Accident Sikorsky S-55 N1255T, Friday 24 July 2009

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Date:	Friday 24 July 2009
Time:	13:45 LT
Type:	Sikorsky S-55
Owner/operator:	Private
Registration:	N1255T
MSN:	55607
Total airframe hrs:	7530 hours
Engine model:	Aireasearch TSE331
Fatalities:	Fatalities: 0 / Occupants: 1
Other fatalities:	0
Aircraft damage:	Substantial
Category:	Accident
Location:	Chelan, Washington - United States of America
Phase:	Manoeuvring (airshow, firefighting, ag.ops.)
Nature:	Unknown
Departure airport:	Chelan, WA
Destination airport:	Chelan, WA
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
The pilot was using rotor wash to dry cherries at low altitude when the helicopter lost hydraulic pressure. After clearing a stand of trees, the pilot made an emergency run-on landing into a vacant field. During the landing, one of the landing skids hit a large hole, and the main rotor severed the tail boom. Post accident examination revealed that an internal seal had leaked resulting in the loss of pressure in the hydraulic system.

Probable Cause: Failure of a seal in the hydraulic system resulting in a loss of hydraulic pressure while maneuvering at low altitude.

Accident investigation: