Earth Cover and Contour Effects on Image Glide Paths. Phase II

摘要

The report presents the results of Phase II of a research and development effort to provide quantitative information on the effects of earth contours and ground plane snow covers on the Null-Reference, Sideband-Reference, and Capture-Effect Glide Path Systems. The mathematical model developed in Phase I (see AD-618 085) was used to predict the amplitude and position of glide path roughness at Pittsburgh, Pennsylvania; Charleston, West Virginia; and Ohio University Airport, Athens, Ohio, due to reflection of signals from irregular terrain in the approach region. Pittsburgh and Charleston predictions were confirmed by comparing with FAA flight inspection data. Development of a second mathematical model begun in Phase I was completed in this phase to provide a clear indication of effects on the monitor produced by snow coverings on the earth between the transmitter and the monitor. Computer calculations demonstrated that the glide path angle may be expected to increase or decrease at the monitor depending on the value of the dielectric constant of the snow. Low values of dielectric constant which are associated with light, fluffy, dry snow produce a decrease in path angle at the monitor and a wet snow with a high dielectric constant produces a raising of this path angle. Evidence from field measurements corroborates the calculated results. (Author)