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NTSB Report
April 4, 1990 · Bell 47G · N739B
La Verne, CA
Overview
Report Status
Probable Cause
Event Type
Accident
Date
April 4, 1990
Injury Outcomes
No injuries (2 uninjured)
Location
La Verne, CA
Aircraft
Bell 47G
Tail Number
N739B
Operator
Airborne Helicopters
Injuries
None
Aircraft Damage
Substantial
NTSB Number
LAX90LA137
ACCORDING TO THE INSTRUCTOR PILOT, THE AIRCRAFT BEGAN TO VIBRATE DURING TERMINATION OF A POWER RECOVERY AUTOROTATION. HE STATED THAT WHEN THE COMMERCIALLY RATED STUDENT PILOT APPLIED POWER, THE ENGINE DEVELOPED POWER, BUT THE ROTOR RPM DECAYED. THE AIRCRAFT COLLIDED WITH THE RUNWAY. THE INSTRUCTOR PILOT WAS LATE IN TAKING THE CONTROLS AND RECOVERING THE AIRCRAFT. AN FAA AIRWORTHINESS INSPECTOR EXAMINED THE HELICOPTER AND FOUND NO PRE-IMPACT MECHANICAL MALFUNCTIONS OR FAILURES.
NTSB Probable Cause
THE HELICOPTER'S ROTOR SYSTEM BEING ALLOWED TO UNDERSPEED AS A RESULT OF IMPROPER USE OF FLIGHT CONTROLS BY THE DUAL STUDENT; IMPROPER SUPERVISION BY THE CERTIFIED FLIGHT INSTRUCTOR; AND DELAYED REMEDIAL ACTION BY THE CERTIFIED FLIGHT INSTRUCTOR WHICH ALLOWED THE IN FLIGHT COLLISION WITH THE RUNWAY.
Full Narrative
ACCORDING TO THE INSTRUCTOR PILOT, THE AIRCRAFT BEGAN TO VIBRATE DURING TERMINATION OF A POWER RECOVERY AUTOROTATION. HE STATED THAT WHEN THE COMMERCIALLY RATED STUDENT PILOT APPLIED POWER, THE ENGINE DEVELOPED POWER, BUT THE ROTOR RPM DECAYED. THE AIRCRAFT COLLIDED WITH THE RUNWAY. THE INSTRUCTOR PILOT WAS LATE IN TAKING THE CONTROLS AND RECOVERING THE AIRCRAFT. AN FAA AIRWORTHINESS INSPECTOR EXAMINED THE HELICOPTER AND FOUND NO PRE-IMPACT MECHANICAL MALFUNCTIONS OR FAILURES.
Flight
Event TypeAccident
Event Time13:58 PDT
Nearest AirportBRACKETT (0nm N)
Runway26R
Runway Length3661 ft
Runway Width75 ft
Flight Plan FiledNone
Aircraft FireNo
Aircraft ExplosionNo
Aircraft
AircraftBell 47G
Tail NumberN739B
Aircraft CategoryHeli
DamageSubstantial
OperatorAirborne Helicopters
Operating RulePart 91
Engines1
Engine TypeReciprocating
Engine DetailsLycoming · VO-435 · Reciprocating · 220
Seats2
People & Injuries
Injury SummaryNo injuries (2 uninjured)
Fatal0
Serious0
Minor0
Uninjured2
Total2
Crew 1Age 40 · Second Class
Conditions
ConditionsVMC
LightDaylight
Wind30° @ 5 kt
Visibility12 sm
CeilingBroken clouds 2500 ft
Temperature / Dew Point64 F / 55
Altimeter0
Observation Time20:46
Weather SourceWFAC