Introduction

The number of passes an aircraft can make on a soft field is limited because rutting of the field occurs with each successive pass. Eventually, absent resurfacing, this rutting will reach a point where further aircraft operations are no longer permissible. The maximum number of passes an aircraft can make is commonly described as a function of the California Bearing Ratio (CBR) of the field and the weight of the aircraft. In many situations, CBR is not the best predictor of maximum passes; however, it is frequently used because of the relative ease with which it can be measured and