- With increasing environmental concerns, short harvesting seasons, salvage
logging needs, and limited road access, helicopter yarding is becoming attractive to many land managers. Most helicopter yarding has occurred on clearcut or evenaged management areas containing large, valuable timber. Very little helicopter
yarding has occurred in stands of smaller, less valuable timber which are often
inaccessible or have other limiting factors which preclude logging by conventional
methods. There has been little research on the use of small to medium-lift helicopters in harvesting of first thinnings of small diameter timber. The purpose of this study was to determine whether the use of small to medium-lift helicopters can
be an economical alternative for commercial thinning ofyoung timber stands in steep, mountainous terrain, and whether the HELIPACE software program
accurately estimates production of a helicopter yarding system. The study area consists of several stands of second-growth Douglas-fir requiring an initial thinning. The stands were thinned using a Sikorsky S-58T helicopter (with an external lift of 5000 pounds) to yard a total of 457 MBF over a period of four weeks. The average yarding distance was 775 feet and the average slope was about 30%. The diameter of the trees removed averaged 11.3 inches, and the average piece size was approximately 40 board feet (net).
A detailed time study was conducted and the results are used to estimate
yarding production and costs for the Wildcat Thin sale for comparison to
HELIPACE computer program estimates and cable estimates from a concurrent
study on the same sale. Regression equations were developed and used to predict total turn time and evaluate the effects of yarding distance and weight per board foot on yarding cost. The detailed time study data was also used in comparing the actual turn times (and production) from 13 individual study areas to predicted turn times from the HELIPACE program. The results of the study indicate that there was no significant difference between HELIPACE estimates of turn times and actual turn times observed. The average difference in turn time was approximately 6%. The results also indicate that using the Sikorsky S-58T can apparently be an economically feasible alternative for commercial thinning. An average yarding cost of $258.32 per thousand board feet was estimated for the helicopter operation, while HELIPACE estimated $242.85 per MBF for yarding. Average total logging costs for the helicopter operation were estimated to be $354.35 per MBF; total logging costs estimated by HELIPACE were $339.08 per MBF; and the total cable logging costs from the concurrent study on the same sale were $23494 per MBF. The cable cost estimates were significantly lower than for the helicopter but at current timber values, helicopter yarding can be profitable. Helicopters should be considered when there are other concerns than strictly economics, such as environmental concerns, time constraints, limited access, and physical limitations of other systems.