Cable Yarding Research Articles

Automated Cable Road Layout and Harvesting Planning for Multiple Objectives in Steep Terrain

Cable yarding is the most commonly used technique for harvesting timber from steep terrain in central Europe. During the planning process, one important task is to define the cable road layout. This means that the harvesting technology and cable road location must be specified for a given timber parcel. Although managers must minimize harvesting costs, it is even more important that such work on forests reduces the potential for damage to the residual stand and ensures that environmental conditions remain suitable for regeneration. However, current methods are geared only toward minimizing harvesting costs and are computationally demanding and difficult to handle for the end user. These limitations hinder broad application of such methods. Further, the underlying productivity models used for cost estimation do not cover all conditions of an area and they cannot be applied over a whole harvesting area. To overcome these shortcomings, we present: (1) a multiobjective optimization approach that leads to realistic, practicable results that consider multiple conflicting design objectives, and (2) a concept for an easy-to-use application. We compare the practical applicability and performance of the results achieved with multiobjective optimization with those achieved with single-objective (cost-minimal) optimization. Based on these points, we then present and discuss a concept for a user-friendly implementation. The model was tested on two sites in Switzerland. The study produced the following major findings: (1) Single-objective alternatives have no practical relevance, whereas multiobjective alternatives are preferable in real-world applications and lead to realistic solutions; (2) the solution process for a planning unit should include analysis of the Pareto frontier; and (3) results can only be made available within a useful period of time by parallelizing computing operations.

Performance Analysis of Log Extraction by a Small Shovel Operation in Steep Forests of South Korea

In South Korea, logs for low-value products, such as pulpwood and fuelwood, are primarily extracted from harvest sites and transported to roadside or landing areas using small shovels. Previous studies on log extraction, however, have focused on cable yarding operations with the goal of improving productivity on steep slopes and inaccessible sites, leaving small-shovel operations relatively unexamined. Therefore, the main objectives were to determine small-shovel extraction productivity and costs and to evaluate the impact of related variables on productivity. In addition, we developed a model to estimate productivity under various site conditions. The study took place in 30 case study areas; each area has trees with stems at a diameter at breast height ranging from 18 to 32 cm and a steep slope (greater than 15%). The areas ranged from 241 to 1129 trees per hectare, with conifer, deciduous, and mixed stands. Small-shovel drives ranged from 36 to 72 m per extraction cycle from stump to landing. The results indicated that the mean extraction productivity of small-shovel operations ranged between 2.44 to 9.85 m3 per scheduled machine hour (including all delays). At the forest level, the estimated average stump-to-forest road log production costs were US $4.37 to 17.66/m3. Small-shovel productivity was significantly correlated with stem size (diameter at breast height and tree volume) and total travelled distance (TTD). However, a Pearson’s correlation analysis indicated that stand density and slope did not have a significant effect on productivity. Our findings provide insights into how stem size and TTD influence small shovel performance and the predictive ability of productivity. Further, this information may be a valuable asset to forest planners and managers.

A short review of cable yarding applications in Australia

The current technology in Australia is mainly large swing tower yarder with grapple. These yarders operate under whole tree or cut-to-length methods in steep terrains of Victoria, Tasmania and South-East Queensland. Cable yarding is often applied in clear fell operations in pine or Eucalypt stands in Australia. Felling operations prior to yarding are carried out manually or using tracked feller-bunchers. Typical terrains for applying cable yarding have slope larger than 30°. There is currently a lack of small to medium size cable yarders that can efficiently operates under different circumstances. Medium size capacity yarders would be required to handle a wide range of situations under uphill and downhill extractions while small capacity highly mobile yarders will be needed for clean-up operations.

Performance and cost of downhill cable yarding operations in a group shelterwood system

ABSTRACTCable yarding operations are conventionally used in steep terrain harvesting, but their share in operations varies widely, tending to be low in many regions. This study evaluated the time consumption, productivity and cost of downhill sledge-yarding operations in group shelterwood extractions deployed in steep terrain beech forests. Relevant operational variables (yarding distance, lateral yarding distance and slope) were selected as predictors to model the time consumption based on a number of 558 work cycles. For an extraction distance of 326 m, a lateral yarding distance of 43 m and a payload of 1.87 m3 per turn, the yarding cycle time was estimated to about 12.5 min. Notable as share in the yarding cycle time were the choking (28%), lateral-in (19%), lateral-out (16%) and unchoking (13%), with the second and the third work elements being significantly affected by very high lateral yarding distances. Estimated productivity and efficiency rates were of 8.80 m3 h−1 and 0.11 h m−3, respectively. Extraction costs were estimated at 7.4 € m−3, in which the operator costs contributed the most (4.3 € m−3). Given the low fossil energy inputs, increased environmental performance due to suspended extraction of the logs, and the acceptable productivity and cost, this system could be extended in low-accessibility, steep-terrain harvesting.

