Subject: AIRWORTHINESS APPROVAL OF

NAVIGATION OR FLIGHT MANAGEMENT

SYSTEMS INTEGRATING MULTIPLE

NAVIGATION SENSORS

Date: 6/14/95

Initiated By: AIR-130

AC No: 20-130A

Change:

FAA Form 1320-15 (4-82) Supersedes WA Form 1320-2

1. PURPOSE. This advisory circular (AC) establishes an acceptable means, but not

the only means, of obtaining airworthiness approval of multi-sensor navigation or flight

management systems (hereafter referred to as multi-sensor equipment) integrating data

from multiple navigation sensors for use as a navigation system for oceanic and remote,

domestic en route, terminal, and non-precision instrument approach [except localizer,

localizer directional aid (LDA) and simplified directional facility (SDF)] operations. This

document does not address systems incorporating differential GPS capability. Like all

advisory material, this AC is not mandatory and does not constitute a requirement. As

such, the terms “shall” and “must” used in this AC pertain to an applicant who chooses to

follow the method presented. The criteria of AC 90-45A, Approval of Area Navigation

Systems for Use in the U.S. National Airspace System, does not apply to certification of

equipment described in this AC. This AC supersedes previous GPS installation guidance

contained in: FAA Notice 8110.48, Airworthiness Approval of Navigation or Flight

Management Systems Integrating Multiple Navigation Sensors, and FAA Interim

Guidance Memoranda dated February 25, 1991; April 5, 1991; March 20, 1992; July 20,

1992; and September 21, 1993. The appropriate information contained in those

documents is incorporated in this AC.

2. CANCELLATION. Advisory Circular 20-130, Airworthiness Approval of Multi-Sensor

Navigation Systems for use in the U.S. National Airspace System (NAS) and Alaska, dated

September 12, 1988, is canceled.

3 RELATED FEDERAL AVIATION REGULATIONS. 14 CFR parts 21, 23, 25, 27, 29,

 43, 91, 121, and 135.

4. RELATED READING MATERIALS.

a. Federal Aviation Administration (FAA) Technical Standard Order (TSO) C115a &

b, Area Navigation Equipment Using Multi-Sensor Inputs; C129, Airborne Supplemental

Navigation Equipment Using the Global Positioning System (GPS); C120, Airborne Area

Navigation Equipment Using Omega/VLF Inputs; C94, Omega Receiving Equipment Operating

Within the Radio Frequency Range 10.2 to 13.6 Kilohertz; and C60b, Airborne Area Navigation

Equipment Using Loran-C Inputs. Copies may be obtained from the Department of
AC 20-130A 6/14/95

2 Par 4

Transportation, FAA, Aircraft Certification Service, Aircraft Engineering Division, AIR-130,

800 Independence Avenue, SW., Washington, DC 20591.

b. RTCA, Inc. Document No. DO-160C, Environmental Conditions and Test

Procedures for Airborne Equipment; Document No. DO-164A, Airborne Omega Receiving

Equipment; Document No. DO-178B, Software Considerations in Airborne Systems and

Equipment Certification; Document No. DO-180A, Minimum Operational Performance

Standards for Airborne Area Navigation Equipment Using a Single Collocated VOR/DME

Sensor Input; Document No. DO-187, Minimum Operational Performance Standards for

Airborne Area Navigation Equipment Using Multi-Sensor Inputs; Document No. DO-190,

Minimum Operational Performance Standards for Airborne Area Navigation Equipment Using

Omega/VLF Inputs; Document No. DO-194, Minimum Operational Performance Standards for

Airborne Area Navigation Equipment Using Loran-C Inputs; Document No. DO-200,

Preparation, Verification and Distribution of User-Selectable Navigation Data Bases; Document

No. DO-201, User Recommendations for Aeronautical Information Services; and Document

No. DO-208, Minimum Operational Performance Standards for Airborne Supplemental

Navigation Equipment Using Global Position System (GPS). Copies may be purchased from

RTCA, Inc., 1140 Connecticut Avenue, NW., Suite 1020, Washington, DC 20036.

c. Department of Defense, Global Positioning System Standard Positioning Service

Signal Specification, November 5, 1993. Copies of this document may be requested from

OASD (C3I) / T&TC3, 6000 Defense Pentagon, Washington, DC 20301-6000.

d. Advisory Circular 20-101C, Airworthiness Approval of Omega/VLF Navigation

Systems for use in the U.S. National Airspace System (NAS) and Alaska; Advisory Circular 20-

121A, Airworthiness Approval of Loran-C Navigation Systems for use in the U.S. National

Airspace System (NAS) and Alaska; Advisory Circular 20-129, Airworthiness Approval of

Vertical Navigation (VNAV) Systems for use in the U.S. National Airspace System (NAS) and

Alaska; Advisory Circular 20-138, Airworthiness Approval of Global Positioning System (GPS)

Navigation Equipment for use as a VFR and IFR Supplemental Navigation System; Advisory

Circular 23-8A, Flight Test Guide for Certification of Part 23 Airplanes; Advisory Circular 25-4,

Inertial Navigation Systems (INS); Advisory Circular 25-7, Flight Test Guide for Certification of

Transport Category Airplanes; Advisory Circular 25-11, Transport Category Airplane Electronic

Display Systems; Advisory Circular 25-15, Approval of Flight Management Systems in

Transport Category Airplanes; Advisory Circular 27-1, Certification of Normal Category

Rotorcraft; Advisory Circular 29-2A, Certification of Transport Category Rotorcraft; Advisory

Circular 90-79, Recommended Practices and Procedures for the use of Electronic Long-Range

Navigation Equipment; Advisory Circular 90-82B, Direct Routes in the Conterminous United

States; Advisory Circular 91-49, General Aviation Procedures for Flight in North Atlantic

Minimum Navigation Performance Specification Airspace; and Advisory Circular 120-33,

Operational Approval of Airborne Long-Range Navigation Systems for Flight Within the North

Atlantic Minimum Navigation Performance Specification Airspace. Copies may be obtained

from the Department of Transportation, General Services Section, M-443.2, Washington, DC

20590.
6/14/95 AC 20-130A

Par 4 3

e. Defense Mapping Agency (DMA) Technical Report DMA TR 8350.2,

Department of Defense World Geodetic System 1984, Its Definition and Relationship With

Local Geodetic Systems. Copies of this document may be requested from the Defense Mapping

Agency, Systems Center, 8613 Lee Highway, Fairfax, VA 22031-2138.

5. BACKGROUND.

a. System Description. Navigation or flight management systems that determine

aircraft position by integrating data from multiple navigation sensors are considered multi-sensor

equipment. Aircraft position may be determined by various methods, depending on factors such

as availability of sensor inputs, accuracy, signal parameters, location and/or flight phase, signal

integrity, etc. Position determination may utilize data from various sensors, such as: distance

measurements from two or more distance measuring equipment (DME) ground stations (DMEDME), bearing and distance from very high frequency omnidirectional range (VOR)/DME

stations, bearing and distance from tactical air navigation (TACAN) stations, Omega/very low

frequency (VLF), Loran-C, inertial navigation system (INS), inertial reference unit (IRU), and

the global positioning system (GPS). The various sensor inputs are normally combined to

determine a best computed aircraft position, but may be used individually in appropriate

circumstances. A more detailed description of the various types of sensors is contained in the

related AC and TSO for that type sensor. The coordinate system used is the Cartesian earthcentered earth-fixed coordinates as specified in the Department of Defense World Geodetic

System 1984 (WGS-84). Navigational values such as distance and bearing to a waypoint, and

ground speed are computed from the aircraft’s latitude/longitude and the location of the

waypoint. Course guidance is usually provided as a linear deviation from the desired track of a

Great Circle course between defined waypoints.

b. System Availability and Reliability. Since multi-sensor equipment determines

aircraft position by integrating data from multiple navigation sensor inputs, system availability

and reliability is dependent upon the characteristics of the sensors incorporated in the system.

(1) Global Positioning System (GPS).

(i) Although basic GPS position determination capability from the 24

satellite constellation is expected to be available world-wide twenty-four hours a day, the

satellite measurement redundancy required to ensure integrity of the GPS position will be neither

world-wide nor continuous. With fewer than 24 satellites operating, GPS navigation capability

may not be available at particular geographic locations at certain times. At least 21 satellites are

expected to be operational with a probability of 98 percent.

(ii) The status of GPS is broadcast as part of the data message

transmitted by the GPS satellites. Additionally, system status is planned to be available through

the Notice to Airmen (NOTAM) system. GPS status information is also available by means of a

telephone data service, (703) 313-5910, or voice, (703) 313-5907, from the U.S. Coast Guard.
AC 20-130A 6/14/95

4 Par 5

(iii) GPS signal integrity monitoring shall be provided by the GPS

navigation receiver using receiver autonomous integrity monitoring (RAIM) or an equivalent

level of integrity provided by the multi-sensor equipment. This monitoring is necessary because

delays up to two hours may occur before an erroneous satellite transmission can be detected and

corrected by the satellite control segment. Availability of RAIM detection capability to meet

non-precision approach requirements in the United States (with 24 satellites operating,

barometric altitude aiding, and a 5 degree mask angle) is expected to exceed 99 percent.

(iv) Only the GPS satellite/ground control system operated by the

U.S. Department of Defense is addressed in this AC. Utilization of other satellite navigation

systems (i.e., GLONASS) is not covered.

(2) Omega/VLF.

(i) Omega system status is available from the U.S. Naval

Observatory, telephone (703) 313-5906. Omega status messages are also broadcast by the

National Bureau of Standards on stations WWV and WWVH at 16 minutes past each hour

(WWV) and 47 minutes past each hour (WWVH). Omega/VLF ground station reliability is

high, however reception of the Omega/VLF signals is susceptible to effects of precipitation

static and atmospheric noise, especially when using an E-field antenna. Omega/VLF signals are

generally usable 24-hours a day anywhere in the world.

(ii) The VLF communications system operated by the U.S. Navy is

not primarily intended for navigation use. The Navy may shut stations down, add new stations,

change frequencies, etc., with no advance notice. Information on current VLF system status is

not published for the aviation user.

(iii) Omega/VLF navigation sensors, while they may use VLF

communications stations to supplement and enhance the Omega system (improve performance,

etc.), must be capable of accurate navigation using Omega signals alone.

(3) Loran-C.

(i) Loran-C ground transmitter reliability exceeds 99 percent

annually, excluding momentary (less than 60 seconds) ground station outages which occur more

frequently (e.g., transmitter switching, adjustments, antenna lightning protection circuitry).

These momentary outages can result in loss of Loran-C navigation capability for several

minutes, depending upon the particular conditions and design of the Loran-C sensor. Airborne

reception of the Loran-C signal (normally using an E-field antenna) is highly susceptible to

adverse effects caused by precipitation static and atmospheric noise. Loran-C signal coverage is

available throughout the continental United States, southern Alaska, southern and eastern

Canada, most of the Gulf of Mexico, the North Atlantic, and various other areas of the world.
4/21/1999 AC 20-130A

Par 5 5

(ii) Loran-C navigation predicated on hyperbolic lines of position

originating from a single chain may not be suitable for IFR use throughout the entire continental

United States and northern Alaska. Equipment utilizing master independent, cross chain, and/or

multiple chain receivers has been approved for IFR use in areas where single chain receivers are

unacceptable.

(iii) Loran-C system status is available through the NOTAM system

and is also available by means of telephone data service (300 or 1200 baud, ASCII) from the

U.S. Naval Observatory, telephone (202) 653-1079.

(4) VOR, VOR/DME, VORTAC, TACAN, and Multiple DME.

(i) Ground station availability of these navigation aids exceeds 99

percent annually.

(ii) Coverage of these navigation aids is limited to within line-of-sight

of the ground station.

(iii) VOR, VOR/DME, VORTAC, TACAN, and DME system status

is available through the NOTAM system.

(5) Inertial Navigation System (INS) and Inertial Reference Unit (IRU).

(i) Inertial navigation/reference systems are self contained and do not

rely upon external navigation aids.

(ii) Some inertial systems are not suitable for alignment and/or

operation at high north and south latitudes (polar regions).

c. System accuracy. Accuracy of multi-sensor equipment is dependent upon the

sensor or combination of sensors in use at a particular time. Various navigation sensor inputs

are integrated, considering signal quality, station geometry, integrity, estimated position error,

etc. for each sensor and computing a best position based upon all available data. Required

system navigational accuracy is specified later in this AC. Individual sensor capabilities are

summarized below:

(1) Global Positioning System. The GPS equipment determines its position

by precise measurement of the distance from selected satellites in the system and the satellites’

known location. The accuracy of GPS position data can be affected by equipment

characteristics and various geometric factors. Many of these errors can be reduced or eliminated

with sophisticated mathematical modeling, while other sources of error cannot be corrected.

Accuracy measurements are affected by satellite geometry, frequently modeled by a geometric
AC 20-130A 6/14/95

6 Par 5

dilution of position (GDOP), which translates the effect of pseudorange errors to the position

domain. The following are sources of pseudorange errors:

(i) Atmospheric propagation delays can cause relatively small

measurement errors, typically less than 100 feet. Both tropospheric and ionospheric

propagation delays can be partially corrected by sophisticated error correction capabilities.

