Accident Bell UH-1E N118HS, Monday 17 April 1989

You can contribute by submitting additional or updated information.

Date:	Monday 17 April 1989
Time:	13:05 LT
Type:	Bell UH-1E
Owner/operator:	Helicopter Systems
Registration:	N118HS
MSN:	155341
Year of manufacture:	1968
Total airframe hrs:	5414 hours
Engine model:	Lycoming T-53-L-11D
Fatalities:	Fatalities: 0 / Occupants: 1
Other fatalities:	0
Aircraft damage:	Substantial
Category:	Accident
Location:	Aiken, SC - United States of America
Phase:	En route
Nature:	Unknown
Departure airport:
Destination airport:
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
THE HELICOPTER WAS BEING OPERD AT APRX 100 FT AGL WITH A HOPPER EXTDD FROM A CABLE. WITNESSES HEARD A LOUD POPPING SOUND. AS THEY LOOKED IN THE DRCTN OF THE HELICOPTER, THEY NOTED THE TAIL ROTOR WAS NOT TURNING & ONE BLADE APPEARED TO BE HANGING. THE PLT RPRTD THERE WAS NO WARNING OF AN IMPENDING ANTI-TORQUE CONTROL PROBLEM WHEN HE LOST CONTROL OF THE HELICOPTER. THE HELICOPTER THEN COLLIDED WITH TREES & CRASHED. INV REVEALED THE PLT HAD RPRTD AN OIL LEAK FM THE 90 DEG GEARBOX ON 4/11/89. THE COMPANY MECHANIC SUBSEQUENTLY REPLACED THE GEARBOX & A FUNCTIONAL TEST FLT WAS COMPLETED. THE ACDNT OCCURRED AFTER APRX ANOTHER 6 HRS OF OPN. AN EXAM OF THE TAIL ROTOR ASSEMBLY REVEALED THAT 1 OF THE 2 RETENTION BOLTS WERE MISSING FM THE TAIL ROTOR PITCH CHANGE CROSSHEAD. THREADED IMPRINTS WERE FND INSIDE THE RESPECTIVE CROSSHEAD RETENTION THRU-BOLT HOLE. THE RETENTION BOLT, NUT, WASHER & COTTER PIN WERE NOT RECOVERED. BOTH TAIL ROTOR BLADES CONTAINED CHORDWISE MARKS WHICH CORRESPONDED TO MARKS ON THE VERTICAL FIN (OPPOSITE OF THE TAIL ROTOR TIP PATH PLANE).

Probable Cause: IMPROPER INSTALLATION OF A TAIL ROTOR PITCH CHANGE CROSSHEAD RETENTION BOLT BY THE COMPANY MECHANIC, WHICH RESULTED IN LOOSENING OF THE BOLT AND EVENTUAL FAILURE OF THE TAIL ROTOR ASSEMBLY/BLADE AND SUBSEQUENT LOSS OF CONTROL. TREES AT THE CRASH SITE CONTRIBUTED TO HELICOPTER DAMAGE.

Accident investigation: