to users via a geosta tionary satellite, using a signal that is simila r to the GPS signal. Sinc e the SBAS satellite sig nal is similar to GPS, it also provide s an additio nal pseudorange measurement to the receiver. The objectives of WAAS are:

(A) to improve the integrity of GPS through real-time monitoring;

(B) to im prove the av ailability of GPS by providing an ad ditional satellite signal; and (C) to im prove the accuracy of GPS by providing differential corrections.

(ii) WAAS provides a level of service th at supports all pha ses of flight including LNAV/VNAV and L PV appro aches. Both LNAV/VNAV and LP V approaches are approach procedures with ve rtical guidance as defined in ICAO Annex 6.

These approaches provide vertical guidance, but do not meet the more stringent standards of a precis ion approach . In th e lo ng term , W AAS will provide Ca tegory I p recision approach services in conjunction with m odernized GPS. The FAA pla ns to decommission a significant percentage of its existing VOR and ILS inf rastructure after WAAS services are av ailable. Although re quirements for surface op erations are not mature, GPS/WAAS is expected to m eet those requirements for a variety of surveillance and navigation applications.

(2) WAAS Availab ility and Reliability. The FAA will provid e NOTAMs to advise pilots of the status of the WAAS. This will also include NOTAMs advising if the operational capability of GPS/WAAS equipment is degraded. WAAS monitors both GPS and WAAS satellites and provides integrity.

(3) WAAS Per formance Requirem ents (w ithin Service Vo lume). W AAS performance defined in this AC is based on a single frequency user as defined in FAA-E2892B. The performance of WAAS is summarized in the following table.

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Table 2. Summary of WAAS Performance En route through Nonprecision Approach LPV Availability 99.999% 99.9% Horizontal Navigation System Accuracy (95%) 33 m

16 m Vertical Navigation System Accuracy (95%) Unspecified 20 m SIS Integrity Probability of misleading information in an hour = 10- 7 Probability of misleading information during an approach = 10-7 Service volume U.S. Airspace Contiguous U.S., parts of Alaska

(4) WAAS General Operational Limitations. The requirements were developed for GPS/WAAS to be used within the SBAS coverage without the need for other radio navigation equipm ent appropriate to the r oute to be flown. Outside of the SBAS coverage, GPS/WAAS equipment reverts to GPS-only operation.

(5) WAAS Equipm ent Classes. RTCA /DO-229C, sectio n 1.4, defines the different classes of GPS/ WAAS equi pment to support different equipm ent configurations.

c. Ground-Based Augm entation System (GBAS) . To im prove the accuracy, integrity and availability of GPS signals, ICAO has defined Standards and Recommended Practices (SARPs) for ground-based augm entation system s (GBAS). The FAA developed the Local Area Augm entation Syst em (LAAS) to provide GBAS service at designated airports throughout the U.S. Th e LAAS is intended to support a level of navigation service that require s g reater p erformance than that prov ided by WAAS.

LAAS is being developed to ensure interopera bility. Sim ilar to th e WAAS concept that incorporates the use of comm unication satellites to broadc ast a correction m essage, the LAAS will broadcast its cor rection m essage via very high f requency (VHF) radio broadcast f rom a groun d-based tr ansmitter. Th e loc alized coverage ar ea will sup port multiple operations to an airport. The LAAS will complement WAAS at locations where WAAS is unable to m eet existing navigation and landing requirements. As the LAAS i s further developed, it will provide a level of service sufficient to support CAT II/III precision approach and landing operations.

8. APPROVAL PROCESS . This paragraph describes the general approval process applicable to GNSS e quipment intended for IFR navigation (paragraph 9 provides guidance addressing installati on of GNSS equipm ent for VF R use). Unique approval issues associated with G PS for Oceanic/R emote Navigation and GLONASS are defined in appendices 1 and 2, respectively.

a. TSO Authorization (TSOA).

(1) Several TS O’s have been written for GNSS-related equipm ent and components (reference paragraph 6a of this AC ). While the TSO process operates on the basis of self-certificatio n by the ap plicant, it is beneficial to involve the ACO (both Par 7 Page 9

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engineers and flight test pilots) in the evaluation of the equipment as early as possible for two primary reasons:

(i) Obtaining a TSOA does not ensure that the equipment will satisfy all of the applicable requirements when it is installed; and

(ii) The design of GNSS 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.

(2) It is recomm ended that the m anufacturer elect to obtain an STC for their equipment concurrent with obtaining the TS OA. This has proven to be an effe ctive means of involving the ACO and identifying issues associated with installing the article.

(3) The installation guidelines should refere nce standard practices used in the installation and should address the unique GNS S issues in paragraphs 11 through 20 of this AC. The installatio n instructions should identify each in stallation configuration that is supported, including the GNSS antenna(s), each autopilot make/model, other GNSS or RNAV equipm ent that is insta lled o n the ai rcraft, and any other articles to which the equipment will in terface (e.g., ex ternal swit ches, barometric altim eter, TAW S). In addition, the installation instructions shoul d address the critical areas unique to each installation, such as antenna placem ent, unit placem ent (for controls/display ), and electromagnetic compatibility.

(4) The operations m anual must address th e operation of the equipm ent. For installations accomplished in accordance with the installation instructions, the operations manual should also cover the operation of related com ponents (e.g., rem ote source selector) for every installation configuration. If there any lim itations associated with the operation of the equipm ent, a sample Airp lane/Rotorcraft Flight Manual Supplem ent (A/RFMS) should also be provided (e .g., the TSO-C129(AR) lim itation for other navigation equipment appropriate to the route to be flown).

b. First-Time Airworthiness Approval . Each TSO’d article should obtain a firsttime airworthiness approval through TC or STC.

(1) The initial certification of GNSS e quipment involves extensive engineering and flight test evaluations as described in paragraphs 11 through 23 of this AC.

Applicants are encouraged to obtain AC 21-40, an Application Guide for Obtaining a Supplemental Type Certificate.

(2) It is recomm ended that the ACO reque st a S pecial Certification Review (SCR) Team when evaluating GNSS stand-alon e navigation equipment for the first tim e, typically as part of an STC. The SCR team should be coordinated through AIR-130. The team assists in applyin g a comm on stand ard, which will result in a more consistent evaluation.

c. Installation of GNSS Equipm ent. For installation of TSO’d articles after the first-time STC, the extent of FAA involve ment and review for a given installation depends on the characteristics of the installation. The insta ller should comply with the guidelines described in paragraph 15 th rough 20, and should ensure continued compliance with the relevant certification regulations.

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(1) Evaluation of installation. The installa tion should be evaluated to classify the installation and determine the type of approval vehicle. The following guidelines are provided:

(i) Major change to type design: Pe r 14 CFR Part 21.93, the applicant should determine if the installation has an appr eciable effect on the st ructural strength or operational characteristics affecting the airwor thiness of the product. An exa mple is installation in m ultiple-pilot aircraft where an other, dissimilar area navigation system is also installed (see paragr aph 18f), which should be thoroughly evaluated under the TC/STC process unless interm ixing of the sa me GNSS equipment was part of the initia l design approval or specifically addresse d under an approved m odel list (e.g., the Brand-A, model X instructions m ay adequately address intermixing with Brand-A model Y equipment).

(ii) Major alteration: Per 14 CFR Part 43 Appendix A, installation of GNSS equipment m ay be a m ajor alteration requir ing FAA-approved data pertinent to that installation. For example, insta llation of the GNSS antenna m ay im pact structural strength, and the GNSS equipm ent m ay be co nnected to other equipm ent that has not been previously determined to be compatible or for which the installation instructions are not adequate to ensure com patibility under all conditions. If the installation is determined to be a m ajor alteration, the appl icant can obtain an STC or a field approval using FAA Form 337 (Major Repair and Alteration).

(iii) Minor alteration: Under the origin al AC 20-138, installation of GPS equipment required the use of approved data (u nder an STC or m ajor alteration) because GPS was a new and unique technology. However, since GPS technology is now common and considerable experience has been obtained in the installation of GPS, approved data for every installation is no longer appropriate. Instead, installations that do not qualify as major alterations above should be accom plished as minor alterations. These installations should be based on acceptable data including the following:

(A) Data previously approved as app licable to the aircraft (e.g., STC, Approved Model List).

(B) Data previously approved as applicable to a dif ferent make/model aircraft (e.g., an initial STC obtained by the equipm ent m anufacturer), provided the installation is installed in accordance with the manufacturer’s instructions, any equipment interfaces are adequately address ed in th e installation instructions for the GNSS equipment and the equipm ent with which it is interfacing, and the equipm ent is installed in accord ance with the guidelin es in this AC. For exam ple, installation of GNSS navigation equipm ent that only interfaces w ith an antenna, power, ground, an external HSI/CDI with a single source selector switch, a nd a left/right (deviation-based) autopilot would typically be considered a minor alteration.

(2) For these installations, any A/RFM(S) associated with the original approved data should be used as the basis f or an A/ RFM(S) for this inst allation. Lim itations imposed on the GNSS equipm ent during the initial approval should be i mposed for follow-on equipm ent approval unless an FAA re-evaluation of the relevan t is sues determines that they do not apply. An A/RFM(S) is not necessary if it was not part of the original installation, if the operating m anual addresses the use of the equipm ent and Par 9 Page 11

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associated installed component s (e.g., rem ote source selecti on), and there are no unique limitations associated with the particular installation.

(3) The installation perform ance tests (paragraphs 22 and 23) m ust be successfully completed. The installation perf ormance tests are usually conducted in two parts, the ground checks and the flight checks. T he aircraft can be approved for return to service following the require d ground checks, however the GNSS equipm ent cannot be used for flight under Instrum ent Flight Ru les (IFR) until the flight checks have been accomplished and would have to be placarded as such.

(4) Upgrading previously-approved installations.

(i) WAAS Upgrade. GPS TSO-C129(AR ) equipment may be upgraded to TSO-C145a or TSO-C146a compliance. Manufacturers who provide an upgrade path are encouraged to use an approved m odel list to stream line the approval of subsequent installations. The guidance in paragraph 8c(1 ) also applies to the upgrade of previously installed equipment.

(ii) Additional GNSS equipm ent. Som e applicants ar e expe cted to re tain existing TS O-C129(AR) equipm ent and add TSO-C146a equipm ent. Com patibility between the equipm ent should be established in accordan ce with paragraph 18f. The original TSO-C129(AR) installation should not be re-evaluated, except f or modifications made as part of the TSO-C146a installation. The re-evaluation should be to the affected functions or perform ance. For example, if the equipment shares a GNSS antenna there will be additiona l signal loss f or the original equipment and com pliance to the o riginal TSO-C129(AR) installation instructions should be verified.

(iii) Re-use of GNSS antenna. W AAS or LAAS equipm ent may be added to an airc raft (as an addition or as m odification to existin g GPS equipm ent) with a previously installed GNSS antenna. This m ay be accomplished by including the antenna under the WAAS or LAAS TSO authorizati on, by establishing com patibility under the WAAS or LAAS TSO authorization, or de monstrating com patibility a t tim e of installation (see p aragraph 17a). I f a W AAS or LAAS TSOA holder dem onstrates compatibility with a previously-approved antenna (approved under TSO-C129(AR)), the installation instructions should state the part number of the compatible antenna. Note that compatibility to support LPV or GLS operations cannot be addressed without new design data on the antenna (see paragraph 11e).

(iv) Marking. When equipm ent is u pgraded to a new TSO (e.g., from TSO-C129(AR) to TSO-C146a), the m arking must be modified to reflect the new configuration and approval. This marking ch ange can be accom plished by a certificated person in accordance with the T SO authoriz ation holder’s instru ctions (e.g., service letters or service bulletins). A certificated person in this context is defined as one who is authorized under 14 CFR section 43.3, Persons authorized to perform m aintenance, preventative maintenance, rebuilding, and alterations.

9. GNSS EQ UIPMENT LIMITED TO VFR USE. GNSS equipm ent m ay be installed on a no-hazard basi s as a supplem ent to VFR navigation. S uch installations need only to verify that the GNSS installation does not introduce a hazard to the aircraft

(e.g., properly secured for crashworthiness, not com bustible, etc). GNSS installations limited to VFR USE ONLY should be evaluated under the criteria described in paragraph Page 12 Par 8

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8c(1) to classify the type of aircraft/appliance m odification. The only exception is that, for installations where the GNSS equipm ent does not in terface with other equ ipment (except a dedicated remote indicator if app licable), the installation can be accom plished without any reference to previously approve d data (i.e., the equipm ent does not need a TSO or prior STC). Installa tion guidelines for such an in stallation are prov ided in appendix 5 of this AC. Loss of or m isleading VFR navigation information is considered a m inor failure condition; therefore, Soft ware Development Assurance Level D is acceptable. A readable placard stating "GPS limited to VFR use only" must be installed in clear view of the pilot, unless th e equipment automatically displays this m essage on start-up and pilot ac tion is required to clea r the message. An A/RFM(S) is not required since the placard or display contains the equipment limitation.

10. TSO AUTHORIZ ATIONS. This paragraph provides guidance on granting TSO Authorizations f or GNSS-rela ted equipm ent. Only issues that are u nique to G NSS equipment are discussed.

a. Applicability of TSO-C129(AR).

(1) TSO-C129(AR) define an accep table standard for GPS equipm ent intended to be used as a supplement to other navigation systems.

(2) There is no plan to cancel TSO-C129a , and m anufacturers may continue to obtain new TSO authorizations un der TSO-C 129a. In addition, th ere is no plan to withdraw TSO-C129(AR) authorizations, so manufacturers of TSO-C129(AR) equipment can continu e to m anufacture that equipm ent, and the equipm ent is still eligib le f or installation in accordance with the guidance in this AC.

b. Multiple TSO Authorizations. Multiple TSO authorizations m ay be granted for equipment that accomplishes multiple functions. However, the num ber of TSO markings on GNSS e quipment should be m inimized to avoid confusion during installation and approval. T he following com binations of TS O authorizations should not be granted, as the TSOs either contradict each other or are superfluous to a TSO with broader scope:

(1) TSO-C129(AR) must not be combined with TSO-C145a or TSO-C146a;

(2) TSO-C145a m ust not be com bined with TSO-C146a Class 1, 2 or 3 equipment. The com bination of TSO-C145a with TSO-C146a Class 4 equipm ent is permitted; and

(3) TSO-C146a must not be combined with TSO-C115(AR).

(4) Any class of TSO-C129(AR) may be combined with TSO-C161, and should be marked accordingly.

c. TSO-C145a and TSO-C146a Deviations.

(1) Under TSO-C129(AR), m any deviat ions have been granted to manufacturers due to the relative immaturity of the TS O, which significantly mod ified the industry standard (RTCA/DO-208). A pplicants for TSO-C145a and TSO-C146a should not expect the sam e latitude when requesting deviatio ns. These TSOs are based on the industry standard (RTCA/DO-229C) wh ich has been internationally harmonized and received a good deal of scrutiny since it was first published in January 1996.

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(2) When requesting a deviation to these TS Os, the applicant must substantiate how their implem entation is equivalent. A primary objective of RTCA/DO-229C is to standardize the interface a nd provide com patibility across equipm ent from different manufacturers. Therefore, the statem ent of e quivalency for deviations to the pilot interface requirem ents must also include how the im plementation is operation ally compatible with other GPS/WAAS equipment.

