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NTSB Report
July 22, 1991 · Sikorsky SK-58 · N58WH
Daggett, CA
Overview
Report Status
Probable Cause
Event Type
Accident
Date
July 22, 1991
Injury Outcomes
No injuries (3 uninjured)
Location
Daggett, CA
Aircraft
Sikorsky SK-58
Tail Number
N58WH
Operator
Associated Helicopter Services
Injuries
None
Aircraft Damage
Substantial
NTSB Number
LAX91LA320
WHILE RETURNING FROM AN EXTERNAL LOAD OPERATION, THE HELICOPTER'S ENGINE STARTED VIBRATING AND THEN STARTED BACK FIRING. THE PILOT REPORTED HEARING A LOUD 'BANG' AND THEN NOTED A DECREASE IN ENGINE POWER. HE PERFORMED NECESSARY EMERGENCY PROCEDURES AND ENTERED AN AUTOROTATION. HE SAID THAT HE TOUCHED DOWN WITH SOME FORWARD SPEED. THE HELICOPTER HIT A DIRT BERM. THE ROTOR BLADES CONTACTED THE GROUND AND THE AIRCRAFT ROLLED OVER. AN ENGINE TEARDOWN WAS PERFORMED UNDER THE SUPERVISION OF AN FAA AIRWORTHINESS INSPECTOR. A BROKEN ROD WAS FOUND DURING THE TEARDOWN. THE TEARDOWN WAS TERMINATED AT THAT POINT AND THE REASON FOR THE BROKEN ROD WAS NOT DETERMINED.
NTSB Probable Cause
THE FAILURE OF AN ENGINE CONNECTING ROD CAUSING A REDUCTION OF ENGINE POWER TO THE POINT WHERE LEVEL FLIGHT COULD NOT BE MAINTAINED. A FACTOR IN THE ACCIDENT WAS THE DARK NIGHT CONDITIONS WHICH RESTRICTED THE PILOT'S ABILITY TO SELECT THE BEST LANDING SITE.
Full Narrative
WHILE RETURNING FROM AN EXTERNAL LOAD OPERATION, THE HELICOPTER'S ENGINE STARTED VIBRATING AND THEN STARTED BACK FIRING. THE PILOT REPORTED HEARING A LOUD 'BANG' AND THEN NOTED A DECREASE IN ENGINE POWER. HE PERFORMED NECESSARY EMERGENCY PROCEDURES AND ENTERED AN AUTOROTATION. HE SAID THAT HE TOUCHED DOWN WITH SOME FORWARD SPEED. THE HELICOPTER HIT A DIRT BERM. THE ROTOR BLADES CONTACTED THE GROUND AND THE AIRCRAFT ROLLED OVER. AN ENGINE TEARDOWN WAS PERFORMED UNDER THE SUPERVISION OF AN FAA AIRWORTHINESS INSPECTOR. A BROKEN ROD WAS FOUND DURING THE TEARDOWN. THE TEARDOWN WAS TERMINATED AT THAT POINT AND THE REASON FOR THE BROKEN ROD WAS NOT DETERMINED.
Flight
Event TypeAccident
Event Time21:40 PDT
Nearest Airport0nm
Runway0
Flight Plan FiledNone
Aircraft FireNo
Aircraft ExplosionNo
Aircraft
AircraftSikorsky SK-58
Tail NumberN58WH
Aircraft CategoryHeli
DamageSubstantial
OperatorAssociated Helicopter Services
Operating RulePart 133
Engines1
Engine TypeReciprocating
Engine DetailsWright · R-1820 · Reciprocating · 1200
Seats3
People & Injuries
Injury SummaryNo injuries (3 uninjured)
Fatal0
Serious0
Minor0
Uninjured3
Total3
Crew 1Age 42 · First Class
Conditions
ConditionsVMC
LightDark Night
Wind270° @ 9 kt
Visibility30 sm
CeilingNone
Temperature / Dew Point0 C / 0 C
Altimeter0
Weather SourcePILO