Simulation of a helicopter yarding system in old growth forest stands

Graduation date: 1975Helicopter yarding systems have become a popular tool in\ud removing timber from steep slopes, sensitive soils, limited access\ud areas, and environmentally sensitive stands. Little is known about\ud the system's dynamics. This study is part of a research project to\ud explore "advanced" logging systems as to their economic efficiency\ud and environmental applications.\ud The objectives of my study were:\ud 1 To identify and isolate variables that significantly\ud influence helicopter yarding efficiency.\ud 2 To develop a simulation model that will simulate the\ud response of the helicopter yarding operations to\ud changes in these variables.\ud I observed a medium lift (Boeing-Vertol 107 Model II) helicopter\ud operation yarding from old growth stands under varying conditions.\ud The helicopter yarding cycle was broken down into four cycle\ud elements and four delay elements. I used the method of continuous\ud timing to observe these elements and obtain values for the variables that influence these elements. Multiple linear regression analysis was used to analyze\ud the effect of these variables on time required to complete each\ud cycle element. Regression equations were developed for two cycle\ud element, outhaul and inhaul. Other cycle elements and delay elements\ud were analyzed employing frequency distributions. A paired\ud t-test was used to establish the reliability of the regression\ud equations to precict element times.\ud A FORTRAN simulation model was used to simulate the\ud yarding system. The model can be used to estimate efficiency,\ud production rates, and delay times for a wide range of yarding\ud situations.\ud I experimented with the finished model and, based on\ud those results, made suggestions for system improvements