(3) Deviations that are granted to these TSOs will be made available and will be incorporated into the ne xt revision of the TSO to ensure th at all m anufacturers have the same opportunity to deviate.

d. Technical Data. Paragraph 9c of Order 8150.1A, Technical Standard Order Procedures states that the ACO m ay elect to do a cursory review of the TSO subm ittal package. Due to the complexity of GNSS equipment, the ACO should:

(1) Evaluate manufacturer supplied bench test data on the equipm ent and verify that the tests com ply with the relevant procedures a nd requirem ents (TSO-C129, and sections 2.4 and 2.5 of RTCA/DO-229C and RTCA/DO-253A as applicable) and that the equipment has passed applicable tests.

(2) Verify co mpliance with the appropr iate environm ental qualification standards and tests in RTCA/DO-160(AR).

(3) Verify compliance to th e design assurance levels consistent with the f ailure condition hazard classification. If the criteria in AC 23-1309-1C for different Classes of Part 23 airc raft is app lied, the ins tallation in structions m ust inc lude a summary of the approval and a lim itation. For exam ple, TSO-C146a Class 3 equipm ent (GPS/WAAS precision approach stand-alone equipm ent) with software devel oped to RTCA/DO-178B Level C would state the following:

“This equipment complies with p aragraph 3a of TSO-C146a for Class I, II, and III aircraft as defined in AC 23-1309-1C. This equipm ent is not eligible for installation in Part 25 or Part 23 Class IV airc raft unless the precision approach m ode is disabl ed through the following equipm ent configuration setting: ….”

(4) Verify compliance with the appropriate software qualification standards and tests in RTCA/DO-178B.

(5) Verify the approval of a data pro cess capable of updating the navigation database for GNSS stand-alone naviga tion equipm ent (TSO-C129(AR) Class A, TSO-C146a). RTCA/DO-200A defines an acceptable m eans of e nsuring that th e aeronautical data process does not corrupt data, from the publication of data by a State to its application in the equipment. The data quality requirements must be defined, including any lim itations or inco mpatibilities between the navigation functi on and the database

(e.g., incompatible ARINC 424 leg types, leg length limitations).

(6) The ACO should review the installati on manual. The m anufacturer should include all known installation limitations, and speci al attention should be given to reviewing those limitations in light o f the var iety of different instal lation configurations that are supported.

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(7) For TSO-C146a, the pilot’s guide should be reviewed by an FAA flight test pilot f amiliar with the equipm ent to ensure it is com plete, con cise, and eas y to understand.

(8) For TSO-C146a, the quick reference guide should be review ed by an FAA flight test pilot familiar with the eq uipment. Recommended f ormat and content f or this guide can be found in appendix 3 of this AC.

(9) For TSO-C146a, the training program should be reviewed by an FAA flight test pilot familiar with the equipment. This training program may be a series of manuals, a videotape, interactive CD-ROM, etc. Due to the inherent complexity in area navigation operations, it is im portant that these training materials are useful and help pilots learn to operate the equipment.

e. Major/Minor Design Changes. The following changes are among those generally considered by the FAA to be major ch anges (per 14 CFR Part 21.611). After consultation with the ACO on a specif ic change, the ACO and manufacturer m ay determine that particular change is a minor design change.

(1) Changes to the navigation or integrity algorithms; and

(2) Changes to navigational display form ats and navigation/function operating procedures.

11. EQUIPMENT P ERFORMANCE – GPS ANTE NNA. This paragraph provides guidance related to the basic functions a nd perfor mance of the GNSS antenna. The antenna does not have to be installed in an ai rcraft to com ply with the m eans defined in this paragraph. Typically, this guidance will be applicable to the m anufacturer who is seeking a TSO Authorization (TSOA). If th e manufacturer does not obtain a TSOA, this paragraph would apply as part of the initial airworthiness approval. These issues do not need to be revisited for antennas that hold a previously granted TSO authorization under TSO-C129(AR) or TSO-C144, or minor m odifications to such equipment. However, the applicant may elect to address these issues to demonstrate that the antenna is compatible with a WAAS or LAAS installation.

a. TSO-C144, Airborne Global Positio ning System Antenna, defines an acceptab le means of com pliance for a GNSS antenna. Applicants shou ld com ply with RTCA/DO-228, Change 1.

b. Antennas authorized under TSO-C129(AR). A num ber of antennas were authorized u nder TSO-C129(AR), before TS O-C144 becam e available. This paragraph addresses the performance of these antennas.

(1) Antennas authorized as part of GPS receiver TSOA. Antennas authorized in conjunction with a GPS receiv er under TSO- C129(AR) m ay continue to be in stalled along with the associated receiv er. These antennas m ust not be installed with a different receiver unless the antenna part number is listed in the receiver installation instructions as being compatible.

(2) Antennas authorized independently fr om a GPS receiver. TSO-C129(AR) does not provide an adequate standard to en sure interoperability between GPS antennas, Par 10 Page 15

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and m ust not be applied to anten nas wit hout reference to a specific GPS receiver.

However, some antennas have been approve d under an authorization to TSO-C129(AR) without reference to a specific GPS receiver. These antennas should not be installed with any new receivers (i.e., one for which a pr evious TC/STC does not exist) unless the antenna part number is listed in the receiver installation instructions as being compatible.

Antenna manufacturers should obtain TSO-C144 for their antennas as quickly as practical to ensure compatibility with receiver equipment and to facilitate installation.

c. Lightning Qualification. The RTCA/DO-160D category for lightning induced transient su sceptibility that bes t represents the trans ient induced in the antenna cable during the Direct Effects of Lightning test (Section 23 of RTCA/DO-160D) should be identified for comparison to the receiver susceptibility at time of installation.

d. Signal Power/Loss. The following issues should be addressed in the installation instructions.

(1) Passive antennas authorized under T SO-C144. Passive antennas are those without a pream plifier (reference RTCA /DO-228, section 2.2.1). The m aximum (and minimum, if applic able) signal loss between the antenna output por t and receiver input port must be defined, to yield the m aximum and minimum receiver s ensitivities defined in section 2.1.1.10 of RTCA/DO-229C. This information should be described as a function of the type and lengths of interc onnecting cable and type and num ber of connectors or specified as the limit of cable loss in dB.

(2) Active antennas authorized under T SO-C144. An active antenna is defined as one that includ es a low noise power am plifier as p art of the antenna ass embly (reference RTCA/DO-228, section 2.2.2). The inst allation instructions must identify the maximum a nd m inimum output power (m ay be specified as pre-am plifier gain) and amplifier noise figure. These guidelines can be compared to the minimum and maximum power inputs defined in the GNSS receiver in stallation instructions. Guidelines on the loss associated with reco mmended cables and co nnectors should be provided so that the installer can determ ine the m aximum and m inimum signal power at the receiver port.

This range will be compared to the range specified by the GNSS receiver manufacturer at time of installation. In addition, the installation ins tructions shou ld identify any conditions under which out-of-band em issions (e.g., SATCOM) c an create in-band intermodulation products that may interfere with receiver operation.

(3) Antennas authorized w ith a specif ic receiver (TSO-C145a, TSO-C146a, TSO-C161). The installation instructions m ust identify the m aximum (and m inimum, if applicable) signal loss between the antenna ou tput port and receiver input port to yield the m aximum and m inimum receiver sensitiv ities def ined f or the rece iver. This information should be described as a function of the type and lengths of interconnecting cable and type and number of connectors or specified as the limit of cable loss in dB.

e. Differential Group Delay. The differential group dela y is defined within section

2.1.4.5 of RTCA/DO-229C and section 2.3.6.4. 1of RTCA/DO-253A. The differential group delay of the antenna m ust be docum ented in the installation instructions for those antennas intended to support LPV and GLS approach operations. Antennas have filters that could affect the d elay. The dif ferential group delay of the antenna is defined in section 2.2.3 of RTCA/DO-228.

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12. EQUIPMENT PERF ORMANCE – GNSS SENSOR. This paragraph provides guidance related to the basic functions a nd perfor mance of the GPS sensor, including those sensors that integrate W AAS or LAAS. This paragraph also applies to sensors embedded within stand-alone navigation eq uipment. A ppendix 2 provides unique guidance material for GPS sensors that inte grate GLONASS. The sensor does not have to be installed in an aircraft to com ply with the m eans defined in this paragraph.

Typically, this guidanc e will be ap plicable to the m anufacturer who is seeking a TSO Authorization (TSOA) for TSO-C129a, TSO-C145a, TSO-C146a, TSO-C161, or TSO-C162. If the m anufacturer does not obtain a TSOA, this paragraph would apply as part of the initial airwor thiness approval. These issues do no t need to be rev isited f or equipment that holds a previously grante d TSO authorization under TS O-C129(AR), or minor modifications to such equipment.

a. Acceptable Means.

(1) GPS. TSO-C129(AR) defines an accep table means of com pliance for GPS equipment that is inten ded to supp lement other navigation equipm ent on the aircraft.

With one exception, GPS equipment that complies with this standard has a limitation that the aircraft must be equipped with other m eans of navigation appropriate to the route to be flown. The exception is the use of this equipment for oceanic and remote operation, if several additional features are provided as described in appendix 1 of this AC.

(2) GPS/WAAS. TSO-C145a and TSO-C146a, which reference RTCA/DO-229C, define an accep table m eans of com pliance for this equipm ent whe n operating in GPS or GPS/ WAAS modes. RTCA/DO-229C is a complete set of standards for GPS a nd GPS/ WAAS. While applic ants m ay elect to use portions of RTCA/DO-229C to supplement the earlier standards for TSO-C129(AR) equipment, it is not appropriate to obtain TSO-C129(AR) au thorization in conjunction with TSO-C145a or TSO-C146a equipm ent. GPS/ WAAS equipment that com plies with the standa rds in DO-229C does not have a lim itation that the ai rcraft must be equipped with other m eans appropriate to the route to be flown.

(3) GPS/WAAS/LAAS sensor. TSO -C145a and TSO-C146a define an acceptable m eans of com pliance f or th is eq uipment when operating in th e GPS or GPS/WAAS m odes. When operating in th e G PS/LAAS mode, the equipm ent should comply with the requirements of TSO-C161 and Section 2 of RTCA/DO-253A.

(4) GPS/LAAS. TSO-C129(AR) and TSO-C145a define two acceptable m eans of compliance for this equipment when operating in GPS mode (i.e., outside the coverage of a selected LAAS ground facility). W hen operating in the GPS/L AAS m ode and conducting a GLS approach, the equipm ent mu st com ply with the requirem ents of Section 2 of RTCA/DO-253A. When operating in GPS/LAAS mode and not conducting a GLS approach, the equipm ent m ust comp ly with the sensor requirem ents of RTCA/DO-253A (for position, velocity and time) and the navigation requirem ents of TSO-C129(AR). For Class B1 and B2 equipm ent, the requirem ents in TSO-C129(AR) paragraph (a)(4)(vii) do not apply when a LA AS-correction position is being used. For Class C1 and C2 equipment, the requirements in TSO-C129(AR) paragraph (a)(5)(vii) do not apply when a LAAS-corrected position is being used. GPS/LAAS equipm ent carries Par 12 Page 17

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the basic GPS lim itation that th e airc raft must be equipped with other m eans of navigation appropriate to the route to be flown.

b. Compatible GNSS Antennas . Compatible antennas should be identified. This may include a generic reference to TSO-C144- compliant antennas, re fer to a specific GNSS antenna (part number) that is included as part of the receiver design approval (e.g., part of receiver TSOA), or a part of another receiver design approval (also by part number). When using an antenna that is pa rt of a separate design ap proval, the receiver manufacturer should use the antenna specifi cation provided by the antenna m anufacturer and should coordinate the com patibility finding with the antenna m anufacturer.

Otherwise, m inor design changes to the antenna could be m ade by the antenna manufacturer that would adversely impact the operation of the GNSS equipment.

c. Non-Standard Mask Angle. All equipment has a mask angle, the elevation angle above the horizon at which the GNSS receiver c onsiders satellites for use in the so lution.

The accuracy and reliability of GPS signals is affected by a num ber of factors, inclu ding shadowing of the signal (by a portion of the aircraf t or loc al terrain), the GPS antenna gain and atmospheric effects (ionosphere and troposphere).

(1) A 5 degree m ask angle is standa rd (7.5 degree m ask angle for TSO-C129(AR)). Sensors may track a satellite below 5 degrees, but must not incorporate it in the navigation position soluti on unless the accuracy is d emonstrated for satellites at the design m ask angle. The sensor m ay use a weighted position solution, w hich deweights satellites at low elevation angles based on the accuracy demonstrated for those elevation angles.

(i) For equipment that ass umes that GPS selective availability is activ e (assumed pseudorange accuracy of ≥33m r ms), the ionospheric, tropospheric, and airframe multipath errors can be considered ne gligible down to 2 degre es. The use of a mask angle below 2 degrees requires validation of the error models for these effects.

(ii) For GPS equipm ent that takes adva ntage of the discontinuance of selective availability (assu med pseudorange accuracy of <33m r ms), the aviation community has validated error m odels down to a 5 degree m ask angle (see RTCA/DO-229C, Appe ndices A and J). The use of a m ask angle below 5 degrees requires validation of the error models for these effects.

(iii) The accuracy must account for th e errors caused by receiv er noise and interference. This m ay be accomplished by calibrating the pseudorange accuracy w ith a measured signal-to-noise ratio, or by using a dem onstrated tracking accuracy at low elevation an gles. To dem onstrate tracking accuracy, the actual an tenna characteristics below 5 degrees m ust be used when dem onstrating com pliance to the perform ance characteristics defined in TSO-C129(AR) , RTCA/DO-229C or RT CA/DO-253A. This means that the received GPS signal power must be adjusted down to reflect the minimum antenna gain relative to -4.5dBic for a sta ndard antenna, while th e interference power cannot be adjusted dow n as the location of the interference em itter is unknown. Any associated limitations on the installation (e.g., standard ground plane) should be identified in the installation instructions.

(2) Prediction programs and ava ilability assessments intended to support flight planning functions must use the equipment mask angle except as follows:

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(i) In order f or the prediction program to take advantage of the discontinuance of selective ava ilability f or sa tellites b elow 5 degr ees, the p rediction program must use the dem onstrated track ing accuracy as described in parag raph 12c(1)(iii) ( including a ccounting f or the spec ific antenna characteri stics and effects of interference). TSO-C144 gain characterist ics may be used if the antenna is TSO-C144 compliant. Alternately, antenna ch aracteristics below 5 degrees m ay be identified, a specification for low-elevation angle performance defined, and the antenna m ust obtain a design and production approval accord ing to that specification. This m ay be accomplished by including the antenna as part of the GNSS manufacturer’s TSOA.

(ii) For en route, term inal and nonprecision approach operations, the predicted mask angle cannot be below 2 degrees.

(iii) For precision approach and LPV, th e predicted m ask angle cannot be below 5 degrees.

d. Interference Testing. The GPS and WAAS si gnal acquisition and track performance, W AAS message lo ss rate, in tegrity and ac curacy requ irements will be verified during m inimum signal conditions an d defined interference conditions. These tests must be conducted in acco rdance with th e test conditio ns and procedures sp ecified in TSO-C129(AR) or RTCA/DO-229C, as appropriate.

e. Prediction Programs. Unlike conventional ground- based navigation aids which have a direct correlatio n between a facili ty o utage (VOR f ails) an d the loss of an operational capability (VOR approach is unava ilable), GPS satellite failures have a nonintuitive impact on operational capability. The operator is responsible for considering the effects of satellite outag es during f light planning. Predictio n programs and availab ility assessments are essential to enabling the operator to fulfill this responsibility.

