NTSB Identification: SEA06LA124.
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Accident occurred Tuesday, June 20, 2006 in Salt Lake City, UT
Probable Cause Approval Date: 01/31/2007
Aircraft: Hughes 369D, registration: N88SE
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

While placing an air conditioning unit on top of a commercial building, the pilot heard the main rotor pitch droop, and confirmed that the rotor rpm was beginning to decrease. He then confirmed the throttle was open in the full flight position, moved the load away from the personnel on the roof, and lowered the collective. The low rotor audio sounded, and the rotor rpm continued to decrease, so the pilot hit the load release switch and autorotated to an emergency landing on top of the roof. After a hard touchdown, the aircraft bounced, touched down again, and then balanced on the right skid before very slowly rolling onto its right side. The load he was placing on the roof weighed less than one-half of what the helicopter was capable of lifting under the ambient conditions, and neither an engine/airframe inspection nor a test run of the engine were able to establish any anomalies or the initiating factor in the rotor droop event.

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

A loss of rotor rpm for undetermined reasons, resulting in a hard landing on top of the commercial building over which the helicopter was working.

Full narrative available

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