AC 90-92

Advisory U.S. Department of Circular Transportation Federal Aviation Administration Amic-40n Subject: GUIDELINES FOR THE OPERATIONAL Date: 6/15/93 AC No: 90-92 USE OF LORAN-C NAVIGATION Initiated by: AFS-430 Change: 1 SYSTEMS OUTSIDE THE U.S. NATIONAL

AIRSPACE SYSTEM (NAS)

1. PURPOSE. This Change corrects a graphical layout error in the original issuance of AC 90-92. The Change number and date of the changed material are carried at the top of the page.

2. PRINCIPAL CHANGES. The original issuance of AC 90-92 contained graphical errors on pages 17 and 18 of Appendix 1. These errors were related to LORAN-C NAS coverage diagrams.

PAGE CONTROL CHART Remove Pages Dated Insert Pages Dated Appendix 1, page 17 2/5/93 Appendix 1, page 17 6/15/93 Appendix 1, page 18 2/5/93 Appendix 1, page 18 6/15/93 Milina I Milito William J. White Deputy Director, Flight Standards Service

Advisory U.S. Department of Circular Transportation Federal Aviation Administration Subject: GUIDELINES FOR THE OPERATIONAL Date: 2/5/93 AC No: 90-92 USE OF LORAN-C NAVIGATION Initiated by: AFS-430 SYSTEMS OUTSIDE THE U.S. NATIONAL

AIRSPACE SYSTEM (NAS)

1. PURPOSE. This advisory circular (AC) contains guidance to be used by pilots for the operational use of Loran-C navigation systems under visual flight rules (VFR) and instrument flight rules (IFR) while operating outside the U.S. NAS and beyond the coverage of standard International Civil Aviation Organization (ICAO) navigation aids (NAVAID's). These NAVAID's include very high frequency omnidirectional range stations (VOR's), with or without distance measuring equipment (DME), and nondirectional beacons (NDB's). This AC also contains guidance which is applicable for use while over the Gulf of Mexico and other coastal waters.

2. DEFINITIONS. Since this AC contains a number of technical terms which may not be familiar to the new Loran-C user, a list of definitions can be found in the Glossary, appendix 2. A list of frequently used acronyms may be found in appendix 3.

3. RELATED READING MATERIAL. The guidelines within this AC complement the following documents:

a. AC's and Operations Manuals. Copies of the following AC's and operations manuals may be obtained from the U.S. Department of Transportation (DOT), General Services Section, M-443.2, Washington, D.C. 20590.

(1) AC 20-121, Airworthiness Approval of Airborne Loran-C Navigation Systems for Use in the U.S. National Airspace System (NAS)," current edition.

(2) AC 90-79, Recommended Practices and Procedures for the Use of Electronic Long-Range Navigation Equipment," current edition.

(3) AC 91-49, General Aviation Procedures for Flight in North Atlantic Minimum Navigation Performance Specifications Airspace, current edition.

(4) "North Atlantic MNPS Airspace Operations Manual," 5" edition, reprinted 1991. (Requires a self-addressed mailing label.)

b. Federal Aviation Administration (FAA) Orders and Operations Manuals.

Copies of the following FAA orders may be obtained from the Government Printing Office (GPO). Please have stock number and credit card available when placing an order by phone.

(1) FAA Order 8300.10, "Airworthiness Inspector's Handbook," S/N 050-007-0922-4.

(2) FAA Order 8400.10, Air Transportation Operations Inspector's Handbook," S/N 050-007-00923-2.

(3) FAA Order 8700.1, "General Aviation Operations Inspector's Handbook," S/N 050-007-00921-6.

(4) "North Atlantic International General Aviation Operations Manual," 1" edition, October 1990, FAA/DOT, Washington, D.C., S/N 050-007-00886-4.

c. ICAO Publications. Copies of the following ICAO publications may be obtained by contacting ICAO. Orders for ICAO publications should be sent to the following address together with the appropriate remittance (by check or postal money order) in U.S. dollars:

Document Sales Unit International Civil Aviation Organization (ICAO) 1000 Sherbrooke Street West, Suite 400 Montreal, Quebec Canada H3A 2R2 (Telephone: (514) 285-8219)

(1) ICAO Annex 2, "Rules of the Air."

(2) ICAO Annex 6, "Operation of Aircraft."

(3) ICAO Document 7030, "Regional Supplementary Procedures."

4. COMMENTS INVITED. Comments regarding this publication should be directed to the following address:

Federal Aviation Administration Flight Standards National Field Office, AFS-500 Advisory Circular Staff P.O. Box 20034, Gateway Building Dulles International Airport Washington, D.C. 20041-2034 Comments may not be deemed to require a direct acknowledgement to the commenter;

however, they will be considered in the development of upcoming revisions to AC's or other related technical material.