(1) The FAA plans to pro vide NOTAM service for all app roach operations using TSO-C145a or TSO-C146a equipm ent, and for GLS operations using LAAS equipment.

(2) For oceanic/remote operation b ased on GPS, a prediction p rogram must be provided to determ ine if GPS satellite outages have an operational im pact on oceanic/remote operations.

(3) For basic R NAV operations in Europe , a prediction program should be provided (see AC 90-96 for additional info rmation). Alternatively, basic R NAV operations can be supported by the ge neric Eurocontrol prediction tool (http://augur.ecacnav.com/).

(4) For non-precision approach operations using TSO-C129(AR) equipm ent, manufacturers m ust provide a prediction availability based upon RAIM. For nonprecision approach operations using GPS/ WAAS equipment, this capa bility should be provided to support GPS operations outside of the WAAS coverage area.

(5) Prediction Program Requirements. Th e following guidelines apply to any prediction program that is intend ed to assess the operational impact of satellite outa ges for flight planning purposes (it does not appl y to the prediction described in paragraph

(a)(3)(xv)4a of TSO-C129(AR)).

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(i) This prediction program can be prov ided on any processing platfor m (in the GPS equipment or not).

(ii) The prediction program software s hould be developed in accordance with at least RTCA/DO-178B/EUROCAE 12B, level D guidelines.

(iii) The program should use either a RAIM algorithm identical to that used in the airborne equipment, or an algorithm based on assumptions for RAIM prediction that give a more conservative result.

(iv) The pr ogram s hould c alculate RAIM availabil ity based on the sa me satellite mask angle used in the equipm ent, but not less than 2 degrees f or en route and terminal operations or 5 degrees for precision approach or LPV operations.

(v) The progra m shoul d have the capab ility to manually desi gnate GP S satellites which are expected to be out-of-service for the intended flight.

(vi) For en route predictions, the program should allow the user to select the intended route (including declared alternates) and the time and duration of the flight. The maximum outage of RAIM (and FDE, if applicable) should be provided, and any predicted o utages of navigation capability must be identif ied. Note that f or oceanic/remote operations, the m aximum duration of an FDE outage cannot exceed 34 minutes for RNP-10 operation (see Order 8400.12a) and 51 minutes for MNPS operation (see AC 90-94). For B-RNAV operations, th e maximum acceptable duration of a RAIM outage is 5 minutes (see AC 90-96).

(vii) For approach predictions, the program should allow the user to select the destination and exp ected time of arrival, and provide a RAIM availability p rediction over an interval of at least +15 minutes computed in interval s of 5 m inutes or less about the ETA.

f. Interface Requirements

(1) Interface to m ulti-sensor naviga tion system s. Equipment requirements applicable to the integration of a GNSS sensor with a multi-sensor navigation system are in TSO-C129(AR) (Class B and C equipment) and TSO-C115b.

(2) Interface to non-navigation systems. GNSS sensors may provide output to a variety of applications, including terrai n awareness and warning sy stems (TAWS), automatic dependent surveillance (ADS), and m oving map displays for situational awareness. The interface should b e specifie d, and com patible equipm ent iden tified to streamline installation approvals.

13. EQUIPMENT PERFORMANCE – STAND-ALONE NAVIGATION EQUIPMENT. In addition to the guidance in this paragraph, stand-alone navigation equipment incorporates an antenna and a sens or and should comply with the guidance in paragraphs 11 and 12 of this AC. T hese issues do not need to be revisited for equipment that holds a previously granted TSO aut horization under TSO-C129(AR), or m inor modifications to such equipment.

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a. Acceptable Means.

(1) GPS. TSO-C129(AR) defines an accep table means of com pliance for GPS equipment.

(2) GPS/WAAS. TSO-C146a defines an acceptable means of com pliance for GPS/WAAS equipm ent. RTCA /DO-229C is a com plete set of standards for GPS and GPS/WAAS and should not be used in conjunction with TSO-C129(AR).

Note: In a ddition to the senso r im provements, there are a num ber of differences between TSO-C129(AR) and TSO-C146a, most notably the compatibility of TSO-C146a equipm ent with RNP RNAV operations, m ore explicit pilot interface requirem ents (see RTCA/DO-229C, section 2.2.1.1), and a Vector-to-Final capability (see RTCA/DO-229C, section 1.8.2.4).

(3) GPS/WAAS/LAAS. TSO-C146a defines an acceptable m eans of compliance f or this e quipment when ope rating in the GPS/ WAAS m ode. When operating in the GPS/L AAS mode and conduc ting a GLS approach, the equipm ent must comply with the requ irements of section 2 of RTCA/DO-253A. When operating in the GPS/LAAS mode and not conducting a GLS a pproach, the equipment must comply with the sensor requirem ents of section 2 of RTCA/DO-253A (for PVT) and the navigation requirements of RTCA/DO-229C (section 2.2).

(4) GPS/LAAS. TSO-C129(AR) defines an accep table m eans of com pliance for this equipm ent when operating in GPS m ode (i.e., outside the coverage of a selected LAAS ground facility). W hen operating in the GPS/LAAS mode and conducting a GLS approach, the equipment m ust com ply wi th the requirem ents of section 2 of RTCA/DO-253A. W hen operating in GPS/ LAAS m ode and not conducting a GLS approach, the equipm ent m ust comply with the sensor requirem ents of section 2 of RTCA/DO-253A and the navigation requirem ents of TSO-C129a, Class A1 or A2 (except the RAIM requirements of paragraph (a)(3)(xv)).

b. Evaluation of Human Factors.a

(1) The applicant is encouraged to involve the ACO as early as possib le in the evaluation of the pilot interface.

(2) Controls.

(i) Appropriate feedback must be supplied during data entry, with confirmation of input action prior to activ ation based upon that input. Any equipm ent prompts must be easily understood. A suitable interface should be provided to allow data input, data output, and control of equipment operation.

(ii) Particular attention should be pl aced on the controls required to perform ope rations that occur with a high fr equency or that m ust be conducted under potentially stressful or busy conditions su ch as term inal area operations and m issed approaches. The workload associated with accessing the Direct-T o function, entering a Hold m ode, executing a m issed approach, and initiating an approach to a dif ferent runway at the sam e airport (or to the a lternate airpor t) f ollowing a m issed approach should be minimized.

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(iii) Controls intended for use in flight should be designed to m inimize errors and, when operated in all possible com binations and sequences, should result in a condition whose presence or continuation woul d not be detrim ental to the continued performance of the equipm ent. Controls should be designed to m aximize operational suitability and m inimize pilot workload. The a mount of force required to activate knobs/buttons should be acceptable, feedback to the pilot should be adequate, and risk of inadvertent activation or deactivation should be minimized. Knob shape and size sho uld not interfere with equipm ent use and should he lp distinguish controls. Reliance on pilot memory for operational procedures should be m inimized. For those procedures that require pilot memory items, the memory item steps should be minimal and as intuitive as possible. The control/display should be operable with the use of only one hand.

(iv) Controls that are norm ally adjust ed in flight should be readily accessible and properly labeled as to their fu nction. Co ntrols th at are no t no rmally adjusted in flight shou ld not b e readily acces sible to th e flight crew . Labels sh ould be horizontally oriented, unobstructed by use of controls, descriptive of control function, and consistent across the equipm ent. The use of abbreviations should be minim ized. When abbreviations are used, they should conform to section 2.2.1.1.5 of RTCA/DO-229C.

(v) Controls sh ould be arranged logica lly acco rding to function al groups, sequence of use, and frequency of use. All displays and controls must be arranged to facilitate equipment usage.

(3) Messages.

(i) Standard pilot terminology should be used and their m eaning should be readily understood.

(ii) Messages should indicate what acti on should be considered or taken and should em ploy the m inimum num ber of wo rds required to conv ey its m eaning.

Messages or annunciation of m essages not rele vant to the execution of an approach, landing, rollout, or m issed approach shoul d be suppressed during the approach.

Messages not requiring pilot action during fl ight should not be sh own during flight.

Messages should be operationally relevant to current or upcom ing phases of flight. P ilot recall of m essages from the m essage storage queue should bring up the m ost important messages first. The hierarchy of messages should be determ ined by the im pact of the message on the saf ety of the f light f or th e current and upcom ing phases of flight.

Presentation of messages should not obscure safety-critical portions of guidance displays.

Messages requiring prompt pilo t action should stay up until action is taken or the pilot cancels the message. Safety-critical messages should be accompanied by an aural alert if that alert is not already provided by anothe r aircraft system. Messages of operational significance to the flight should not time out.

(4) Prompts. Where possible, prom pts should specifically indicate what programming action should be done next (e.g., “enter next waypoint”). Where possible, prompts should indicate the sp ecific control that should be us ed next, rather than relying on pilot m emory. Multiple prom pts requiri ng different actions should be presented sequentially rather than concurrently.

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(5) Cross-Track Deviation Display. Minimum discernible movement, accuracy of the cen tered display, resolution of the e lectrical output, linearity of the display and/or electrical output, and display latency sh ould be as specified in sectio n 2 of RTCA/DO-229C for a pplicable navigation m odes. Deviation display designs with display ranges and resolutions outside the bounds of the required values should be substantiated by dem onstration, by referen ce to appropriate em pirical data, or by similarity to previous certified range/resolution displays.

(6) For TSO-C146a equipm ent, the flight crew workload requirem ents in section 2.2.1.1.3 of RTCA/DO-229C are particul arly im portant and compliance to the requirements should be verified. The m anufacturer must also have specific and detailed rationale for deviating from any of the recommendations defined in Table 2-4 of RTCA/DO-229C.

(7) For TSO-C146a equipm ent, the manufact urer must identify any acronym s that do not com ply with the recomm endation in RTCA/DO-229C, section 2.2.1.1.7 for the terms listed. A specific and detailed rationale for deviating must be documented.

(8) For TSO-C146a equipm ent, complianc e to the requirem ents should be demonstrated by the m anufacturer under the test procedures specified in section 2.5.11.3 of RTCA/DO-229C. Som eone not fa miliar w ith the d evelopment of the equip ment should cond uct these tests to p roperly evalua te the pilot in terface, docum entation, and training information. This person should have minimal experience with the equipm ent, other than the opportunity to review the docum entation and training m aterials to be supplied with the equipment.

c. Navigation Database. For area navigation equipm ent, the navigation database i s an essential com ponent of th e ability of the equipm ent to perform its intended function.

Guidelines pertaining to the navigation da tabase can be found in RTCA/DO-200A. The manufacturer should pay particul ar attention to the specifica tion of the form at of data loaded into the navigation database, as described in RTCA/DO-200A, Appendix C.

(1) Database Process. The equipm ent manufacturer is usu ally the la st link in the aeronau tical data processing ch ain, as the for mat for t he data loaded in the final database is typically pro prietary. The applic ant for a TSOA must def ine the data qua lity requirements for the database, and there m ust be an aeronautical da ta process which will be accessible to the equipm ent users. RTCA/DO-200A provides an acceptable m eans of compliance for defining the data quality re quirements, and for the aeronautical data process.

(2) Reference System. The operations manual or A/RFM(S) should explain that GNSS navigation is referenced to the W GS-84 coordinate system. The following text is recommended: “Navigation information is re ferenced to WGS-84 reference system , and should only be used where the Aeronautical Information Publication (including electronic data and aeronautical charts) conform to WGS-84 or equivalent.”

(3) Government-Provided Electronic Database. Electronic databases sponsored by a governm ent organization should follow the same database assurance processes as described above and in RTCA/DO-200A. GNSS equi pment compatibility w ith government-provided electronic databases must be verified.

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d. Conversion of data for WAAS L NAV/VNAV approaches . As des cribed in section 2.2.4.3.1 of RTCA/DO-229C, a final approach segm ent (FAS) datablock is not provided for standalone L NAV/VNAV approaches. The vertical path for such approaches is defined by the threshold loca tion, threshold crossing height, and glidepath angle. However, the altitude of the threshol d is published as the height above m ean sea level (MSL ), rather than as the height above the W GS-84 ellipso id. Therefore, the published MSL height (interpreted as a he ight above the W GS-84 geoid) m ust be converted to height above the WGS-84 ellipsoid prior to bein g used. This conversion is not considered alteration of data per RT CA/DO-200A section 2.4.2, since it changes the reference system but not the actual vertical location. It is recom mended that this conversion be accomplished within the GNSS equipment itself so that there are consistent navigation database requirem ents for GN SS LNAV/VNAV equip ment and baro metric VNAV equipment.

14. EQUIPMENT PERFORMANCE – LAAS VDB RECEIVER.

a. Section 2 of RTCA/DO-253A defines an acceptable m eans of com pliance for LAAS VHF data broadcast receivers.

b. The receiver should be tested using the te st procedures specified in section 2.5.2 of RTCA/DO-253A.

15. INSTALLATION ISSUES – GENERAL . The following issues apply to the installation of all GNSS equipment intended for IFR use.

a. Failure Classification.

(1) From en route and term inal operations , the loss of navi gation function is typically considered to be a major failure condition for th e aircraft (see AC 25.1309-1;

AC 23.1309-1; AC 27-1; or AC 29-2 as appli cable to the aircraft ). Other aircraft navigation system s should be considered when determ ining the loss of the GNSS navigation function, which could be m ajor (no other navigation systems) or minor (other applicable navigation system s). GNSS naviga tion data is c onsidered to be m isleading when unannunciated po sition errors exis t. For en rou te, term inal, an d non-precision approach (NPA) and LNAV/VNAV approaches, presenting misleading information to the flight crew is also considered to be a m ajor failure condition for the aircraft. For LPV and GLS approaches, presenting m isleading information to the f light crew is conside red to be a hazardous failure condition. Thes e failure classifications are summarized in Table 3.

Table 3. Typical Hazard Classifications

En route/ Terminal Area/ NPA (LNAV) NPA with Vertical Guidance (LNAV/VNAV) LPV Approach GLS Precision Approach (Cat. I) Loss of Navigation Major Major Major Major Misleading Information Major Major Hazardous Hazardous Page 24 Par 13

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(2) The applicant m ust conduct a safety assessm ent of the GNSS equipm ent installation to v erify tha t des ign erro rs and failure modes m eet th e prob ability requirements for that failure class. AC 25.1309-1, AC 23.1309-1, AC 27-1, or AC 29-2, per the latest revision levels as applicable, provide an acceptable m eans for showing that the hardware complies with pertinent airworthiness requirements.

b. Software Considera tions. AC 20- 115, curren t edition, d efines an acceptab le means of qualifying so ftware. The applicant is encouraged to subm it the Plan for Software Aspects of Certification (PSAC) ear ly in the software developm ent process.

Early submittal will a llow tim ely resolution of issues such as partition ing and determination of software levels.

c. Installation Instructions.

(1) The equipment m ust be installed in accordance with the in structions and limitations provided by the manufacturer of the equipment.

(2) Equipment should be inst alled with separation be tween wires of redundant equipment (see AC 43.13-1B).

d. Environmental Considerations.

(1) Most equip ment will have been tested by the m anufacturer to the environmental categories described in RTCA /DO-160(AR), with resu lts described in an environmental qualification form . For this equipment, the environm ental categories (or criteria) to which the e quipment has been te sted m ust be com patible with the a ircraft environment in which the GNSS equipment is installed.

