TAHOE CITY, CA, USA
N205DF
Bell UH-1H
The public-use helicopter was transporting fire fighting personnel to a nearby forest fire at a small lake in the Sierra Nevada Mountains. The pilot said he calculated the allowable load for the hottest time of the day when he reported for work that morning. After dispatch for the fire mission, the pilot flew to the small lake where he determined that the area, 'appeared large enough to land and that the obstructions were fifty-foot tall trees.' He made an approach over the lake and landed on the beach and was told that they were no longer needed. The pilot said that as he lifted off from the lake edge he ran out of blade pitch and available power as he tried to climb above the trees and was forced to reverse direction. At the middle of the turn the aircraft began descending rapidly toward the water, and he attempted to accelerate the aircraft and pulled power until the rotor rpm began to droop. The helicopter settled into the lake with about 10 knots of forward airspeed. The pilot said the helicopter remained upright on the water with the skids immersed and a dropped main rotor rpm. The pilot reduced collective and recovered rpm with the intention of hovering the helicopter back to the beach area. After the rpm returned to normal, he increased collective, and the helicopter rolled to the right and sank inverted. Review of the cargo manifest, load calculation sheet, and hover ceiling chart show that the helicopter was about 800 pounds over the hover out of ground effect ceiling for the temperature and pressure altitude. The density altitude was computed to be approximately 9,500 feet.
On August 15, 1997, at 1038 hours Pacific daylight time, a Bell UH-1H helicopter, N205DF, crashed into Lake Watson near Tahoe City, California, and sank. The helicopter was operated by the Nevada Division of Forestry (NDF) as a public-use aircraft and was transporting fire fighting personnel to a nearby forest fire. The helicopter sustained substantial damage. The pilot and five of the six firefighters were not injured; however, one firefighter sustained minor injuries. Visual meteorological conditions prevailed at the time and a company flight plan was filed. The flight originated at the Minden, Nevada, airport at 1011 on the morning of the accident on a mutual aid fire response mission for the U.S. Forest Service in the Lake Tahoe basin. According to the pilot's written and verbal statement, he reported for work that morning and calculated the allowable load for the hottest time of the day and determined when one Helitack crew members would have to be bumped. After receiving the dispatch for the fire mission, the pilot flew to Lake Watson and circled the fire incident site several times, attempting to establish communications with the ground crew on scene. While circling the site the pilot determined that the area, "appeared large enough to land and that the obstructions were fifty-foot tall trees." The helicopter made an approach over the lake and landed on the beach where they were informed that they were no longer needed. The pilot reported to the NDF that as he lifted off from the camp site at the edge of the lake, he ran out of blade pitch and available power as he tried to climb above some trees, so he tried to reverse direction. At the middle of the turn the aircraft began descending rapidly toward the water, so he attempted to accelerate the aircraft and pulled power until the rotor rpm began to droop. The helicopter settled into the lake with about 10 knots of forward airspeed and broke the chin bubbles. The pilot stated, "at this point, we are upright on the water, rpm is still drooped, and the aircraft is beginning to turn slowly to the right." The pilot said that he reduced collective to recover rpm, with the intention of hovering the helicopter back to the beach area. After the rpm returned to normal, he increased collective, and the helicopter rolled to the right and sank inverted. Review of the cargo manifest, load calculation sheet, and hover ceiling chart provided to the Safety Board by the NDF show that the helicopter was approximately 800 pounds over the hover out of ground effect ceiling for the existing temperature and pressure altitude. The temperature was reported as 68 degrees Fahrenheit and the elevation at the accident site was listed as 7,800 feet mean sea level. The density altitude was computed to be approximately 9,500 feet. (All referenced charts and documents are attached to the report). A review of the helicopter documents and registration data on file with the FAA Aircraft Registry revealed that the helicopter was a military surplus unit and not certificated in any category.
The pilot's decision to attempt a takeoff in environmental conditions which exceeded the helicopter's performance capability, and his improper use of the collective, which caused a decay of the main rotor rpm, the collision with the lake, and the subsequent rollover. Factors in the accident were the high density altitude and the confined area.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