(ii) Slight inaccuracies in the atomic clocks on the satellites can cause

a small position error of approximately two feet.

(iii) Receiver processing (mathematical rounding, electrical

interference, etc.) may cause errors that are usually either very small (which may add a few feet

of uncertainty into each measurement) or very large (which are easy to detect). Receiver errors

are typically on the order of four feet.

(iv) Conditions that cause signal reflections (multipath) of the

satellites’ transmitted signal to the receiver can cause small errors in position determination or

momentary loss of the GPS signal. While advanced signal processing techniques and

sophisticated antenna design can be used to minimize this problem, some uncertainty can still be

added to a GPS measurement.

(v) Satellite ephemeris data can contain a small error of approximately

four feet.

(vi) Selective Availability (SA) is essentially a method by which the

Department of Defense can artificially create a significant clock and ephemeris error in the

satellites. This feature is designed to deny an enemy the use of precise GPS positioning data.

Selective Availability is the largest source of error in the GPS system. When SA is active, the

DOD guarantees horizontal position accuracy will not be degraded beyond 100 meters 95

percent of the time and 300 meters 99.99 percent of the time. System performance

specifications contained in this AC assume SA is active.

(vii) Block II GPS satellites incorporate an anti-spoofing alert flag to

advise the user that the user range accuracy may be degraded. GPS navigation systems should

recognize the presence of this flag.

(2) Omega/VLF. Omega/VLF equipment determines its present position by

adding incremental changes in position calculated from the continuously measured phase of each

received Omega signal to the initial position established at the time of system initialization. VLF

signals may be used in conjunction with Omega and therefore navigation may be based on an

Omega/VLF mix. The accuracy of Omega/VLF position data can be affected by equipment and

geometry. Typically, Omega/VLF position determination can be expected to be within 3.0 nmi

of the true position. Omega signals must be used to provide integrity to a VLF/Omega system,

since VLF is not an approved navigation system and does not provide integrity. Consequently,
4/21/1999 AC 20-130A

Par 5 7

when no Omega signals are available, the equipment may continue to provide a navigation

solution with no integrity using only the VLF system. This condition requires a unique

indication from the sensor. The multi-sensor equipment may either provide the requisite

integrity using an alternate approved sensor, or provide a unique annunciation to the pilot that

the navigation solution does not have integrity. If integrity is not provided, the system does not

meet IFR navigation certification criteria.

(i) Omega and VLF navigation can be degraded by errors due to

phase disturbances of the signals as they propagate from the station to the aircraft.

(ii) Improper modeling of the signal propagation changes caused by

diurnal shift surface conductivity, etc. can cause errors in position determination.

(iii) Accuracy measurements are affected by station geometry, which

magnifies the effect of other errors in the system.

(3) Loran-C. Loran-C equipment determines its present position using

multiple hyperbolic lines of position established by precise measurement of the time of arrival of

synchronized pulsed signals from a series of ground transmitting stations. The accuracy of

Loran-C navigation can be affected by various factors, including equipment, signal propagation,

and geometric factors. Typically, Loran-C position determination within approved operating

areas will be within 1.0 nmi and within 0.3 nmi (for systems receiving triad corrections for

approach operations) of the true position.

(i) Position errors can be caused by slower signal propagation over

land and fresh water than over sea water. These errors appear to be quite constant over

distances of several miles. The effect of these errors is a shift or bias in the computed position in

the local area. Area calibration or more sophisticated propagation models can be used to reduce

the effect of these bias errors.

(ii) Position errors can be caused by abrupt changes in terrain and

weather fronts which affect the propagation of the signal from the ground station.

(iii) Atmospheric noise and precipitation static adversely affect the

ability of the equipment to precisely track the synchronized pulsed signals. Incorrect cycle

tracking or loss of signal can result in significant position determination errors.

(iv) Accuracy measurements are affected by ground station geometry,

which magnifies the effect of other errors in the system.

(4) VOR, VOR/DME, TACAN. Equipment utilizing VOR, VOR/DME, or

TACAN sensors determines its present position by measuring the bearing or bearing and

distance from a reference ground station. Typically, position determination using this type of
AC 20-130A 6/14/95

8 Par 5

sensor will be within 1.0 nmi of the true position, however accuracy is highly dependent upon

distance from the reference station.

(5) Multiple DME. Equipment utilizing a multiple DME sensor determines

its present position by precise distance measurements from two or more reference ground

stations. With good geometry, systems using high quality DME sensors are capable of position

determination within 0.2 nmi of the true position.

(6) Inertia l. Equipment utilizing an inertial navigation or inertial reference

sensor(s) determines its present position by precise tracking of all movement of the aircraft from

a known starting point. Accuracy of inertial sensors degrades over time. Position determination

with an inertial system can degrade at a rate of 2 nmi per hour for flights up to 10 hours in

duration.

d. General Operational Limitations.

(1) Sensor Requirements. Depending upon the particular sensors

incorporated into the system, multi-sensor equipment can be approved for oceanic and remote,

en route, terminal, and instrument approach use. This document assumes that each sensor used

in the multi-sensor equipment has been demonstrated to meet the applicable design criteria for

that sensor (i.e. TSO, MOPS, etc.), or that the multi-sensor system is shown to have equivalent

performance.

(i) A system may be approved for oceanic and remote navigation

provided at least one of the following sensors is utilized in the multi-sensor equipment: GPS,

Omega/VLF, Loran-C (in limited areas), INS/IRU.

(ii) A system may be approved for en route use as a supplemental

navigation system provided at least one of the following sensors is used by the multi-sensor

equipment: GPS, Omega/VLF, Loran-C (in limited areas), VOR/DME, Multiple DME,

TACAN, INS/IRU.

(iii) A system may be approved for terminal area use as a supplemental

navigation system provided at least one of the following sensors is used by the multi-sensor

equipment: GPS, Loran-C (in limited areas), VOR/DME, Multiple DME, TACAN.

(iv) A system may be approved for instrument approach navigation

(except ILS, LOC, LOC-BC, LDA, SDF, and MLS) provided the required sensor(s) outlined in

Table 1 is used by the multi-sensor equipment.

(v) All sensor accuracy and integrity requirements must be met

without the need for operator input of required data, except that operator entry of Loran-C time

difference correction values shown on a charted Loran-C instrument approach procedure may be

used in satisfying approach accuracy requirements.
4/21/1999 AC 20-130A

Par 5 9

Table 1

Instrument Approach Sensor Requirements

Type of Instrument Approach Required Sensor*

Published RNAV approaches GPS or VOR/DME

Published Loran-C approaches GPS or Loran-C

Published VOR or VOR/DME approaches GPS or VOR/(DME)

Published TACAN approaches GPS or TACAN

Published GPS approaches GPS

Published NDB or NDB/DME approaches GPS or NDB/(DME)

*The required sensor identifies a single sensor/sensor combination which,

when demonstrated to meet the accuracy requirements of this AC, can be

used to conduct these approaches. Alternatively, multi-sensor equipment

can be shown to meet the accuracy requirements with a combination of

sensors.

(2) IFR Navigation Equipment. Aircraft employing multi-sensor equipment

for IFR navigation must also be equipped with an approved and operational alternate means of

navigation appropriate to the intended route to be flown. Within the contiguous United States,

Alaska, Hawaii, and surrounding coastal waters, this requirement can be met with an

operational, independent VOR receiver, although data from this receiver can provide an input to

the multi-sensor equipment. For oceanic and remote operations, an alternate means of

navigation is required unless the multi-sensor equipment incorporates within itself a sensor

approved individually for the particular area of operations (some oceanic airspace may require

additional redundancy).

(3) Operating Limitations. Particular multi-sensor equipment may require

operational areas be limited to those areas in which the equipment has been demonstrated to

meet the performance specifications of this AC because of system characteristics and other

factors affecting system operation. Operating limitations that may affect the approved operating

area for particular multi-sensor equipment must be specified in the operating limitations section

of the Airplane/Rotorcraft Flight Manual Supplement (AFMS/RFMS) (i.e., extreme north and

south latitudes, data base coverage, sensor coverage, etc.). FAA approval of GPS navigation

equipment does not constitute approval to conduct GPS-based navigation in airspace controlled

by foreign airworthiness authorities. Systems that do not provide for coordinate reference

system conversions of the displayed navigation information should not be used in airspace that is

not referenced to the WGS-84 or NAD-83 geodetic datums. Operating limitations relating to

geodetic datums for particular GPS navigation equipment should be included in the limitations

section of the AFMS/RFMS.

e. Equipment Classes. GPS sensors installed in accordance with the guidance

provided by this AC for IFR operations shall meet the requirements for Class B() or C()

equipment as defined in TSO-C129 (hereafter referred to as Class B() or C() GPS sensor). GPS
AC 20-130A 6/14/95

10 Par 5

sensors integrated in multi-sensor equipment limited to VFR only shall meet the accuracy

requirements in paragraph 7 of this AC.

f. Future Air Navigation System (FANS) Concept. Information in this AC is not

intended to restrict the development, certification, or operational approval of current or future

multi-sensor equipment installations designed to comply with required navigation performance

(RNP) or other FANS design requirements.

6. DEFINITIONS. Any terms used in this AC that have a meaning specific to the context

of this AC are contained in APPENDIX 3. GLOSSARY.

7. SYSTEM ACCURACY.

a. 2D Accuracy Requirements (95 percent probability).

(1) For equipment incorporating a Class B() or C() GPS sensor, the total

position fixing error of the multi-sensor equipment shall be equal to or less than that shown in

Table 2 when GPS data is used in the position/navigation computation:

Table 2

2D Accuracy Requirements, Equipment Incorporating Class B() or C() GPS Sensor

Error Type Oceanic

and

remote

(nmi)

En Route

(Domestic)

(nmi)

Terminal

(nmi)

Non-Precision

Approach *

(nmi)

Position Fixing

Error **

0.124 0.124 0.124 0.056

CDI Centering

***

0.2 0.2 0.2 0.01

 * Non-precision approach criteria only applies to equipment incorporating

a Class B1, B3, C1, or C3 GPS sensor.

** Equipment error assumes an average GPS HDOP of 1.5, GPS

equipment waypoint input resolution of 0.01 minute, and output

resolution of 0.01 minute for approach and 0.1 minute otherwise.

*** The maximum difference between the displayed cross track

deviation and the computed cross track deviation.

(2) For equipment not incorporating a GPS sensor (or when GPS data is not

used in a system including a GPS sensor), the total position fixing error of the multi-sensor

equipment shall be equal to or less than that shown in Table 3:
4/21/1999 AC 20-130A

Par 7 11

Table 3

2D Accuracy Requirements, Equipment Not Incorporating a GPS Sensor

Error Type Oceanic

and

remote

(nmi)

En Route

(Domestic)

(nmi)

Terminal

(nmi)

Non-Precision

Approach

(nmi)

Position Fixing

Error *

12.0 2.8 1.7 0.3

(0.5 if navigation data

derived from a single

collocated VOR/DME

station)

CDI Centering ** 0.2 0.2 0.2 0.1

* Equipment error assumes multi-sensor equipment waypoint input resolution of

0.01 minute, and output resolution of 0.01 minute for approach and 0.1 minute

otherwise.

** The maximum difference between the displayed cross track deviation and the 

computed cross track deviation.

