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The Federal Aviation Administration (FAA) has accepted the Loran-C navigation system as a supplemental navigation aid for enroute use. Extension of Loran-C utilization to instrument approaches requires establishment of a process by which the current level of performance of the system is always known by the pilot. This system 'integrity' translates into confidence that, if the system is made available to the pilot, the guidance will be correct. Early in the consideration of Loran-C for instrument approaches, the Loran-C Planning Work-Group (LPW) was formed with membership from the FAA, the US Coast Guard, various state governments, aviation users, equipment manufacturers and technical experts. The group was hosted and co-chaired by the National Association of State Aviation Officials (NASAO). This forum was ideal for identification of system integrity issues and for finding the correct process for their resolution. Additionally, the Wild Goose Association (WGA), which is the international Loran-C technical and user forum, regularly brings together members of the FAA, Coast Guard, and the scientific community. Papers and discussions from WGA meetings have been helpful. Given here is a collection of the issues in which Ohio University became involved. Issues definition and resolution are included along with the recommendations in those areas where resolution is not yet complete. Lilley, Robert W. and Brooks, N. Kent Unspecified Center NAG1-816...
As of October 1, 1993, the U.S. Coast Guard (USCG) supports and operates fifteen Loran-C chains. With the introduction of the Global Positioning System (GPS) and the termination of the Department of Defense (DOD) overseas need for Loran-C, the USCG will cease operating the three remaining overseas chains by December 31, 1994. Following this date, the USCG Loran-C system will consist of twelve chains. Since 1971, management of time synchronization of the Loran-C system has been conducted under a Memorandum of Agreement between the U.S. Naval Observatory (USNO) and the USCG. The requirement to maintain synchronization with Coordinated Universal Time (UTC) was initially specified as + or - 25 microseconds. This tolerance was rapidly lowered to + or - 2.5 microseconds in 1974. To manage this synchronization requirement, the USCG incorporated administrative practices which kept the USNO appraised of all aspects of the master timing path. This included procedures for responding to timing path failures, timing adjustments and time steps. Conducting these aspects of time synchronization depended on message traffic between the various master stations and the USNO. To determine clock adjustment, the USCG relied upon the USNO's Series 4 and 100 updates so that the characteristics of the master clock could be plotted and controls appropriately applied. In 1987, Public Law 100-223, under the Airport and Airway Improvement Act Amendment, reduced the synchronization tolerance to approximately 100 nanoseconds (ns) for chains serving the National Airspace System (NAS). This action caused changes in the previous administrative procedures and techniques. This paper presents the actions taken by the USCG to meet the requirements of this law.
This report describes an extensive evaluation of Loran-C for use by general aviation. Flight, ground, and antenna tests were done. Flight tests measured the accuracy and the ability to make approaches. Receiver reliability and susceptibility to atmospheric noise were also studied. Ground tests looked into grid stability and grid war page. Antenna tests were done to evaluate three antenna configurations -- ADF, vertical whip, and trailing wire antennas. The measured accuracy met FAA AC 90-45A requirements for all phases of flight. Loran-C was found to be satisfactory for approaches within AC 90-45A specifications. Reliability was 99.7%, the receiver was insensitive to atmospheric noise. The time difference grid was stable in the long run. Antenna tests showed the ADF and vertical whip antennas to be suitable for airborne use. It is concluded that Loran-C is suitable for navigation as an alternative to VHF RNAV. This navigation system is suitable for use in general aviation aircraft.