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4. Helicopter harvesting in the hill mixed dipterocarp forests of Sarawak - Danny Chua Kee Hui*

* Forest Engineer, Forest Department Sarawak, Wisma Sumber Alam, Petra Jaya 93660 Kuching, Sarawak, Malaysia Tel: ++(60 82) 31 9280, Fax: ++(60 82) 44 5640, E-mail:


Helicopter harvesting is an aerial harvesting system whereby logs are removed vertically from the forest and flown to a roadside landing or drop zone. Other aerial systems include the use of balloons and airships, but these have not been successful. Commercial helicopter harvesting has been carried out since the early 1970s in the Pacific Northwest of the USA and has proved to be a harvesting system with low environmental impact.


Helicopter harvesting was introduced to Sarawak in April 1993 when a local timber company, WTK Organization, brought in a Sikorsky S-64E aircrane to lift logs from forest areas with difficult terrain in the Kakus-Pandan Protected Forest. Because of its high production performance, its ability to lift logs out of forest areas where ground-based and cable systems cannot be used and the minimal damage it causes to the surrounding forest, the helicopter is now used by many timber operators in Sarawak. Currently, helicopter harvesting is concentrated in forest areas that are either inaccessible, or located on steep terrain that was not harvested previously by crawler tractors. As harvesting of the hill forests proceeds towards remote regions and more difficult terrain in Sarawak, the Forest Department is encouraging timber operators to intensify the use of helicopters in their future operations.


Currently, three types of helicopters are being used in various parts of Sarawak (Table 1). The helicopters can operate in a wide range of weather conditions except when foggy or misty conditions affect the visibility of the pilot or when there are turbulent winds. The Sikorsky S-64F has been used for harvesting for many years in the USA. The Oregon-based company operating this type of helicopter is, therefore, very experienced in helicopter logging. The Russian MIL 8 has been used for commercial helicopter harvesting in New Zealand since 1993 and also in Papua New Guinea. The KAMOV Ka-32 is the latest type of helicopter to be used for harvesting in Sarawak. Appendix 1 illustrates these three helicopters.

Table 1. Types of helicopters used for harvesting the hill mixed dipterocarp forests


Country of origin

Lifting capacity of helicopter



5 000 kg



5 000 kg

Sikorsky S-64F


11 000 kg

Other types of helicopters, which were brought in for use, included the Sikorsky S-64E, Chinook 234 and the MIL Mi-26, but these helicopters are not in service at the moment.

In most of the helicopter harvesting operations, a small support helicopter is necessary for transporting the tree fellers to remote logging blocks, spotting missing logs, bringing spare parts to the base camp, aerial reconnaissance, forward planning and for overall supervision of the operations.


Felling operation

The felling operation has to be planned properly, coordinated and monitored by the timber operator to ensure that the helicopter has an adequate volume of logs to lift each day during the period when it is stationed in the operating area of the timber concession. It is even more critical when the timber operator utilizes different types of helicopters to lift logs from the same area. This is because the felling crew has to select the right trees to be felled depending on which helicopter is coming in first to do the lifting. Felling of trees is normally carried out at least two to four weeks before the helicopter is scheduled to arrive. A felling crew of two persons can only cut down an average of five trees per day because of the difficult working conditions and the need to select good, merchantable trees for felling.

After a tree has been felled, it has to be bucked properly to ensure an optimum load per trip but not exceeding the lifting capacity of the helicopter. The log is then clearly painted with numbers so that it can be spotted easily and identified by the helicopter pilot. Heavy logs are also distinguished by special symbols.

The tree feller has to prepare the log for lifting by removing any obstacles from the log and ensuring that it has been cut cleanly at both ends with no hang-ups. To ensure that the logs are visible to the helicopter pilot, the felling crew sometimes fell surrounding trees. Normally this is not necessary because a sufficiently large canopy opening is created when the tree falls to the ground. The felling crews are trained by the loadmasters or felling supervisors of the helicopter companies in the proper felling techniques and the preparation of logs for the helicopter to lift.