(3) For times when the equipment is using data from only a single collocated

VOR/DME station (such as during an RNAV approach) and no other sensor input is

contributing to the position solution, the total maximum position fixing error of the airborne

multi-equipment shall be equal to or less than that shown in Table 4. To find the cross track and

along track error at this point, enter the table with the tangent distance and distance along track

from the tangent point.
AC 20-130A 6/14/95

12 Par 7

Table 4

2D Accuracy Requirements, Equipment Utilizing Only a Single Collocated VOR/DME

Along-Track Distance

0 5 10 15 20 25 30 35 40 50 60 70 80 90 100 110 120 130

0 xtk

atk

0.6

0.6

0.8

0.6

1.1

0.6

1.4

0.6

1.7

0.7

2.0

0.7

2.3

0.8

2.6

0.8

3.2

0.9

3.9

1.0

4.5

1.0

5.2

1.1

5.8

1.2

6.4

1.3

7.1

1.4

7.7

1.5

8.4

1.6

5 xtk

atk

0.6

0.6

0.6

0.6

0.8

0.7

1.1

0.7

1.4

0.7

1.7

0.8

2.0

0.8

2.3

0.8

2.6

0.9

3.3

0.9

3.9

1.0

4.5

1.1

5.2

1.2

5.8

1.3

6.4

1.4

7.1

1.5

7.7

1.6

8.4

1.7

10 xtk

atk

0.6

0.8

0.7

0.8

0.9

0.8

1.1

0.8

1.4

0.9

1.7

0.9

2.0

0.9

2.3

1.0

2.6

1.0

3.3

1.1

3.9

1.2

4.5

1.2

5.2

1.3

5.8

1.4

6.5

1.5

7.1

1.6

7.7

1.7

8.4

1.8

15 xtk

atk

0.6

1.0

0.7

1.0

0.9

1.0

1.1

1.1

1.4

1.1

1.7

1.1

2.0

1.2

2.3

1.2

2.6

1.2

3.3

1.3

3.9

1.4

4.5

1.4

5.2

1.5

5.8

1.6

6.5

1.7

7.1

1.7

7.7

1.8

8.4

1.9

20 xtk

atk

0.6

1.3

0.7

1.3

0.9

1.3

1.2

1.3

1.4

1.3

1.7

1.4

2.0

1.4

2.3

1.4

2.7

1.4

3.3

1.5

3.9

1.6

4.6

1.6

5.2

1.7

5.8

1.8

6.5

1.9

7.1

1.9

7.7

2.0

8.4

2.1

T

a

25 xtk

atk

0.7

1.5

0.8

1.5

1.0

1.6

1.2

1.6

1.5

1.6

1.8

1.6

2.1

1.6

2.4

1.7

2.7

1.7

3.3

1.7

3.9

1.8

4.6

1.9

5.2

1.9

5.8

2.0

6.5

2.1

7.1

2.1

7.8

2.2

8.4

2.3

n

g

30 xtk

atk

0.7

1.8

0.8

1.8

1.0

1.8

1.2

1.8

1.5

1.9

1.8

1.9

2.1

1.9

2.4

1.9

2.7

2.0

3.3

2.0

3.9

2.1

4.6

2.1

5.2

2.2

5.9

2.2

6.5

2.3

7.1

2.4

7.8

2.4

8.4

2.5

e

n

35 xtk

atk

0.8

2.1

0.8

2.1

1.0

2.1

1.3

2.1

1.5

2.1

1.8

2.2

2.1

2.2

2.4

2.2

2.7

2.2

3.3

2.3

4.0

2.3

4.6

2.4

5.2

2.4

5.9

2.5

6.5

2.5

7.1

2.6

7.8

2.7

8.4

2.7

t 40 xtk

atk

0.8

2.4

0.9

2.4

1.1

2.4

1.3

2.4

1.5

2.4

1.8

2.4

2.1

2.4

2.4

2.5

2.7

2.5

3.3

2.5

4.0

2.6

4.6

2.6

5.2

2.7

5.9

2.7

6.5

2.8

7.1

2.9

7.8

2.9

8.4

3.0

D

i

50 xtk

atk

0.9

2.9

1.0

2.9

1.1

3.0

1.3

3.0

1.6

3.0

1.9

3.0

2.2

3.0

2.5

3.0

2.8

3.0

3.4

3.1

4.0

3.1

4.6

3.2

5.3

3.2

5.9

3.3

6.5

3.3

7.2

3.4

7.8

3.4

8.4

3.5

s

t

60 xtk

atk

1.0

3.5

1.0

3.5

1.2

3.5

1.4

3.5

1.7

3.5

1.9

3.6

2.2

3.6

2.5

3.6

2.8

3.6

3.4

3.6

4.0

3.7

4.7

3.7

5.3

3.8

5.9

3.8

6.6

3.8

7.2

3.9

7.8

3.9

8.5

4.0

a

n

70 xtk

atk

1.0

4.1

1.1

4.1

1.3

4.1

1.5

4.1

1.7

4.1

2.0

4.1

2.3

4.1

2.6

4.2

2.9

4.2

3.5

4.2

4.1

4.2

4.7

4.3

5.3

4.3

6.0

4.4

6.6

4.4

7.2

4.4

7.9

4.5

8.5

4.5

c

e

80 xtk

atk

1.1

4.6

1.2

4.7

1.4

4.7

1.6

4.7

1.8

4.7

2.1

4.7.

2.3

4.7

2.6

4.7

2.9

4.7

3.5

4.8

4.1

4.8

4.7

4.8

5.4

4.9

6.0

4.9

6.6

5.0

7.3

5.0

7.9

5.0

8.5

5.1

90 xtk

atk

1.2

5.2

1.3

5.2

1.4

5.2

1.6

5.2

1.9

5.2

2.1

5.3

2.4

5.3

2.7

5.3

3.0

5.3

3.5

5.3

4.2

5.4

4.8

5.4

5.4

5.4

6.0

5.5

6.7

5.5

7.3

5.5

7.9

5.6

8.6

5.6

100 xtk

atk

1.3

5.8

1.4

5.8

1.5

5.8

1.7

5.8

1.9

5.8

2.2

5.8

2.4

5.9

2.7

5.9

3.0

5.9

3.6

5.9

4.2

5.9

4.8

6.0

5.4

6.0

6.1

6.0

6.7

6.1

7.3

6.1

7.9

6.1

8.6

6.2

110 xtk

atk

1.4

6.4

1.5

6.4

1.6

6.4

1.8

6.4

2.0

6.4

2.3

6.4

2.5

6.4

2.8

6.4

3.1

6.5

3.6

6.5

4.2

6.5

4.9

6.5

5.5

6.6

6.1

6.6

6.7

6.6

7.3

6.7

8.0

6.7

8.6

6.7

120 xtk

atk

1.5

6.9

1.6

7.0

1.7

7.0

1.9

7.0

2.1

7.0

2.3

7.0

2.6

7.0

2.8

7.0

3.1

7.0

3.7

7.1

4.3

7.1

4.9

7.1

5.5

7.1

6.1

7.2

6.8

7.2

7.4

7.2

8.0

7.3

8.6

7.3

130 xtk

atk

1.6

7.5

1.7

7.5

1.8

7.5

2.0

7.6

2.2

7.6

2.4

7.6

2.6

7.6

2.9

7.6

3.2

7.6

3.7

7.6

4.3

7.7

4.9

7.7

5.6

7.7

6.2

7.7

6.8

7.8

7.4

7.8

8.0

7.8

8.7

7.9

NOTE 1: Equipment error assumes a waypoint input resolution of 0.01 minute, and 

output resolution of 0.01 minute for approach and 0.1 minute otherwise.

NOTE 2: Equipment error assumes the maximum allowable difference between the 

displayed cross track deviation and the computed cross track deviation.

NOTE 3: Multi-sensor equipment accuracy shown in the above table does not 

necessarily satisfy accuracy requirements for operation in certain airspace. For 

example, navigation on published J and V routes requires the distance along-track from

the tangent point and distance from the tangent point to VOR/DME to be less than

approximately 50 nmi to meet airway width criteria.
4/21/1999 AC 20-130A

Par 7 13

NOTE 4: The above table is a result of an RSS combination of the below error 

elements. The accuracy tables are computed assuming that the waypoint is always

at the tangent point and the aircraft is at the along-track distance measured from the 

same tangent point. This is important in the test procedures because the resulting crosstrack error from the course setting is a function of distance to waypoint.

 Ground Equipment Error: Airborne Equipment Error:

VOR 1.4 degrees VOR 3.0 degrees

DME 0.1 nmi DME 0.2 nmi + 1%

CSE 1.6 degrees

Computation Error 0.5 nmi

b. Flight Technical Error (FTE). Since FTE factors are normally beyond the control

of equipment manufacturers or installers, these error sources are not included in the accuracy

specifications of paragraphs 7(a)(1) and (2). The FAA has determined that when properly

installed in an aircraft, multi-sensor equipment (except equipment incorporating a Class C() GPS

sensor) meeting the operational and display characteristics contained in this AC, related discrete

sensor AC’s, TSO-C115b, and related discrete sensor TSO’s, provides for acceptable values of

FTE. FTE should not exceed 1.0 nmi for en route, 1.0 nmi for terminal or approach transition,

or 0.25 nmi (for equipment using GPS data) or 0.5 nmi (for equipment not using GPS data) for

approach operating modes on a 95 percent basis. Equipment integrating a Class C() GPS sensor

must include display and system integration capabilities that provide an acceptable value of

FTE, and is evaluated based upon the particular installation to determine the suitability of

proposed operational and display characteristics.

c. VNAV Accuracy Requirements. For equipment that includes a vertical

navigation capability (VNAV), see AC 20-129 for Vertical Navigation Requirements.

8. AIRWORTHINESS CRITERIA FOR MULTI-SENSOR EQUIPMENT LIMITED TO

VISUAL FLIGHT RULES (VFR) ONLY.

a. Application Process. Persons wishing to use multi-sensor equipment for

operations limited to VFR only may obtain approval of the installation by Type Certificate (TC)

or Supplemental Type Certificate (STC). For equipment that has already obtained installation

approval via the TC or STC process, approval may also be obtained via data approved by the

FAA (responsible Flight Standards District Office) on FAA Form 337 (Major Repair and

Alteration). The approval for return to service must be signed by one of the entities noted in 14

CFR part 43; i.e., repair station, manufacturer, holder of an inspection authorization, etc.

b. Airworthiness Considerations. Multi-sensor equipment approved for VFR use

only does not require TSO-C115b authorization, however it must at least meet the en

route/terminal system accuracy criteria contained in paragraph 7a of this AC. Each individual

sensor must also meet any additional performance criteria (besides accuracy) applicable to VFR
AC 20-130A 6/14/95

14 Par 8

only approval that is contained in the respective AC applicable to that type sensor. The

installation verification should ensure, but is not limited to, the following:

(1) Electromagnetic Compatibility. The multi-sensor equipment installation

does not interfere with the normal operation of other equipment installed in the aircraft.

(2) Environmental Conditions. The multi-sensor equipment is appropriate to

the environmental categories (or criteria) in which it is installed.

(3) Equipment Mounting. The installation of the multi-sensor equipment,

including antenna, must be sufficient to meet all structural mounting, dynamic, and emergency

landing loads appropriate to the aircraft category. It is acceptable to use the criteria in

AC 43.13-2A, “Acceptable Methods, Techniques, and Practices - Aircraft Alterations.”

(4) Navigation Source Annunciator. A navigation source annunciator is

provided on or adjacent to each affected display if the multi-sensor equipment installation

supplies any information to displays such as a horizontal situation indicator (HSI), course

deviation indicator (CDI), distance display, electronic map, etc., that can also display

information from other systems normally used for aircraft navigation.

(5) Computer Software. The AC 20-115B, which refers to RTCA/DO-178B,

provides an acceptable means for showing that software complies with applicable airworthiness

requirements. The applicant should substantiate software levels in the safety assessment. As an

alternative to substantiating software level(s) in a safety assessment, the applicant may develop

all software that contains or affects navigation and integrity functions to at least the Level D

criteria, as defined in RTCA/DO-178B. The FAA recommends that the standards for IFR

equipment contained in paragraph 8b(1) be followed if the system is intended to be upgraded to

IFR use in the future.

(6) Failure Protection. Any probable failure of the multi-sensor equipment

must not degrade the normal operation of other required equipment or create a flight hazard.

Likewise, normal operation of the multi-sensor equipment cannot adversely affect the

performance of other aircraft equipment. The interfaces with other aircraft equipment must be

designed such that normal or abnormal multi-sensor equipment operation does not adversely

affect the operation of other equipment. Operation of other equipment shall not adversely affect

the multi-sensor equipment operation.

(7) System Controls, Displays and Annunciators. All displays, controls, and

annunciators must be readable under all normal cockpit conditions and expected ambient light

conditions (total darkness to bright reflected sunlight). Night light provisions must be consistent

with other cockpit lighting. All displays and controls should be arranged to facilitate equipment

usage. Controls that are normally adjusted in flight shall be accessible and properly labeled as to

their function. System controls and displays should be designed to maximize operational

suitability and minimize pilot workload. System controls should be arranged to provide
4/21/1999 AC 20-130A

Par 8 15

protection against inadvertent system turnoff. Reliance on pilot memory for operational

procedures shall be minimized.

(8) Navigation/Integrity Annunciation. The multi-sensor equipment should

indicate, independent of any operator action:

(i) The following conditions by means of a navigation warning flag

on the navigation display:

(A) The absence of power required for the navigation function.

(B) Probable equipment malfunctions or failures affecting the

navigation function.

(C) Loss of navigation function.

(ii) If an integrity monitoring function (such as GPS RAIM) is

provided, an appropriately located annunciator shall be provided to indicate loss of the integrity

monitoring function.

NOTE 1: For equipment not incorporating an external navigation display

(CDI, HSI, etc.), complete blanking of the control display is acceptable.

NOTE 2: Presentation of a failure/status annunciation (flag or integrity

annunciation) does not require removal of navigation information from the

navigation display.

(9) Autopilot/Flight Director Coupling. The multi-sensor equipment may be

coupled to an autopilot and/or flight director provided the multi-sensor equipment has a

deviation or steering output that is compatible with the autopilot/flight director system and no

unusual interface is required.

(10) VFR Limitation Placard. A placard stating “GPS not approved for IFR”

must be installed in clear view of, and readable by, the pilot.

(11) Pressure/Barometric Altitude Inputs. If the multi-sensor equipment

incorporates Class B1, B2, C1, or C2 GPS sensor(s) and uses a barometric pressure altitude

input, that input must be appropriate to the equipment.