Assessing Harvested Sites in a Forested Boreal Mountain Catchment through Global Forest Watch

Global Forest Watch (GFW) provides a global map of annual forest cover loss (FCL) produced from Landsat imagery, offering a potentially powerful tool for monitoring changes in forest cover. In managed forests, FCL primarily provides information on commercial harvesting. A semi-autonomous method for providing data on the location and attributes of harvested sites at a landscape level was developed which could significantly improve the basis for catchment management, including risk mitigation. FCL in combination with aerial images was used for detecting and characterising harvested sites in a 1607 km2 mountainous boreal forest catchment in south-central Norway. Firstly, the forest cover loss map was enhanced (FCLE) by removing small isolated forest cover loss patches that had a high probability of representing commission errors. The FCLE map was then used to locate and assess sites representing annual harvesting activity over a 17-year period. Despite an overall accuracy of >98%, a kappa of 0.66 suggested only a moderate quality for detecting harvested sites. While errors of commission were negligible, errors of omission were more considerable and at least partially attributed to the presence of residual seed trees on the site after harvesting. The systematic analysis of harvested sites against aerial images showed a detection rate of 94%, but the area of the individual harvested site was underestimated by 29% on average. None of the site attributes tested, including slope, area, altitude, or site shape index, had any effect on the accuracy of the area estimate. The annual harvest estimate was 0.6% (standard error 12%) of the productive forest area. On average, 96% of the harvest was carried out on flat to moderately steep terrain (<40% slope), 3% on steep terrain (40% to 60% slope), and 1% on very steep terrain (>60% slope). The mean area of FCLE within each slope category was 1.7 ha, 0.9 ha, and 0.5 ha, respectively. The mean FCLE area increased from 1.0 ha to 3.2 ha on flat to moderate terrain over the studied period, while the frequency of harvesting increased from 249 to 495 sites per year. On the steep terrain, 35% of the harvesting was done with cable yarding, and 62% with harvester-forwarder systems. On the very steep terrain (>60% slope), 88% of the area was harvested using cable yarding technology while harvesters and forwarders were used on 12% of the area. Overall, FCL proved to be a useful dataset for the purpose of assessing harvesting activity under the given conditions.

Using Conjoint Analyses to Improve Cable Yarder Design Characteristics: An Austrian Yarder Case Study to Advance Cost-Effective Extraction

Steep country harvesting has been identified as the main bottleneck to achieving greater profitability in the forestry sector of New Zealand and Australia. An improvement of efficiency, work safety and environmental sustainability should be realized by developing an advanced steep terrain timber harvesting system based on innovative Austrian technology. To identify the best suitable configuration of a cable yarder for steep terrain harvesting, user preferences based on an online survey (conjoint analysis) have been evaluated to answer the following questions: (1) What attributes of a new yarder design are most important to consumers? (2) Which criteria do stakeholders consider when selecting a cable yarder? (3) What are the weights representing the relative importance of criteria? Using eight specific design scenarios a fourth question, being which cable yarder concept is the best, was also answered. This case study shows that conjoint analyses is an effective tool to assess, rate and subsequently integrate design characteristics. Based on the results of the analysis, a cable yarder prototype will be manufactured in Austria and transferred to New Zealand for testing and demonstration.

Behavior and assessment of mobile anchors in cable yarding systems

Cable yarding systems transport logs hoisted off the ground by a system of cables and a carriage that moves along the cable. Ground anchors are used at the end points to maintain sufficient tension between the two ends points of the cable and keep it in the air during operation. Traditional anchoring methods employ tree stumps, but as shorter stand rotations result in younger weaker stumps and because of the inability to visually inspect root structures to calculate a stump’s anchoring capacity, alternative methods of anchoring are being used more frequently. In this paper, the capacity of an alternative anchoring method, known as equipment anchoring or mobile anchoring, is assessed for guyline and skyline applications. Some critical components that are observed to influence anchor capacity are equipment weight, slope, blade embedment, angle of cable pull, and soil type. An analytical design solution for mobile anchor capacity is compared with the results of over two dozen field tests to determine the effectiveness of predicting anchor capacity. In addition to estimating the capacity of mobile anchors, a relationship between skyline and guyline loading recorded on harvest operations is analyzed.

