NTSB Identification: FTW04FA143.
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Accident occurred Friday, May 28, 2004 in League City, TX
Probable Cause Approval Date: 02/28/2006
Aircraft: Eurocopter AS355N, registration: N355CV
Injuries: 4 Minor,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.

"THIS CASE WAS MODIFIED MAY 30, 2006."

The 13,800-hour airline transport pilot and five passengers departed on a short pleasure flight after satisfactorily completing a maintenance check with the engines running on the ground. The pilot flew to a local airport and made a normal straight-in approach, executed an autorotation with a power recovery, then proceeded back to the home airport. While en route, after the helicopter crossed over a large row of power lines, the pilot reported the helicopter lost all engine power. However, none of the anticipated aural warnings, annuciator lights, abnormal vibrations or sounds associated with a power failure was observed. The pilot entered an autorotation and the helicopter contacted the ground hard and rolled over. Examination of the helicopter revealed continuity to all flight controls and the main gearbox. The #1 engine was placed on a test cell, started immediately, and was run at various power settings without interruption. Due to impact damage the #2 engine could not be test-run. Examination of the #1 and #2 engines' main gearbox coupling shafts by an NTSB Materials Specialist revealed that the shafts were both fractured at the reduced section adjacent to the main gear box input splines. The fracture plane, presence of dimpling, and direction of fracture were consistent with ductile torsional overstress with the engines running. In addition, data retrieved from the digital engine control units and damage to the main gear drive shafts indicated that both engines were operating at the time of impact. No mechanical deficiencies were noted that would have attributed to a loss of power on either engine. Several attempts were made to obtain a copy of NTSB Form 6120.1/2, Pilot/Operator Accident Report; however, the pilot failed to submit a completed report.




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

"THIS CASE WAS MODIFIED MAY 30, 2006."

The pilot's misjudged flare during an autorotation, which resulted in a hard landing and subsequent rollover.

Full narrative available

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