Summary of Buckling and Tension Tests of Landing Mats as Related to C-5A Aircraft Bow Wave Problems

In order to better understand and define the problems associated with the C-5a and landing mat, several investigations were conducted at the U.S. Army Engineer Waterways Experiment Station and Utah State University to study the characteristics of landing mats subjected to horizontal C-5A loads. Several mat configurations with various connector designs were evaluated in buckling, skid, joint slack, and traffic tests. Mats both with and without water seals were used in the tests; however, the heavy-duty truss web mat designs with their extra weight and additional strength were given primary consideration. In the buckling tests conducted, it was determined that panel width, mat unit weight, and formation width were factors which affect the buckling load of a mat system. The horizontal load at which buckling occurs depends almost exclusively on the vertical eccentricities existing in the mat system at the time the load is applied. These eccentricities or irregularities could be initiated by the presence of warped panels, damaged joints, uneven subgrade, etc. It is concluded that the approximately square truss web mat designs sustained a much higher load per foot of width prior to the development of a bow wave or buckling. Square mats without water seals give higher resistance to sliding between mat rows that mats with seals. However, membrane beneath mat provides a lower coefficient of friction which enhances mat sliding. During the normal placement of mat, there is free slack in the panel joints which, although necessary for contraction and expansion, contributes to potential runway movement.