 The accident you are about to review involved a CH-47D helicopter and occurred at 1750 on 23 September 1994, about 35 miles northeast of the town of McCall, Idaho. Portions of the unit had been working with the U.S. Forest Service, engaged in fighting forest fires for most of the fire season. The accident crew had been deployed for 27 days. The first mission of the day was to transport 60 passengers to a rear area at 1800 and then provide fire bucket service until released. The day prior, a unit representative had conducted a ground reconnaissance of the landing zone and reported to the crew that it was a big area with no hazards and only a slight slope. The landing zone had been previously burned and its surface was covered with dust and ash. To reduce the hazard of blowing dust, the Forest Service arranged to have three water bucket drops in the landing area. The last water bucket drop was in progress as the CH-47 arrived. The crew circled the landing area carrying an empty water bucket on a 120 foot sling and made their approach generally to the north. They planned to approach to the left of the landing area, set the bucket on the hillside, then hover to the right and land to load the passengers. They would leave the water bucket on the landing zone and retrieve it after the passenger halls were completed. Their point of intended landing was perceived by the crew to be on a slight slope, approximately 2 to 3 degrees upslope to the front and 2 to 3 degrees upslope to the right. This perception proved to be erroneous, however, as the slope where they attempted to land was actually 11 degrees up to the front, not the 2 to 3 degrees that they had anticipated. As they placed the forward landing gear on the ground and reduced thrust to lower the aft gear, the helicopter slid down the slope to a point where the forward rotor blades struck the ground. Immediately after contacting the ground, the forward rotor blades impacted the fuselage, severing the drive shaft, flight control tubes, and all the hydraulic lines and electrical wiring routed along the top of the cabin. The forward rotor lost power at that point, but the aft rotor was still being driven by the engines. The aft rotor lifted the rear of the aircraft until it rotated over the nose. It then rolled about 120 degrees to the right and came to rest on its right side, facing generally south. One crew member was fatally injured, and the other three received minor cuts and bruises. A Forest Service passenger escaped injury. The aircraft was totally destroyed. The three surviving crew members and one passenger egressed unassisted. The fatally injured crew member was inside the aircraft but covered with debris. The crew searched for several minutes before locating his body. Smoke from the post-crash fire and the noise and concern generated by the left engine, which continued to operate after the crash, added to the confusion of the moment. A Medevac helicopter was called immediately and arrived on the scene in approximately 20 minutes. A small post-crash fire developed in the rear of the cabin and was extinguished by a pilot using one of the aircraft handheld fire extinguishers. That one guy is still in there. The left engine was torn from its physical mounts and only dangled by its fuel and oil lines. It continued to run after the crash. The crew attempted to shut the engine down by closing the manual fuel valve inside the cabin. However, damage to the airframe prevented the fuel valve from being completely closed. It allowed enough fuel through the line to sustain the engine at near idle RPM. The engine operated for nearly two hours before trained maintenance personnel could be brought to the site, remove the metal from around the valve and shut the engine down. The cause of this accident was human error. The crew of the CH-47 was unable to accurately identify the most suitable portion of the landing area and as a result attempted to land on an unexpected 11 degree slope. The crew's error was a result of environmental conditions that existed at the landing zone and a reliance on the accuracy of a unit representative's description of the landing zone's suitability. The terrain features were not properly identified during the landing area reconnaissance. When the crew descended into the area from a near vertical position, they perceived the landing area to be fairly level. This was due to the angle from which they were viewing the area and also because the area had been burned by the fire, there was nothing left to provide contrast. The vegetation was totally burned away and the color was constant throughout the landing zone. In addition, the area of intended landing had been watered down to settle the dust. The water-soaked ground also contributed to the lack of contrast as no shadows were visible on the darkened surface. All unit personnel should be briefed on the facts and circumstances of this accident with particular emphasis placed on the importance of effective landing area reconnaissance and also on how a lack of contrast can distort slope perceptions. This accident claimed one life and totally destroyed the aircraft. The estimated cost of damage of this accident is $13,770,360.