Lifting operation

After the trees have been cut, the helicopter is brought in to extract the logs. Lifting is done using a long line attached to the main aircraft frame with a grapple at the other end. The length of the long line ranges from 75 to 100 m. Different types of grapples, which can be electrically, hydraulically or mechanically controlled, are used. The lifting operation is carried out without any assistance from the ground. The helicopter pilot has to be very experienced and well-trained for the pilot has to locate the prepared log and manoeuvre the helicopter so that the grapple is placed precisely on the log. The log is then lifted vertically out from the forest and flown to the roadside landing or drop zone. The flying range is kept within 2 km from the landing or drop zone for helicopter harvesting to be economically viable. Heavy logs, indicated with the special symbol, are lifted out during the last few turns before refuelling when the helicopter is lighter. Normally, one log is lifted per turn.

For the three types of helicopters, the lifting operation requires a flight crew of two pilots, one to fly the helicopter and control the grapple and the other to monitor the instruments in the aircraft. The helicopters involved in this type of work consume a large quantity of fuel and have to be refuelled every hour. Refuelling pads are therefore located close to the working areas.

Landing/drop zone operation

The location of the landing or drop zones have to be planned properly and spaced out to facilitate the helicopter approach and to ensure optimum flying distance.

The logs are placed gently at the landing or drop zone by the helicopter to avoid damage or breakage. Experienced pilots will normally place the logs in an orderly manner. A landing receives a substantial volume of logs each day because of the continuous operation of the helicopter and short return times. The landing has to be sufficiently large to accommodate a drop zone and stacking area. Logs have to be debarked, tagged, measured and carried away as soon as possible to avoid congestion at the landing. The number of personnel working at the landing is kept to a minimum because it is very dangerous to move around with the helicopter arriving every few minutes to drop logs.

Safety factor

There is a high emphasis on safety for all aspects of the helicopter harvesting operation from the felling of trees through to the landing or drop zone. The helicopter must be properly and continuously maintained to Aviation Regulation Standards. Its estimated maintenance time for every flying hour is four person-hours. The pilots require a high level of concentration for this type of work; therefore, their number of flying hours for any period of time is also limited by Aviation Regulations to avoid pilot fatigue.

No tree fellers can be in the vicinity when the helicopter is picking up logs. This is because the rotor downwash from the helicopter may break some of the tree branches of the surrounding stand and cause injuries or fatalities to persons on the ground. The number of persons working in the landing or drop zone must also be kept to a minimum when the helicopter is dropping logs.


Detailed time studies were carried out by the Forest Department on the Sikorsky S-64F and the MIL 8. The performances are given in Table 2.

Table 2. Performance of the Sikorsky S-64F and MIL 8

Sikorsky S-64F


Lifting capacity

11 000 kg

5 000 kg

Average volume per turn

7.24 m3

3.54 m3

Average turn time (within 2 km flying range)

2.94 minutes

3.5 minutes

Average no. of logs lifted out per effective working day



Average volume per effective working day

760 m3

261 m3

Estimated volume per month (information obtained from helicopter company)

20 000 m3

6 000 m3

No detailed time studies were carried out on the KAMOV Ka-32, which has a similar lifting capacity of 5 000 kg as that of the MIL 8. Its performance is therefore expected to be the same as that of the MIL 8.

Advantages of helicopter harvesting



An assessment of the harvesting damage, open space created and stream turbidity in the helicopter- and tractor-harvesting area has been carried out by the Forest Department (Chua, 1993; 1995).

Table 3. Comparison of environmental impacts of helicopter and tractor harvesting


Helicopter harvesting

Tractor harvesting

No. of trees/ha felled and extracted

1.4 to 3.5


No. of trees damaged or removed per tree extracted*

1.45 to 3.13


Open space created by canopy openings and skid trails as a % of harvesting area

4 % to 11 %**

15.91 %

Stream turbidity during dry days

2.9 NTU***

35 NTU

Stream turbidity during wet days

21 NTU

287 NTU

* All dipterocarps and nondipterocarps of 10 cm diameter at breast height and above were recorded

** No exposed ground surface due to the absence of skid trails

*** Nephelometric Turbidity Units

The number of surrounding trees that are damaged or totally removed per tree felled and extracted in the helicopter-harvesting area is between 1.45 to 3.13, whereas in the tractor-harvesting area, it is 5.49. In the helicopter-harvesting area, there is no exposed ground surface due to the absence of skid trails. Skid trails occupy 6.3 percent of the tractor-harvesting area. The open space in the helicopter-harvesting area is created by the canopy opening, when the tree falls, and some site clearing around the felled tree to enable the helicopter pilot to locate the log. It is much smaller compared to ground-based systems. Stream turbidity in the area worked by the helicopter is also much lower under all weather conditions (Table 3). Based on the results, helicopter harvesting can therefore be considered a low impact “environmentally friendly” harvesting system.