TRam Ceas Thomas C. Accardi Director, Flight Standards Service Ili (and iv)

CONTENTS Paragraph Page

1. System Description Figure 1. Table of Loran-C Chains

2. System Characteristics Figure 2. Predictable Accuracy Table 3

3. Oceanic Airspace Coverage 4 Figure 3. Worldwide Loran-C Coverage 5 Figure 4. Loran-C NAS Coverage Diagram 6

4. Applicability 7 Figure 5. North Atlantic (NAT) MNPS Airspace 10 Figure 6. Canadian MNPS Airspace 11

5. Installation and Operational Guidance for the Use of Loran-C in Oceanic Operations 12 Figure 7. Sample "Page One" From AFM/POH Supplement 14 Figure 8. Sample AFM/POH Approval Endorsement to Operate Loran-C in MNPS Airspace 15 Appendix 1. Loran-C Oceanic and NAS Coverage Diagrams (18 pages) 1 Canadian West Coast Chain - 5990 1 United States West Coast Chain - 9940 North Central United States Chain - 8290 South Central United States Chain - 9610 4 United States Great Lakes Chain - 8970 5 Southeast United States Chain - 7980 6 Northeast United States Chain - 9960

CONTENTS (Continued) Page Canadian East Coast Chain - 5930 Labrador Sea Chain - 7930 9 Icelandic Chain - 9980 10 Norwegian Sea Chain - 7970 . 11 Mediterranean Sea Chain - 7990 12 Saudi Arabia (North) Chain - 8990 13 Saudi Arabia (South) Chain - 7170 14 East Asia Chain - 5970 15 Northwest Pacific Chain - 9970 16 Alaska - North Pacific Chain - 9990 17 Alaska - Gulf of Alaska Chain - 7960 18 Appendix 2. Glossary. (13 pages) 1 Figure 9. Baseline Extension 2 Figure 10. Loran-C Sky Wave and Ground Wave Signals 11 Appendix 3. Acronyms (1 page) vi

1. SYSTEM DESCRIPTION.

a. Loran-C is a low frequency 100 kilohertz hyperbolic radio navigation system. A Loran-C chain consists of a master station (identified as "M") and two or more secondary stations identified as "V," "W," "X," "Y," and "Z." A prescribed signal-to-noise ratio (SNR) level and geometric dilution of precision (GDOP) accuracy define the geographical coverage of a Loran-C chain. The receiver computes lines of position (LOP's) based on the difference between the arrival times of signals from two time-synchronized transmitting stations of a chain. Normally, two LOP's are required to obtain a position fix. Loran-C chains are identified by the group repetition interval (GRI) used to time-synchronize the signal (see figure 1 for a list of the worldwide Loran-C chains).

NOTE: Loran-C accuracy is severely degraded (to nonexistent) along a baseline extension, such as the extension of a line connecting two or more Loran-C stations (see figure 9 in appendix 2).

b. Loran-C equipment may be designed to provide one (or more) of three basic operational modes:

(1) VFR use only (not certified for IFR operations)

(2) IFR en route and terminal

(3) IFR approach

c. Loran-C units may be portable, installed, single-sensor units (for example, Loran-C only), or contained as part of a multisensor (for example, Loran-C and global positioning system (GPS)) flight management system (FMS). Portable, hand-held Loran-C units are not currently FAA approved. "Strap-down" portable units with external antenna systems are generally considered to be portable electronic devices that do not require FAA approval;

however, some antenna installations may constitute a major alteration to the airframe. All permanently installed equipment must be FAA approved. For any permanently installed unit, specific limitations and operating instructions must be accessible by the flightcrew during normal operations.

d. Only properly installed and FAA-approved Loran-C units are authorized for use in IFR navigation. Hand-held, portable units and non-FAA-approved "strap-down" units should not be used for IFR navigation. Also, potential users of Loran-C units should not be misled and assume that a technical standard order (TSO) means that a particular Loran-C unit is approved for IFR use.

Par 1

FIGURE 1

TABLE OF LORAN-C CHAINS Geographic presentation order begins on the U.S./Canada west coast border and continues in an easterly direction around the world.

(see also figure 3) CHAIN NAME GRI # STATION APPENDIX 1 IDENTIFIER Page Canadian West Coast 5990 M, X, Y, L 1 U.S. West Coast 9940 M, W, X, Y 2 North Central U.S. 8290 M, W, X, Y 3 South Central U.S. 9610 M, V, W, X, Y, Z 4 U.S. Great Lakes 8970 M, W, X, Y, Z 5 Southeast U.S. 7980 M, W, X, Y, Z 6 Northeast U.S. 9960 M, W, X, Y, Z 7 Canadian East Coast 5930 M, X, Y, Z 8 Labrador Sea 7930 ° M, W, X 9 Icelandic 9980 M, W, X 10 Norwegian Sea 7970 M, W, X, Y, Z 11 Mediterranean Sea 7990 M, X, Y, Z 12 Saudi Arabia (North) 8990 M, V, W, X, Y, Z 13 Saudi Arabia (South) 7170 M, W, X, Y, Z 14 East Asia 5970 M, W, X, Y 15 Northwest Pacific 9970 M, W, X, Y, Z 16 Alaska - North Pacific 9990 M, X, Y, Z 17 Alaska - Gulf of Alaska 7960 M, X, Y, Z 18 2

2. SYSTEM CHARACTERISTICS. The following are Loran-C system characteristics:

a. Predictable Accuracy FIGURE 2

PREDICTABLE ACCURACY TABLE

OPERATIONAL SEGMENT TYPE NAV ACCURACY COMMENTS

FIX (NM) Oceanic IFR Any fix 5.8 At this time, there are no published accuracy standards (including oceanic operations) for VFR Loran-C equipment.

This level of accuracy requires that the Loran-C unit be operated within the coverage limits as specified by the manufacturer (see figure 8).

En route IFR - - airway only, Any fix on or off 2.8 This level of accuracy NAS, and Gulf of Mexico airway (given requires that the Loran-C suitable obstacle unit be operated within clearance) the coverage limits as specified by the manufacturer.

Terminal IFR -- NAS, and Gulf of Any SID/STAR 1.7 Mexico waypoint plus IAF'S; also from MAP holding fix Approach IFR - - for published From IAF to FAF, 0.3 This 0.3 nm level of Loran-C approaches in the NAS and then to MAP accuracy applies to only Gulf of Mexico those instrument approaches that have been FAA approved.

Par 2 3

b. Repeatable Accuracy: 60-300 feet (18.3-91.4 meters)

c. Relative Accuracy: 60-300 feet (18.3-91.4 meters)

d. Operational Availability: Greater than 95 percent NOTE: Operational availability determines what percentage of the time the pilot can expect the Loran-C signal to be usable. Signal coverage, reliability, and system capacity parameters each contribute to availability, but are only part of the equation. Antenna location, flight control bonding, precipitation, electrostatic discharge wick availability and condition, precipitation static, and atmospheric conditions also affect total operational availability. A high-powered surface transmitter can attenuate a Loran-C signal if the pilot is operating near a high-powered antenna.

e. Reliability (Triad): 99.7 percent

f. Capacity: Unlimited

g. Fix Dimension: "2D"

h. Fix Rate: 60 per minute

i. Ambiguity Potential: Low (for example, positions are easily resolved)

3. OCEANIC AIRSPACE COVERAGE. Figure 3 depicts worldwide Loran-C coverage.

Figure 4 depicts Loran-C coverage over the United States (excluding Canadian chains) and surrounding oceanic areas, including the Gulf of Mexico and the Caribbean. Detailed coverage charts are found in appendix 1.

CAUTION! Individual Loran-C units may not be certified for use everywhere;

therefore, pilots should consult their airplane flight manual (AFM)/pilot's operating handbook (POH) or aircraft operating manual (ACOM).

a. Loran-C Chain Closures or Transfers. All overseas Loran-C chains operated by and for the U.S. Government will either be turned over to foreign governments or closed by December 31, 1994. Specific closure or transfer dates have yet to be established. This includes the following Loran-C chains:

European area Asian-Pacific area Icelandic Sea Chain • Northwest Pacific Chain Norwegian Sea Chain Mediterranean Sea Chain Par 2

FIGURE 3 2/5/93

WORLDWIDE LORAN-C COVERAGE 135°W 90°W 45°W 45°E 90°E 135°E 180° 60°N 30°N Legend Coverage over land Coverage over water 30°S No land coverage No water coverage Contours represent the range limits in which the signal-to-noise ratio (SNR) falls to 1:3 (or -10 db SNR) and the accuracy limits AC 90-92 in which the GDOP falls to 7,700 ft/us.

FIGURE 4

LORAN-C NAS COVERAGE DIAGRAM United States and Surrounding Oceanic Areas Parameters

• Contour: SNR -10 db; Oceanic GDOP 7,700 ft/us;

• NAS GDOP 4,200 ft/us

• NAS Contour Symbology: -

• Average Atmospheric Noise: 64 db

• Surface to FL 600

• Flight Verified 25° 20° 15° W 130° 125° 120° 115 110° 105° 100° 95° 90° 85° 80° 75° 70° 65° W