(2) For equipm ent which has not been test ed to the environm ental ca tegories described in RTCA/DO-160(AR), comparable testing must be conducted and a thorough definition of the aircraft environm ent must be developed through testing of the norm al and abnorm al environm ents. At a m inimum, the environm ental perform ance requirements identified in section 2.4 of RTCA/DO-229C m ust be m et for all components in the airborne GNSS equipment.

16. INSTALLATION ISSUES – GPS ANTENNA . This paragraph provides guidance related to the installation of a GPS antenna.

a. Antenna Placement.

(1) The antenna installation should m inimize the potential for signal blockage by any portion of the aircraft during airc raft m aneuvering. Shadowing by aircraft structure can adversely affect the operation of the GNSS equipm ent. Typically, a GNSS antenna is located forward or aft of the wings on the top of the fuselage.

(2) The installer m ust ensure that a 5 degree mask angle (or lower if the receiver ins tallation ins tructions id entify a lower m ask angle) is provided by the installation. This includes consid eration of antenna location and blockage, with the aircraft at typical cruising attitude. The antenna should also be located to m inimize the effects of airplane shadowing during typical maneuvers.

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(3) The antenn a should be separated as m uch as practical from transm itting antennas (e.g., VHF, TCAS, SATCOM, and HF). For small aircraft, the antenna should also be separated as m uch as practical fr om the windscreen to pr event case-to-antenna coupling.

(4) For insta llations on rotorcraft, th e e ffects of the rotor b lades on antenna performance must be considered.

(5) For multiple-sensor installations, th e installer should reduce the likelih ood that a single lightning strike affects all the sensors (i.e., do not plac e them in a stra ight line from the front to the rear of the fuselage).

b. Anti-Ice Protection. If the aircraft is approved for flight into know n icing conditions, the antenna must not be susceptible to ice buildup (i.e., is installed in a nonicing location on the aircraft, or is of a suf ficiently lo w profile that ice does not accumulate on the antenna). Alternatively, the equipm ent can be shown to operate satisfactorily when the antenna is subject to icing if there are no harmful effects of the ice build-up, such as possible ingestion into the engine of accumulated ice or degradation in aerodynamic performance. The effects of ice accumulation on the antenna, if any, can be found in the m anufacturer's installation instructions. See AC 23.1419-2A and AC 25-1419-1 for additional guidance.

c. Antenna Cables. Double shielded cables should be used to prevent interference coupling into the cable.

d. Structure. Any m odifications to th e aircraft to insta ll a ne w antenna n eed to be evaluated f or th eir im pact on aircraft s tructure. Fo r s pecific gu idance relatin g to modifications in the f uselage s tructure f or Part 23 aircraft, see AC 23-5, Cutouts in a Modified Fuselage of Small Airplanes.

17. INSTALLATION ISSUES – GNSS SENSO R. This paragraph provides guidance related to th e installation of a GPS sensor , including those sensors that integrate WAAS or LAAS. This paragraph also applies the insta llation of st and-alone navigation equipment, since that equipm ent has an em bedded sensor. This guidance applies to all installations, but is only expected to be sp ecifically ev aluated as part of the in itial airworthiness approval.

a. Antenna/Sensor Compatibility.

(1) Using the guidelines in the installati on instructions, verif y the antenna installation is compatible with the G NSS equipment. This m ay be accomplished by one of the following:

(i) The antenn a (pa rt nu mber) is id entified in the GNSS equipm ent installation instructions as compatible;

(ii) The GNSS equipm ent installation instru ctions state that the equipm ent is com patible with any standard, passive TSO-C144 antenna. In this case the antenna should have authorization to TSO-C144. Compare the RTCA/DO-160(AR) category for lightning-induced tr ansients spe cified in the a ntenna in stallation in structions with the category defined in the receiver installation instructions; or Page 26 Par 16

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(iii) The GNSS equipm ent installation instru ctions state that the equipm ent is compatible with any standard, active TSO-C144 antenna. A signal power budget must be defined that takes the output power at the low-nois e am plifier of the antenn a (a s defined in the antenna installation instructi ons) and matches that to the receiver dynam ic range and sensitivity (as de fined in the GNSS equipm ent installation instructions).

Compare the RTCA/DO-160(AR) category for light ning-induced transients specified in the antenna installation instructions with the category defined in the receiver installation instructions.

(2) Use the gu idelines in the ins tallation instructions when d etermining what cables and connecto rs to use to co nnect th e antenna to the receiver, includ ing cable lengths that result in acceptable loss of signal power.

(3) Ensure antenna and GNSS equipm ent co mpatibility for aircraft equipped with SATCOM. Som e equipment may have been qualified to less stringent interf erence levels for aircraft installations without SATCOM.

b. Interference - Electromagnetic Compatibility (EMC).

(1) The equipm ent must not be the s ource of objectionable conducted or radiated interference or be a dversely affected by conducted or radiated interference from other equipment or systems installed in the aircraft.

(2) Proper grounding of GNSS and other eq uipment is es sential to ensu ring EMC.

(3) When possible, do not install the sensor near a VHF radio.

(4) The following paragraphs identify poten tial so urces of interference and means of mitigating that interference:

(i) SATCOM. Out-of-band SATCOM e missions and in-band intermodulation between m ultiple channel SA TCOM installations can affect GNSS.

GNSS equipm ent m ust not be ins talled in aircraft with multiple SA TCOM channels unless the sim ultaneous use of i nterfering frequencies can either be prevented or demonstrated not to interfere with the operation of the GNSS equipment. Note that some equipment is not compatib le with SATCOM installations at all, as noted in the installation instructions.

(ii) VHF Communications. Harm onic, s purious, and local oscillator harmonics from VHF equipm ent can cause inte rference to GNSS. In terference can be mitigated by:

(A) Insta lling f ilters at the output of th e VHF tran smitter to p revent antenna-to-antenna interference. S uch filters s hould have an insertion loss of 2 d B or less, or the installed VHF transceiver performance will have to be re-evaluated.

(B) Installing th e GNSS equipm ent as far away as feasible from any VHF transmitter equipment (to prevent case-to-case interference).

(C) Replacing the VHF equipment.

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(iii) ELT. An ELT can re-radiate DME or VHF signals that can interfere with GPS. Notch filters on the ELT antenna cable or rep lacing the EL T can elim inate this problem.

(iv) DME. DME has been known to cause interference to GPS. Replacing the DME transceiver can eliminate the problem for some equipment.

(v) Direction Finding (DF) equipment. Moving the DF antenna to the b elly of the aircraft has been found to eliminate this problem.

c. Interface Requirem ents. Ensure sensor compatib ility f or airc raft system s utilizing the position output (e.g. flight m anagement system , autom atic dependent surveillance system). Systems should use th e same bus standard (e.g., ARINC 429 with ARINC 743 data, RS-232 with RTCA/DO-229 Appendix H data).

(1) Operation of the GNSS equipm ent m ust not adversely affect th e performance of other aircraft equipm ent. Likewise, operation of the GNSS equi pment must not interfere with the operation of other equipment installed in the aircraft.

(2) Additional inf ormation on inte rfacing a GNSS sensor with a m ulti-sensor system can be found in AC 20-130A.

(3) GNSS sensors m ay provide output to a variety of applications, including terrain awareness and warning s ystems (T AWS), autom atic dependent surveillance (ADS), and m oving m ap displays for situati onal awareness. The guidance m aterial in this AC for sensors applies to all of these integrations, and should be used in conjunction with the gu idance m aterial f or th e applicat ion. For spe cific inf ormation rela ting to TAWS equipm ent, see TSO-C151a. G PS, GPS/ WAAS, or GPS/LAAS posi tion information m ay be used as the position determination as addressed in Appendix 1, paragraph 5 of TSO-C151a and paragraph 11 of AC 25-23. Guidan ce for electronic m ap displays can be found in RTCA/DO-257A, Minimum Operational Performance Standards for the Depiction of Navigation Inform ation on Electronic Maps . Guidelin es f or interfacing with ADS-broadcas t equipment can be found in RTCA/DO-242A, Minimu m Aviation System Perfor mance Standards for ADS-B. Failure of the GNSS equipm ent should not cause failure of the interfaced equipment.

d. GPS Equipment (with or without LAAS) . Equipm ent that uses TSO-C129(AR) as the bas is for the GPS f unctions has a lim ited ability to meet navigation requirements.

This limitation should be docum ented in the A/ RFM(S) as follows: “T he aircraft mus t have other approved navigation equipm ent in stalled and operating appropriate to the route of flight”.

18. INSTALLATION ISS UES – S TAND-ALONE NAVI GATION EQUIPME NT.

This paragraph provides guidanc e rela ted to the installati on of stand-alone navigation equipment. In additio n to the guidance in this paragraph, stand-alone navigation equipment incorporates an antenna and a sens or and should comply with the guidance in paragraphs 16 and 17 of this AC. This guidan ce applies to all ins tallations, but is only expected to be specifically evaluated as part of the initial airworthiness approval.

a. GNSS Configuration Strapping. Often, GNSS equipm ent uses software configuration straps or installation set parameters entered either manually by the installer Page 28 Par 17

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or by using an Aircraft Persona lity Module (APM). These so ftware configuration straps or parameters disable/enable functionality, configure the in put/output formats, determine the displayed units of m easure, and m ore. The software configuration programm ing documentation must become a part of the inst allation package and shou ld be included in the Master Drawing List. W hen using an Approved Model List (see paragraph 8), multiple configurations may be specified.

b. General Human Factors Considerations.

(1) Control Accessibility. Controls inst alled for in-flight operation should be readily accessible from the pilot's seated position. Only single-hand operation should be required, the controls should be readily identifiable, and the use of c ontrols should not obscure pertinent displays.

(2) Inadvertent Turnoff. System contro ls should be arranged to provide adequate protection against inadvertent system turnoff.

(3) Control/Display Visibility.

(i) The appropriate flight crew m ember(s) should have an unobstructed view of displayed data when in the seated position.

(ii) Compliance with lim itations in the installation instructions for display readability should be verified.

(iii) All displays, controls, and annunciato rs must be easily readable under all norm al cockpit conditions and expected am bient light c onditions (total darkness to bright, reflected sunlight).

(4) Annunciations.

(i) Visual annu nciations m ust be cons istent with the c riticality of the annunciation and m ust be readable under a ll norm al cockpit illum ination cond itions.

Visual annunciations must not be so bright or startling as to reduce pilot dark adaptation.

(ii) Audible alarm s should be sufficien tly loud and of a ppropriate pitch quality, duration and pattern. Alarm s shoul d be easily deactivated (but not easily deactivated inadvertently). Audible alarm s m ust not in terfere with o ther aircraft audio alarms or alerts of higher priority (e.g. stall warnings, gear warning, or chip-detect).

c. Source Selection. For installations where GNSS outputs can drive a display that is shared with other navigation equipm ent (e.g., VOR/DME, ILS, MLS), the pilot must be able to select the source of guidance, an d the selected source must be clearly annunciated to the flightcrew, on or near th e affected display. GNSS- based navigation (GPS, GPS/WAAS, GPS/LAAS) need not be dif ferentiated. W hen applica ble, annunciation of the selected source should be driven by the same relay switch to preclude erroneous information in case of switch failur e. Autopilot o peration should be inhib ited if the displayed source is not the sam e as the source driving the autopilo t. This is particularly critical for approach operations (i.e., autopilot in approach mode).

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d. Navigation Display.

(1) The horizontal (and vertical) deviation(s) display(s) and failure annunciation should be located within the pilot' s prim ary field of view, as should any indication requiring immediate aircrew action. For the pur pose of this AC, the primary field of view is within 15 degrees of the pilot’s primary line of sight.

(2) Displays used for loss of integrity m onitoring, waypoint sequencing, start of a turn, turn anticipati on, active waypoint, di stance to active waypoi nt, desired track and actual track (track angle e rror), TO/FROM indication, appr oach mode annunciation, and automatic mode switching should be located w ithin the pilot’s normal field of view. The normal field of view is such that the pilot w ould notice an annuncia tion during norm al aircraft operation. Guidelines for the norm al field of view include: the lateral normal field of view is from the center of the airspeed indicator to and including the equipment if installed in the center radio stack. Alternatively, if the equipment is installed to the left of the airspeed indicator, the lateral normal field of view is the center of the altimeter to and including the equipm ent. The vertical norm al field of view incl udes immediately above and below the basic “T ” instruments (may also be anywhe re with in the lateral field of view).

e. Failure Indications.

(1) It is important to install the equ ipment such that all f ailure conditions result in appropriate displays.

(2) For installations not incorporating an external navigation display (CDI, HSI, etc.), complete blanking of the Control Display Unit (CDU) display is acceptable.

(3) Presentation of a failure/status annunc iation (flag or inte grity annunciation) does not require removal of navigation information from the navigation display.

(4) A unique annunciation of the loss of integrity m onitoring should be provided.

f. Dual GNSS Installations.

(1) Synchronization. Synchronization refers to the ability for control inputs to one RNAV equipm ent to autom atically update the other equipm ent. Dual installations should be synchronized whenever possible to reduce crew workload and prevent confusion over which system/flight plan is driving the naviga tion data. If the Functional Hazard As sessment requires du al GNSS or is o perationally required, then synchronization is required. If the navigation equipm ent are not synchronized, then the following issues should be evaluated:

(i) The pilot and co-pilot (if applicable) should be able to view and enter data in the of fside equipment. This m ust not interfere with throttle le vers, flap handle, etc.

(ii) The workload associated with m anually updating both equipm ent to maintain consistency between them should be evaluated.

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(iii) There should be no possible confusi on as to the equipm ent that is driving the autopilot and navigation displays.

(iv) Displays and annunciations should be evaluated for possible inconsistencies that result from diffe rences in the equipm ent (e.g., different flight plans could result in one equipment going into approach mode while the other does not). These inconsistencies m ust no t cau se a misleading situation. Thes e are of particu lar concern when the co ckpit architecture allows for cr oss coupling (e.g. GNSS- 2 switched to drive side 1 displays).

(2) Intermixing of RNAV equipm ent. W here multiple RNAV systems are intended to be used simultaneou sly (typically in two-pilot a ircraft), ins tallation of area navigation equipm ent with different crew inte rfaces can be very confusing and lead to problems since they m ay have conflicting m ethods of operation and conflicting display formats. There can be problem s even when interm ixing different versions of the s ame equipment. At a m inimum, considerations should be given to the following potential incompatibilities, especially wh en the cockpit arch itecture allows for cross coupling (i.e.

GNSS-2 switched to drive side 1 displays).

(i) Data entry: The equipment m ust have consistent methods of data entry, and similar pilot procedures for accom plishing common tasks. RTCA/DO-229C section

2.2.1.1.3 identifies a minim um set of comm on ta sks that should be considered. Any differences should be evaluated for pilot workload. If the wrong procedures are used (the procedures for data entry on the offside are used), th ere m ust be no m isleading information and it should be easy to identify and recover from the mistake.

(ii) CDI scaling: Sensitivity m ust be consistent or annunciated. Standalone nav igation equip ment that com plies with RTCA/DO-229C will have cons istent scaling provided the flight plans be tween the equipm ent are identical (see synchronization issues above).

(iii) Display symbology and m ode annunc iations: There should be no conflicting sym bols or annuncia tions (e.g., a common symbol used for two different purposes), and differences should be specifi cally evaluated to evaluate the potential confusion they may cause.

(iv) Mode logic: The modes internal to the equipment and interfaced to the rest of the aircraft should be consistent.