Operative loading in cable yarding systems: field observations of static and dynamic tensions in mobile anchor systems

Cable yarding systems are an effective means of facilitating harvesting operations in steep terrain, but require sufficient anchoring for safe performance. Design and safe operation often dictates that cable loading remain at a safe level, yet the actual loads incurred for anchoring systems, particularly for “mobile” or “equipment” anchors, are ill-quantified. Furthermore, these anchors are subject to loading that is rather dynamic in nature, realizing impulse loads from various operation occurrences, particularly breakout. This study describes the measured static and dynamic cable loads during yarding for 21 mobile anchor systems operated by eight different contractors during active logging operations. The mean dynamic loading observed for guyline and skyline anchors was 49% and 44% greater than static tensions, respectively. Maximum dynamic loads exceeded approximately double static tensions. In the observed tests, cable tensions were well below the cable elastic and endurance limits but did approach the allowable tension in some cases. Although the monitored cable loads in this study were all within a safe range, the observed dynamic loads are useful guidance when considering higher static loads and consequently higher dynamic loads that may be unsafe.

Yarding productivity of tree-length harvesting using a small cable-yarder in steep slope, South Korea

Tree diameter, topography, and stand accessibility have been major issues to consider when selecting the optimal equipment to extract logs from steep slopes. With an increasing interest using cable logging systems from steep slopes in South Korea, the yarding productivity and cost were evaluated for a small scale cable yarder. A standard time and motions study method were applied for three clearcut units in larch (Larix kaempferi) stands located in Pyeongan, Gogil, and Ungyo in Eastern Gangwon of South Korea. The average yarding productivity and cost were calculated at 5.7/scheduled machine hour (SMH) and $27.9/, respectively. The regression analysis reveals that the mean diameter class was found to have greatly influenced yarding productivity. Among the factors determining the yarding cost, tree volume was found to have the greatest influence, followed by lateral distance and yarding distance. Other factors that may contribute to reducing delay and improving yarding productivity included operational planning (i.e. corridor layout considering topographic conditions), pre-inspection, and post-maintenance/management of the yarder system, and specialized technical training to enhance yarding productivity.

Strip Clear-Cutting Application and Logging Typologies for Renaturalization of Pine Afforestation—A Case Study

Renaturalization treatment in black pine afforestation is an important topic that should be considered. There is a need to favor the evolution of artificial pine forests toward natural forest systems. Overall, this study focused on pine forests, and suggests one typology of clear-cutting (dismantling cutting) on strips, which is associated with different extraction management techniques. Some ecological and environmental aspects associated with renaturalization treatments that have been applied by different mechanizations in black pine afforestation have been highlighted, as well as how renaturalization and the active ecological management of these stands could affect soil and vegetation. The main objectives of this research were to: (1) analyze the impact of silvicultural treatment and logging activities on forest soil, and (2) assess tree regeneration and floristic biodiversity in an ecological management system, in terms of both quantity and quality characteristics. These analyses were planned to obtain an overview of the environmental impact related to a multifunctional approach to the forest management of black pine afforestation. Essentially, the answers to the main research questions are: (1) less invasive extraction systems seem to use a cable yarder and forest winch; (2) a clear soil recovery trend with good capabilities is visible, in particular for the two extraction systems by cable; however, over a three-year period, only a partial but substantial recovery has been shown; (3) in general, silvicultural treatment showed qualitative and quantitative improvement in terms of tree regeneration; in particular, the extraction systems by forest winch and cable yarder showed better results; (4) silvicultural treatment seems not to have led to improvement at the level of the herbaceous and shrubby layers; however, clear differences are shown among the different harvesting systems. Significant recovery after use of the cable yarder was observed.