(12) Manufacturer’s Instructions. The multi-sensor equipment, including

antenna(e), must be installed in accordance with the instructions and limitations provided by the

manufacturer of the equipment.

c. VFR Airworthiness Approval. There are two types of VFR airworthiness approval

which differ significantly as to test requirements and data analysis.
AC 20-130A 6/14/95

16 Par 8

(1) First-Time VFR Airworthiness Approval (for a Particular Type of MultiSensor Equipment). This type of approval refers to the first time an applicant presents a

particular (hardware and software configuration) model of multi-sensor equipment integrating

multiple navigation sensors for FAA airworthiness installation approval and certification for

VFR navigation use. The first approval of particular multi-sensor equipment must be

accomplished through the TC or STC process. Each new model of multi-sensor equipment or

significant changes (hardware or software) to existing equipment shall undergo the same

approval process as the original equipment unless it can be shown by analysis and tests

acceptable to the Administrator that the new model will function as well or better than the

approved equipment. A first-time approval is conducted in four phases:

(i) Lab/Bench Tests and Equipment Data Evaluation. This phase

consists of the following:

(A) Review of the manufacturer’s procedures for development

of software and review of supporting documentation in accordance with the guidelines of

paragraph 8b(5) of this AC.

(B) Analysis of failure modes and annunciations.

(C) Review of reliability data to establish that all probable

failures are detected and that hazardously misleading failures are shown to be improbable.

(D) Review of installation and maintenance manuals.

(E) Evaluation of the operator’s manual (pilot’s guide).

(ii) Aircraft Installation Data Evaluation. Normally the manufacturer

of the multi-sensor equipment will provide an aircraft as a test bed for the first time installation

approval. This approval may serve as a basis for subsequent installation approvals. The

following assessments are made:

(A) Review of the equipment installation in the aircraft.

(B) Verification that the multi-sensor equipment is appropriate

to the environment in which it was installed. (DO-160C testing is acceptable to meet this

requirement.)

(C) Analysis of a data flow diagram in order to review which

equipment provides what data to which other equipment.
4/21/1999 AC 20-130A

Par 8 17

(D) Verification that the installation of the multi-sensor

equipment, including antenna, is sufficient to meet all structural mounting, dynamic, and

emergency landing loads appropriate to the aircraft category.

(E) Verification that a placard stating “GPS not approved for

IFR” is installed in clear view of, and readable, by the pilot.

(F) Verification that the multi-sensor equipment does not

interfere with the normal operation of other equipment installed in the aircraft. (May interface

with IFR equipment.)

(G) Evaluation of the antenna installation. A critical aspect of

many multi-sensor equipment installations is the installation of the antenna(e). It is important

that the antenna for each sensor be one that is approved for the particular type (make and

model) sensor installed.

(iii) Ground Test Evaluations. For multi-sensor equipment

incorporating a Class B() or C() GPS sensor, static ground tests are conducted to verify the

installed GPS equipment configuration (including antenna) provides position data meeting the

accuracy criteria specified in paragraph 7a(1) of this AC. These tests shall cover a continuous

period of 12 hours with a maximum sample interval of five minutes.

NOTE: The 12-hour ground accuracy test may be performed on the aircraft or

by use of a representative mock-up configuration. If a mock-up test fixture is

used, the entire installed multi-sensor equipment configuration, including

antenna(e), must consist of the hardware to be used in the installation and be

representative of the installed system configuration.

(iv) Flight Test Evaluations. Flight tests are conducted to verify

proper operation and accuracy of the multi-sensor equipment as installed in the aircraft. Flight

tests should include at least the following:

NOTE: Required flight evaluations for the first-time airworthiness approval

of particular multi-sensor equipment are accomplished by the cognizant

Aircraft Certification Office unless specific tests are delegated by the ACO

to a flight test pilot designated engineering representative (DER).

(A) Evaluation of installed multi-sensor equipment to verify

that it is functioning safely, and operates in accordance with the manufacturer’s specifications.
AC 20-130A 6/14/95

18 Par 8

(B) If coupled to an autopilot, evaluation of steering response

while autopilot and/or flight director is coupled to the multi-sensor equipment during a variety

of different track and mode changes. Additionally, all available display sensitivities shall be

evaluated.

(C) Evaluation to verify the multi-sensor equipment

installation does not adversely affect other onboard equipment (this test may be partially

accomplished as a ground test).

(D) Evaluation of the accessibility of all controls pertaining to

the multi-sensor equipment installation.

(E) Evaluation of the visibility of the controls, displays, and

annunciators relating to the multi-sensor equipment installation during day and night lighting

conditions. No distracting cockpit glare or reflections may be introduced, and all controls must

be illuminated for identification and ease of use. Night lighting shall be consistent with other

cockpit lighting.

(F) Validate multi-sensor equipment navigational accuracy in

each operating mode (e.g. oceanic, en route, and terminal) for which approval is requested. In

addition to overall system navigation performance, particular test requirements for navigational

accuracy will vary depending upon the particular sensors integrated in the multi-sensor

equipment and whether sensor accuracy performance data has previously been obtained. As an

alternative to demonstrating the required accuracy with each specific sensor noted below, the

multi-sensor equipment can be shown to have the requisite accuracy with various combinations

of sensors.

(1) GPS sensor accuracy should be verified in each

operating mode by at least 5 low altitude over flights of one or more surveyed locations (ensure

survey point coordinates are relative to WGS-84 or NAD-83). An acceptable method of

conducting this accuracy demonstration is to accomplish low altitude (less then 100 feet AGL)

overflight of a runway threshold and record the GPS position as the aircraft crosses the

threshold. The system accuracy is the distance between the coordinate position determined by

the GPS and the coordinate position of the surveyed location (runway threshold). Runway

threshold coordinates may be obtained from the airport operator or regional flight procedures

office. If coordinate data conversion to WGS-84/NAD-83 is necessary, contact the National

Flight Data Center at (202) 267-9277.

(2) Initial certification for systems including an

Omega/VLF, Loran-C, VOR/DME, multiple (scanning) DME, INS or IRU sensor that has not

previously been certified shall be based upon a demonstration of system accuracy by recording

(at not greater than 15 minute intervals) the sensor position and comparing it to the actual
4/21/1999 AC 20-130A

Par 8 19

position during evaluation flights representative of the area in which approval is desired. This

flight test should be at least two hours in duration in order to provide a sufficient data set.

(2) Follow-On VFR Airworthiness Installation Approvals. This type of

approval refers to installation approvals in any model or type of aircraft after a first time

airworthiness approval of the particular multi-sensor equipment has been issued. Follow-on

approvals may use the first time airworthiness approval, which was either a TC or an STC, as a

basis for installation approval. Follow-on installation approvals may be accomplished by TC,

STC, or data approved on FAA Form 337, if the flight standards inspector determines that there

are no design changes as a result of the installation. The determination of a design change will be

dependent upon the integration with other avionics and not on the basis of aircraft make and

model. Since the GPS equipment operates on principles that are not dependent upon the aircraft

make and model, the engineering evaluation of one aircraft model is applicable to a different

aircraft provided the integration with the other equipment is equivalent.

The applicant or installing agency requesting a follow-on multi-sensor equipment installation

utilizing this method of data approval should:

(i) Unless otherwise provided, contact either the manufacturer or

organization responsible for obtaining the first time airworthiness approval of the multi-sensor

equipment in order to:

(A) Obtain a sample airplane or rotorcraft flight manual

supplement (or supplemental flight manual, if appropriate), if required for the aircraft.

(B) Obtain verification of the equipment approval status,

including antenna, software, autopilot/flight director interface, and system integration

requirements, etc.

(C) Discuss any problem areas and seek assistance in their

solution.

(D) Verify that the maximum operating speed for which the

multi-sensor equipment is qualified is compatible with the maximum expected ground speed of

the aircraft.

(ii) Conduct a similar data evaluation as outlined in paragraph

8c(1)(ii) of this AC.

.

(iii) Conduct a functional flight evaluation covering the items listed in

paragraphs 8c(1)(iv)A through 8c(1)(iv)E of this AC. In addition, the flight test should

demonstrate multi-sensor equipment navigational performance (including, as applicable to the

sensors integrated in the system, Loran-C chain selection/switching, P-static protection, etc.) has

not been affected by the installation in the aircraft.
AC 20-130A 6/14/95

20 Par 8

NOTE: Required flight evaluations for follow-on equipment

installations approved via the Form 337 process may be conducted

by the installer.

9. AIRWORTHINESS CRITERIA MULTI-SENSOR EQUIPMENT USED UNDER

INSTRUMENT FLIGHT RULES (IFR)

a. Application Process. Persons wishing to obtain approval of multi-sensor

equipment integrating any combination of GPS, Omega/VLF, Loran-C, VOR/DME, Multiple

DME, or INS/IRU sensors for IFR operations may do so via the Type Certificate (TC) or

Supplemental Type Certificate (STC) process. For equipment approved via the TC or STC

process, approval may also be obtained via data approved by the FAA (responsible Flight

Standards District Office) on FAA Form 337 (Major Repair and Alteration). The approval

for return to service must be signed by one of the entities noted in 14 CFR part 43; i.e., repair

station, manufacturer, holder of an inspection authorization, etc.

(1) The initial (first-time airworthiness approval) certification of multisensor equipment requires extensive engineering and flight test evaluations and must be

accomplished via the TC or STC approval process.

(2) Subsequent (follow-on) installations of the same multi-sensor

equipment (hardware and software) in other aircraft are approved using a less extensive

evaluation process since the basic engineering design has already been evaluated. Approval of

follow-on installations may be accomplished via the TC, STC, or FAA Form 337 process. The

extent of required evaluations depends upon the degree of integration of the navigation system

with other aircraft systems, the similarity between the initial and follow-on aircraft models, and

other changes that may have been incorporated in the multi-sensor equipment. The decision to

allow an applicant to use FAA approved engineering data in support of an FAA Form 337

approval is left to the field inspector’s judgment. The FAA Airworthiness Inspector’s

Handbook (FAA Order 8300.10) provides guidance applicable to multi-sensor equipment

installations. Changes to software accomplishing navigation, integrity, or availability

functions; changes in the number, type, or mix of sensors integrated in the system; changes

to/addition of approved operating areas; or significant changes to operating limitations cannot

be accomplished using the FAA Form 337 process and must use TC or STC procedures.

(3) Approval of multi-sensor equipment integrating a Class C() GPS sensor

with any other combination of sensors for IFR operations must use the TC or STC process.

Because of the unique enhanced display and system integration requirements applicable to this

integration of sensors and displays, appropriate test requirements and procedures must be

determined based upon the particular application. These tests must establish the equivalent

display capability of the installation and the display requirements for Class A() sensors.

Reference AC 20-138 for the specific requirements.

b. Airworthiness Considerations. Multi-sensor equipment to be approved for

oceanic and remote, domestic en route, terminal, and non-precision instrument approach
6/14/95 AC 20-130A

Par 9 21

(except localizer, LDA and SDF) operations must meet the minimum navigation performance

and operation standards for the appropriate equipment specified in TSO-C115b and this AC

(including GPS equipment classes in TSO-C129 as referenced in TSO-C115b for multi-sensor

equipment incorporating a GPS sensor). Additionally, each individual sensor must at least

meet the navigation performance and operation criteria (besides accuracy) contained in the

respective TSO and AC applicable to that type sensor.

(1) System Integrity and Software Development. Loss of navigation or

flight management information is considered to be a major failure condition for the aircraft as

defined in AC 25.1309-1A, AC 23.1309-1A, AC 27-1, or AC 29-2A, as applicable to the

aircraft. Hazardously misleading information to the flight crew is also considered to be a

major failure condition for the aircraft. Navigation data is considered to be hazardously

misleading when unannunciated position errors exist that are greater than those specified by

the multi-sensor equipment or individual sensor requirements (e.g., GPS position integrity

performance requirements in Table 2-1 of RTCA/DO-208). The applicant should conduct a

system safety assessment to verify that design errors and failure modes that produce major

failure conditions are improbable.

(i) AC 25.1309-1A, AC 23.1309-1A, AC 27-1, or AC 29-2A, as

applicable, provides an acceptable means for showing that the hardware complies with

pertinent airworthiness requirements.

(ii) AC 20-115B, which refers to RTCA/DO-178B, provides an

acceptable means for showing that software complies with pertinent airworthiness

requirements. The applicant should substantiate software levels in the safety assessment. As

an alternative to substantiating software level(s) in a safety assessment, the applicant may

develop all software that contains or affects navigation and integrity functions to at least the

Level C criteria, as defined in RTCA/DO-178B.

(iii) The cognizant Aircraft Certification Office may grant a

deviation to TSO-C115a or TSO C-129 (Classes B and C) to permit the applicant to use the

procedures of RTCA/DO-178B instead of RTCA/DO-178A.

