A study was undertaken to evaluate the interrelationship collisions with the ground. The data were obtained during the period 1953-1960 and are to be contrasted with data previously reported for the period 1942-1952. Seat failure now occurs more frequently than belt failure. The curve of belt failure plotted as a function of impact velocity does not accelerate as rapidly relationship between primary impact variables, seat and belt tie-down effectiveness, and injuries sustained by occupants of 342 light planes involved in spin-stall crashes or collisions with the ground. The data were obtained during the period 1953-1960 and are to be contrasted with data previously reported for the period 1942-1952. Seat failure now occurs more frequently than belt failure. The curve of belt failure plotted as a function of impact velocity does not accelerate as rapidly as that from the earlier data, whereas the seat -failure curves from the two sets of data are comparable. Injuries are found to be more severe when seats fail than when belts fail. When tie-down is considered to be effective, injuries are less severe for the more recent data. Injury severity was found to increase little as a function of impact velocity, but did increase rapidly as a function of angle of impact.