TECHNICAL AND OPERATIONAL EVALUATION OF WIDE-AREA COVERAGE NAVIGATION SYSTEMS IN THE CONTINENTAL UNITED STATES

Donald W. Richardson

Peer Reviewed

Abstract:	The United States Federal Aviation Administration (FAA) is actively interested in furthering the technical and operational evaluation of wide area coverage navigation systems suitable for consideration for either replacement of or supplements to the existing VOR system of airborne navigation within the United States National Airspace System (NAS). Potential applications include the enroute, terminal and approach phases of flight. In order to facilitate the certification of these systems the Radio Technical Commission for Aeronautics (RTCA) has chartered a Special Committee, SC-137, with the responsibility for generating a series of documents called Minimum Operational Performance Standards (MOPS). These MOPS documents are then utilized, by reference, by the FAA in defining standards for certification of airborne equipment for operation within the NAS. In conjunction with this RTCA activity the FAA is in the process of sponsoring a series of flight evaluations over a large portion of the continental U.S. for the purpose of gathering quantitative data concerning the performance of representative wide-area coverage airborne navigation systems in both the enroute and approach environments. This FAA data-gathering activity is supplemental to similar activities being performed by individual manufacturers as part of their (manufacturers) attempts to obtain certification for their specific systems. The FAA effort is aimed at establishing an overall standardized data base covering such particular issues as: - Data quantifying flight technical error as one element in an overall navigation system use error budget - Signal coverage and accuracy data throughout the continental United States for Loran-C, Omega and Omega/VLF - Detailed data regarding propagation errors, signal to noise ratios, bias errors, etc. - Operational use data such as pilot workload, blunders, pilot-controller communications, etc. At the present time the FAA has established lateral (or 2D) accuracy criteria for three operational flight environments, namely the enroute, terminal area and approach phases of flight. FAA Advisory Circular 90-45A contains these criteria. Various VOR/DME-based area navigation systems have been certified for operation under the terms of this advisory circular, some for all three phases, some only for enrout.e and terminal operations. To this date no non-VOR/DME system has been certified for the approach phase, although several have achieved certification for enroute and terminal operation. Efforts are continuing in both the private and government sectors to quantitatively determine the capability of non-VOR/DME RNAV systems, particularly Loran-C, to meet the approach accuracy criteria of AC 90-45A. In addition to the primary objective of acquiring a substantial data base regarding the lateral (2D) accuracy performance of wide-area coverage (non-VOR/DME) navigation systems, the FAA has initiated an investigation into the feasibility of providing some measure of 3D vertical guidance based in part on information generated by these sensors. The concept which motivated this development was the desire to provide the capability to conduct instrument approach procedures with let-down guidance at airports which have no ILS or MLS glideslope equipment. This capability requires the availability of an area coverage navigation sensor with good accuracy and stability, such as Loran-C, and other instrumentation required to process altitude and position data in order to calculate descent guidance. Currently the objective of this activity, which is in the feasibility flight test demonstration phase, is to provide “pilot assist” vertical guidance information only in order to facilitate the operational performance of a non-instrumented runway or landing area. It is not intended to replace the precision vertical guidance performance provided by ILS or MLS. While this particular 3D program is being sponsored by the FAA helicopter R&D community as a means of assisting the helicopter pilot in making steep approaches to remote landing sites, the basic concept is equally applicable to similar fixed-wing operations. The remainder of this paper will briefly describe some of the technical and operational considerations involved in the overall FAA-sponsored data gathering activity treating these separate but directly related issues.
Published in:	NAVIGATION: Journal of the Institute of Navigation, Volume 29, Number 4
Pages:	261 - 270
Cite this article:	Richardson, Donald W., "TECHNICAL AND OPERATIONAL EVALUATION OF WIDE-AREA COVERAGE NAVIGATION SYSTEMS IN THE CONTINENTAL UNITED STATES", NAVIGATION: Journal of The Institute of Navigation, Vol. 29, No. 4, Winter 1982-1983, pp. 261-270.
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