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ASN Wikibase Occurrence # 45991
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Type:Silhouette image of generic B412 model; specific model in this crash may look slightly different    
Bell 412SP
Owner/operator:Care Flight
Registration: N412SM
MSN: 33197
Fatalities:Fatalities: 1 / Occupants: 1
Other fatalities:0
Aircraft damage: Written off (damaged beyond repair)
Location:Grand Junction, CO -   United States of America
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Departure airport:Grand Junction, CO (29CO)
Destination airport:
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
During a test flight, following maintenance on the helicopter, which required a functional flight check for vibration and autorotation, the helicopter was observed by witnesses to enter a rapid descent. During this maneuver, the rotor system was observed to slow down and the rotor blades to "fold" over the top of the helicopter. Pieces, which were later identified as fragments from the transmission cowling, were observed exiting the helicopter when the rotor system slowed down. The helicopter descended into the ground in a right hand turning maneuver. Examination of the wreckage revealed no evidence of either a structural or system failure or malfunction. According to the helicopter's manufacturer, as the main rotor system slows while under aerodynamic load, the main gear box can "walk" (horizontal orbital movement) on its mounting structure, which can result in contact between the transmission cowling and the main rotor control rod ends. Examination of the engines revealed evidence that engine power was applied when the rotor system was at low rotational speed. No evidence of preimpact engine failure or malfunction was found. According to available information, the pilot had received no training from the operator regarding the conduct of a maintenance test flight, not does the FAA require such training.
Probable Cause: the pilot's failure to maintain rotor speed during an intentional autorotation, which resulted in a loss of control.



Revision history:

28-Oct-2008 00:45 ASN archive Added
13-Aug-2010 15:07 Alpine Flight Updated [Operator, Other fatalities, Location, Nature, Departure airport, Destination airport, Source]
06-Nov-2013 16:32 TB Updated [Operator, Source]
21-Dec-2016 19:24 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
10-Dec-2017 10:32 ASN Update Bot Updated [Operator, Nature, Destination airport, Source, Narrative]

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