In the last 25 years, helicopter extraction of timber has developed as an important harvesting alternative in mountainous areas. Typical helicopter operations include the extraction of valuable timber from stands with inadequate road networks, large areas of difficult to reach wind-throw, and sensitive sites where the negative impact on soil and water must be minimized. An empirical study provides information on the effect of silvicultural treatment and pilot experience on the productivity of the K-Max helicopter. The productivity model is a function of the average stem piece size, the horizontal distance between stump and landing, the silvicultural treatment, and the experience of the pilot. The productivity obtained when harvesting from a clear-cut was greater than from the `femel-cut' (patch-cut) extraction site by 0.20 m3/min, or 21% at an average piece size of 1.5 m3. The inexperienced helicopter pilot had timber extraction experience but just 30 flight hours on the K-Max while the experienced pilot had 22,000 K-Max flight hours. The experienced pilot yielded a 0.37 m3/min increase in productivity, which is a 63% increase at an average piece size of 1.5 m3. This indicates that operator experience on a particular machine may be very important when comparing harvesting systems based on time studies.
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