Accident Hiller UH-12E N3829, Monday 22 May 1989

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Date:	Monday 22 May 1989
Time:	10:00 LT
Type:	Hiller UH-12E
Owner/operator:	A.i.r. Helicopter Service, Inc
Registration:	N3829
MSN:	1425
Total airframe hrs:	5851 hours
Engine model:	Lycoming VO-540-C2A
Fatalities:	Fatalities: 0 / Occupants: 1
Other fatalities:	0
Aircraft damage:	Substantial
Category:	Accident
Location:	Waterford, WI - United States of America
Phase:	En route
Nature:	Ferry/positioning
Departure airport:	Waterford, WI
Destination airport:
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
WHILE IN NORMAL CRUISE FLIGHT THE HELICOPTER EXPERIENCED A VIBRATION. THE PILOT ELECTED TO MAKE A PRECAUTIONARY LANDING AND DURING ATTEMPTED AUTOROTATION CONTROL WAS LOST. THE INVESTIGATION REVEALED THE MAIN ROTOR DRIVE TRAIN TORSIONAL COUPLING HAD FAILED.

Probable Cause: THE PILOT'S INABILITY TO MAINTAIN CONTROL DURING AN AUTOROTATIONAL LANDING ATTEMPT FOLLOWING THE FAILURE OF THE MAIN ROTOR DRIVE TRAIN TORSIONAL COUPLING.

Accident investigation: