Advisory IJ.S. Department of lransporlation 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 OUTSllBE 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 olitside the U.S. NAS and beyond the coverage of standard International Civil Aviation Organization (ICAO) navigation aids (NAVAID's). These NAVAUD's include very high frequency omnidirectional range stations (VOR's), with or without distance measuring equipment (DME), and nondirectional beacons @DB's). This AC also contains guidance which is applicable for use while over the Gulf of Mexico and other coastal waters.
2. DEFNTIONS. Since this AC contains a number of technical terns 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. SRIELATED Rl3ADI[NG MATE L. The guidelines within this AC complement the following documents:
a. AC's and Operations LWanuals. Copies of the following AC's and operations manuals may be obtained fram the U.S. Department of Transportation (DOT), General Services Section, M-443.2, Washington, D.C. 20590.
(1) AC 20-121, "Ailworthiness Approval of Airborne Loran-C Navigation Systems for Use in the U.S. National Airspace System (NAS)," current edition.
(2) AG 90-79, "Recommended Practices and Procedures for the Use of Electronic Eong-Range Navigation Equipment," current edition.
(3) AC 91-49, "General Aviation Procedures for Flight in North Atlantic Minimum Navigation Fe~formance Specifications Airspace," current edition.
(4) "North Atlantic S Airspace Operations Manual," 5thedition, reprinted 199 1. (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 wlien placing an order by phone.
(1) FAA Order 8300.10, "Aiswort:hiness Inspector's Handbook," SIN 050-007-0922-4.
(2) FAA Order 8400.10, "Air Transportation Operations Inspector's Handbook," S/N 050-007-00923-3.
(3) FAA Order 8708.1, "General Aviation Operations Inspector's Handbook," SIN 050-007-0092 1-6. ,--T
(4) "North Atlantic International General Aviation Operations Manual," 1"' edition, October 1990, F QT, Washington, D.C., S/N 050-007-00886-4.
c. ICAB PubBications. Copies of the foflowiwg IGAO publications may be obtained by contacting 6CAO. Orders for ICAO publications should be sent to the following address together with the appropriate remiittance (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 2R.2 (Telephone: (5 14) 285-82 19) (I) IGAO hex 2, "Rules of the Air."
(2) ICAO Annex 6, "Operation of Aircraft."
(3) ICAO Documen"r7830, "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.
Thomas C. Accardi Director, Flight Standards Service iii (and iv)
CONTENTS Paragraph Page
1. System Description1
Figure 1 . Table of Loran-C Chains2
2. System Characteristics3
Figure 2. Predictable Accuracy Table3
3. Oceanic Airspace Coverage4
Figure 3 . Worldwide Loran-C Coverage5
Figure 4. Loran-C NAS Coverage Diagram6
4. Applicability7
Figure 5. North Atlantic (NAT) MNPS Airspace10
Figure 6. Canadian MNPS Airspace11
5. Installation and Operational Guidance for the Use of Loran-C in Oceanic
Operations12
Figure 7 . Sample "Page One" From AFM/POH Supplement Figure 8. Sample AFMBOH Approval Endorsement to Operate Loran-C in
.14
MNPS Airspace15
Appendix 1 . Loran-C Oceanic and NAS Coverage Diagrams ........... (18 pages) 1
Canadian West Coast Chain .59901
United States West Coast Chain .99402
North Central United States Chain .8290 ...*.*3
South Central United States Chain .96104
United States Great Lakes Chain .89705
Southeast United States Chain .79806
Northeast United States Chain .99607
CONTENTS (Continued) Page
Canadian East Coast Chain .59308
Labrador Sea Chain .79309
Icelandic Chain .998010
Nolwegian Sea Chairr .747011
Mediterranean Sea Chain .799012
Saudi Arabia (Nodh) Chain .899013
Saudi Arabia (Smth) Chain .717014
East Asia Chain .597815
,-
Nofibwest Pacific Chain .997016
Alaska .Nodl Pacific Chain .999017
Alaska .Gulf of Alaska Chain ."79g18
Appendix 2. Glossay ............. ........................ (13 pages) 1
Figure 4. Baseline Extension2
Figure 10. Pdoran-6 Sky Wdve and Ground Wave Signals11
Appendix 3. Acrsnps .................................... (1 $?age) 1
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 "Mu) 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 1
FIGURE 1 TABLE OF LOW-6 CI-bUhyS 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) So~~theastU.S.
2. SYSTEM CHARACTEIUSTICS. The following are Loran-C system characteristics:
a. Predictable Accuracy FIGURE 2
PREDICTABLE ACCURACY TABLE
OPERATIONAL SEGMENT Oceanic IFR En route IFR - - airway only, NAS, and Gulf of Mexico Terminal IFR - - NAS, and Gulf of Mexico Approach IFR - - for published Loran-C approaches in the NAS and Gulf of Mexico
TYPE NAV FIX Any fix Any fix on or off ainvay (given suitable obstacle clearance) Any SIDISTAR waypoint plus IAF's; also from MAP holding fix From IAF to FAF, then to MAP
ACCURACY 0
COMMENTS 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).
This level of accuracy requires that the Loran-C unit be operated within the coverage limits as specified by the manufacturer.
This 0.3 nm level of accuracy applies to only those instrument approaches that have been FAA approved.
Par 2 3
b. Repeatable Accuracy: 60-300 feet (1 8.3-91.4 meters)
c. Relative Accuracy: 40-300 feet (1 8.3-9 1.4 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 my 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:
Ewopean area Asian-Pacific area Icelandic Sea Chain Northwest Pacific Chain
- Norwegian Sea Chain Mediterranean Sea Chain Par 2
FIGURE 3
WORLDWIDE LORAN-C COVERAGE Contours represent the range Emits in which the signal-to-noise ratio (SNR) falls to 1:3 (or -10 db SNR) and the accuracy limits in which the CDOF falls to 7,700 ft/CLs.
FIGURE 4 -C NAS COVERAGE DUGRAM United States and Surrounding Oceanic Areas Parameters Contour: SNR -10 db; Oceanic GDOP 7,700 Wps;
NAS GDOP 4,200 ft/vs + NAS Contour Symbology: --- Average Atmospheric Noise: 64 db Surface to FL 600 Flight Verified