Accident Hughes 369E N5200W, Saturday 11 April 1987

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Date:	Saturday 11 April 1987
Time:	07:35 LT
Type:	Hughes 369E
Owner/operator:	Kensrue Development Corp.
Registration:	N5200W
MSN:	0025E
Total airframe hrs:	333 hours
Engine model:	Allison 250-C20B
Fatalities:	Fatalities: 0 / Occupants: 2
Other fatalities:	0
Aircraft damage:	Substantial
Category:	Accident
Location:	Palm Desert, CA - United States of America
Phase:	Manoeuvring (airshow, firefighting, ag.ops.)
Nature:	Private
Departure airport:	Bermuda Dunes, CA
Destination airport:	Hemet, CA (17L)
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
THE HELICOPTER DSCNDD UNCONTROLLED & CRASHED IN A RESIDENTIAL AREA. AFTER THE ACDNT, THE PLT SAID HE AGREED TO ORBIT THE RESIDENCE OF HIS PAX. AT THE APRX 135 DEG POINT OF A LEFT ORBIT, HE FELT 'A BANG & SEVERE VIBRATION IN THE TAIL.' THE PLT LOST DRCTNL CTL & THE HELICOPTER BEGAN SPINNING TO THE RIGHT. AN EXAM OF THE TAIL ROTOR GEAR BOX (T/R GB) ASSY REVEALED 3 OF 4 T/R GB MOUNTING STUDS HAD FAILED FROM CYCLIC FATIGUE DUE TO BENDING WHICH HAD RESULTED FROM A LOSS OF CLAMP-UP TORQUE. SUBSEQUENTLY, THE LOWER RIGHT EAR OF THE T/R GB (AT THE LCTN OF THE 4TH STUD) FAILED FROM OVERLOAD & THE T/R GB SEPD. FURTHER INVESTIGATION REVEALED THAT 3 WASHERS HAD BEEN INSTALLED ON EACH OF THE MOUNTING STUDS, BUT ONLY ONE WAS PERMITTED. THE WASHERS WERE INSTALLED DURING COMPLIANCE WITH AD 86-20-07, 78 FLT HRS BEFORE THE ACDNT.

Probable Cause:

Accident investigation: