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Aviation safety reports, made easier to study

NTSB Reports is an independent research and search tool for public aviation accident and incident records. It brings NTSB aviation reports, structured fields, docket files, extracted figures, photos, videos, and update history into one searchable interface.

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NTSB Report

April 30, 1992 · Bell 47-G2A · N52HB

Dousman, WI

Overview

Report Status
Probable Cause
Event Type
Accident
Date
April 30, 1992
Injury Outcomes
2 injuries (1 serious injury, 1 minor injury)
Location
Dousman, WI
Aircraft
Bell 47-G2A
Tail Number
N52HB
Operator
Mc Dermott Enterprises
Injuries
Serious
Aircraft Damage
Substantial
NTSB Number
CHI92LA137

THE FLIGHT INSTRUCTOR (CFI) REPORTED THE DUAL INSTRUCTIONAL FLIGHT PROCEEDED WITHOUT INCIDENT FOR THE FIRST HOUR. WHILE RETURNING TO THE AIRPORT IN CRUISE FLIGHT, A SUDDEN AND VERY VIOLENT VIBRATION OCCURRED. THE CFI TOOK THE FLIGHT CONTROLS AND BEGAN AN AUTOROTATION TO AN OFF-AIRPORT SITE, STRIKING TREES DURING THE DESCENT. INSPECTION OF THE ROTOR HEAD DISCOVERED A MISSING SWASH PLATE DRIVE LINK BOLT, WHICH ALLOWED THE DRIVE LINK TO DISCONNECT. BOTH THE CFI AND STUDENT RECALLED CHECKING THE BOLT AND ASSOCIATED NUT AND COTTER PIN PRIOR TO THE FLIGHT AND FOUND NO ANOMALIES. THE BOLT WAS NEVER LOCATED.

NTSB Probable Cause

THE IN-FLIGHT LOSS OF THE SWASH PLATE DRIVE LINK BOLT WHICH ALLOWED THE SWASH PLATE DRIVE ASSEMBLY TO DISCONNECT.

Full Narrative

THE FLIGHT INSTRUCTOR (CFI) REPORTED THE DUAL INSTRUCTIONAL FLIGHT PROCEEDED WITHOUT INCIDENT FOR THE FIRST HOUR. WHILE RETURNING TO THE AIRPORT IN CRUISE FLIGHT, A SUDDEN AND VERY VIOLENT VIBRATION OCCURRED. THE CFI TOOK THE FLIGHT CONTROLS AND BEGAN AN AUTOROTATION TO AN OFF-AIRPORT SITE, STRIKING TREES DURING THE DESCENT. INSPECTION OF THE ROTOR HEAD DISCOVERED A MISSING SWASH PLATE DRIVE LINK BOLT, WHICH ALLOWED THE DRIVE LINK TO DISCONNECT. BOTH THE CFI AND STUDENT RECALLED CHECKING THE BOLT AND ASSOCIATED NUT AND COTTER PIN PRIOR TO THE FLIGHT AND FOUND NO ANOMALIES. THE BOLT WAS NEVER LOCATED.

Flight

Event TypeAccident
Event Time10:45 CDT
Nearest Airport0nm N
Runway0
Flight Plan FiledNone
Aircraft FireNo
Aircraft ExplosionNo

Aircraft

AircraftBell 47-G2A
Tail NumberN52HB
Aircraft CategoryHeli
DamageSubstantial
OperatorMc Dermott Enterprises
Operating RulePart 91
Engines1
Engine TypeReciprocating
Engine DetailsLycoming · VO-435-A1F · Reciprocating · 240
Seats2

People & Injuries

Injury Summary2 injuries (1 serious injury, 1 minor injury)
Fatal0
Serious1
Minor1
Uninjured0
Total2
Crew 1Age 51 · Second Class

Conditions

ConditionsVMC
LightDaylight
Wind50° @ 10 kt
Visibility8 sm
CeilingNone
Temperature / Dew Point55 / 0 C
Altimeter30.00 inHg
Observation Time15:50
Weather SourceWFAC

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Appendix: Source Data