Production rates and costs for yarding by cable, balloon, and helicopter compared for clearcuttings and partial cuttings

This report supplements Research Bulletin 18 (1975) of the Forest Research Laboratory, School of Forestry, Oregon State University. Bulletin 18 summarized analyses of data for the first field season of the Pansy Basin Study. This Bulletin extends those analyses to the second, and final, field season. Time-study observations during the second field season were made of three yarding systems: running skyline, balloon haulback, and heavy-lift helicopter. The running skyline was observed in a partial cutting, the balloon in a clearcutting, and the helicopter in both clearcuttings and partial cuttings. All of the cutting units were designed to reduce damage to the appearance of the landscape. Results of the analyses suggest that productive yarding time is a function of yarding distance, volume per turn and per log, chordslope, and numbers of logs or chokers per turn. For the running skyline and the balloon, lateral yarding distance was also an important determinant of productive yarding time. In addition, the number of men in the rigging crew was found to be a statistically significant predictor for the running skyline, as was tagline length for the balloon. For the running skyline system, the data in this study support the hypothesis that yarding production rates are significantly influenced by silvicultural treatment. For the helicopter, however, no significant difference appeared in yarding rates between the clearcutting and partial cutting treatments. The effect of cutting unit design on yarding efficiency for cable systems cannot be generalized, although it did not appear to be significant for the cutting units in the Pansy Basin Study. Certainly, cutting units can be designed for which unit shape is an important determinant of cable yarding productivity. Shape of cutting unit would not be expected to influence helicopter yarding productivity, however.