Flight Testing for Use of GPS in the National Airspace System

Alan Lawer, Kerry King, Dirk deDoes, Ron Gray and Ken Rhoades

Abstract:	Previous tests have not been designed to address specific instrument procedures for the use of GPS in the National Airspace System (NAS). Planned to replace VOR/DME, VORTAC and TACAN facilities for the DoD, GPS is being introduced as a sole means navigation aid for enroute, terminal area maneuvering and landing approaches. Described is an ongoing test program designed to provide data to exploit fully the DoD use of GPS in the NAS. The objectives for the GPS instrument flight procedures evaluation include the determination of the operational limits of GPS when used for enroute, terminal maneuvering and landing approaches, the exploration of innovative techniques using GPS and the collection of data for the development of GPS terminal instrument procedures. Existing approach procedures can be emulated or specific GPS ap proaches designed and used. The test program involves examination of nonprecision approach capability, precision-type capability, holding patterns and departure procedures. The initial test phase has been completed, with specific GPS approaches having been flown, and a Time Space Position Information system for providing aircraft position information using differential GPS verified. The next phase will emulate an ILS approach and several types of TACAN approaches. The NT-39A test aircraft used has GPS fully integrated with a smart control display unit, INS and other avionics such that the pilots’ horizontal situation and attitude director indicators (HSI and ADI) receive suitable GPS-derived inputs. The significance of magnetic variation for emulations of existing proce- dures is discussed and the statistical analyses for approach data and obstacle clearance described. Only a preliminary examination of some of the data has so far been possible. Initial results show a left bias in the lateral errors during approaches, while the scaling sensitivities of the receiver’s horizontal and vertical track deviations have not been found to be optimal. Accurate receiver entry data is crucial to achieve the full potential of GPS. The outcome of the program will form a basis for future testing.
Published in:	Proceedings of the 4th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1991) September 11 - 13, 1991 Albuquerque, NM
Pages:	179 - 190
Cite this article:	Lawer, Alan, King, Kerry, deDoes, Dirk, Gray, Ron, Rhoades, Ken, "Flight Testing for Use of GPS in the National Airspace System," Proceedings of the 4th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1991), Albuquerque, NM, September 1991, pp. 179-190.
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