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ASN Wikibase Occurrence # 45137
Last updated: 21 June 2021
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Type:Silhouette image of generic B06 model; specific model in this crash may look slightly different
Bell 206L-3 LongRanger III
Owner/operator:Bureau of Indian Affairs, Fort Apache Indian Res.
Registration: N6184D
MSN: 51253
Fatalities:Fatalities: 2 / Occupants: 4
Other fatalities:0
Aircraft damage: Written off (damaged beyond repair)
Location:Whiteriver, AZ -   United States of America
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Departure airport:Whiteriver, AZ (E24)
Destination airport:
Investigating agency: NTSB
During a right turn to return to a mountain landing site, the helicopter began to spin and struck trees. The flight's mission was to insert a helicopter fire attack crew at the location of a wildfire. The landing zone (LZ) closest to the fire was in a small area surrounded by trees. The density altitude was calculated to be 11,968 feet. The pilot first landed at a meadow about a mile away and off-loaded two fire fighters, then proceeded to the LZ, and dropped off the one remaining fire fighter and tools. He returned to the meadow, where he picked up the additional crewmembers. The flight returned to the landing site, overflew the LZ and continued up the drainage before making a right turn back towards the LZ. One witness seated in the front left seat noted that on the first takeoff from the meadow the torque gauge was at 100 percent and the helicopter was "hard to get off the ground" and the climb out was slow and labored. On the return flight to the LZ, the first fire fighter dropped at the LZ saw that the helicopter was flying slowly about 20 feet above the tree line. He believed they would land with the wind; however, the pilot flew the helicopter past the LZ and continued up the drainage. A surviving witness in the left front seat noted that the torque gauge read 100 percent. As the pilot initiated the right turn to return the LZ, the torque reading went from 100 to 105 and then 110 percent. He asked the pilot if the tail rotor was going to stall, but received no response. The witness noted that the airspeed gauge read zero. At that point the pilot started to rapidly move the collective, cyclic, and "his feet." The helicopter then spun two times to the right. Both a ground witness and a rescue flight crew noted that the LZ had a slope to it and was located in very tight area, with reported winds southwesterly between 2-4 knots. During the on-scene investigation, investigators noted that the compressor blades in the engine were folded opposite the direction of rotation and that tree fibers had been ingested by the compressor impellor, a condition indicative an operational engine at high power at the time of impact. The engine teardown revealed that additional tree fibers were found throughout the gas path from the compressor section through to the combustion and exhaust sections. There were no other discrepancies noted with the airframe or engine that would have precluded normal operation.
Probable Cause: The pilot's failure to maintain a minimum translational lift airspeed while maneuvering in high density altitude conditions at near maximum required torque and above the in ground effect hover altitude, that resulted in a loss of tail rotor effectiveness and a loss of control. The pilot's inadequate in flight planning in his failure to note and account for the power requirements necessary to conduct takeoffs and the slow maneuvering flight at the accident site were also causal.




Revision history:

28-Oct-2008 00:45 ASN archive Added
21-Dec-2016 19:24 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
08-Dec-2017 18:56 ASN Update Bot Updated [Nature, Departure airport, Source, Narrative]

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