Problem of Multiple Solutions in Area Navigation and Computed CenterlineOperations with the Microwave Landing System

摘要

In normal geometries of siting of the ground units, the Microwave Landing System(MLS) observations in the avionics of azimuth and elevation angles plus slant range from a Distance Measuring Equipment (DME) transponder yield a unique solution for the aircraft location. However, for some unconventional geometries of the ground units in a very few, preexisting installations, these observations can be consistent with two solutions for aircraft location within the MLS coverage volume. It appears that the basic MLS concept has not dealt with this multiple solutions situation, which is possible within the present international agreements. This report shows that the MLS avionics position reconstruction algorithms, which determine the aircraft location in Cartesian coordinates and are essential in area navigation, computed centerline approach, and ground operations such as deceleration and turnoff, cannot from internal data tell which of the two solutions is true and which is false. The problem can be avoided by new constraints on the permitted sites for the MLS ground units, by restrictions on the aircraft flight paths, or by Kalman filters or equivalents in the avionics. These constraints, restrictions, and filters, are defined.