(v) Equipment f ailure: The ef fect of fa ilure of one equipm ent m ust not result in misleading information on the other equipment.

(vi) Displayed data: The display of primary navigation param eters (waypoint distance, bearing, de sired track/actual track, track angle error, num eric crosstrack deviation) must use consistent units and a consistent notation. Any inconsistency in the display of the primary information should not be approved.

(vii) Database differences: Di fferences i n the area navigation database and RNAV equipment response can resu lt in contradictory guidance between two dissim ilar types of RNAV equipm ent. A m eans of ensuring compatible updates between the equipment must be defined and documented in the operations manual or A/RFM(S).

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g. Interface to Flight Guidance System (FGS). This paragraph describes guidelines for interfacing the GNSS stand-alone naviga tion equipment with a flight guidance system. These issues may be addressed th rough operating lim itations in the A/RFM(S).

When used in this paragraph, the word “consistent” m eans that the installed GNSS equipment does not alter the cockpit desi gn philosophy or intended function of an FGS mode, switch or annunciation.

(1) Connection to the autopilot must be consistent with the autopilot installation instructions and the GNSS installation instructions.

(2) Operational com patibility be tween the GNSS equipm ent and th e F GS should be verified. Protection should exist in the GNSS or the FGS to keep the aircraft within the approved operational env elope (e.g. roll, pitch, speed, and altitud e). See the relevant guidelines for the particular aircraft (e.g., AC 23-17A and AC 25.1329).

(3) A positive, continuous and unam biguous indication should be provided of the FGS modes actually in operation, as well as those that are arm ed for engagement. In addition, where engagement of a m ode is automatic, clear indication must be given when the m ode has been arm ed by ei ther action of a m ember of the flight crew, or automatically by the system.

(4) The GNSS equipment must be compatible with the FGS modes of operation.

For example the arm, engage and disengage sequence of the GNSS equipm ent should be consistent in the annunciation and engage/d isengage tim ing of the FGS. This is particularly im portant during W AAS approa ches, which include different levels of service (reference section 2.2.4.7.4 of RTCA/DO-229C).

(5) If the GNSS equipm ent is connected to a reduced bank selector, the GNSS bank angle, like the FGS, m ust not be lim ited by this switch selection during approach.

Consistency in the operation must be maintained.

(6) Some aircraft operate in areas of th e operational flight envelope where buffet onset can occur when norm al maneuvering load factors are pr esent (e.g. at higher altitudes). This is a co ncern, s ince the GNSS equipm ent can autom atically sequ ence waypoints and initiate turn maneuvers which may or may not have the pilots attention. If buffet protection is no t provided for in th e GNSS or FGS (e.g. bank an gle limiting, or limiting of cruise altitude based upon buffet margin), an A/RFM(S) limitation should be added to the performance section, prohibi ting cruise operation at weight/a ltitude combinations that result in buffet margins less than 1.4g.

(7) For those aircraft that have incorpor ated bank angle lim iting, consideration should be given to whether the GNSS equipment is defining a path that cannot be flown.

h. Interface to Magnetic/True Switch. If a MAG/TRUE heading reference switch is installed in the aircraft, the GNSS equipm ent should be driven by the sam e switch to maintain consistency in the displays and operation for both m anual and automatic heading reference changes.

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i. Interface to Barometric Altimeter.

(1) If there is an air data s ource select switch, when the pilo t de-selects a n air data source the de-selected source must no longer be used by the GNSS equipment. This becomes important for barometric-aided FDE, since erroneous altitude inputs to the FDE algorithm could lead to improper satellite detection and exclusion.

(2) If the GNSS equipm ent requires barom etric corrected (or pressure) altitude data for certain operations (identified in the GNSS installation ins tructions), the installation should prov ide an auto matic altitu de input from the air data system to the GNSS such that additional pilot actions are not required.

(3) If barometric corrected altitude is required by the GNSS equipm ent and an automatic input of the barometric corrected altitude is not a vailable, an alert for the pilot during approach m ust be provided indicating th e need to e nter the bar ometric pr essure setting in th e GNSS. If the equipm ent requires multiple entries to en ter the co rrection, the workload should be evaluated during an approach.

19. INSTALLATION ISS UES – LP V AND GL S APP ROACHES. This paragraph provides guidance related to the installation of WAAS and LAAS equipm ent supporting LPV or GLS approaches. This guidance applie s to all installations, but is only expected to be spe cifically evaluated as p art of the initial airworthin ess a pproval. GNSS equipment intended for LPV or precision ap proach operation m ust provide for the following:

a. Update Rate. For sensors that support an LPV or precision approach capability (Class 3 equipment of TSO-C145a, LAAS equipment), the position used for the approach must be output at 5 Hz. If the TSO-C145a equipm ent provides a 1 Hz output, the installation must use inertial aiding or other method to obtain deviations at 5 Hz.

b. Differential Group Delay. If the G NSS equipment is ins talled with an antenna that has no t previou sly been de termined to be com patible, verif y that the d ifferential group delay of the antenna is less than or e qual to the requirem ent for the receiver (as specified in RTCA/DO-229C, section 2.1.4.5). The differential group delay of the antenna will be do cumented in th e ins tallation instructions, and the requirem ent for differential group delay will be do cumented in the receiver ins tallation ins tructions.

Antennas h ave filters that cou ld affect the delay. If the antenna instructions do not document the differential group delay, then th e data should be obtained and found to be within the limits specified in the rec eiver installation instructions before approval can be given for approach operations.

c. Performance Monitoring. Suff icient information must be provided in the flight deck to allo w the pilots to m onitor the progr ess and safety of the approach operation.

This in-flight performance monitoring must include:

(1) Unambiguous identification of the intended path for the approach, (e.g. LPV or GLS approach, identifier, frequency or channel number, and selected navigation source), and

(2) Indication o f the positio n of the aircraf t with r espect to th e intended path

(e.g. cross track and vertical deviation information).

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d. System Status. The flig ht crew m ust have a m eans to evalu ate the c apability of the a ircraft equipm ent to ac complish the lo w visibility operation prior to an d af ter departure. The flight crew must be advised of failed ai rcraft sys tems or equ ipment affecting the decision to continue to the destination or divert to an alternate.

e. Annunciations. For installations containing m ore than one approach navigation source, the navigation source (e.g. ILS, GL S) selected for the approach m ust be positively indicated in the normal field of view at each pilot station.

f. Accessibility.

(1) Single equ ipment installations m ust be accessib le and us able by the p ilot.

For aircraft requiring tw o crew members, the equipment should be accessible and usable by either pilot located at a pilot or copilot crew station.

(2) Dual (or more) equipm ent installa tions m ust have a convenient and expedient way to update da ta, infor mation and program s, and a m eans to ensure consistency between the equipm ent (e.g., a “c rossload” capability can ensure identical data) (also addressed under paragraph 18f for stand-alone navigation equipment).

20. INSTALLATION ISSUES – LAAS VDB RECEIVER . This paragraph provides guidance related to the installation of a VDB receiver, including those embedded within a multi-mode receiver. This guidance applies to all installations, but is only expected to be specifically evaluated as part of the initial airworthiness approval.

a. Interference – EMC. The VDB receiver may be susceptible to interference from VHF communications equipment on the aircraft.

(1) For horizontally polarized VDB antenna operating in the presence of a +40 dBm (EIRP) vertically polarized VHF communications transmission, at least 53 dBc of isolation is required to prot ect the VDB rece iver from desensitization. This isolation may be achieved through a com bination of 15 dBc of cross-polariz ation rejection and -38 dBc of antenna coupling.

(2) For aircraft using a vertically polari zed VDB ant enna, the full 53 dBc m ust be achieved through an tenna coup ling. It is not feasible to accom plish this isolation simply due to free space path loss: special considerations will be required.

b. Compatibility with other systems. The VDB receive r may use the loc alizer or VOR antenna. In this case, the performance of the localizer or VOR receivers m ust be re-assessed due to the degradation in sign al strength resulting f rom the splitte r.

AC 23-8A, AC 25-7A, AC 27-1B, and AC 29- 2A provide guidance material on th ese installations.

c. VDB aircraft im plementation loss. The aircraft im plementation loss should be less than 6 dB (gain) and greater than -15 dB (loss) for horizontally polarized antenna, or less than 6 dB (gain) and grea ter than -11 dB (loss) for ve rtical polarized antenna. The total im plementation loss is the algebr aic s um (in dec ibels) of the antenna gain (referenced to an iso tropic radiator) and th e attenuation (as a negative num ber) between the antenna and the VDB receiver. The a ttenuation includes line dissipation and VSWR mismatch losses. The implem entation loss sh ould be verified over the frequency range

108.000 to 117.95 MHz.

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d. The VDB antenna should be installed so that the maximum received power from any on-board transm itter does not e xceed the d esensitization levels of the VDB receive r specified in section 2.2.9.1 of RTCA/DO-253A.

**21. INSTALLED PERFORMANCE - DATA SUBMITTAL.**

a. General. T his paragraph id entifies docum entation typica lly required by th e aircraft certification au thorities to support installation a pproval. For equipm ent that has not obtained a TSOA, the equipm ent issues described in paragraph 11 through 14 of t his AC must also be addressed as part of th e installation. For equipm ent that has a T SO marking, the item s under paragraph 11 through 14 should be evaluated during the first installation approval in any m ake/model aircraft. The data desc ribed in this paragraph is applicable to obtaining an STC, an amended TC, or an amended STC.

(1) Project Spe cific Cer tification Plan. Provid e a plan tha t estab lishes the certification basis, how the program will be adm inistered, m ethod of com pliance, and schedule. When establishing the certificatio n basis, the plan should identify how the product will m eet the applicable airworthiness requirem ents and any special conditions.

The FAA and Industry Guide to Avionics Approvals provides guidance on developing a project specific certification plan. A dditional infor mation can be found in AC 21-40, Application Guide for Obtaining a Supplemental Type Certificate.

(2) Design Data.

(i) Provide the installation instruction manual from the original equipment manufacturer.

(ii) Provide ins tallation drawings de picting all interface co nnections, switching, wire diagram s, external annunc iations, configurati on programm ing and cockpit layout.

(iii) Provide reliability data or analysis to establish that all probable failures affecting the navigation functi on are detected. Qualitative analysis may be used under AC 23.1309-1C.

(iv) Provide a system safety assessm ent to conf irm that all f ailure conditions have been identified, classified and described in func tional and operational terms. Hardware and software design assurance levels must be substantiated.

(3) Structural Analysis. The insta llation of the GNSS equipm ent, including antenna, m ust be sufficient to m eet all structural m ounting, dynam ic, and em ergency landing loads appropriate to the aircraft. The installer must verify whether antenna installations penetrating the pressure vessel require a damage tolerance assessment of the installation, considering the uni que installation and the aircra ft type certificate basis of airworthiness.

(4) Power Supply. Provide an electrical load analysis to verify that the total electrical lo ad requirem ents are within the capabilities of the aircraft' s electrical generating system. Verify that the supplied elec trical power is consistent with applicable equipment reliability requirements.

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(5) Equipment Com patibility. Provide a da ta f low diagram to identif y which equipment interfaces with the newly instal led GNSS equipm ent. Th e typical interfaces are to a barometric altimeter, flight management system, and Flight Guidance System. If the data flow diagram indicates that there are additional interfaces, the applicant and FAA should develop ground and flight tests to ensure proper functioning of these interfaces.

(6) Environment. Provide qualification da ta subs tantiating th at the a ircraft environment in which the GNSS equipm ent is to b e installed is app ropriate to the environmental categories (or criteria) in RTCA/DO-160(AR) to which the equipment has been tested.

b. Stand-Alone Navigation Equipment Installation.

(1) Pilot’s Guide. An o perations m anual (pilot’s guide) describing the equipment, functions and procedures m ust be provided with the GNSS equipm ent. It is essential that the pilot’s guide be complete, concise, and easy to understand. The pilot’s guide should be reviewed by a flight test pilot familiar with the equipment.

(2) Quick Reference Guide. A quick reference guide must be provided with the GNSS equipment as a training aid for th e operation of the GNSS e quipment. The guide should be evaluated by a flight tes t pilo t fam iliar with the equipm ent. Recommended format and content for this guide is in Appendix 3 of this AC.

(3) Operations m anual or A/RFM(S). An operations m anual or A/RFM(S) containing the limitations and operating procedur es applicable to the equipment installed must be provided. It must address the operation of the equipm ent and the related components as they are installed (e.g., rem ote source selector). If the operations manual does not address the use of the installed equipm ent, if the installation is based on a prior approval that had an A/RFM(S), or if there any limitations associated with the oper ation of the equipm ent, an A/RFM(S) is requ ired. Standard wordi ng for the general and limitations sections of an A/RFM(S) is provided in Appendix 4.

(4) Ground and Flight Test Plans (functi onal and EMI/EMC testing). The applicant must subm it the proposed ground and flight test plans to dem onstrate the equipment performance (as described in paragraphs 22 and 23) and EMI/EMC testing.

**22. INSTALLED PERFORMANCE - GROUND TEST.**

a. General.

(1) Power Supply. Assess all switching and transfer func tions, including electrical bus switching, pertaining to the GNSS installation.

(2) Accuracy. The accuracy of GNSS e quipment is no t a function of the installation, and should not be evaluated for each installa tion. The accuracy of the equipment will be dem onstrated under the evaluation of the sensor, typically as part of a TSO Authorization.

(3) Interference.

(i) The lack of interference from VHF radio should be demonstrated on the completed GNSS installation by tuning each VHF transmitter to the frequencies listed Page 36 Par 21

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below and transm itting for a per iod of 35 seco nds while o bserving the signal status of each satellite being received. Degradation of individually received satellite signals below a point where navigatio n is no longer possibl e is not acceptable and will require that additional isolation m easures be taken. Reevaluation of instal led VHF transceiver performance is not necessary if the filter insertion loss is 2 dB or less.

(ii) Evaluate the following VHF frequencies (25 kHz channels):

121.150 MHz 131.250 MHz

121.175 MHz 131.275 MHz

121.200 MHz 131.300 MHz

(iii) For VHF radios with 8.33 kHz channe l spacing, evaluate the following VHF frequencies:

121.185 MHz 130.285 MHz

121.190 MHz 131.290 MHz

(iv) For ins tallations on ro torcraft, en sure that the roto rblades do no t interfere with the GPS/WAAS received signals . This problem has been experien ced in some rotorcraft and varies with the rotation rate.

(4) Antenna to Aircraft Navigation Refere nce Offset. If applicable, for GNSS equipment supporting precision approach or LP V capability, confirm that the antenna to aircraft center of navigati on offset is appropriate to the insta llation (ref erence RTCA/DO-229C section 2.2.4.3.3).

b. Sensor Installation. No ground tests are recommended for the sensor. Guidance relating to the interface betw een the sensor and the naviga tion system can be found in AC 20-130A.

c. Stand-Alone Navigation Equipment Installation.

(1) Visibility of the controls, displays , and annunciators relating to the GNSS installation should be evaluated during day a nd night lighting conditi ons. No distracting cockpit glare or reflections m ay be introduced and all con trols must be illuminated for identification and ease of use. Night lighting should be c onsistent with other cockpit lighting.

(2) Layout of the installed equipm ent should be evaluated with e mphasis on equipment contro ls, ap plicable circuit brea kers (labels a nd accessib ility), switching arrangement, and related indicators, displays, annunciators, etc.