(iv) If software was developed using RTCA/DO-178A procedures

(as is specified in TSO-C115a), the applicant may need to further evaluate some features of

the software. RTCA/DO-178A does not address some applications of digital technology

commonly found in multi-sensor equipment (e.g., use of user-modifiable software including

data bases, option-selectable software, software development and verification tools, previously

developed software in modular architectures, and field loadable software capabilities). In

these cases RTCA/DO-178A does not provide adequate procedures and the applicant must

include in the software aspects of certification plan the means for showing that these features

comply with pertinent airworthiness requirements. One acceptable means for demonstrating

such features comply with the pertinent airworthiness requirements is to comply with pertinent
AC 20-130A 6/14/95

22 Par 9

portions of the criteria contained in RTCA/DO-178B, which would supplement the basic

criteria contained in RTCA/DO-178A.

(v) The FAA strongly recommends that the applicant use the

procedures described in RTCA/DO-178B (or later revision), as referenced in AC 20-115B, to

show that the software aspects of a system comply with pertinent airworthiness requirements.

For software developed prior to the availability of RTCA/DO-178B, Section 12.1.4 of

RTCA/DO-178B provides a method for upgrading a baseline for software development so that

changes can be made in accordance with the criteria contained in RTCA/DO-178B.

(vi) If application specific integrated circuits (ASIC’s) or other

complex logic devices are used, they must be developed using a structured process similar to

that used for software developed under RTCA/DO-178B. If deterministic tests exhaustively

consider all possible input values and verify that the ASIC completely meets all pertinent

requirements, then a structured development process is not required. Either methodology

should be approved in advance by the cognizant ACO.

(2) Display Format/Operating Procedure Changes. Changes to navigational

display formats and navigation/function operating procedures (implemented through hardware

or software) may constitute major changes requiring additional evaluation.

(3) Location of System Displays. Each display element (i.e., the course

deviation indicator (CDI), horizontal situation indicator (HSI), map display, etc.), used as a

primary flight instrument in the guidance and control of the aircraft, for maneuver anticipation,

or for failure/status/integrity annunciation, shall be located where it is visible to the pilot (in the

pilot’s primary field of view) with the least practicable deviation from the pilot’s normal

position and line of vision when looking forward along the flight path.

NOTE 1: CDI displays contained in the CDU will most likely not be

acceptable for IFR operations.

NOTE 2: Flight technical error (FTE) can be reduced when numeric

display information is integrated with the non-numeric display or is

located within the pilot’s primary field of view. Both digital cross

track and track angle error have been shown to reduce FTE. This

information should be displayed together (either within the CDU or

remotely displayed near the non-numeric display) for better tracking

performance. The use of non-numeric cross track data integrated with

non-numeric track angle error data into one display may provide the

optimum of situation and control information for the best overall

tracking performance.

(4) Failure Protection. Any probable failure of the multi-sensor equipment

shall not degrade the normal operation of other required equipment or create a flight hazard.

Likewise, normal operation of the multi-sensor equipment installation shall not adversely affect
6/14/95 AC 20-130A

Par 9 23

the performance of other aircraft equipment. The interfaces with other aircraft equipment

must be designed such that normal or abnormal multi-sensor equipment operation shall not

adversely affect the operation of other equipment nor shall operation of other equipment

adversely affect the multi-sensor equipment operation.

(5) Environmental Conditions. The aircraft environment in which the

multi-sensor equipment is installed shall be found to be compatible with the environmental

categories (or criteria) in RTCA/DO-160C to which the equipment was tested.

(6) Electromagnetic Compatibility. The multi-sensor equipment installation

should not be the source of objectionable electromagnetic interference, nor be adversely

affected by electromagnetic interference from other equipment in the aircraft.

(i) For systems incorporating a GPS sensor, the GPS equipment

should be shown to meet the 2D accuracy requirements of paragraph 7a(1) of this AC when

subjected to a radiated signal with continuous wave (cw) modulation at a frequency of

1.57542 GHz and an electric field strength of 20 mv/meter measured at the exterior case of the

GPS receiver. The radiated susceptibility test procedures of RTCA/DO-160C, Section 20,

should be followed when conducting this test. The test should be conducted with simulated

satellite inputs and should not result in the loss of track of any satellite used for navigation.

The duration of the test must be sufficient to determine if tracking has been lost (20 seconds

should normally be long enough, depending on the coasting features used by the GPS

equipment). This test will usually be conducted by the GPS equipment manufacturer, but if

not, the applicant is responsible for conducting the test.

(ii) For systems incorporating a GPS sensor, intermodulation effects

are possible between multiple channel SATCOM installations and GPS. GPS equipment

should not be installed in aircraft with multiple SATCOM channels unless the SATCOM

equipment is modified to prevent simultaneous use of interfering frequencies. Current multichannel SATCOM equipment (as of 1/1/94) has not been modified in this manner and should

not be installed with GPS equipment. In addition, certain GPS manufacturers have been

granted a deviation to the requirements of TSO-C129 and will include a limitation in their

installation instructions that states that the GPS equipment can not be installed in aircraft with

SATCOM equipment. If such GPS equipment is installed in an aircraft the TC, STC, or FAA

Form 337 should appropriately limit the future installation of SATCOM equipment in the

aircraft.

(iii) For systems incorporating a GPS sensor, harmonic interference

from VHF transmissions on 121.150, 121.175, 121.200, 131.250, 131.275, and 131.300 MHz

may adversely affect reception of the GPS signal if less than 100 dB isolation is provided.

Low pass or notch filters installed at the output of the VHF transmitter to attenuate the

undesired VHF signal should have an insertion loss of 2 dB or less to preclude the need for

reevaluation of installed VHF transceiver performance.
AC 20-130A 6/14/95

24 Par 9

(7) P-Static Protection. If an E-Field antenna (whip, plate, or blade type)

is used (such as with an Omega/VLF or Loran-C sensor), the aircraft should be protected by

acceptable bonding techniques and installation of static dischargers. These protective devices

should be specified as part of the approved design data for the multi-sensor installation. The

capability to provide satisfactory P-static protection for the system should be demonstrated as

part of the initial certification program. This testing may be accomplished by ground or static

testing if sufficient data is provided to demonstrate that the proposed technique is equivalent

to flight testing. If a flight demonstration is selected it must be conducted at speeds up to

Vne, Vmo, or Mmo through known P-static conditions such as a cloud of ice crystals.

Momentary loss of signal when encountering heavy P-static conditions may be acceptable

provided the equipment is capable of providing acceptable navigation information during such

conditions. P-static charging of the aircraft can cause degradation of the signal-to-noise ratio

by one of three major mechanisms:

(i) Sparkover of Isolated Metal Panels. Sparkover of isolated

metal panels can be handled by appropriate bonding. This bonding needs to occur on all

control and trim surfaces as well as isolated access panels. Bonding should be evaluated by a

careful ohmic survey (an electrical bonding limit of 10 milliohms is considered acceptable) of

techniques.

(ii) Streamer currents. The effects caused by streamer currents can

be reduced by placing the receiving antenna as far as possible from any nonconductive surfaces

such as windshields. The nonconductive surfaces may be coated with a conductive coating.

Temporary spray coatings are not satisfactory.

(iii) Corona discharge. Corona discharge can be reduced by the

appropriate placing of orthodecoupled static dischargers on the extremities of the aircraft. A

number of recent studies have shown that the frayed-wick types of dischargers constructed

with a high resistance rod and metal pins are recommended although other types may also be

used if they can demonstrate ability to provide protection from radio frequency (RF) coupling

to the sensor antenna. The number, type, and location of these static dischargers to be

installed on a particular aircraft model should be determined by following the instructions

provided by the manufacturer of the static discharger for P-static protection.

(8) Anti-Ice Protection. If the aircraft in which the multi-sensor equipment

is installed is approved for flight into known icing conditions, any antennae must have anti-ice

protection or be found not to be susceptible to ice buildup (i.e., is installed in a non-icing

location on the aircraft, or is of a sufficiently low profile that ice does not accumulate on the

antenna). Alternatively, the equipment can be shown to operate satisfactorily when the

antenna is subject to icing provided there are no harmful effects, such as possible ingestion of

accumulated ice or degradation in aerodynamic performance. (The effects of ice accumulation

on the antenna, if any, can be found in the manufacturer’s installation instructions.)
6/14/95 AC 20-130A

Par 9 25

(9) System Controls. All displays, controls, and annunciators must be

readable under all normal cockpit conditions and expected ambient light conditions (total

darkness to bright reflected sunlight). Night lighting provisions must be compatible with other

cockpit lighting. All displays and controls must be arranged to facilitate equipment usage.

Controls that are normally adjusted in flight shall be accessible and properly labeled as to their

function. System controls and displays shall be designed to maximize operational suitability

and minimize pilot workload. System controls shall be arranged to provide protection against

inadvertent system turnoff. Reliance on pilot memory for operational procedures shall be

minimized.

(10) Navigation Data Base. For equipment incorporating a TSO-C129 GPS

sensor, the multi-sensor equipment shall incorporate an appropriately updatable navigation

data base (in the WGS-84 or NAD-83 coordinate datum). This data base must contain at least

the following location information in terms of latitude and longitude with a resolution of 0.01

minute or better for the area(s) in which IFR operations are to be conducted: all airports,

VOR’s (and VORTAC’s), NDB’s, and all named waypoints and intersections shown on en

route charts. For equipment including a terminal mode, the data base shall also contain all

named waypoints and intersections shown on terminal area charts, Standard Instrument

Departures (SID’s) and Standard Terminal Arrival Routes (STAR’s). For equipment

including an approach mode, the navigation data base must also include all waypoints and

intersections included in published non-precision instrument approach (except localizer, LDA,

and SDF) procedures. Instrument approaches must be conducted using a current database.

User entry or modification of navigation data base data shall not be possible. (This does not

preclude the storage of “user defined data” within the equipment.) Additional data base

coding, storage, and approach waypoint presentation requirements as specified in the

applicable TSO’s must be provided. Navigation data bases shall meet the standards specified

in sections 3, 4, and 5 of RTCA/DO-200, “Preparation, Verification and Distribution of User

Selectable Navigation Data Bases” and sections 2 through 7 of RTCA/DO-201, “User

Recommendations for Aeronautical Information Services.”

(11) Pressure/Barometric Altitude Inputs. If the multi-sensor equipment

incorporates a Class B1, B2, C1, or C2 GPS sensor(s) and uses a barometric pressure/altitude

input, that input must be appropriate to the equipment.

(12) Manufacturer’s Instructions. The multi-sensor equipment, including

required antenna(s), shall be installed in accordance with the instructions and limitations

provided by the manufacturer of the equipment.

c. IFR Airworthiness Approval. There are two types of IFR airworthiness

approval which differ significantly as to test requirements and data analysis.

(1) First-Time IFR Airworthiness Approval (for a Particular Type of MultiSensor Equipment). This type of approval refers to the first time an applicant presents a

particular (hardware and software configuration) model multi-sensor equipment integrating
AC 20-130A 6/14/95

26 Par 9

multiple navigation sensors for FAA airworthiness installation approval and certification for

IFR navigation use. The first approval of particular multi-sensor equipment must be

accomplished through the TC or STC process. Each new model of multi-sensor equipment by

the same manufacturer or significant changes (hardware or software) to existing equipment

shall undergo the same approval process as the original equipment unless it can be shown by

analysis and tests acceptable to the Administrator that the new model will function as well or

better than the approved equipment. A first-time approval is conducted in four phases:

(i) Lab/Bench Tests and Equipment Data Evaluation. This phase

consists of the following:

(A) Analysis of the manufacturer’s procedures for

development of software and review of supporting documentation in accordance with the

guidelines of paragraph 9b(1) of this AC.

(B) Verification of compliance with the appropriate

environmental qualification standards and tests specified in the individual sensor TSO’s and in

RTCA/DO-160C.

(C) Verification of compliance with the applicable minimum

performance and operation standards specified in TSO-C115b and other TSO’s applicable to

the individual sensors incorporated in the system.

(D) Analysis of failure modes and annunciations.

(E) Review of reliability data to establish that all probable

failures are detected and that failure rates meet acceptable criteria (e.g. as detailed in AC

25.1309-1A).

(F) Evaluation of the ease of use of the controls and of the

viewing ease (e.g. brightness, contrast, intensity, dimming, etc.) of the displays and

annunciations from a human factors point of view.

(G) Review of installation and maintenance manuals. Special

attention should be given to the manufacturer’s instructions for locating all antennas on the

aircraft. Refer to paragraph 9.c.(1)(ii)(G) of this AC for specific information that should be

included in these instructions.

(H) Evaluation of the operator’s manual (pilot’s guide).

(ii) Aircraft Installation Data Evaluation. Normally the

manufacturer of the multi-sensor equipment will provide an aircraft as a test bed for the first

time installation approval. This approval may serve as a basis for subsequent installation

approvals. The following assessments are to be made:
6/14/95 AC 20-130A

Par 9 27

(A) Review of installation drawings, wiring diagrams, and

descriptive wiring routing.

(B) Evaluation of the cockpit layout of the installed

equipment with emphasis on equipment controls, applicable circuit breakers (labels and

accessibility), switching arrangement, and related indicators, displays, annunciators, etc.

(C) Analysis of a data flow diagram in order to review which

equipment provides what data to which other equipment.

