Graduate Project
 

The use of small helicopters for commercial thinning in steep, mountainous terrain

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https://ir.library.oregonstate.edu/concern/graduate_projects/bv73c527j

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  • A great deal of research has taken place in an effort to find more economically efficient yarding systems for commercial thinnings. Almost all of this research has centered on tractors or small yarders with limited capabilities in terms of long yarding distances. The purpose of this study is to determine whether using helicopters can be an economical alternative for commercial thinning in steep, mountainous terrain. The study area consists of a second-growth stand of Douglas-fir and mixed true fir species. The stand was thinned using a Lama SA- 315B helicopter (external lifting capacity of 2500 lbs.) to yard a total of 383 mbf (800.5 cunits) over a period of 3 weeks. Average yarding distance was approximately 2500 feet and the average slope was 40%. The diameter of the trees removed averaged 15 inches and the average piece size was approximately 87 board feet (.182 cunits). Gross production data were kept by the project manager for the logging company. This information is used to compare costs actually experienced during the operation with costs that might have occurred had the stand been cable yarded. The stand had originally been planned for uphill cable yarding using intermediate supports. A Thunderbird TNY 50 yarder is used as the hypothetical comparison operation. A detailed time study was conducted and the results are used to evaluate the effects of turn weights and yarding distance on the helicopter operation. Regression equations were developed and used to predict hook time, haul time, and total turn time for specific conditions. A damage survey was conducted after yarding to assess the condition of the residual stand. Results of this survey are compared with the amount of damage predicted for a cable system using a regression formula developed by Caccavano (1982) The results of the study indicate that using the Lama helicopter can be an economically feasible alternative for commercial thinning. An average yarding cost per thousand board feet of $179.21 was estimated for the helicopter operation; the cablesystem would have cost an estimated $159.73 per mbf for yarding, with an additional $55.21 per mbf for necessary road and landing construction. The helicopter yarding resulted in no damage to the residual stand. An estiniated 44.6 sq. ft. of scar area per acre would have resulted had the stand been cable yarded.
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