(3) Navigation parameters displayed on coc kpit instruments such as HSI, CDI, distance display, electronic f light instrum ents system (E FIS), m oving m aps, flight management systems, etc. should be evaluate d against the criteria described in paragraph 18 of this AC.

(4) Failure m odes and associated annunciations, such as loss of electrical power, loss of signal recep tion, GNSS equi pment failure, au topilot/flight d irector response to flags, etc. should be reviewed against the criteria described in paragraph 18 of this AC.

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(5) Manual approach selection or manua l tuning of the approach should override any autom atic selection. Once an approach has been selected, appropriate feedback to the pilot (e.g. display of approach na me (including runway), airport and reference path identifier) m ust be given to in dicate the approach has been correctly selected.

**23. INSTALLED PERFORMANCE - FLIGHT TEST.**

a. Sensor Installation. Conduct a functional flight te st. Verify continuity of navigation data during norm al aircraft m aneuvering for the navigation m odes to be validated (e.g. bank angles of up to 30 degrees and pitc h angles associated with approaches, m issed approaches and depa rtures, as applicable). A C 20-130A has guidance on the interface between the sensor and the navigation system.

b. Stand-Alone Navigation Equipment Installation.

(1) Continuity of Navigation. Verify c ontinuity of naviga tion data during normal aircraft m aneuvering for the navigati on modes to be validated (e.g., bank angles of up to 30 degrees and pitch angles associ ated with take-off, departures, approaches, landing and missed approaches as applicable).

(2) Equipment Operation. Verify the ov erall operation of the GNSS equipm ent to include at least the following: hold at a de signated waypoint, intercept and track to or from a waypoint on a selected course, turn anticipation, waypoint sequencing, selection of an approach and the general presentation of navigational data (depiction of the “TO” waypoint, distance to waypoint, estimated time of arrival, estimated time en route, ground speed, etc.). Evaluate the overall operation on all of the types of procedures or paths that the equipment supports (e.g., straight legs, DME arcs, and radius to fix legs).

(3) Flight Tech nical Error. Verify that flight technical error (FTE) can be maintained at less than 1.0 NM for en route and approach transition operating modes, and less than 0.25 NM for non-precision approach , both with and without autopilot and/or flight director use, as applicable. This test may not be n ecessary if the FTE has been previously estab lished for the aircraft. One acceptable way of assessing FTE is to monitor the measured cross-track deviation using the navigation display provided.

(4) Interface to Flight Guidance System (FGS). The following issues should be evaluated w hen the eq uipment is interfaced with a flig ht guid ance system . The objective of this paragraph is to en sure that the GNSS equipm ent interface is compatible with the aircraft; the ob jective is not to verify FGS perf ormance. If these issues cannot be addressed for a particular autopilot (e.g., because the autopilot does not respond to flag indications), the GNSS equipm ent m ay still be installed but either should not be connected to the autopilot or, if the discrepancy is consistent with the rest of the aircraft’s navigation capabilities, the issue can be a ddressed in the A/RFM(S) through consistent crew procedures for all types of navigation.

(i) Evaluate steering respons e while flight director and/or autopilot is coupled to the GNSS e quipment during a variet y of different track and m ode changes.

This evaluation should include, as applicable , transition from en route to approach transition to approach to m issed approach m odes and vice-versa. Additionally, evaluate all available display sensitivities.

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(ii) Execute several fly-by turns with va rying wind conditions for flight director and autopilot. Verify the equipm ent accomplishes the turn as a fly-by waypoint and discou rages ove rshoot. Fly-by turns ar e turns where the equip ment initia tes th e turning m aneuver before sequencing the wa ypoint by an am ount equal to the turn anticipation distance.

(iii) Verify that the late ral m aneuver anticipation supplied by the GNSS equipment is appropriate for the aircraft type . Verify that an a ppropriate annunciation of impending waypoint crossing is provided.

(iv) Verify that execution of the Direct-T o function with a re sultant aircraft heading change does not overshoot and cause “S” turns. Reinitialization of the Direct-To function af ter com pletion of most of the requ ired track ch ange m ay be an acceptable means of compliance for equipm ent which does not inherently account for the change in aircraft heading.

(v) Evaluate the autopilot response to a GNSS fault by pulling the circuit breaker for the GNSS equipm ent. This test should be done in all of the GNSS en route and approach modes.

(vi) GLS and LPV Approaches (A) For installations where the autopilot has not been modified and the GNSS equipment provides ILS-like deviations, conduct several approaches while flying raw data, flight director and coupled to the au topilot, as applicable. The objective of this test is to ensure that the GNSS equipm ent interface is com patible with the aircraft; the objective is not to verify approach perfor mance. For aircraft with a potentially large difference between heading and track (e.g., airs hip), evaluate the effects of the offse t between th e GPS antenna or aircraft cente r of navigation during approaches (see paragraph 22a(4) of this AC).

(B) For insta llations where the au topilot has been m odified, the autopilot lateral/vertical control channel perform ance has not been assessed, or nonstandard deviations are provided (not ILS-like), then the approach performance will need to be evaluated per AC 23-17A, 25.1329-1, or equivalent means.

(C) For m anual contro l to the app roach flight path, the appropriate flight display(s) m ust provide sufficient information to maintain the app roach path and make alignm ent with the runway or go-ar ound without excessive reference to other cockpit displays.

(5) Interface to Barom etric Altimeter. If the equipm ent uses barom etric input, verify that the equipm ent properly interprets the barom eter reading. For equipm ent that requires manual entry of barom etric correction, the entry should be accom plished during an approach to evaluate the crew workload.

(6) Switching and Transfer Functions. Veri fy/assess all switching and trans fer functions, including electrical bus switching, perta ining to the G NSS installation .

Evaluate the aircraft system response during switches to all altern ate navigation sources and ensure that the switch is accom plished as expected, that it is clearly annunciated, and that the switching itself does not induce any inaccurate guidance.

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(7) Failure Modes/Annunciations. Review and verify where appropriate various failure m odes and associated annunciations, such as loss of electrical power, loss of signal reception, GNSS equipment failure, FGS response to GNSS flags, etc. Verify that a warning associated with lo ss o f navigati on is accom panied by a visible indication within the pilot’s primary field of view.

(8) Crew Workload. An analysis of cr ew workload when operating the GNSS equipment in association with other piloting requirements should be conducted during all phases of flight, including those non-normal procedures that can be evaluated in flight.

c. LAAS Positioning and Navigation Equipment Installation.

(1) Continuity of Navigation. Verify c ontinuity of naviga tion data during normal aircraft maneuvering for the navigation modes to be validated (e.g. bank angles of up to 30 degrees and pitch angles associated with approaches, m issed approaches and departures).

(2) Interface to Flight Guidance System (FGS).

(i) Evaluate steering respons e while flight director and/or autopilot is coupled to the LAAS equipment during a variety of different mode changes and approach intercepts. Additionally, all available display sensitivities should be evaluated.

(ii) Evaluate the autopilot response to a GNSS fault by pulling the circuit breaker for the GNSS equipm ent. This test should be done in each of th e GNSS modes, if applicable.

(iii) Conduct several approaches while flyi ng raw data, flight director only and coupled to the autopilot, as applicable. The object ive of the test is to ensure that the GNSS equi pment interface is com patible with the aircraft a nd is not a verification of approach perform ance. This objective is va lid only for installati ons with existing and proven performance (e.g. GNSS pr oviding ILS like deviations to replace or supplem ent an existing ILS). For installations w here the autopilot has been modified or the autopilot lateral/vertical control channel perform ance has not been assessed, th en the approach performance will need to be evaluated per AC 23-17A, AC 25.1329-1A, or equivalent means. For aircraft with a potentially la rge difference between heading and track (e.g., airship), evaluate th e effects of the offset be tween the GPS antenna or aircraft cen ter of navigation during approaches (see paragraph 22a(4)).

(iv) For m anual control to the approach f light path, the appropriate flight display(s) must provide sufficient inform ation without excessive reference to other cockpit displays, to en able a suitably train ed pilot to m aintain the app roach path, make alignment with the runway or go-around.

(v) For Part 25 aircraft, the criteria in AC 120-29A, Appendix 2, should also be con sidered. Th e criteria define d for MLS m ay be used to qualify the LAAS functions.

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Appendix 1

d. LAAS VDB Receiver Installation.

(1) To ensure com patibility between the VDB a nd VHF c ommunications equipment, a flight test should b e acco mplished using the highest available V DB broadcast, and transm itting VHF communica tion at 100 kHz above the VDB channel.

For VHF comm unications equipment that cannot transm it below 118.000 MHz, the n

118.000 MHz should be used.

(2) VDB receiving capability should b e dem onstrated in flight. Unlike ILS, where th e ILS facility is always lo cated in front of t he ai rcraft on approach, a LAAS facility cou ld be lo cated anywhere with r espect to the ap proach pa th. Theref ore, the flight test should verify VDB signal reception at all angles relative to the airframe.

Stephen Van Trees Acting Manager, Aircraft Engineering Division Aircraft Certification Service

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Appendix 1

**APPENDIX 1. GPS OCEANIC/REMOTE NAVIGATION**

The following criteria define an acceptab le means of compliance for TSO-C129(AR) GPS equipm ent intended for oceanic and re mote operation without reliance on other long-range navigation system s. Equipm ent which previously dem onstrated compliance to Notice 8 110.60 is still eligib le for oceanic and remote operation and need not be reevaluated. Note that GPS/WAAS equipment should not be evaluated against this criteria.

GPS/WAAS equipment is inherently capable of supporting this operation if the operator obtains a fault detection and exclusi on (F DE) prediction program ; no additional evaluation is necessary.

**1. APPROVAL PROCESS.**

a. TSO Authoriza tion. The cr iteria in this a ppendix is in additio n to the requirements of RTCA/DO-208, Minim um Op erational Perform ance Standards for Airborne S upplemental Navigation Equipm ent Using Global Positioning System , as modified by Technical Standard Order, TSO-C129(AR). The ACO should issue a separate letter of design approval stating th at the equipment (including part num ber) and software prediction program (including revi sion num ber) m eet the criter ia in this appendix.

b. Installation Approval.

(1) The applicant obtains installatio n approval of the GPS navigation equipment.

(2) If the m anufacturer has previously obtained a letter of design approval as described in paragraph 1a of this appendix, fu rther evaluation as described in paragraphs 2 and 3 of this appendix is not required.

(3) If the m anufacturer has not obtained a letter of design approval, then the applicant must demonstrate compliance with the requirements in paragraphs 2 and 3 of this appendix.

(4) The failure of the long-range navi gation function is a m ajor failure condition. For many oceanic/remote operations, this requires equipping the airplane with at least two (or more) independent (i.e., dual control display unit, dual GPS antenna, dual power sources, dual GPS sensors, etc.) navi gation equipment with a m ean time between failures of at least 1000 hours each (for dual equipage).

(5) Once the installation has been appr oved, the A/RFM(S) should be updated to state: "The XXX GPS equipm ent as inst alled has been found to co mply with the requirements for GPS oceanic and rem ote navigation, when used in con junction with the XXX prediction program. This does not constitute an operational approval."

c. Operational Approval. The applicant should be aware that an operational approval m ust be obtained before conducting Class II n avigation (rem ote/oceanic).

Applicants should contact the appropriate F light Standards Distri ct Office to seek approval (reference HBAT 95-09, Guidelines for Operational Approval of GPS to provide the Prim ary Means of Class II Na vigation in Oc eanic and Rem ote Are as of Operation).

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Appendix 1

**2. EQUIPMENT PERFORMANCE.**

a. TSO-C129(AR). The GPS equipment must meet the criteria of TSO-C129(AR).

b. Fault Detection and Exclusion (FDE).

(1) The GPS equipm ent must be able to detect a nd exclude a GPS satellite failure by means of a f ault detection and exclusion (FDE) algorithm including receiver autonomous integrity m onitoring (RAIM) for detection. The exclus ion of a satellite failure must be autom atic: pilot action is not permitted to accom plish exclusion. The FDE algorithm m ust be aided by b arometric a ltimetry measurements, as requ ired by TSO-C129. Additional augm entations (such as clock aiding ) are no t precluded. F DE terms are defined in RTCA/DO-229C.

(i) Missed alert probability. The probabili ty of missed alert must be le ss than or equal to 0.001 for every geom etry and every navigation m ode. This requirement is on the m issed alert rate external to the GPS equipm ent. W hen related to the in ternal algorithm, it includes both probabilities of missed detection and false exclusion.

(ii) False alert probability. The probability of false alert must be less than or equal to 0.002/hour. This requi rement is on the false aler t rate external to the GPS equipment. When related to the in ternal algorithm, it includes both probabilities of false detection and the failure to exclude the false detection.

(iii) Failed exclusion proba bility. The probability of failed exclusion must be less than or equal to 10 -3 for every geom etry and ever y navigation mode for which exclusion is im plemented. Exclusion m ust be implemented for the oceanic m ode. This requirement is on the alert rate external to the GPS equipment due to failed exclusion.

(iv) Time-to-alert. The tim e-to-alert for oceanic/remote navigation mode is defined to be at least 30 seconds, but must not exceed 5 minutes.

(2) In addition to FDE, the equipm ent must use an acceptable means to detect and exclude from the navigation solution any satellite that experiences a failure wh ich causes a pseudorange step. A ps eudorange step is a sudden change in the m easured distance to a satellite. It can be written as:

PRSTEP = | PRPREDICTED - PRMEASURED | where PRPREDICTED is the predicted pseudorange at the time of measurement, based on previous measurements, and PRMEASURED is the pseudorange at the time of the measurement.

(i) The equipm ent m ust detect a pse udorange step erro r greater than 1000 meters, including steps, which cause loss of lock for less than 10 seconds.

(ii) If a pseudorange step is detected fo r a satellite, that satellite m ust be excluded from use in the navigation algor ithm until its integrity can be verified, and fault detection (RAIM) is available. The m anufacturer is free to choose any m ethod to calculate the predicted pseudor ange. However, any m ethod used should properly take into account satellite m ovement and aircraft dynam ics up to a groundspeed of 750 knots (kts) and accelerations up to 14.7 meters/second/second (1.5 g's).

Page A1-2

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Appendix 1

(3) The GPS equipm ent must exclude, without pilot actio n, any satellite designated unhealthy by any of the GPS navigati on data. The satellite must be excluded within 5 m inutes of the designation as unhea lthy by the satellite. A description of the parameters that m ust be checked ar e in RTCA/DO-229C, section 2.1.1.5.5, except a satellite broadcasting “111 101” must not be used.

(4) If a GPS satellite failure results in loss of GPS navigation (due to the failure to exclude or to loss of a cr itical satellite), an appropr iate indication [ TSO-C129(AR), paragraphs (a)(3)(xiii)1c, (a)(4)(iv)10, and (a)(5)(iv)9)] of the failure must be provided to the flight crew.

(5) The equipment m ust provide, upon reque st, an indication of the current estimate of position uncertainty in term s of na utical miles (NM). This estim ate must be based on measurement inconsistency and must bound the true error with high confidence (approximately 99.9 percent). It is related to th e test statistic calculated as part of FDE.

This estimate will not be available if there are only four measurements available (because there is no redundancy). This output is in tended to provide inform ation about the approximate magnitude of a potential positi oning failure, when the horizontal integrity limit (HIL) exceeds the alert limit or when a positioning failure has been detected but not excluded.

3. PREDICTION PROGRAM . A prediction program is required to support operational departure restrictions. See paragraph 12e of this AC.