(D) Review of a structural analysis of the equipment

installation, including antenna(e), in order to ascertain whether structural mounting, dynamic,

and crash load requirements are satisfied.

(E) Review of an electrical load analysis in order to verify

that the total electrical load requirements are within the capabilities of the aircraft’s electrical

generating system. Determine that the supplied electrical power is consistent with applicable

equipment reliability requirements.

(F) Verification that the aircraft environment in which the

multi-sensor equipment is installed is appropriate to the environmental categories (or criteria)

as identified in 9.c.(1)(i)(B) or the individual TSO to which the equipment has been tested.

(G) Evaluation of the antenna installation. A critical aspect

of many multi-sensor equipment installations is the installation of the antenna(e). It is

important that the antenna for each sensor is approved for the particular type (make and

model) sensor installed.

(1) Adequate isolation must be provided between a

GPS antenna and any other transmitting antenna(s) installed on the aircraft in order to prevent

interference. Shadowing by aircraft structure can adversely affect the operation of GPS

equipment. Typically, a GPS antenna is located forward of the wings on the top of the

fuselage to minimize effects of the wings, tail, etc. during aircraft maneuvering. For

installations on helicopters, the effects of the rotor blades on antenna performance must be

considered.

NOTE: The GPS signal is typically below the value of the background

noise. Electrical noise in the vicinity of the antenna can adversely affect

the performance of the system. Antenna installation in close proximity

to traffic alert and collision avoidance system (TCAS), satellite

communication (SATCOM), and other transmitting antennas

(particularly “L” band) should be carefully evaluated for potential

mutual interference.
AC 20-130A 6/14/95

28 Par 9

(2) E-field antennas (whip, plate, or blade type) are

typically used with Loran-C sensors and many Omega/VLF sensors. Precipitation static has an

adverse effect upon the signal receiving capability of this type of antenna. The adverse effects

of P-static can be minimized by use of the proper antenna type and location, by proper

installation of high-quality static dischargers, and by proper bonding of airframe surfaces. The

manufacturer’s installation or maintenance manual usually describes acceptable E-field antenna

installation practices. Each aircraft should be subjected to a careful ohmic survey of electrical

airframe bonding (an electrical bonding limit of 10 milliohms is considered acceptable). Pstatic protection is a required part of the system installation and must be maintained for proper

system operation.

(3) H-field antennas (loop type) are typically used

with Omega/VLF sensors. The signal receiving quality of this type of antenna is adversely

affected by aircraft electrical skin currents, particularly by 400 Hz ac. P-static has no

appreciable effect on an H-field antenna, and its effects are usually not observed. A procedure

called skin mapping is normally employed to determine a good mounting location for H-field

antennas. It should be noted that shifting major aircraft electrical components to different

locations within the aircraft or installing new equipment subsequent to antenna installation may

render a previously determined skin map location unsuitable. A simple test to verify the

effectiveness of an H-field antenna installation located by skin mapping is to park the aircraft

away from any external electrical noise source. Then, using only the aircraft’s battery, and

with all other electrical equipment off, activate the multi-sensor equipment and record signalto-noise values (or quality factors) for all receivable stations of the appropriate sensor. Repeat

this process of recording signal-to-noise values (or quality factors) with engine(s) running and

all electrical/electronic equipment operating on aircraft power. If the antenna installation is

satisfactory, there should not be any significant degradation in signal reception.

(iii) Ground Test Evaluations. For multi-sensor equipment

incorporating a Class B() or C() GPS sensor, static ground tests are conducted to verify the

installed GPS equipment configuration (including antenna) provides position data meeting the

accuracy criteria specified in paragraph 7a(1) of this AC. These tests shall cover a continuous

period of 24 hours with a maximum sample interval of five minutes.

NOTE: The 24-hour ground accuracy test may be performed on the

aircraft or by use of a representative mock-up configuration. If a

mock-up test fixture is used, the entire installed GPS equipment

configuration, including antenna, must consist of the hardware to be

used in the installation and be representative of the installed system

configuration.

(iv) Flight Test Evaluations. Flight tests are conducted to

verify proper operation and accuracy of the multi-sensor equipment as installed in the

aircraft. Flight tests should include at least the following:
6/14/95 AC 20-130A

Par 9 29

NOTE 1: Required flight evaluation for any new sensor should be

conducted according to the AC for installation of that sensor

(Reference 4.d).

NOTE 2: Required flight evaluations for the first-time airworthiness

approval of a particular multi-sensor equipment are accomplished by

the cognizant Aircraft Certification Office unless specific tests are

delegated by the ACO to a Flight Test Pilot Designated Engineering

Representative (DER).

(A) Evaluation of all operating modes of the multi-sensor

equipment. Particular attention should be given to mode switching and transition requirements

associated with the approach mode for equipment incorporating Class B1, B3, C1, and C3

GPS sensors.

(B) Evaluation of the interface (function) of other equipment

connected to the multi-sensor equipment.

(C) Review of various failure modes and associated

annunciations, such as loss of electrical power, loss of signal reception, equipment failure,

individual sensor failure, autopilot/flight director response to system flags, etc.

(D) Evaluation of steering response while autopilot and/or

flight director is coupled to the multi-sensor equipment during a variety of different track and

mode changes. This evaluation shall include, as applicable, transition from en route to

approach transition to approach modes and vice-versa. Additionally, all available display

sensitivities shall be evaluated.

(E) Evaluation of displayed multi-sensor equipment

parameters on interfaced cockpit instruments such as HSI, CDI, distance display, electronic

flight instruments system (EFIS), moving maps, fuel management systems, etc.

(F) Assessment of all switching and transfer functions,

including electrical bus switching, pertaining to the multi-sensor equipment installation.

(G) Evaluation to determine satisfactory electromagnetic

compatibility (EMC) between the multi-sensor equipment installation and other onboard

equipment (this test may be partially accomplished as a ground test).

NOTE 1: For systems incorporating a GPS sensor, particular

attention should be given to other “L” band equipment, such as TCAS

or SATCOM equipment, VHF transmissions on the frequencies stated

in paragraph 9b(6)(iii) of this AC, high frequency (HF)
AC 20-130A 6/14/95

30 Par 9

communications systems, and other transmitting equipment (ACARS,

AFIS, Flightfone, etc.).

NOTE 2: Installation instructions for each GPS receiver installation

shall include the requirement for verification of adequate isolation

from the harmonic interference of VHF communication transceivers.

These tests shall be conducted on the completed GPS installation by

tuning each VHF transmitter to the frequencies listed below and

transmitting for a period of 20 seconds while observing the signal

status of each satellite being received. Degradation of individually

received satellite signals below a point where navigation is no longer

possible is not acceptable and will require that additional isolation

measures (low pass or notch filters installed at the output of the VHF

transmitter, additional spacing between the VHF transmitter and the

GPS antenna, replacement of the VHF transmitter with a unit having

no excessive harmonic emissions, etc.) be included in the aircraft

installation. Reevaluation of installed VHF transceiver performance is

not necessary if the filter insertion loss is 2 dB or less.

The following VHF frequencies shall be evaluated:

121.150 MHz 131.250 MHz

121.175 MHz 131.275 MHz

121.200 MHz 131.300 MHz

Proper radio regulations (FCC Rules) must be observed.

NOTE 3: For Omega/VLF and Loran-C systems that incorporate an

E-Field antenna, testing should be conducted in accordance with

paragraph 9.b.(7).

(H) Evaluation of the accessibility of all controls pertaining

to the multi-sensor equipment installation.

(I) Evaluation of the visibility of the controls, displays, and

annunciators relating to the multi-sensor equipment installation during day and night lighting

conditions. No distracting cockpit glare or reflections may be introduced, and all controls

must be illuminated for identification and ease of use. Night lighting shall be consistent with

other cockpit lighting.

(J) Analysis of crew workload when operating the multisensor equipment in association with other piloting requirements.
6/14/95 AC 20-130A

Par 9 31

(K) Validate multi-sensor equipment navigational accuracy

in each operating mode. In addition to overall system navigation performance, particular test

requirements for navigational accuracy will vary depending upon the particular sensors

integrated in the multi-sensor equipment and whether sensor accuracy performance data has

previously been obtained. The performance of each navigation sensor should be evaluated

separately and in combination with other sensors as applicable. Note that the accuracy

associated with a GPS sensor must be demonstrated to enable potential operating benefits.

(1) GPS sensor accuracy should be verified in each

operating mode by at least 5 low altitude over flights of one or more surveyed locations

(ensure survey point coordinates are relative to WGS-84). An acceptable method of

conducting this accuracy demonstration is to accomplish low altitude (less then 100 feet AGL)

overflight of a runway threshold and record the GPS position as the aircraft crosses the

threshold. The system accuracy is the distance between the coordinate position determined by

the GPS and the coordinate position of the surveyed location (runway threshold). Runway

threshold coordinates may be obtained from the airport operator. If coordinate data

conversion to WGS-84/NAD-83 is necessary, contact the National Flight Data Center at (202)

267-9277.

(2) Initial certification for systems including an

Omega/VLF sensor that has not previously been certified shall be based upon a demonstration

of system accuracy by recording (at not less than 15 minute intervals) the Omega/VLF sensor

position and comparing it to the actual position during evaluation flights representative of the

area in which approval is desired. Suitable accuracy and navigation capability must be

demonstrated using Omega only. VLF signals may be used to augment and expand areas of

coverage, but the system must be demonstrated to be capable of meeting all navigation

performance requirements using Omega signals only in an area of nominal Omega coverage.

Recorded data should include sufficient signal parameters and sensor performance data to

provide a clear indication of satisfactory sensor performance. The particular flight paths

should be selected based upon an analysis of critical signal characteristics, station geometry,

aircraft movement, time of day, etc. The system should demonstrate its ability to re-acquire

Omega/VLF signals after power interruptions of less than seven minutes and more than seven

minutes, as well as in areas of marginal performance. It should demonstrate its ability to

detect inadequate navigation capability, poor signal quality, etc.

(3) Initial certification for systems including a LoranC sensor that has not previously been certified shall be based upon a demonstration of system

accuracy by recording (at not less than 15 minute intervals) the Loran-C sensor position and

comparing it to the actual position during evaluation flights representative of the area in which

approval is desired. Recorded data should include sufficient signal parameters and sensor

performance data to provide a clear indication of satisfactory sensor performance. The

particular flight paths should be selected based upon an analysis of critical signal

characteristics, station geometry, chain/station selection criteria, known poor signal areas,

aircraft movement, seasonal effects (i.e., snow pack vs. trees, water vs. ice, etc.), time of day,
AC 20-130A 6/14/95

32 Par 9

etc. The system should demonstrate its ability to detect poor signal conditions, inadequate

navigation capability, operations outside approved operating areas, and the ability to reacquire

the Loran-C signal following momentary signal interruptions and prolonged (more than 5

minutes) in-flight power failure, etc.

(4) Initial certification for systems including a

VOR/DME or multiple (scanning) DME sensor that has not been previously certified shall be

based upon a demonstration of system accuracy by recording (at not greater than 15 minute

intervals) the VOR/DME and/or DME/DME sensor position and comparing it to the actual

position during evaluation flights. Recorded data should include sufficient signal parameters

and sensor performance data to provide a clear indication of satisfactory sensor performance,

The particular flight paths should be selected based upon an analysis of critical signal

characteristics, station geometry, signal coverage (including limited station availability with

acceptable range), aircraft movement, etc. The system should demonstrate its ability to detect

poor signal conditions, inadequate navigation capability, recovery from in-flight power failure,

etc. The VOR/DME auto-tune logic should be reviewed and tested to verify that all three

types of VOR/DME ground stations are identified and tuned correctly.

(5) Initial certification for systems including an

inertial navigation system (INS) or inertial reference unit (IRU) that has not been previously

certified shall be based upon a demonstration of system accuracy by recording (at no greater

than 15 minutes intervals) the INS/IRU sensor position and comparing it to the actual position

during evaluation flights representative of the area in which approval is desired. Recorded

data should include sufficient sensor performance parameters to provide a clear indication of

satisfactory sensor performance and drift rates. The system should demonstrate its ability to

detect inadequate navigation capability, operations outside approved operating areas, recovery

from power failure, reinitialization in flight, alignment in limiting areas, etc. This

demonstration should include 150 system flights at greater than 3 hours. At the end of the

flight, the systems must exhibit less than 2.0 nmi drift rates. For systems that will be operated

for more then 10 hours, the system must stay within 20 nmi x 25 nmi for the maximum

deviation allowed (See AC 25-4).

(L) Verify continuity of navigation data during normal

aircraft maneuvering, including holding patterns and turns at up to at least 30 degrees of bank

for a 360 degree turn left and right.

(M) Verify that flight technical error (FTE) can be

maintained at less than 1.0 nmi for en route, 1.0 nmi for terminal (approach transition), and

0.25 nmi (for equipment that is seeking credit for GPS data) or 0.5 nmi (for equipment not

using or not seeking credit for GPS data) for approach operating modes, both with and

without autopilot and/or flight director, as applicable.

