NTSB Identification: CHI97FA149.
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Accident occurred Tuesday, May 27, 1997 in BOISE, ID
Probable Cause Approval Date: 04/10/1998
Aircraft: Bell 206L3, registration: N35CH
Injuries: 3 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 was executing an autorotation maneuver for a FAR Part 135 flight check. This autorotation maneuver was to be a 180-degree reversal autorotation to a predetermined spot landing with a power termination. The pilot executed the maneuver, but during the level-off received a low RPM warning horn, and attempted to recover using power. During the attempt to increase power the helicopter's throttle interfered with a nut which had been installed for an external torque meter approximately one week before the accident. The nut on the torque meter installation interfered with the throttle controls in certain positions only. A discrepancy with the helicopter's throttle was noticed by the pilot-in-command, and reported to the FAA examiner before the beginning of the flight check.

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

the improper torque meter installation by maintenance personnel, attempting flight with known discrepancies by the pilot-in-command and the check airman, and an improper autorotation by the pilot-in-command with improper oversight of the autorotation maneuver by the check airman.

Full narrative available

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