Productivity and cost of a small-scale cable yarder in an uphill and downhill area: a case study in South Korea

ABSTRACTTree diameter, topography, and stand accessibility have been major factors to consider when selecting the optimal equipment to extract logs from stump to landing area. In Korea, forest land has 6.4 million ha of forest, comprising 64% of its total land area. Small and medium (15–30 cm in diameter at breast height [DBH]) size of trees located on steep slopes (> 30°) is approximately 80% of total forest area. Therefore, there has been an increasing interest in the application of a small-scale cable yarding system. We performed uphill and downhill yarding experiments using an 80 hp farm tractor mounted tower yarder (HAM300) to evaluate productivities and costs associated with primary transportation of tree length logs in mixed conifer stands. In addition, sensitivity analyses were performed to find the effects of different yarding directions and distances on yarding productivities and costs. Results showed that uphill and downhill yarding productivities were 9.04 m3/PMH (Productivity Machine Hours) and 7.87 m3/PMH at a cost of US$9.06 and US$10.04/m3, respectively. The yarding direction greatly affected productivity and cost: decreasing productivity may be significantly affected by working conditions. Our results support the effectiveness of an HAM300 yarder in extracting logs for small-scale cable yarding operations.

Automatic recognition of work phases in cable yarding supported by sensor fusion

ABSTRACT Cable yarding is a semi-mechanized timber harvesting system that relies on human machine interaction where a considerable share of the work is done by forest workers. The system is used in mountain forests around the world. Automation of one or more functions could contribute to increased productivity, reduced physical workloads and improved safety conditions. This paper presents a method for sensor data fusion in order to automatically distinguish work phases using Partial Least Squares Discriminant Analysis (PLS-DA). The Robot Operation System (ROS) is implemented to allow for real-time data processing with a maximum latency of 0.16 s. Global Positioning System (GPS), Inertial Measurement Unit (IMU) and camera integration provided a robust solution for 78% correct process segmentation. These results provide a basis for further development from which there is a possibility of expanding this approach for semi-automation, remote control, and autonomous operation.

Effect of Topping Trees on Biomass and Nitrogen Removal in the Thinning of Norway Spruce Stands

In Central Europe, full-tree (FT) harvesting is an increasingly common harvesting method in steep terrain harvesting due to the increased use of highly economical processor tower yarders. In conventional FT harvesting, nutrient removal from harvest sites is substantially higher than in cut-to-length (CTL) harvesting due to the extraction of nutrient-rich branches and foliage. One strategy to reduce the adverse impact of FT harvesting is to cut off the tops of felled trees prior to extraction (topping). The purpose of this study was to assess the effect of implementing topping treatments in FT harvesting on biomass and nutrient removal. The effect of conventional FT harvesting on the amount of logging residues left on the site was assessed in three different Norway spruce (Picea abies)-dominated stands following cable yarding operations by collecting logging residues from the forest floor. The additional effect of topping trees on the amount of logging residues was assessed by using biomass models. These models were created based on the data of 25 sample trees, which were felled and sampled destructively within the stands. The results show that conventional FT harvesting considerably increases nutrient removal in comparison to CTL, but still do not remove all nutrients from the sites. After conventional FT harvesting, 5–18% of the nutrients remained on the sites. Topping trees at a diameter of 8 cm substantially increased the amount of remaining nutrients to 30–34%.

STUDIES OF NATURAL- PRODUCTION ASPECTS OF MOUNTAIN LOGGING (ON THE EXAMPLE OF THE STATE ENTERPRISE "SLAVSKE FORESTRY")

The article presents the results of analytical studies of the natural-production conditions of management in the forests of a particular region. As initial data, the materials of the basic forest inventory of 2008 and reports on logging of the state enterprise Slavske forestry for 2010-2015 were used. Productive high-yielding tree stands of the I class and upper class of bonitet (79.1 %) is dominated in the enterprise. The third part of the forest is located on steep slopes. Medieval forest stands are predominate (42.2 %). The basis of the forest cover is formed by stand that includes spruce (73.6 %), where the average volume of ripe and overmature plantations consist 473 m3/ha. However, there is a low resistance of this specie to various pathogens of diseases and natural disasters. In recent years, there has been an increase in the volume of improvement thinning conducted on 84.0 % of all harvesting areas, where 68.6 % of the total volume of timber was harvested. The dynamics of the increase of the areas of sanitary felling is noted, which is associated with a large scale drying of spruce stands. The technological processes of logging operations at the enterprise are mainly based on ground aids of primary timber transportation, causing significant damage to the surface of the cutting area and the adjacent territories. Typically, a tractor trailing is used, with which 90.7 % of the total volume of harvesting is performed. The volumes of trailing by caterpillar and wheel tractors are almost identical. Less often, animal skidding (8.6 %) and cable yarding systems (0.7 %) are used. The distance of trailing of wood for all means of primary transportation exceeds the recommended values. The average distance of trailing by animal skidding on all type of cutting is 0.35-0.41 km. Caterpillar tractors on final cutting and improvement thinning have average distance of trailing, respectively, 1.48 km and 1.23 km. For wheeled tractors, the average distance of trailing on final cutting and improvement thinning is 1.26 km and 0.90 km, respectively. At the same time there are positive trends in reducing the distance of trailing on all types of cutting, connected with the construction of new forest roads. The main factor influencing the forest environment is the primary transportation of wood, the optimization of which is an urgent task for mountain logging.