(N) For equipment including an approach mode, conduct a

sufficient number of approaches using the navigation data base to verify the proper operation

of annunciations, waypoint sequencing, and display sensitivity changes, as appropriate, in
6/14/95 AC 20-130A

Par 9 33

accordance with the requirements specified in TSO-C115b and other TSO’s applicable to the

specific sensors incorporated in the multi-sensor equipment. This evaluation should include at

least: turn anticipation, waypoint sequencing, display sensitivity changes, annunciations,

procedure turns at the final approach fix (FAF), holding patterns at the missed approach

holding fix, transitions from TO-FROM operation to TO-TO operation, heading legs after the

initial approach fix (IAF) to intercept the final approach course both before and after the FAF,

and DIRECT TO operation before and after the IAF.

(2) Follow-On IFR Airworthiness Installation Approvals. This type of

approval refers to installation approvals in any model or type of aircraft after a first time

airworthiness approval of the particular multi-sensor equipment has been issued. Follow-on

approvals may use the first time airworthiness approval, which was either a TC or an STC, as

a basis for installation approval, if the flight standards inspector determines that there are no

design changes as a result of the installation. The determination of a design change will be

dependent upon the integration with other avionics and not on the basis of aircraft make and

model. Since the GPS equipment operates on principles that are not dependent upon the

aircraft make and model, the engineering evaluation of one aircraft model is applicable to a

different aircraft provided the integration with the other equipment is equivalent.

(i) Unless otherwise provided, contact either the manufacturer or

organization responsible for obtaining the first time airworthiness approval of the multi-sensor

equipment in order to:

(A) Obtain a sample airplane or rotorcraft flight manual

supplement (or supplemental flight manual, if appropriate).

(B) Obtain verification of the equipment approval status,

including antenna, software, autopilot/flight director interface, and system integration

requirements, etc.

(C) Discuss any problem areas and seek assistance in their

solution.

(D) Verify that the maximum operating speed for which the

multi-sensor equipment is qualified is compatible with the maximum expected ground speed of

the aircraft.

(ii) If the aircraft is approved for flight in known icing conditions,

verify the suitability of the antenna installation in accordance with the guidance specified in

paragraph 9b(8) of this AC.

(iii) Conduct a similar data evaluation as outlined in paragraph

9c(1)(ii) of this AC.
AC 20-130A 6/14/95

34 Par 9

(iv) Conduct a functional flight evaluation covering at least the

following items:

NOTE: Required flight evaluations will be conducted by the cognizant

Aircraft Certification Office (ACO) or, when authorized, by a flight test

pilot designated engineering representative (DER) in accordance with the

procedures used by the cognizant ACO. Depending upon the level of

similarity between the initial and follow-on installations, including aircraft

type, the Flight Standards District Office (FSDO) Inspector may accept

flight evaluations conducted by the installer.

(A) Overall operation of the installed multi-sensor

equipment, including interface with other equipment in the aircraft.

(B) The effect(s) of multi-sensor equipment and sensor

failure (open circuit breaker), including autopilot /flight director response, if applicable.

(C) If interfaced with an autopilot or flight director, steering

response while the autopilot or flight director is coupled to the multi-sensor equipment.

(D) Displayed navigation parameters on all interfaced

cockpit instruments.

(E) The effect(s), if any, of switching and transfer functions,

including electrical bus switching, pertaining to the multi-sensor installation.

(F) Evaluation to determine satisfactory electromagnetic

compatibility (EMC) between the multi-sensor equipment installation and other equipment as

specified in paragraph 9c(1)(ii)(G) of this AC.

NOTE: Verification of adequate isolation from harmonic interference of

VHF communication transceivers in each individual aircraft is required

for installation of multi-sensor equipment using GPS. This test should

be repeated if a VHF transceiver is replaced or added, or if a new or

replacement VHF communications antenna is installed.

(G) Evaluation of the accessibility and visibility of all

controls and displays pertaining to the multi-sensor equipment installation.

(H) Validate multi-sensor equipment navigational accuracy

in each operating mode. Previously approved sensors need only be evaluated to the extent

necessary to verify accuracy has not been degraded by the equipment installation in the

particular aircraft.
6/14/95 AC 20-130A

Par 9 35

(1) GPS sensor accuracy is evaluated as specified in

paragraph 9c(1)(iv)(K)(1) of this AC.

(2) Omega/VLF sensor accuracy is evaluated by

conducting a short flight (approximately 100 nmi) and verifying position accuracy by

overflight of at least 3 reference locations or comparison to a valid GPS, Loran-C, or

DME/DME position.

(3) Loran-C sensor accuracy can be evaluated in the

same manner as that specified for GPS sensors, except that five different locations should be

used.

(4) VOR/DME and DME/DME sensor accuracy can

be evaluated in the same manner as that specified for GPS sensors, except that five different

locations should be used.

(5) INS/IRU sensor accuracy can be evaluated as an

average drift over the entire flight (should be less than 2.0 nmi/hr.)

(I) Verify continuity of navigation data during normal

aircraft maneuvering, including holding patterns and turns at up to at least 30 degrees of bank

for left and right 360 degree turns.

(J) Monitor displayed cross-track error to verify that flight

technical error (FTE) is less than 1.0 nmi for en route, 1.0 nmi for terminal (approach

transition), and 0.25 nmi (for equipment using GPS data) or 0.5 nmi (for equipment not using

GPS data) for approach operating modes, both with and without autopilot and/or flight

director, as applicable.

(K) For equipment including an approach mode, conduct at

least three published instrument approaches (retrieved from the database) to verify the proper

operation of the equipment in the approach environment. This test should be conducted

separately for each sensor, for which approach approval is sought. If multiple sensors are to

be used, then all combinations should also be tested.

10. OPERATIONAL CONSIDERATIONS.

a. Flight Manual Supplement. An appropriate Airplane or Rotorcraft Flight Manual

Supplement (or, for aircraft without an FAA Approved Flight Manual, a Supplemental Flight

Manual) containing the limitations and operating procedures applicable to the equipment

installed should be provided for each installation of multi-sensor equipment for IFR approval. A

Flight Manual Supplement or Supplemental Flight Manual may be necessary for installations

limited to VFR use only, depending upon the complexity of the installation and need to identify

necessary limitations and operating procedures.
AC 20-130A 6/14/95

36 Par 10

b. Other Navigation Equipment Required. Aircraft employing multi-sensor

equipment for IFR navigation must also be equipped with an approved and operational alternate

means of navigation appropriate to the intended route to be flown. Within the contiguous

United States, Alaska, Hawaii, and surrounding coastal waters, this requirement may be met

with an operational, independent VOR receiver, although data from this receiver can provide an

input to the multi-sensor equipment. For oceanic and remote operations, an alternate means of

navigation is required unless the multi-sensor equipment incorporates within itself a sensor

approved individually for the particular area of operations (some oceanic airspace may require

additional redundancy).

c. Alternate Airport Requirements. An alternate airport (if required by the

applicable operating rules) must be served by an approved instrument approach procedure based

on a navigation system other than GPS or Loran-C and the aircraft must be properly equipped to

conduct that approach.

d. Operational Area. Operators and their flight crews must consult the approved

flight manual supplement for their aircraft to determine approved operational areas that may

apply to particular systems and/or sensors. Flight crews must be aware that operational areas

for different systems/sensors may be different, and the appropriate operating area(s) for a

particular system can only be determined by reference to the approved flight manual supplement

or other FAA approved documents.

JOHN K. McGRATH

Manager, Aircraft Engineering Division
6/14/95 AC 20-130A

Appendix 1

Par 1 1

APPENDIX 1. PROCEDURES FOR OBTAINING FAA APPROVAL OF FOLLOW-ON

MULTI-SENSOR EQUIPMENT INSTALLATIONS FOR IFR/VFR OPERATIONS BY FAA

FORM 337

1. FOLLOW-ON MULTI-SENSOR EQUIPMENT INSTALLATIONS LIMITED TO

VFR USE ONLY. Approval of follow-on multi-sensor equipment installations limited to VFR

use only (where the initial approval was accomplished using the TC or STC process) are

normally obtained using FAA Form 337 approved by the responsible Flight Standards District

Office (FSDO). Such installations can usually be approved for return to service by one of the

entities noted in 14 CFR part 43; i.e., repair station, manufacturer, holder of an inspection

authorization, etc., provided the installation:

a. General Installation Methods. Conforms to the acceptable methods, techniques,

and practices contained in AC 43.13-1A, Acceptable Methods, Techniques and Practices -

Aircraft Inspection and Repair, and AC 43.13-2A, Acceptable Methods, Techniques, and

Practices - Aircraft Alterations.

b. Installation Criteria. Is in accordance with the criteria specified in paragraph

8c(1)(ii) of this AC. A certification from the manufacturer to confirm that the en route/terminal

accuracy requirements of paragraph 6 and ground accuracy test requirements of paragraph

8c(1)(iii) have been met should be provided. This certification can be accomplished by reference

to the first time TC/STC approval.

NOTE: Limited test data may be required to verify/demonstrate that the

applicable requirements have been satisfied.

c. Aircraft Flight Manual Supplement/Placard(s). Except for those installations

where placards address required limitations, an airplane or rotorcraft flight manual supplement

(or supplemental flight manual) prepared by the applicant and containing at least the following

information must be presented for FAA approval. The proposed flight manual supplement (or

supplemental flight manual) is submitted for approval along with the other data associated with

the installation.

(1) Equipment operating limitations.

(2) Emergency/abnormal operating procedures (if applicable).

(3) Normal procedures for operating the multi-sensor equipment and any

interfaced equipment. (May be provided in a pilot’s guide that is referenced in the flight manual

supplement.)

(4) General description of system (or reference to a pilot’s guide that

provides an equipment description).
AC 20-130A 4/21/1999

Appendix 1

2 Par 1

d. Functional Flight Evaluation. A functional flight evaluation covering the items

listed in paragraph 8c(2)(iii) is accomplished by the installer. The results of this evaluation are

included with the data provided to the FSDO.

2. FOLLOW-ON MULTI-SENSOR EQUIPMENT INSTALLATIONS FOR IFR USE.

Approval of follow-on multi-sensor equipment installations for IFR use (where the initial

approval was accomplished using the TC or STC process) may be obtained using an FAA Form

337 approved by the responsible FSDO.

a. Data Submitted by the Applicant. Alteration data for the equipment installation

is submitted with a properly executed FAA Form 337, and a certification from the manufacturer

to confirm that the accuracy requirements of paragraph 7a and ground accuracy test

requirements of paragraph 9c(1)(iii) of this AC and system performance specifications of TSOC115a or b have been met. (This certification can be accomplished by reference to TSO-C115a

or b approval and the original TC/STC approval.) The FAA Form 337, along with all required

data pertaining to the installation, should be submitted to the responsible FSDO

b. Additional Data That May be Required. If required by the FSDO (or an ACO

when consulting with the FSDO when reviewing the data/conducting necessary tests requested

by the FSDO) approving the technical data/installation, the applicant may also be required to

furnish a copy of the equipment data (for equipment not produced under TSO-C115a or b

authorization), manufacturer’s operating and installation instructions, fault analysis for

installation, installation details and/or photographs, structural substantiation, system wiring

diagrams, and ground test evaluation results.

c. Aircraft Flight Manual Supplement. An airplane or rotorcraft flight manual

supplement (or supplemental flight manual) prepared by the applicant and containing at least the

following information must be presented for FAA approval. The proposed flight manual

supplement (or supplemental flight manual) is prepared using the guidance contained in

Appendix 2 and submitted to the FSDO.

(1) Equipment operating limitations.

(2) Emergency/abnormal operating procedures.

(3) Normal procedures for operating the multi-sensor equipment and any

interfaced equipment. (May be provided in a pilot’s guide that is referenced in the flight manual

supplement.)

(4) General description of system (or reference to a pilot’s guide that

provides an equipment description).

d. Functional Flight Evaluation. A functional flight evaluation covering the items

listed in paragraph 9.c.(2)(iv) is accomplished. The inspector may authorize the installer to
6/14/95 AC 20-130A

Appendix 1

Par 2 3

conduct the flight evaluation. In situations where additional FAA evaluation is necessary,

required flight evaluations will be conducted by the cognizant ACO or, when authorized, by a

Flight Test Pilot Designated Engineering Representative (DER) in accordance with the

procedures used by the ACO.

6/4/95 AC 20-130A

Appendix 2

Par 1 1

APPENDIX 2. SAMPLE AIRPLANE FLIGHT MANUAL SUPPLEMENT

(FAA Form 337 Approval Process).

1. The following sample Airplane Flight Manual Supplement (AFMS) is provided as an

example of the format to be used and information to be included when preparing required

supplements. An AFMS must follow the organization of the flight manual being supplemented.
AC 20-130A 6/14/95

Appendix 2

2 Par 1

FIGURE 1. SAMPLE AIRPLANE FLIGHT MANUAL SUPPLEMENT

Installation Center/Repair Station Model XXX Multi-Sensor

123 Fourth Street Navigation System

Anytown, USA

FAA APPROVED AIRPLANE FLIGHT MANUAL SUPPLEMENT

ABC MODEL XXX MULTI-SENSOR 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 Multi-Sensor navigation system when it has been installed in

accordance with <manufacturer’s installation manual number and date> and FAA Form 337

dated <insert date>.

