Every spring the federal government departments must submit to Congress their proposed spending estimates for inclusion in the President’s budget for the next fiscal year. The estimates go first to separate appropriations committees in the House and Senate for review and the inclusion of any changes the legislators believe are necessary before being combined into the final budget. This year, in response to the FAA’s FY 2003 request for $13 million to cover continuing loran development, the House proposed almost doubling the allocation to $25 million while the Senate proposed increasing it to $21 million.
Such differences in the respective committees’ proposed amendments–of which there are normally hundreds–are resolved by a joint House/Senate Conference Committee, which usually meets in the fall but, because of last month’s elections, will now meet early next year. However, the FAA seems assured of getting between $8 million and $12 million more to spend on loran in FY 2003 than it originally planned. In situations like this, where Congress commits an agency to a higher spending level than planned, legislators are displeased when the additional money it has allocated– and which may not be used for other programs–remains unspent.
Congress believes that the FAA is not putting as much effort into loran as it should. In the words of the House Appropriations Committee: “The committee remains disappointed that the FAA proposes to reduce funding for this initiative to fund lower-priority activities.”
One such activity is the national differential GPS (ndgps) project, which would use former medium-frequency marine NDBs to transmit GPS accuracy corrections for surface users via special, non-aeronautical receivers. ndgps is a somewhat orphaned project, having been sponsored and managed at various times by other DOT agencies, such as the Highways and Railroad Administrations, and the Coast Guard. The FAA inherited it in FY 2003, requesting $6 million for the project. Without mincing words, the House committee promptly axed the total amount, stating, “The value of this effort is far from clear, and the use of trust-fund revenue, paid by air travelers, for an activity with minimal relevance to air travel seems highly inappropriate.”
Loran ‘Best’ Backup to GPS
In their loran deliberations, congressional members were probably mindful of the Volpe GPS interference report of September 10 last year, and of the DOT’s subsequent action plan, which stated the intent to assess and then mandate candidate GPS backup systems, including loran. They may also have studied a July independent analysis of Loran, commissioned by the FAA from Booz Allen Hamilton consultants, covering performance, suitability for aviation use and potential enhancements. The analysis, based on technology assessments and results from ongoing FAA flight-test results, concluded that loran “is theoretically the best option as a redundant system for GPS.”
Booz Allen’s analysis reported that loran provides an independant source of navigation with the potential to meet RNP-0.3 Rnav requirements; is not subject to the vulnerabilities of GPS; provides redundant and, in some cases, primary capability as a source for precise timing; and can provide a backup and potentially redundant ground-based communication channel for WAAS broadcasts.
The analysis was based on the use of “all in view” loran technology, where new receivers now in development would pick up and process all loran signals. In the continental U.S. this would mean receiving signals from as many as 30 different transmitters. Current thinking is that loran receivers would cease to be standalone, panel-mounted units; instead they would be a single circuit board within a GPS/WAAS receiver. No pilot operation would be required, and the loran would operate in the background, simply shadowing the GPS until the satellite service was interrupted, when it would take over navigation until GPS was reliably restored.
Flight tests of all-in-view loran receivers by FAA’s technical center in Atlantic City, N.J., have proved the concept, and Rockwell Collins has developed a prototype multimode GPS/ILS receiver that includes a loran board. Other avionics makers are expected to follow suit.
Loran industry officials welcomed the House and Senate budget recommendations, which they believe should certainly accelerate the development process and the ongoing upgrades to the present ground-based transmitter network. But they also caution that much work still needs to be done in such areas as confirming the RNP-0.3 coverage throughout the U.S., continuing flight evaluations and developing certification specifications before commercial production can begin in about four or five years.