The helicopter pilot landed a high skid, turbine-powered helicopter at a remote drilling site, and the three passengers disembarked. The remote landing site was constructed of 6-inch by 6-inch wooden beams, which required that the pilot land perpendicular to and on the beams with the helicopter's skids. The pilot reported that after landing he retarded the engine throttle to flight idle to begin the mandatory 2 minute engine cool down procedure. He then got out of the helicopter to check the placement of the helicopter's skids on the beams, and it subsequently tipped backwards, with the tail rotor striking terrain. In his written statement to the NTSB, the pilot wrote, in part: "While waiting, I stepped out of the helicopter to look under the helicopter to verify that my bear paws were both securely placed on the supporting timber. Within a moment of stepping out, I noticed movement and watched as the helicopter tipped backwards until it came to rest on the tail rotor and stinger." A postaccident inspection revealed that while landing, the pilot inadvertently placed the helicopter's skids behind the aft wooden beam, and the helicopter tipped backwards once the pilot exited the helicopter. The pilot said there were no preimpact mechanical problems with the helicopter. The helicopter sustained substantial damage to the tail boom, tail rotor drive system, and tail rotor gearbox.