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NTSB Report
January 25, 1991 · Robinson R-22 HP · N21439
Scottsdale, AZ
Overview
Report Status
Probable Cause
Event Type
Accident
Date
January 25, 1991
Injury Outcomes
No injuries (1 uninjured)
Location
Scottsdale, AZ
Aircraft
Robinson R-22 HP
Tail Number
N21439
Operator
Arizona Wing & Rotor
Injuries
None
Aircraft Damage
Substantial
NTSB Number
LAX91LA079
THE PILOT, AFTER SEEING THE HELICOPTER'S CLUTCH CAUTION LIGHT ILLUMINATE, HEARD A LOUD 'BANG'. HE LOWERED THE COLLECTIVE AND ENTERED AN AUTOROTATIVE DESCENT. HE TERMINATED LOW TO THE TERRAIN, AND THE AIRCRAFT STRUCK TAIL STINGER FIRST, CAUSING IT TO BOUNCE AND THEN ROLL OVER. A VISUAL INSPECTION OF THE HELICOPTER REVEALED TWO OF THE DRIVE BELTS HAD FAILED, CAUSING A DRIVE TRAIN SEPARATION. THE HELICOPTER MANUFACTURER DISCOVERED THE BELTS FAILED AS A RESULT OF EXCESSIVE WEAR ON THE CLUTCH ASSEMBLY UPPER SHEAVE. THE EXCESSIVE WEAR ON THE SHEAVE WAS CAUSED BY THE BELTS, GRITS, AND SAND. THIS CREATED A SHARP EDGE ON THE SHEAVE WHICH CAUSED THE FAILURE OF THE BELTS.
NTSB Probable Cause
THE FAILURE OF THE DRIVE BELTS DUE TO EXCESSIVE WEAR OF THE CLUTCH ASSEMBLY UPPER SHEAVE AND THE PILOT'S INACCURATE FLARE DURING THE TERMINATION OF THE AUTOROTATION. A FACTOR IN THE ACCIDENT WAS THE INADEQUATE DESIGN OF THE CLUTCH ASSEMBLY UPPER SHEAVE.
Full Narrative
THE PILOT, AFTER SEEING THE HELICOPTER'S CLUTCH CAUTION LIGHT ILLUMINATE, HEARD A LOUD 'BANG'. HE LOWERED THE COLLECTIVE AND ENTERED AN AUTOROTATIVE DESCENT. HE TERMINATED LOW TO THE TERRAIN, AND THE AIRCRAFT STRUCK TAIL STINGER FIRST, CAUSING IT TO BOUNCE AND THEN ROLL OVER. A VISUAL INSPECTION OF THE HELICOPTER REVEALED TWO OF THE DRIVE BELTS HAD FAILED, CAUSING A DRIVE TRAIN SEPARATION. THE HELICOPTER MANUFACTURER DISCOVERED THE BELTS FAILED AS A RESULT OF EXCESSIVE WEAR ON THE CLUTCH ASSEMBLY UPPER SHEAVE. THE EXCESSIVE WEAR ON THE SHEAVE WAS CAUSED BY THE BELTS, GRITS, AND SAND. THIS CREATED A SHARP EDGE ON THE SHEAVE WHICH CAUSED THE FAILURE OF THE BELTS.
Flight
Event TypeAccident
Event Time08:40 MST
Nearest Airport0nm N
Runway0
Runway Length0
Runway Width0
Flight Plan FiledNone
Aircraft FireNo
Aircraft ExplosionNo
Aircraft
AircraftRobinson R-22 HP
Tail NumberN21439
Aircraft CategoryHeli
DamageSubstantial
OperatorArizona Wing & Rotor
Operating RulePart 91
Engines1
Engine TypeReciprocating
Engine DetailsLycoming · O-320-B2C · Reciprocating · 160
Seats2
People & Injuries
Injury SummaryNo injuries (1 uninjured)
Fatal0
Serious0
Minor0
Uninjured1
Total1
Crew 1Age 25 · Second Class
Conditions
ConditionsVMC
LightDaylight
WindCalm
Visibility10 sm
CeilingNone
Temperature / Dew Point55 / 0 C
Altimeter0
Weather SourcePILO