Helicopter harvesting is generally more expensive than tractor harvesting because of high operating costs and higher contract rates for felling crews. A direct cost comparison between helicopter harvesting and the conventional tractor-harvesting operation under similar difficult terrain conditions in the Model Forest Management Area (MFMA) project area in Sarawak indicated that helicopter-harvesting cost was twice the tractor-harvesting cost (ITTO, 2000).

Since 1993 when helicopter harvesting first started, the main challenge facing the timber operators and the helicopter companies has been to find ways to reduce the cost of harvesting. Recognizing that it is a low impact harvesting system, the Forest Department of Sarawak is encouraging its use by allowing all logs extracted by helicopter to be exported. Reduced royalty rates are also applied to timber extracted by helicopter. Unfortunately, logs extracted by helicopter do not fetch better prices compared to logs extracted by tractor and with fluctuating log prices, which are beyond the control of log-producing countries, helicopter harvesting in Sarawak continues to have its ups and downs.

Over the years, timber operators in Sarawak have tested six types of helicopters with different lifting capacities (i.e. Sikorsky S-64E, Sikorsky S-64F, Chinook 234, MIL 8, MIL Mi-26, KAMOV Ka-32). However, only three types are in use today, i.e. Sikorsky S-64F, MIL 8 and KAMOV Ka-32 as the timber operators found them to be more cost-effective. In some timber concessions, a combination of big and small helicopters is used to optimize the lifting of logs of different sizes.

Coordination and understanding between the timber operator and helicopter company

In helicopter harvesting, felling of trees is managed and handled by the timber operator while the helicopter company only comes in to lift logs. Therefore, excellent coordination and understanding between the two parties are vital to reduce downtime and delays and to ensure that logs are fresh when brought out to the landings. Only then will helicopter harvesting be financially viable.

Recognition of intangible benefits

The use of helicopters in timber harvesting definitely has low environmental impacts due to reduced road construction, absence of skid trails, reduced damage to the forest stand and ground surface and less soil erosion and stream sedimentation. Therefore, the intangible benefits derived should be considered and recognized by both timber operators and tropical timber consumers.


Helicopter harvesting in Sarawak is not intended to replace the existing ground-based crawler tractor system completely. Over the last three years, the volume of logs lifted out by helicopters has accounted for only 5 percent of the total log production from the hill forest. The gentle and undulating forest areas will still be worked by tractors incorporating reduced impact logging (RIL) procedures. However, harvesting of the hill mixed dipterocarp forests in Sarawak is progressing towards the interior regions where the terrain is steep and more difficult. The potential or opportunity for helicopter harvesting lies in these areas. In such terrain, tractor harvesting with RIL procedures is less effective (particularly in reducing stream sedimentation) and is presently difficult to implement for the following reasons:

(a) Effective area for harvesting is reduced considerably.

(b) Lack of trained and committed manpower in the timber industry.

(c) Capacity building of Forest Department staff to carry out supervision of RIL for sustainable forest management has not been completed yet.

Notwithstanding the high cost of operation, the use of helicopters will definitely improve the sustainability of the forest and at the same time preserve its environmental values.


Efforts should be made to convince tropical timber consumers that logs produced by the helicopter-harvesting system (or even by RIL with tractors) should be accorded premium prices in view of the high cost of extraction. Timber operators and helicopter companies should continue to collaborate closely to improve planning and harvesting procedures in order to reduce the cost of extraction. The possibility of testing alternative types of helicopters should also be looked into.


Chua, D. 1993. A case study on helicopter harvesting in the hill mixed dipterocarp forests of Sarawak. Research Report No. FE 1/93, Forest Department, Kuching, Sarawak.

Chua, D. 1995. Helicopter harvesting in the hill mixed dipterocarp forests of Sarawak using the Boeing 234 Chinook. Case Study Report No. FE 1/95, Forest Department, Kuching, Sarawak.

ITTO. 2000. Model forest management area (Phase II) Final Report. ITTO Project Report (Draft).




Sikorsky S-64F

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