Page A1-3 (and A1-4)

### Page 51

Appendix 2

**APPENDIX 2. INTEGRATION OF GLONASS WITH GPS OR GPS/WAAS**

GLONASS must be supplemental to other approved means of navigation. This appendix defines an acceptable means of compliance for GNSS equipment to use GLONASS.

**1. APPROVAL PROCESS.**

a. TSO Authorization. Equipm ent that com plies with th e criteria of this Appendix can obtain a TSO-C145a, TSO-C146a, or TSO-C129a authorization. The ACO s hould issue a separate letter of de sign approval, stati ng that the applian ce (including part number) complies with this Appendix.

b. Installation Approval.

(1) The applicant obtains installatio n approval of the GPS navigation equipment.

(2) If the m anufacturer has previously obtained a letter of design approval as described in paragraph 1a of this appendix, further evaluation as described in paragraph 2 of this appendix is not required.

(3) If the m anufacturer has not obtained a letter of design approval, then the applicant must dem onstrate com pliance with the requirements in paragraph 2 of this appendix.

(4) Approval of equipm ent which does not satisf y the interf erence criteria specified in paragraph 2f of this appendi x should include a lim itation in the A/RFM(S):

“The GLONASS capa bility may be lost due to interference encountered during norm al operations, and is limited to be a supplement to other navigation.”

c. Operational Approval.

(1) Until the FAA declares GLONASS operational for U.S. aviation, GLONASS signals cannot be us ed in predicting RAIM av ailability f or nonprecision approach, or for FDE availab ility for oceanic /remote operations (see ap pendix 1 of this AC).

(2) When the FAA declares GLONASS operational, integrated GPS/GLONASS equipment which meets the interference criteria in paragraph 2f of this Appendix will be able to take advantage of GLONASS signals when predating RAIM approach availability and availability of FDE for oceanic and rem ote operations. For equipment tha t does not meet the interference criteria, no predictive cred it can be given for GLONASS even after it is declared operational for U.S. aviation.

**2. EQUIPMENT PERFORMANCE.**

a. Performance without GLONASS. In the absence of GLONASS signals, the equipment must satisfy all of th e criteria for GPS/WAAS or GPS equipment as described in this AC. This includes susceptibility to in-band and out-of-band interference.

b. GLONASS Receiver. GLONASS functions must be developed in accordance with the GLONASS Interface Control Document.

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Appendix 2

c. Accuracy. Use of GLONASS m ust not deg rade the sy stem accuracy. The accuracy requirem ents of TSO-C129(AR) an d RTCA/DO-208 m ust be satisfied using both GPS a nd GLONASS. Differences between GPS and G LONASS in reference time and coordinate reference fram es m ust be addressed. Inte rfrequency bias among GLONASS channels, and between GPS and GLONASS must be considered.

d. Integrity. Failure of GLONASS space or contro l seg ment must not cause misleading information. Therefore, the receiver must be capable of detecting all position errors that result from using GLONASS.

e. Continuity. Failure of GLONASS space or con trol segment must not cause loss of navigation unless navigation is not possible with GPS alo ne. Therefo re, the receiver must be able to exclude GLONASS measurements when a failure is detected, reverting to using only GPS if necessary. W hen a failur e is detected but ca nnot be isolated, the equipment must exclude all GLONASS measurem ents and revert to GPS navigation. If the resulting set of GPS satellites d oes not provide fault d etection, the equipm ent must indicate that RAIM is not available.

f. Interference Environment.

(1) The interf erence env ironment f or GLONASS is specif ied belo w.

GLONASS accuracy must be maintained in the specified interference environment.

(2) GLONASS equipm ent, which does not m eet this requirem ent, can be approved, but is lim ited to supplem ental operation and no credit can be taken for GLONASS capabilities. Regardless of the signal rejection in the GLONASS band, the GPS(WAAS) portion of the integrated equi pment must satisfy its requirem ents for interference. Approval of equipment which does not satisfy the interference criteria specified above should include a limitation: “The GLONASS capability m ay be lost due to interference encountered during norm al operations, and is lim ited to be a supplement to GPS navigation.”

(3) Prior to the year 2005, the required signal rejection results in the rejection of GLONASS channels f7 through f24. I mplementing this rejection before 2005 would reduce the size of the usable GLONASS constellation to those satellites using channels f0 through f6. Equipm ent may be de signed to use satellites above f6 to receive as m any signals as possible, but since the U.S. is n ot comm itted to protecting GLONASS operation above 1605 MHz then such equipm ent would also allow interference into its passband, precluding the use of any GLONASS satellites.

(4) GLONASS Spectrum Consideratio ns. Prior to 1998, G LONASS will operate between 1602.5625 MHz and 1615.5 MHz, ± 0.511 MHz. By 2005, the GLONASS operating band will be 1598.0625 MHz to 1605.375 MHz. GLONASS channel assignments are defined as shown in Table 1.

(5) GLONASS Interference Environm ent. International po licy is still being developed for the frequency protection of GLONASS signals. The criteria defined below are based on the U.S. position, w hich is to protect the use of GLONASS in its final configuration for precision approach operati ons. In addition, the use of GLONASS channels within the final band will be pr otected for nonprecision approach operations Page A2-2

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Appendix 2

from now until the GL ONASS tra nsition is c omplete. T wo levels o f interf erence are specified: one applies to equipm ent intended for en route through NPA operations, and one applies to equipment intended to support precision approach operations.

(6) All interference levels specified within this app endix are defined relative to received satellite signal levels (at antenna port) of -135.5 dBm . This satellite signal level represents that received at the an tenna port given a m inimum standard antenna gain of -4.5 dBi. For non-standard antennas with a different m inimum gain, the signal and interference levels can be adjusted accord ingly, as l ong as the relative interference-tosignal level is maintained. In other words, if the minimum antenna gain were 0 dBi, then the received satellite signal and the interference level would be increased by 4.5 dB.

(i) Narrowband Interference. Continuous Wave (CW) interfering signals can be as high as shown in figure 1. The corner frequencies in this figure are as stated in Table 2.

Table 1. GLONASS Channel Assignments

GLONASS Channel Frequency (±0.511 MHz) 1998- 2005 2005- f-7 1598.0625 MHz in use f-6 1598.6250 in use f-5 1599.1875 in use f-4 1599.7500 in use f-3 1600.3125 in use f-2 1600.8750 in use f-1 1601.4375 in use f0 1602.0000 in use in use f1 1602.5625 in use in use f2 1603.1250 in use in use f3 1603.6875 in use in use f4 1604.2500 in use in use f5 1604.8125 in use test f6 1605.3750 in use test f7 1605.9375 in use f8 1606.5000 in use f9 1607.0625 in use f10 1607.6250 in use f11 1608.1875 in use f12 1608.7500 in use f13 1609.3125 f14 1609.8750 f15 1610.4375 f16 1611.0000 f17 1611.5625 f18 1612.1250 f19 1612.6875 f20 1613.2500 f21 1613.8125 f22 1614.3750 f23 1614.9375 f24 1615.5000

Page A2-3

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Appendix 2

(ii) In-band and Near-band Interfe rence. The equip ment could receive an interfering signal with a center frequency on any GLONASS center frequency, and with a total bandwidth of BWI, that is as high as the levels shown in Figure C-2 of appendix C to RTCA/DO-229C.

(iii) Pulsed Interference. Integrated GPS/GLONASS equipm ent must continue tracking GPS and GLONASS signa ls without degradatio n to the position solution or integrity performance with in-ban d or out-of-band pulse interference sources with the following characteristics:

Peak Power +20 dBm Pulse Width 1 ms Pulse Duty Cycle 10%

Figure 1. CW Interference Levels 8

21.5 -120.5 -12 -12 -30 -130 -110 -90 -70 -50 -30 -10 10 30 50 1500 1550 1600 Frequency (MHz) Interference Level (dBm)

GLONASS with satcom GPS Table 2. CW Interference Levels

Frequency (MHz) Interference Level (dBm) GLONASS GPS With Satcom (both) 1315 25.5 25.5 1525 -12 -12 1565 -120.5 -120.5 1585.5 -120.5 -120.5 1605.886 -120.5 -45.2 1610 -30 -30 1618 -12 -12 -12 1626.5 -11.3 -11.3 8 2000 21.5 21.5 21.5 Page A2-4

### Page 55

Appendix 3

**APPENDIX 3. EXAMPLE FORMAT FOR A QUICK REFERENCE GUIDE**

A quick reference guide should be provided wi th the GNSS equipm ent as a training aid for the operation of the GNSS equipm ent. The quick reference guide should not be used as a checklist or as a replacem ent for the p rocedures and limitations of the equ ipment as stated in the FAA-approved operations manual or A/RFM(S).

Arrange the quick reference guide in sections to provide the pilot a quick reference to those procedures and clarifica tions applicable for that mode of operation. Sections m ay be added or deleted as appr opriate. Exam ple CDU page di splays and page flow s are encouraged.

Messages 1 of 3 GNSS

**QUICK**

REFERENCE GUIDE Procedure Turns/Holding Patterns 1 of 1 Missed Approach 1 of 1 Direct To 1 of 1 Approach 1 of 5 STARs 1 of 2 En route holding 1 of 1 SIDs 1 of 3 Flight plans 1 of 4

Page A3-1

### Page 56

Appendix 3

EXAMPLE FORMAT FOR A QUICK REFERENCE GUIDE (Continued)

Creating Flight Plans

1. Rotate left outer knob to FPL.

2. Rotate left inner knob to blank flight plan pages.

3. Press left CRSR.

4. Rotate left inner and outer knobs to input desired waypoint.

5. Press ENT

6. Press ENT

7. Repeat 4, 5, and 6 until all desired waypoints are entered.

Procedure Turns/Holding Patterns 1 of 1 Missed Approach 1 of 1 Flight Plans 1 of 4 Direct To 1 of 1 Messages 1 of 3 Approach 1 of 5 STARs 1 of 2 En route holding 1 of 1 SIDs 1 of 3 Editing Flight Plans

Inserting waypoints

1. Rotate left outer knob to flight plan pages.

2. Rotate left inner knob to desired flight plan page.

3. Press left CRSR

4. Rotate left outer knob to the point in the flight plan where you want to insert the new waypoint.

5. Rotate left inner and outer knobs to input new waypoint.

See next page for more instructions.

Flight Plans 3 of 4 SIDs 1 of 3

6. Press ENT Deleting Flight Plans

1. Rotate left outer knob to flight plan pages.

2. Rotate left inner knob to desired flight plan page.

3. Press left CRSR

4. Rotate left outer knob to place cursor over waypoint to be deleted.

5. Press CLR

6. Press ENT

5. Press ENT Procedure Turns/Holding Patterns 1 of 1 Missed Approach 1 of 1 Approach 1 of 5 Direct To 1 of 1 Messages 1 of 3 STARs 1 of 2 En route holding 1 of 1 Routes 2 of 4 Activating Flight Plans

1. Press left CRSR

2. Press ENT

Page A3-2

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Appendix 3

EXAMPLE FORMAT FOR A QUICK REFERENCE GUIDE (Continued) If steps 9 – 10 are not required, go to step 13.

If required to choose a SID runway:

9. Rotate right outer knob to select desired runway.

10. Press ENT If steps 10 – 11 are not required, go to step 13.

If required to choose a SID runway transition:

11. Rotate right outer knob to select desired transition.

12. Press ENT and go to step 13

13. Press ENT Flying the selected SID

1. Press left CRSR

2. Rotate right outer knob to desired waypoint

3. Press D

4. Press ENT

SIDs 3 of 3 Messages 1 of 3 Procedure Turns/Holding Patterns 1 of 1 Missed Approach 1 of 1 Direct To 1 of 1 Approach 1 of 5 STARs 1 of 2 En route holding 1 of 1 SIDs 2 of 3 Selecting SIDs

1. Rotate right outer knob to airport pages.

2. If the desired airport is not displayed, press right CRSR

3. Rotate right inner and outer knobs to input desired airport.

4. Press right CRSR

5. Rotate right inner knob to select APT 7 page.

6. Press right CRSR

7. Rotate right outer knob to select desired SID.

8. Press ENT See next page for more instructions.

SIDs 1 of 3 Messages 1 of 3 Procedure Turns/Holding Patterns 1 of 1 Missed Approach 1 of 1 Direct To 1 of 1 Approach 1 of 5 STARs 1 of 2 En route holding 1 of 1 Reversing Flight Plans

9. Rotate left outer knob to flight plan pages.

10. Rotate left inner knob to select flight plan to be reversed.

11. Press left CRSR

12. Rotate left outer knob to display blinking “USE?INVRT?” page.

13. Press ENT

Routes 4 of 4 Page A3-3

### Page 58

Appendix 3

EXAMPLE FORMAT FOR A QUICK REFERENCE GUIDE (Continued) Messages 1 of 3 En route holding 1 of 1 Procedure Turns/Holding Patterns 1 of 1 Missed Approach 1 of 1 Direct To 1 of 1 Approach 1 of 5 STARs 1 of 2 En route holding

1. Press GPS CRS switch to display “OBS”.

2. Press D

3. Press ENT

4. Set course for intercept into HSI.

Selecting STARs

1. Rotate right outer knob to airport pages.

2. If desired airport is not displayed, press right CRSR

3. Rotate right inner and outer knobs to input desired airport.

4. Press right CRSR

5. Rotate right inner knob to APT 7 page.

6. Press right CRSR

7. Rotate right outer knob to select desired STAR.

8. Press ENT

See next page for more instructions.

Messages 1 of 3 STARs 1 of 2 Procedure Turns/Holding Patterns 1 of 1 Missed Approach 1 of 1 Direct To 1 of 1 Approach 1 of 5 Page A3-4

### Page 59

Appendix 3

EXAMPLE FORMAT FOR A QUICK REFERENCE GUIDE (Continued)

If steps 10 – 11 are not required, go to step 12.

If required to choose an IAF:

10. Rotate right outer knob to select desired IAF.

11. Press ENT and go to step 12

12. Press ENT Vectored approaches

This function not available

Messages 1 of 3 Direct To 1 of 1 Approach 3 of 5 Repeating an approach

1. Rotate left outer knob to select “FPL 0” page.

2. press left CRSR

3. Rotate left outer knob to select desired approach waypoint from which to repeat the approach.

4. Press D

5. Press ENT If steps 6 – 11 are not required, go to step 12.

If required to intercept approach course:

6. Rotate left outer knob to select “FPL 0” page.

See next page for more instructions.

Missed Approach 1 of 1 Procedure Turns/Holding Patterns 1 of 1 Arming approaches

1. If GPS APR switch is in proper position, approach will auto arm and switch will display “ARM”.

2. If within 30 miles of destination, and GPS APR switch does not display “ARM”, press GPS APR switch Approach 2 of 5 Selecting approaches

1. Rotate right outer knob to airport pages.

2. Rotate right inner knob to APT 1 page.

3. If desired airport is not displayed, press right CRSR

4. Rotate right inner and outer knobs to select desired airport.

5. Press right CRSR

6. Rotate right inner knob to APT 8 page.

7. Press right CRSR

8. Rotate right outer knob to select desired approach.

9. Press ENT

See next page for more instructions.

Messages 1 of 3 Approach 1 of 5 Direct To 1 of 1 Procedure Turns/Holding Patterns 1 of 1 Missed Approach 1 of 1

If steps 9 – 10 are not required, go to step 11.

