Statistical and Spectral Analysis of Data From Helicopter Test Flights Using GPS Lateral Guidance and Barometric Vertical Navigation

David P. Stapleton and Mike Monroney

Abstract:	Data from hand-flown helicopter approaches at the Federal Aviation Administration Technical Center (FAATC) in Atlantic City, New Jersey is evaluated, in which flights employ a so-called “LNAV/VNAV” guidance system. In this system, the Global Positioning System (GPS) solution is applied for lateral guidance and barometric instruments provide the vertical guidance for pilots’ instruments along a straight-path glideslope. It is observed that the barometric guidance generally causes the pilots to fly above the glideslope, but that the size and variation of vertical navigation errors decreases during descent. Also, it is found that vertical navigation errors are substantially smaller during cold temperatures than during hot temperatures and the overall variation in the vertical solution is substantially less than that of the lateral solution. In the GPS positioning, the solution on some approaches is found to vary as the pilot turns the helicopter. Large oscillations arise in the lateral position during two of the approaches, leading to missed approach conditions. Many approaches display a characteristic frequency of total system error (side-to-side and/or up-and-down) but the frequency - when present, is found to vary substantially from approach to approach, so that no overall characteristic frequency appears.
Published in:	Proceedings of the 2004 National Technical Meeting of The Institute of Navigation January 26 - 28, 2004 The Catamaran Resort Hotel San Diego, CA
Pages:	1087 - 1093
Cite this article:	Stapleton, David P., Monroney, Mike, "Statistical and Spectral Analysis of Data From Helicopter Test Flights Using GPS Lateral Guidance and Barometric Vertical Navigation," Proceedings of the 2004 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2004, pp. 1087-1093.
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