NTSB Identification: SEA99FA013.
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Accident occurred Tuesday, November 10, 1998 in MARSHALL, WA
Probable Cause Approval Date: 01/11/2000
Aircraft: Hiller UH-12E, registration: N752GB
Injuries: 1 Fatal.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
While climbing out after takeoff from the helicopter pad located at the pilot's residence/place of business, the bolt that connected the lower end of the upper-firewall lateral cyclic linkage bellcrank to its push rod separated from the aircraft. With the bolt missing from the control linkage, the necessary increase of the angle of attack (cyclic feathering) of the retreating blade (port blade) could not take place. Without this feathering, which is produced by the lateral position of the cyclic, the forward-moving blade (starboard side)produced considerably more lift than the retreating blade. This resulted in an uncontrolled roll to the left and an uncontrolled descent into the terrain.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The loss of the bolt that connects the lateral cyclic linkage push rod to the lower end of the upper firewall-mounted lateral cyclic linkage bellcrank, resulting in an uncontrolled descent into the terrain. Full narrative available
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