For airplanes with an FAA Approved Airplane Flight Manual, this document serves as the FAA

Approved ABC Model XXX Multi-Sensor navigation system Flight Manual Supplement. For

airplanes that do not have an approved flight manual, this document serves as the FAA

Approved ABC Model XXX Multi-Sensor navigation system 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

Date: Page < > of < >
6/4/95 AC 20-130A

Appendix 2

Par 1 3

FIGURE 1. SAMPLE AIRPLANE FLIGHT MANUAL SUPPLEMENT (continued)

Installation Center/Repair Station Model XXX Multi-Sensor

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

Date: Page < > of < >
AC 20-130A 6/14/95

Appendix 2

4 Par 1

FIGURE 1. SAMPLE AIRPLANE FLIGHT MANUAL SUPPLEMENT (continued)

Installation Center/Repair Station Model XXX Multi-Sensor

123 Fourth Street Navigation System

Anytown, USA

SECTION 1 - GENERAL

1. <Provide a very brief (i.e., one paragraph) general description of the multi-sensor navigation

system installed in the aircraft.>

2. Provided the ABC Model XXX multi-sensor navigation system is receiving usable signals, it

has been demonstrated capable of and has been shown to meet the accuracy specifications

of:

VFR/IFR en route oceanic and remote, en route domestic, terminal, and instrument approach

(GPS, Loran-C, VOR, VOR-DME, TACAN, NDB, NDB-DME, RNAV) operation (specify

operations, i.e., en route oceanic and remote, en route domestic, terminal, instrument approach,

etc., as applicable to the particular approval.) within the U. S. National Airspace System and

latitudes bounded by < > North and < > South using the WGS-84 (or NAD 83) coordinate

reference datum in accordance with the criteria of AC 20-130A, AC 91-49, AC 120-33, and

<list additional applicable ACs>. Satellite navigation data is based upon use of only the Global

Positioning System (GPS) operated by the United States.

SECTION 2 - LIMITATIONS

1. The ABC Model XXX Multi-Sensor Navigation System Pilot’s 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. The software

status stated in the Pilot’s Guide must match that displayed on the equipment.

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

3. IFR en route and terminal navigation is prohibited unless the pilot verifies the currency of the

data base or verifies each selected waypoint for accuracy by reference to current approved

data.

4. Instrument approaches must be accomplished in accordance with approved instrument

approach procedures that are retrieved from the multi-sensor equipment data base. The

multi-sensor equipment data base must incorporate the current update cycle.

 FAA Approved

Date: Page < > of < >
6/4/95 AC 20-130A

Appendix 2

Par 1 5

FIGURE 1. SAMPLE AIRPLANE FLIGHT MANUAL SUPPLEMENT (continued)

Installation Center/Repair Station Model XXX Multi-Sensor

123 Fourth Street Navigation System

Anytown, USA

(a) Instrument approaches must be conducted in the approach mode and GPS integrity

monitoring (for systems incorporating a GPS sensor) must be available at the Final

Approach Fix.

(b) Accomplishment of ILS, LOC, LOC-BC, LDA, SDF, and MLS approaches are not

authorized.

(c) When an alternate airport is required by the applicable operating rules, it must be served by

an approach based on other than GPS or Loran-C navigation, the aircraft must have

operational equipment capable of using that navigation aid, and the required navigation aid

must be operational.

(d) <if applicable> This system has been demonstrated to meet the accuracy and availability

requirements of the MNPS airspace.

5. The aircraft must have other approved navigation equipment installed and operating

appropriate to the route of flight.

6. <Specify any airspace limitations that may be applicable to systems that do not provide for

coordinate reference system conversions of the displayed navigation information for airspace

that is not referenced to the WGS-84 or NAD-83 geodetic datums.

7. <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 multi-sensor equipment navigation information is not

available or invalid, utilize remaining operational navigation equipment as

required.

2. If “GPS INTEGRITY NOT AVAILABLE” message is displayed, continued navigation

using the GPS equipment or reversion to an alternate means of navigation appropriate to the

route and phase of flight is necessary. When continuing to use GPS navigation, position should

be verified every 15 minutes using another IFR-approved navigation system.

FAA Approved

Date: Page < > of < >
AC 20-130A 6/14/95

Appendix 2

6 Par 1

FIGURE 1. SAMPLE AIRPLANE FLIGHT MANUAL SUPPLEMENT (continued)

Installation Center/Repair Station Model XXX Multi-Sensor

123 Fourth Street Navigation System

Anytown, USA

SECTION 4 - NORMAL PROCEDURES

NOTE: Transmission on VHF communication frequencies 121.150, 121.175, 121.200,

131.250, 131.275, and 131.300 MHz may adversely affect reception of the GPS signal.

Transmissions in excess of approximately 15 seconds may result in loss of GPS signal

reception. Navigation will be restored within 5 seconds after the completion of the

transmission.

1. Normal operating procedures are outlined in the ABC Model XXX Multi-Sensor Equipment

Pilot’s Guide, P/N <insert part number>, dated <insert date> (or later appropriate revision).

2. <Describe approach mode sequencing and signal integrity capability.>

3. System Annunciators

a. Waypoint - <describe each annunciator>

b. Message - <describe each annunciator>

c. Approach - <describe each annunciator>

d. <describe any other annunciators>

4. System Switches

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

FAA Approved

Date: Page < > of < >
6/4/95 AC 20-130A

Appendix 2

Par 1 7

FIGURE 1. SAMPLE AIRPLANE FLIGHT MANUAL SUPPLEMENT (continued)

Installation Center/Repair Station Model XXX Multi-Sensor

123 Fourth Street Navigation System

Anytown, USA

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

c. <describe any other switches>

5. Pilot’s Display <describe the pilot’s multi-sensor navigation data display(s)>

6. Flight Director/Autopilot Coupled Operation <describe the procedures for coupling multisensor equipment navigation information 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

Date: Page < > of < >

6/14/95 AC 20-130A

Appendix 3

Par 1 1

APPENDIX 3. GLOSSARY

1. Availability. The availability of the overall system or a particular sensor is the percentage

of time that the services of the system/sensor are usable. Availability is an indication of the

ability of the system to provide usable service within the specified coverage area. Signal

availability is the percentage of time that navigational signals transmitted from the satellites or

ground stations are available for use.

2. Area Calibration. Area calibration is a procedure where time measurement correction

factors are input into the Loran-C system to reduce the effect of propagation anomalies.

3. Barometric altitude. Altitude in the earth’s atmosphere above mean standard sea level

pressure datum plane, measured by a pressure (barometric) altimeter and corrected for local

barometric pressure setting.

4. Differential GPS. A technique used to improve GPS system accuracy by determining

positioning error from the GPS satellites at a known fixed location and subsequently transmitting

the determined error, or corrective factors, to GPS users operating in the same area.

5. Distance Root Mean Square (DRMS). The root-mean-square value of the distances

between the measured and true location in a collection of measurements. The two dimensional

circular error distribution, where 95 percent of the position solutions must lie within the defined

radius of the circle, is represented by two times the DRMS (2DRMS).

6. En Route Operations. The phase of navigation covering operations between departure

and termination phases. The en route phase of navigation has two subcategories: en route

domestic and en route oceanic/remote.

7. En Route Domestic. The phase of flight between departure and arrival terminal phases,

with departure and arrival points within the U.S. National Airspace System (NAS).

8. En Route Oceanic and Remote. The phase of flight between the departure and arrival

terminal phases, with an extended flight path over an ocean.

9. Flight Technical Error (FTE). Navigation error introduced by the pilot’s (or autopilot’s)

capability to utilize displayed guidance information to track the desired flight path.

10. Geometric Dilution of Precision (GDOP). A measure of the satellite geometric effects

that degrade a user’s position determination.

11. GPS Equipment Classes A(), B(), and C(). GPS equipment is categorized into the

following classes (ref. TSO-C129):
AC 20-130A 6/14/95

Appendix 3

2 Par 11

a. Class A(). Equipment incorporating both the GPS sensor and navigation

capability. This equipment incorporates Receiver Autonomous Integrity Monitoring (RAIM).

Class A1 equipment includes en route, terminal, and non-precision approach navigation

capability. Class A2 equipment includes en route and terminal navigation capability only.

b. Class B(). Equipment consisting of a GPS sensor that provides data to an

integrated navigation system (i.e., flight management system, multi-sensor navigation system,

etc.). Class B1 equipment includes RAIM and provides en route, terminal, and non-precision

approach capability. Class B2 equipment includes RAIM and provides en route and terminal

capability only. Class B3 equipment requires the integrated navigation system to provide a level

of GPS integrity equivalent to RAIM and provides en route, terminal, and non-precision

approach capability. Class B4 equipment requires the integrated navigation system to provide a

level of GPS integrity equivalent to RAIM and provides en route and terminal capability only.

c. Class C(). Equipment consisting of a GPS sensor that provides data to an

integrated navigation system (i.e., flight management system, multi-sensor navigation system,

etc.), which provides enhanced guidance to an autopilot or flight director in order to reduce

flight technical error. Installation of Class C() equipment is limited to aircraft approved under

14 CFR part 121 or equivalent criteria. Class C1 equipment includes RAIM and provides en

route, terminal, and non-precision approach capability. Class C2 equipment includes RAIM and

provides en route and terminal capability only. Class C3 equipment needs the integrated

navigation system to provide a level of GPS integrity equivalent to RAIM and provides en route,

terminal, and non-precision approach capability. Class C4 equipment requires the integrated

navigation system to provide a level of GPS integrity equivalent to RAIM and provides en route

and terminal capability only.

12. Horizontal Dilution of Precision (HDOP). The satellite geometric effects which perturb

a user’s horizontal error (east and north). Combination of east dilution of precision and north

dilution of precision.

13. Integrity. The probability that the system will provide accurate navigation as specified or

timely warnings to users when navigation data from a particular sensor should not be used for

navigation.

14. Mask Angle. A fixed elevation angle referenced to the user’s horizon below which GPS

satellites are ignored by the receiver software. The mask angle is driven by the receiver antenna

characteristics, the strength of the transmitted signal at low elevations, receiver sensitivity and

acceptable low elevation errors.

15. Non-Precision Approach Operations. Those flight phases conducted on charted nonprecision Instrument Approach Procedures (IAP’s) commencing at the initial approach fix and

concluding at the missed approach point or the missed approach holding fix, as appropriate.
6/14/95 AC 20-130A

Appendix 3

Par 15 3

16. Operating Modes. Multi-sensor equipment modes associated with various phases of

flight: i.e., oceanic, en route, terminal, and non-precision approach.

17. Precipitation Static (P-Static). P-static is electromagnetic noise generated by the

dissipation of an electrical charge from an aircraft into the atmosphere. The aircraft becomes

charged by flight through particles suspended in the atmosphere such as dust, ice, rain, or snow.

Unprotected aircraft may create so much noise that the Loran-C or Omega/VLF sensor can no

longer detect the transmitted signal.

18. Pressure Altitude. Altitude in the earth’s atmosphere above mean standard sea level

pressure datum plane, measured by a pressure (barometric) altimeter set to standard pressure

(29.92 inches of mercury).

19. Receiver Autonomous Integrity Monitoring (RAIM). A technique whereby a civil GPS

receiver/processor determines the integrity of the GPS navigation signals using only GPS signals

or GPS signals augmented with altitude. This determination is achieved by a consistency check

among redundant measurements. At least one satellite in addition to those required for

navigation must be in view for the receiver to perform the RAIM function.

20. Stand-Alone Navigation System. Stand-alone equipment is equipment that is not

combined with other navigation sensors or navigation systems. Stand-alone GPS equipment

can, however, include other augmentation features such as altimeter smoothing, clock coasting,

etc.

21. Standard Positioning Service (SPS). The standard specified level of positioning, velocity

and timing accuracy that is available, without qualifications or restrictions, to any user of the

GPS system on a continuous worldwide basis. The navigation service associated with SPS is

specified to be 100 meters 2 DRMS horizontal error. 2 DRMS is defined to represent 95

percent.

22. Supplemental Air Navigation System. An FAA-approved navigation system that can be

used for navigation provided an alternate navigation system, which meets all of the regulatory

requirements for the route of flight, is also installed on the aircraft.

23. Terminal Area Operations. Those flight phases conducted on charted Standard

Instrument Departures (SID’s), on Standard Terminal Arrivals (STAR’s), or other flight

operations between the last en route fix/waypoint and an initial approach fix/waypoint.

24. Time Difference (TD). The elapsed time, in microseconds, measured at the receiver,

between the arrival of a set of pulses from one Loran-C station’s signal to the arrival of a set of

pulses from another Loran-C stations signal.

25. Track Angle Error. Track angle error is the difference between the desired track and

actual track (magnetic or true).
AC 20-130A 6/14/95

Appendix 3

4 Par 25

26. Triad. The collective name given to the three stations from a Loran-C chain from which

navigational information is being derived.