How Climate Change Will Affect Forest Composition and Forest Operations in Baden-Württemberg—A GIS-Based Case Study Approach

In order to accommodate foreseen climate change in European forests, the following are recommended: (i) to increase the number of tree species and the structural diversity; (ii) to replace unsuitable species by native broadleaved tree species, and (iii) to apply close-to-nature silviculture. The state forest department of Baden-Württemberg (BW) currently follows the concept of Forest Development Types (FDTs). However, future climatic conditions will have an impact on these types of forest as well as timber harvesting operations. This Geographic Information System (GIS)-based analysis identified appropriate locations for main FDTs and timber harvesting and extraction methods through the use of species suitability maps, topography, and soil sensitivity data. Based on our findings, the most common FDT in the state forest of BW is expected to be coniferous-beech mixed forests with 29.0% of the total forest area, followed by beech-coniferous (20.5%) and beech-broadleaved (15.4%) mixed forests. Where access for fully mechanized systems is not possible, the main harvesting and extraction methods would be motor manual felling and cable yarding (29.1%). High proportions of large dimensioned trees will require timber extraction using forestry tractors, and these will need to be operated from tractor roads on sensitive soils (23.0%), and from skid trails on insensitive soils (18.4%).

Roundwood and bioenergy production from forestry: Environmental impact assessment considering different logging systems

The aim of this paper is to analyse the environmental performances of three different extraction systems for forestry considering three different scenarios concerning the valorisation of forest residuals are analysed.The compared tree extraction systems are characterised by felling and processing performed with chainsaw and three different extraction methods: i) by farm tractor equipped with a winch; ii) by skidder and iii) by cable crane. The “Full Tree System” was adopted for all the felling sites; trees were felled and transported to roadside with branches and top intact. For wood chips produced from branches and tops, different scenarios were considered: heat and electricity generation and substitution of wood-chip production.To evaluate the environmental performance the Life Cycle Assessment (LCA) approach was applied. The selected functional unit (FU) is 1 m3 of roundwood; the system boundary involves all the operations carried out in forestry (felling, bunching, extraction, processing, chipping of forest residuals), the transport of the produced wood chips and all the related inputs and emissions. A comparison with previously carried out studies in similar geographic areas were performed.The study's outcomes show how, the environmental results among the different logging systems are not univocal and the best logging system depends on the considered impact category. Though cable yarder is recognised as an extraction method able of reducing the physical impacts on residual stand (wounding) and soil (disturbance and compaction), for 10 of the 12 impact categories evaluated in this study, achieves the worst performances. The logging systems in which the extraction is performed using the tractor and the skidder show the best performance for 6 of the 12 evaluated impact categories. Finally, regarding wood residues utilisation and the impact of particulate matter formation, the energetic valorisation of wood chips does not involve any benefit but involves a worsening of the environmental performances due to wood combustion emissions.

AVALIAÇÃO DO DESEMPENHO E CUSTOS DE DOIS SISTEMAS DE CABOS AÉREOS NA EXTRAÇÃO DE MADEIRA DE EUCALIPTO

Objetivou-se com este trabalho avaliar o desempenho e determinar os custos de dois sistemas de cabos aéreos na extração de madeira de eucalipto em região montanhosa. A análise técnica baseou-se em estudo de tempos e movimentos do ciclo operacional e produtividade de dois sistemas de extração: Sistema 1 (trator Massey Ferguson 297 e guincho Penzsaur K301-T) e Sistema 2 (escavadora Caterpillar 320L e guincho Koller), operando em plantios com idade de sete anos e de segunda rotação. A produtividade média na extração de madeira foi de 13,63 m3 h-1 para o Sistema 1 e 14,70 m3 h-1 para o Sistema 2, para distância média de 150 m, eficiência operacional de 46% e 51% e disponibilidade mecânica de 91% e 59%, respectivamente. O aumento da distância de extração implicou em aumento no tempo para realizar as atividades do ciclo operacional e em redução da produtividade. O Sistema 2 mostrou-se mais produtivo, porém, apresentou maior custo de produção.

