During mustering operations the pilot landed on two occasions in order to visually check the amount of fuel remaining. Although the second of these checks revealed an estimated endurance of 20 minutes, the pilot elected to carry out a further short mustering task before returning to the refuelling area about 4 kilometres away. While enroute to the refuelling point the engine suddenly stopped. The pilot entered auto-rotation but had to manoeuvre to avoid trees and the aircraft subsequently landed heavily. The investigation revealed that the aircraft was serviceable but the engine had failed due to fuel exhaustion. The last landing to check the fuel quantity was probably made on sloping ground and could account for the overestimation of fuel remaining, although below required reserves, at that time.
