Pilot selection criteria for the AH-64 helicopter.

Abstract

An experimental study was performed to devise a technique for measuring the volume backscattering from sediments. This experimental technique has never been performed in the laboratory. The volume backscattering was to be determined by comparing the echoes returned from the sediment with the echo returned from the water/air interface. Measurements made on echoes returned from the water/air interface indicated that the apparatus, data acquisition system, and analysis system were performing correctly. Two types of sediments (fine sand and aggregate gravel) were used. The fine sand did not produce measureable volume backscattering and the aggregate showed results that depended on the region of sediment ensonified. It is recommended that a sediment more homogeneous than the aggregate, but with more backscattering than the fine sand be used in future studies.