TESTS WITH A C-130E AIRCRAFT ON UNSURFACED SOILS.
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS
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The Waterways Experiment Station participated in an offrunway flight test program of the C-130E aircraft to the extent of assisting in the selection of test sites, obtaining soil data for evaluation of soil strength at each site, determining effects of C-130E operations on soil strength, and obtaining runway roughness data and analyzing them by the power-spectral method. Three test sites, representing low, medium, and high soil strengths, were each tested in 27 C-130E operations takeoff, landing, and taxiing. Test results showed that the soil strengths at the high- CBR 10 and medium-strength CBR 4 to 8 test sites were greater than required for the aircraft operations imposed. The loose, dry sand of the low-strength test site posed no serious problems to C- 130E maneuverability. From the analysis of the roughness data it was found that although power-spectral density bears a relation to runway profile and can be used to define runway roughness, it does not provide an indication of the juxtaposition of bumps causing maximum response. It is recommended that profile data from other unsurfaced runways be collected for power-spectral analysis, and that tests be conducted to establish operational limitations on landing-gear structure with respect to rut depths. The basic concepts of the power-spectral technique for analyzing runway roughness are summarized in Appendix A. Author