NTSB Identification: FTW98LA144.
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Accident occurred Wednesday, March 11, 1998 in JEANERETTE, LA
Probable Cause Approval Date: 02/15/2001
Aircraft: Bell 47D1, registration: N13012
Injuries: 1 Minor,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.

The dual student pilot was practicing landings in the local practice area, and had completed 4 to 5 landings. On the next landing, they were heading west, level at 350 feet agl, with an airspeed of 35 mph. As the student lowered the collective to initiate a steep approach, a severe vertical vibration was encountered. About 2 to 3 seconds later, a severe lateral vibration began. The flight instructor took the controls and continued the descent towards the landing area. At about 10 feet the instructor tried to reduce forward airspeed and descent rate by moving the cyclic aft and raising the collective. 'Neither of those inputs seemed to help a lot and we impacted hard.' The helicopter rolled over to the left before coming to rest heading to the east. There were no reported problems with tail rotor control. Examination of the helicopter by the FAA inspector revealed that the scissor hinge bolt which attaches the scissor to the swash plate was missing. He added that according to the maintenance records, the 5, 258 helicopter, underwent a 100 hour inspection on February 15, 1998, approximately 20 hours prior to the accident.

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

The in-flight disconnect of the rotating scissors due to the separation of its hinge bolt.

Full narrative available

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