On August 26, 2002, approximately 1630 mountain daylight time, a Bell 206L-3, N801HM, registered to Redding Air Service, Redding, California, and operated by the United States Forest Service (USFS), Golden, Colorado, was substantially damaged when it collided with trees and impacted terrain during landing approach 15 miles west-northwest of Saguache, Colorado. The commercial pilot was seriously injured and three passengers received minor injuries. Visual meteorological conditions prevailed. No FAA flight plan was filed, but a USFS flight plan was filed and the helicopter was being flight followed by the Forest Service. The public use flight, operating under Title 14 CFR Part 135, originated at Salida, Colorado, approximately 1545. The following is based upon a report submitted by the U.S. Forest Service accident investigator. The pilot reported for duty at 0800. He had been off the previous two days. At midday, the pilot was dispatched to a fire site near Salida and was forced to abandon two landing attempts due to loss of tail rotor effectiveness associated with wind conditions (this landing site was 50 miles north of the accident site). At 1530, the pilot was dispatched to a wildland fire on Trickle Mountain approximately 15 miles northwest of Saguache. The helicopter departed Salida at 1545. On board were three firefighters and various fire fighting tools and equipment. The helicopter arrived on scene at 1620. Upslope smoke indicated the wind was from the east. A firefighter on the ground with a "belt weather kit" measured the wind direction and velocity from the southwest at 15 knots. This information was not relayed to the pilot. The pilot approached the fire from the north and circled in a counterclockwise direction. He sighted a suitable landing site in a saddle (elevation approximately 9,840 feet msl) south of Trickle Mountain and circled again. As he made his landing approach from the west, the helicopter lost tail rotor effectiveness and began to rotate to the right. The pilot added power and the helicopter moved off in a southeast direction and struck several trees. [After reviewing this report, a USFS safety manager said the pilot did not add additional power until after the rotor blades contacted the trees. He added power in an attempt to fly out of the situation.] Rotation increased and the pilot reduced power and collective pitch. The helicopter impacted terrain in a near vertical descent on a southerly heading. The skids collapsed, the fuselage hit the ground, and the helicopter rolled over on its left side and the main rotor blades struck the ground. An 8-foot portion of one rotor blade was hurled 100 feet away. At the time of the accident, the temperature was approximately 78 degrees F. The pilot said the helicopter was not equipped with a high altitude tail rotor kit. Forest Service personnel consulted Bell Helicopter-Textron and learned that there is no high altitude tail rotor kit available for the Bell 206L-III.