NTSB Identification: LAX97FA149.
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Accident occurred Monday, April 07, 1997 in LOS ANGELES, CA
Probable Cause Approval Date: 12/31/1998
Aircraft: Aerospatiale AS350D, registration: N317LT
Injuries: 2 Uninjured.

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.

The pilot exited the helicopter to escort a deplaning passenger. The student pilot rated passenger was left sitting in the helicopter with instructions not to touch the controls. While the pilot was standing nearby, the helicopter began bouncing up and down in a resonant mode. The pilot ran back to the helicopter and pulled the fuel flow control lever into the cut-off position. The helicopter yawed to the right and settled back on the deck. Investigation revealed the full down position of the collective was spring loaded to keep tension against the control lock. An inspection of the helicopter revealed that the collective was not down and locked, nor were the frictions tightly applied. The manufacturer reported instances in which the collective lock was not seated properly, and consequently, the collective became released while the engine was running. If the lock slips off collective, the spring's tension could force the control to move upward. No malfunction or failure was found with the engine or rotor systems.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

the pilot's failure to ensure that the collective lock was properly seated before deplaning.

Full narrative available

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