A general discussion of crash sensor requirements is provided, with emphasis on the advantages of long inflation times. An explanation of the basic radar system is offered, and various designs, broken down both by antenna configuration and carrier modulation, are investigated. After careful study it is found that all radar sensors suffer from the same inadequacy-the inability to correctly classify obstacles into hazardous and nonhazardous categories. Several approaches to solving this problem are discussed. The conclusion is reached that radar crash sensors will be unavailable for MY 1976 air cushion requirements.