If required to choose a STAR transition:

9. Rotate right outer knob to select desired transition.

10. Press ENT and go to step 11.

11. Press ENT

STARs 2 of 2 Page A3-5

### Page 60

Appendix 3

EXAMPLE FORMAT FOR A QUICK REFERENCE GUIDE (Continued)

Missed Approach 1 of 1 Procedure Turns/Holding Patterns 1 of 1 Messages 1 of 3 Direct To 1 of 1 Messages 1 of 3 Approach 5 of 5 Direct To 1 of 1 Procedure Turns/Holding Patterns 1 of 1 Missed Approach 1 of 1 Changing an approach

1. Rotate left outer knob to select “FPL 0” page.

2. Press left CRSR

3. Rotate left outer knob to display blinking “CHANGE APR” page.

4. Press ENT

5. Rotate right outer knob to select desired approach.

6. Press ENT If steps 7 – 8 are not required, go to step 9.

If required to choose an IAF:

7. Rotate right outer knob to select desired IAF.

8. Press ENT and go to step 9.

9. Press ENT

Approach 4 of 5

7. Press GPS CRS switch to display “OBS”.

8. Set desired course into HSI.

9. Press left CRSR

10. Rotate left outer knob to waypoint at end of desired course segment.

11. Press D and go to step 12.

12. Press ENT

Missed approach

Direct to a waypoint

1. Press D

2. Press ENT

Intercepting a course to a waypoint

1. Press GPS CRS switch to display “OBS”.

2. Press D

3. Press ENT

4. Set inbound course into HSI.

Page A3-6

### Page 61

Appendix 3

EXAMPLE FORMAT FOR A QUICK REFERENCE GUIDE (Continued) Holding Patterns

1. Press GPS CRS switch to display “OBS”.

2. Press D

3. Press ENT

4. Set course for intercept into HSI.

Procedure Turns/Holding Patterns 1 of 1 Messages 1 of 3 Direct To 1 of 1 Procedure turns

1. Prior to the FAF outbound, press GPS CRS switch to display “OBS”.

2. Fly outbound course and procedure turn as specified.

3. Set inbound course into HSI.

4. Prior to the FAF inbound, press GPS CRS switch to display “LEG”.

Direct to the FAF

1. Rotate left outer knob to select flight plan pages.

2. Rotate left inner knob to select desired flight plan.

3. Press left CRSR

4. Rotate left outer knob to place cursor over the FAF.

5. Press D

6. Press ENT

2. Press ENT

3. Pull out right inner knob

4. Rotate right inner knob to select desired airport.

5. Push in right inner knob

6. Press D

7. Press ENT Direct to the nearest waypoint

This function available only for airports.

Direct to the nearest airport

1. Press MSG Direct To 1 of 1 Messages 1 of 3 Page A3-7

### Page 62

Appendix 3

EXAMPLE FORMAT FOR A QUICK REFERENCE GUIDE (Continued)

**RAIM NOT AVAILABLE**

**APR MODE INHIBITED PREDICT RAIM ON STA 5**

1. Rotate left outer knob to STAT

2. Predict RAIM to determine when approach can be flown.

3. Rotate left inner knob to “STAT 5” page.

**RAIM NOT AVAILABLE**

**CROSS CHECK POSITION**

1. Cross-check with other means of navigation.

**RAIM POSITION ERROR**

**CROSS CHECK POSITION**

1. Cross-check with other means of navigation.

Messages

ADJ NAV IND CRS TO _____

1. Set course into HSI.

2. Press MSG

**ARM GPS APPROACH**

1. Press GPS APR switch

**BAD SATELLITE GEOMETRY**

1. See EPE on “STS 2” page, or

2. Use other means of navigation

BAD SATELLITE GEOMETRY and

**RAIM NOT AVAILABLE**

1. Appears only when receiver is in approach active mode.

2. Use other means of navigation.

**PRESS ALT TO SET BARO**

1. Press ALT

2. Rotate left inner and outer knobs to input altitude.

3. Press left CRSR

4. Press ALT

Messages 1 of 3 Messages 3 of 3 Messages 2 of 3

**SATELLITE COVERAGE**

**INADEQUATE FOR NAVIGATION**

1. Use other means of navigation.

Page A3-8

### Page 63

Appendix 4

**APPENDIX 4. SAMPLE AIRPLANE/ROTORCRAFT FLIGHT MANUAL**

**SUPPLEMENT**

Installation Center/Repair Station Model XXX GPS 123 Fourth Street Navigation System Anytown, USA

**FAA APPROVED AIRPLANE FLIGHT MANUAL SUPPLEMENT**

**ABC MODEL XXX GPS NAVIGATION SYSTEM**

AIRPLANE MAKE:

AIRPLANE MODEL:

AIRPLANE SERIAL NO.:

REGISTRATION NO.:

This document must be carried in the airplane at all times. It describes the operating procedures for the ABC Model XXX GPS navigation system when it has been installed in accordance with <manufacturer's installation manual number and date>.

For airplanes with an FAA Approved Airplane Flight Manual, this document serves as the FAA Approved ABC Model XXX GPS Flight Manual Supplement. For airplanes that do not have an approved flight manual, this document serves as the FAA Approved ABC Model XXX GPS Supplemental Flight Manual.

The information contained herein supplements or supersedes the basic Airplane Flight Manual dated <insert date> only in those areas listed herein. For limitations, procedures, and performance information not contained in this document, consult the basic Airplane Flight Manual.

**FAA APPROVED**

_____________________ Title Office Federal Aviation Administration City, State

FAA Approved Page <> of <> Date: ________

Page A4-1

### Page 64

Appendix 4

SAMPLE AIRPLANE/ROTORCRAFT FLIGHT MANUAL (Continued)

Installation Center/Repair Station Model XXX GPS 123 Fourth Street Navigation System Anytown, USA

Table of Contents

Section … Page

1 General. ............................................< >

2 Limitations........................................< >

3 Emergency/Abnormal Procedures....< >

4 Normal Procedures ...........................< >

5 Performance......................................< >

6 Weight and Balance..........................< >

7 System Description...........................< >

FAA Approved Page <> of <> Date: ________

Page A4-2

### Page 65

Appendix 4

SAMPLE AIRPLANE/ROTORCRAFT FLIGHT MANUAL (Continued)

Installation Center/Repair Station Model XXX GPS 123 Fourth Street Navigation System Anytown, USA

SECTION 1 - GENERAL <Include the appropriate statement to describe the equipment capability:>

GPS TSO-C129a Class A1: The installed ABC system complies with AC 20- 138A for IFR navigation using GPS for en route, terminal area, and nonprecision approach operations (including “GPS”, “or GPS”, and “RNAV” approaches).

GPS TSO-C129a Class A2: The installed ABC system complies with AC 20- 138A for IFR navigation using GPS for en route and terminal area operations.

GPS/WAAS TSO-C146a Class 3: The installed ABC equipment complies with AC 20-138A for navigation using GPS and WAAS (within the coverage of a Space-Based Augmentation System complying with ICAO Annex 10) for en route, terminal area, non-precision approach operations (including “GPS”, “or GPS”, and “RNAV” approaches), approach procedures with vertical guidance (including “LNAV/VNAV” and “LPV”), and precision approaches (including “GLS” approaches).

GPS/WAAS TSO-C146a Class 2: The installed ABC equipment complies with AC 20-138A for navigation using GPS and WAAS (within the coverage of a Space-Based Augmentation System complying with ICAO Annex 10) for en route, terminal area, non-precision approach operations (including “GPS”, “or GPS”, and “RNAV” approaches), and approach procedures with vertical guidance (including “LNAV/VNAV”).

GPS/WAAS TSO-C146a Class 1: The installed ABC equipment complies with AC 20-138A for navigation using GPS and WAAS (within the coverage of a Space-Based Augmentation System complying with ICAO Annex 10) for en route, terminal area, and non-precision approach operations (including “GPS”, “or GPS”, and “RNAV” approaches).

GPS/WAAS TSO-C146a Class 1/TSO-C161: The installed ABC equipment complies with AC 20-138A for navigation using GPS, WAAS (within the coverage of a Space-Based Augmentation System complying with ICAO Annex 10), and LAAS (within the coverage of a Ground-Based Augmentation System complying with ICAO Annex 10) for en route, terminal area, nonprecision approach operations (including “GPS”, “or GPS”, and “RNAV” approaches), approach procedures with vertical guidance (including “LNAV/VNAV” and “LPV”), and precision approaches (including “GLS” approaches).

G PS TSO-C129/TSO-C161: The installed ABC system complies with AC 20- 138A for navigation using GPS and LAAS (within the coverage of a groundbased augmentation system complying with ICAO Annex 10) for en route, terminal area, and non-precision approach operations (including “GPS”, “or GPS”, and “RNAV” approaches). The installed ABC system complies with AC 20-138A for navigation using GPS and LAAS for precision approach operations (including “GLS” approaches).

FAA Approved Page <> of <> Date: ________ Page A4-3

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Appendix 4

SAMPLE AIRPLANE/ROTORCRAFT FLIGHT MANUAL (Continued)

Installation Center/Repair Station Model XXX GPS 123 Fourth Street Navigation System Anytown, USA

<The following statement applies to all types of stand-alone equipment.> Navigation information is referenced to WGS-84 reference system, and should only be used where the Aeronautical Information Publication (including electronic data and aeronautical charts) conform to WGS-84 or equivalent.

<For TSO-C146a equipment and TSO-C129(AR) equipment that complies with the requirements in Appendix 1 of this AC:> The ABC equipment as installed has been found to comply with the requirements for GPS Oceanic/Remote Navigation, when used in conjunction with the ABC prediction program. This does not constitute an operational approval.

**SECTION 2 - LIMITATIONS**

1. The ABC Model XXX GPS Quick Reference Guide, P/N <insert part number>, dated <insert date> (or later appropriate revision) must be immediately available to the flight crew whenever navigation is predicated on the use of the system.

2. The system must utilize software version <insert version identification>.

3. A valid and compatible database must be installed and contain current data.

<Limitation for TSO-C129(AR) equipment (whether or not LAAS is also provided):>

4. The aircraft must have other approved navigation equipment installed and operating appropriate to the route of flight.

5. <Specify any additional limitations applicable to the particular installation.>

**SECTION 3 - EMERGENCY/ABNORMAL PROCEDURES**

EMERGENCY PROCEDURES No Change

**ABNORMAL PROCEDURES**

1. If ABC Model XXX GPS navigation information is not available or invalid, utilize remaining operational navigation equipment as appropriate.

2. If Loss of Integrity Monitoring message is displayed, revert to an alternate means of navigation appropriate to the route and phase of flight or periodically cross-check the GPS guidance to other, approved means of navigation.

**SECTION 4 - NORMAL PROCEDURES**

1. Normal operating procedures are outlined in the ABC Model XXX GPS Pilot's Guide.

2. <Describe approach mode sequencing.> FAA Approved Page <> of <> Date: ________ Page A4-4

### Page 67

Appendix 4

SAMPLE AIRPLANE/ROTORCRAFT FLIGHT MANUAL (Continued)

Installation Center/Repair Station Model XXX GPS 123 Fourth Street Navigation System Anytown, USA

3. System Annunciators <applicable to installations with external annunciators>

a. Waypoint - <describe each annunciator>

b. Message - <describe each annunciator>

c. Approach - <describe each annunciator>

d. <describe any other annunciators>

4. System Switches <applicable to installations with external switches>

a. Nav/GPS - <describe switch use and function>

b. RMI Switch - <describe switch use and function>

c. <describe any other switches>

5. Pilot's Display <describe the pilot's GPS display(s)>

6. Flight Director/Autopilot Coupled Operation <describe the procedures for coupling GPS to the flight director and/or autopilot system(s)>

7. < include any other normal operating procedures necessary>

**SECTION 5 - PERFORMANCE**

No Change

**SECTION 6 - WEIGHT AND BALANCE**

<Refer to revised weight and balance data, if applicable.>

**SECTION 7 - SYSTEM DESCRIPTION**

<Provide a brief description of the system, its operation, installation, etc.>

FAA Approved Page <> of <> Date: ________

Page A4-5 (and A4-6)

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Appendix 5

**APPENDIX 5. INSTALLATION OF EN ROUTE GPS EQUIPMENT FOR VFR**

**USE ONLY**

1. GENERAL. This appendix provides guidelines fo r the installation of stand-alone GPS systems used for en route, VFR navigation only.

2. APPLICABILITY. All un-pressurized aircraft less than 6000 pounds where the modification is classified as a minor alteration.

3. TECHNICAL INSTRUCTIONS. Install the GPS as follows:

a. The GPS equipm ent should be lo cated in a position which is viewable and accessible to the pilot from his/her norm ally seated p osition. The installed GPS equipment should not:

(1) Restrict access to or view of any control, display or indicator;

(2) Restrict movement of the flight controls;

(3) Interfere with the pilot’s vision along the flight path; or

(4) Restrict pilot/passenger egress.

b. The installation should be carried out in accordance with the m anufacturer’s installation instru ctions, the airc raft m aintenance m anual and th e guideline s in AC43.13-2A. The installation should conform to the following requirements:

(1) Manufacturer-supplied or standard parts should be used.

(2) If a ‘non-standard’ method of instal lation is used, the m anufacturer’s recommended procedures are to be followed.

(3) The GPS mounting sho uld be te sted to ensur e that it will be res trained throughout the flight envelope.

(4) Where a modification is required to the aircraft stru cture to sh ow compliance with paragraph 3b(3), the modification is to be carried out in accordance with the aircraft maintenance manual and the guidelines in AC43.13-1B and AC 43.14-2A.

c. If required, install a remote GPS antenna as follows:

(1) Determine a suitable location for the GPS antenna on the upper fuselage.

Particular care should be taken to ensure that at leas t the m inimum separation is maintained between the GPS antenna and VHF communications and ELT antennas.

(2) Install the m anufacturer-approved G PS antenna in accord ance with the manufacturer’s installation instructions, the aircraft m aintenance manual and the guidelines in AC 43.13-2A. The GPS antenna inst allation should be test ed to ensure that it would be restrained throughout the flight envelope.

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Appendix 5

(3) If using an internally mounted, m anufacturer-supplied rem ote antenna, install the antenna in accordance with the manufacturer’s installation instructions. Ensure that th e antenna and associated cable will not interfere with pilo t’s vision, aircraft controls or displays, or pilot/passenger egress.

d. Install and placard an appropriately rated circuit breaker or fuse.

e. If required, install a remote GPS indicator as follows:

(1) Determine a suitable location for the G PS indicator. The indicator should be located in the instrum ent panel and readily viewable to the pilot from his/her normally seated position.

(2) Install the indicator in accord ance w ith the m anufacturer’s installation instructions, the aircraft maintenance manual and the guidelines in AC 43.13-2A.

(3) Interconnect the GPS, power supply, i ndicator and antenna (as required) in accordance with the manufacturer’s installation instructions.

f. Unless the equipm ent autom atically disp lays a m essage on start-up and pilot action is required to clear the message, install the following placard in the vicinity of the GPS and in clear view of the pilot: GPS APPROVED FOR VFR USE ONLY.

g. Close the GPS circuit breaker or install the fuse.

h. Carry out a functional test of the G PS installation in a ccordance w ith th e manufacturer’s ins tallation/operation instru ctions. Checks ar e also to be carr ied out to determine satisfactory operation of all disturbe d system s, that there is no in terference between GPS and other system s, no effect on th e aircraft compass system and that there is no interference with the aircraft flight controls.

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