Selection logging in the tropics is increasingly moving to systems that reduce the impact of harvesting operations on forests and soils. While much of the focus has been on modifying the tractor logging system using RIL principles, alternative harvesting systems have also been introduced. One of the alternative systems is the use of helicopters, which eliminates the need for skid trails and reduces the number of roads required. WTK pioneered helicopter logging in Malaysia when it started using the helicopter logging system in Sarawak in the early 1990’s. Beginning in 2002, the company started using Sikorsky helicopters and since then has used three different models, including the Sikorsky 61F, 64E and 64F. While the use of helicopters creates a significant improvement in environmental impact of logging, the operating cost of helicopters is also significantly higher. Given the cost of using helicopters, a key element of harvest planning is understanding the factors that influence productivity. This paper provides an analysis of logging productivity in the tropics for the Sikorsky helicopters using daily production data collected by WTK on three different timber licenses between 2002 and 2009. The regression results show that average hourly volume produced is a function of the average distance flown per turn, the weighted average number of logs carried per turn, and the type of helicopter. The results also show the importance of pre-harvest inventory and planning that ensures that helicopters are used productively.