The flight was to transport two Telstra employees to a radio transmission tower on Lumley Hill 800 metres west of Cairns Airport. The pilot said he departed Cairns Airport at about 0925 EST and proceeded to the helipad which is about 800 feet above sea level. On arrival in the area he carried out an inspection of the helipad by making a left hand circuit. He then commenced a final approach from the north of the helipad from a distance of about 400 metres and on a shallow approach path. During the approach he became aware that there was only one entry and egress, which was in the direction from which he was approaching .The wind was light and variable at the time and he noticed numerous high trees on the southern side of the helipad. At about 100 feet from the pad he became aware that he was undershooting. However, he felt that he was then committed to land as there was not enough power available to exit at that point. The helicopter was landed on uneven ground, about ten feet short of the helipad, the front of the left skid touching first. It then slid backwards down the hill for about five feet and impacted against a log which damaged the tailboom struts, and the tailboom and tailrotor assembly separated from the aircraft. The pilot and passengers were able to exit the helicopter safely after the engine had been shut down and the main rotor had ceased spinning.