NTSB Identification: FTW96FA265.
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Nonscheduled 14 CFR
Accident occurred Friday, June 21, 1996 in SABINE PASS, TX
Probable Cause Approval Date: 03/31/1998
Aircraft: Mbb BO-105, registration: N2906T
Injuries: 4 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.

The twin engine helicopter was en route to an oil platform located 90 miles south of Sabine Pass, Texas, in the Gulf of Mexico. The pilot called company dispatch and reported off Sabine at 0711 with 2.5 hours of fuel on board. The company's flight following radio log shows that the pilot made a normal position report at 0729 and reported that he was 67 miles from destination. The pilot transmitted another normal position report at 0744 and reported that he was 38 miles from destination. No other radio transmissions were received from the aircraft. According to the chief pilot, the altitude at which the helicopter would have been cruising at would most likely have been between 500 and 1,000 feet AGL. No abnormalities were discovered with the engines during detailed examinations. Tear down of the main transmission revealed that the sun gear had failed, thus resulting in the main rotor system not being driven. Structural deformations of the airframe revealed that the helicopter impacted the water vertically in a high rate of descent.

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

The failure of the sun gear within the main transmission resulting in the main rotor system not being driven.

Full narrative available

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