Mechanisation of different logging operations : environmental impact assessment using life cycle assessment (LCA) approach

Different logging systems (or harvesting systems) can be used for wood extraction. Cable logging system is typically carried out on steep slopes and other rough terrain. In these contexts, also cable yarding can be an efficient and effective harvesting system. Ninety-five per cent of timber production in southern Italy comes from terrain classified as very steep slope, limiting the use of machines for ground-based extraction. Cable extraction is a desirable alternative to either a skidder or forwarder on a sensitive site. To each harvesting system a different environmental load is associated depending on machine productivity and site characteristics. In this study, three different logging systems were analysed and compared using the Life Cycle Assessment approach. The compared logging systems are characterised by felling with chainsaw and three different extraction methods: by farm tractors equipped with a winch; by a skidder; and by a cable crane. The Full Tree harvesting method was adopted for both felling sites; trees were felled and transported to roadside with branches and top intact. The functional unit is 1 m3 of wood; the system boundary involves all the operations carried out in the forestry (felling, bunching and extraction) and all the related inputs (diesel fuel, lubricating oil, capital goods such as chainsaw, tractors, skidder, cable yarder) and related emissions. Inventory data were collected in three different test sites located in southern Italy and concern working times, productivity, wood yield, fuel consumption. The cable yarder shows the worst performances for 7 of the 8 evaluated impact categories. The use of skidder shows a lower impact for 5 of the 8 evaluated impact categories while, for the remaining 3, the best performances are achieved by the logging system in which tractor is used. For climate change, the impact is equal to 8.57, 8.04 and 10.46 kg CO2eq/m3 for the harvesting system with extraction carried out using tractor, skidder and cable yarder, respectively.

Work accidents during cable yarding operations in Central Europe 2006 – 2014

Aim of study: This study is focused on detailed analysis of accidents in yarding during the years 2006–2014. There is still not enough information about such accidents in Central Europe in the literature available.Area of study: We collected the data on occupational accidents recorded in timber yarding from the databases of the Slovak state forest enterprise. Material and Methods: The data on occupational accidents were recorded according to actual European Regulation, the form of the record meets the requirements of the ESAW (European Statistics on Accidents at Work) methodology. To analyze the data, we used the multiple regression and correlation analysis, contingency tables, and a χ2 –test.Main results: Almost half of the accidents were the foot injuries and the most frequent type of injury was fracture of a bone. The most hazardous operation was yarding. Most of the accidents occurred between 1301-1400 h (22 %). The most frequent agent causing accidents were Particles, dust, splinters, fragments, etc. (14.05 by ESAW). Research highlights: This study informs about the most important risk factors in timber yarding, the most hazardous parts of shift, as well as the days when the most accidents occur during the week, and as such contributes to better understanding of how the accidents happen in timber yarding. The information can be subsequently used in knowledge-based improvement of safety trainings in forest enterprises.

Skyline tension, shock loading, payload and performance for a European cable yarder using two different carriage types

The authors describe a study conducted under controlled conditions, with the goal of analysing the dynamic tension in the skyline of a yarder resulting from hauling known loads. The rigging was a classic three-cable configuration common to European yarder operations; with a single-span standing skyline and the mainline and haulback used to move the carriage back and forth along the span. Two carriage types were used to gauge tension differences between clamped (Hochleitner BW4000) and unclamped (SEIK Skybull 30/60) carriages. Tension was recorded at 0.5-s intervals through a measuring device with a nominal measuring range of 200 kN. Results showed that: (1) The recommended safe working load (safety factor = 3) was often exceeded by peak loads during lateral skidding and inhaul; (2) the endurance limit of the skyline was never reached; and (3) the Skyline XL software used for payload calculation grossly overestimated payload potential. Since study conditions could be considered representative of some commercial yarding operations in the European Alps, this finding suggests that local loggers may operate within safe limits considering the engineering properties of wire rope, while formally exceeding legal requirements.