2008-12-04 Skidder Slides on Logs and Overturns

Big Creek Operating Area – Approx 150 km Southwest of Williams Lake
Date of Incident / Close Call: 
Company Name: 
Ken Ilnicki Developments Ltd.
Details of Incident / Close Call: 

A skidder operator was pulling a drag of trees downhill on an approximate 20% slope. The operator was working the slope from west to east, cleaning up all the wood to the west of him before moving eastward. In the process of doing so, the operator had been driving over a couple of green spruce logs that were pinned beneath another drag of trees. The operator mentioned that he had crossed these logs numerous times. The spruce logs were situated such that they were pointing downhill, not straight up and down, but rather at a 45-degree angle. Immediately adjacent to one of the logs was a stump on the uphill side. In addition, the two spruce logs appeared to be almost “perfectly spaced”. It is to the belief of the investigator and fellow crew members that the front tires of the skidder crossed the front log at the same time the rear tires crossed the rear log. It also appears that the right rear tire of the skidder caught a portion of the previously mentioned stump, causing the weight of the machine and payload to shift to the two left tires on the downhill side. Having been crossed a number of times previously, some of the bark from the spruce logs had been chewed off from the tire chains, thereby exposing a slippery surface. The logs essentially acted like a boat launch, forcing the skidder to shoot down the hill and overturn.

Another contributing factor to this incident may be that the drag of trees in the grapple was too close to the machine, possibly butting up against the guarding and creating an inability to turn properly. 

Main / Immediate Cause:

Crossing of green logs or logging debris pointing in a downslope direction. Putting the skidder in a position which compromises machine stability.

Root Cause:

Misjudgment on the operators behalf as to the possible implications of crossing debris pointing downslope. The decision to do so may have been justified by the presence of tire chains on all four tires. These logs should have been removed from the path of travel.


Learnings and Suggestions: 

Discussion of incident with all operators, showing pictures taken from the incident. Review established safe work practice with worker.

For more information on this submitted alert: 

Ben Korving, RPF

Ken Ilnicki Developments Ltd. 

File attachments
2008-12-04 Skidder Slides on Logs and Overturns.pdf
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