Aerial Logging Systems

The ideal extraction system would simply lift logs from the forest and transport them to the landing without traffic through the forest.  Aerial systems offer that potential, but with some significant constraints.  Although several types of aerial logging systems have been attempted (including balloons and combinations of a helicopter and balloons), the only currently viable aerial method is helicopter logging.   The interest in logging with helicopters began in the 1950’s and 1960’s in Scotland, Canada, and Norway.  Early helicopters, however, had limited lifting capacity and were not suitable for logging applications. Heavy-lifting helicopters are now available, including some designs that are specifically intended for logging.  A helicopter logging job is a large, well-organized operation that is focused on keeping the helicopter flying productively as much as possible.  This involves on-site fueling, maintenance, and tie-down areas; highly trained fallers and chokersetters; and a large landing “drop zone” with sufficient loading capacity to keep the wood out of the way.  By maintaining full payloads and high utilization, helicopter logging can be cost-effective in many logging applications.  Aerial logging is particularly suited where products have high value, sale volumes are large, roads are lacking, or environmental impact concerns are high.

The logging helicopter is equipped with a hanging cable, called a tagline.  At the bottom end of the tagline is an electrically activated hook.  When the helicopter arrives for a load, the hook is quickly caught by a chokersetter and connected to a prechoked bunch of wood.  As soon as the ground crew is clear, the helicopter rises and lifts the load clear of the ground.  Flying to the landing zone, the pilot will release the hook, drop the load to the ground, and return to the woods.  The entire cycle is completed in a matter minutes.  The woods crew is kept busy assembling loads that are near maximum payload.  The landing crew is responsible for keeping the landing zone clear, sorting material and loading trucks.   The crew can be between 14 to 28 people made up of 3 to 5 faller/buckers, 1 to 2 turn markers, 2 hookers, 4 chokersetters, 2 or 3 chasers and knot bumpers, 1 loader operator, 4 or 5 pilots, 4 or 5 maintenance mechanics, and 1 project supervisor.  This size of operation is needed to fully utilize the helicopters capability of 80-100 MBF/day (Sloan 2001).  Helicopter operations are sensitive to weather, with operations curtailed due to visibility, wind, or cold temperatures.

Two key variables of helicopter logging systems are lift capacity and the speed of the helicopter. The lift requirement in the eastern and southeastern United States is 3,000 to 5,000 pounds. The helicopter’s travel speed depends on the steepness of the slope. On moderate slopes of up to 20 percent the aircraft can operate near maximum speed of 80 to 100 miles per hour. As the slope increases to between 30 and 45 percent, the speed will decline to between 40 and 60 miles per hour.  Optimal extraction distances are between 2,500 and 4,000 feet. At this distance, the helicopter completes one turn in 1.5 to 3 minutes.

In 1994 the K-Max helicopter was studied in the Jefferson National Forest in Virginia. The K-Max was specifically designed for logging operations. It has a 6,000-pound lift capacity because its unique “Synchro lift” main rotor saves 30 percent of its power by eliminating the tail rotor.  A new K-Max costs about $3.5 million and has operating and support costs between $1,300 and $1,700 per hour.  A local logging crew felled, bucked and pre-bunched the timber into 5,000-pound loads. The helicopter carried approximately thirty loads per productive hour to the landing, at an average distance of 1,900 feet. It required refueling every 1 to 1.5 hours and used 80 to 85 gallons of fuel per hour. Production rates were estimated at 9.0 to 9.3 MBF/hour, with a resulting cost of between $140 and $190/MBF (Sloan and others 1994).