A Measure of Aircraft Installed LAAS System Interface Performance Via the VHF Data Broadcast (VDB) Link Without Interconnection and Interference

John F. Michaels

Abstract:	There will be a need to ven~ aircraft installed GNSS based LAAS precision approach system response to Message Type 1 through Type 5 as defined in [1]. A method has been evolved that gives the pilot and crew the ability to veri~ that the installed DGNSS system can properly process data interrupts, warnings, approach inhibits, data within and outside protection levels and alert limits, alarm verification, andlor any condition that could effect a flight decision, in particular 10SSof integrity. The flightline tester is located within 30 meters of the aircraft. The tester contains a VHF Data Broadcast (VDB) receiver and transmitter, whose performance is similar to that used by the aircraft and the LAAS Ground Reference Station respectively. It will receive the reference station VDB (Message Type 1-8) as it processes the satellite data and outputs differential corrections and other pertinent information. The tester will receive, detect and process this data, adding on dynamically varying differential correction for each satellite in view to simulate aircraft motion and output new dynamic VDB (Message Type 1-8) to the aircraft. [ 1] will receive the existing ground reference station VDB daita on the frequency designated for the airport and transmit the modified VDB data on a selected test frequency, separated sufficiently from the LAAS ground reference station frequency, so as not to compromise airport operations. [2] Because the LAAS ground reference station has multipath limiting antennas and is located at an airport site to further reduce multipatb effects on the received data, the use of its VDB for the processing of correction data will be as good as the reference station expected performance. For those airports that do not contain a LAAS ground reference station, the tester will contain a GPS receiver capable of processing all satellites in view. Although its expected that multipath will contribute additional unwanted errors, the tester processing of dynamic pseudorange corrections and the outputting of data within and outside protection levels and alert limits described above, will be able to test aircraft systems integrity, -. availability and continuity while stationary on the ramp, without any direct system interconnection.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	489 - 494
Cite this article:	Michaels, John F., "A Measure of Aircraft Installed LAAS System Interface Performance Via the VHF Data Broadcast (VDB) Link Without Interconnection and Interference," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 489-494.
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