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NTSB Report
September 25, 1991 · Boland/Poe Tsunami · NX39JR
Pierre, SD
Overview
Report Status
Probable Cause
Event Type
Accident
Date
September 25, 1991
Injury Outcomes
1 injury (1 fatality)
Location
Pierre, SD
Aircraft
Boland/Poe Tsunami
Tail Number
NX39JR
Operator
John Richard Sandberg
Injuries
Fatal
Aircraft Damage
Destroyed
NTSB Number
CHI91DTK04
THE ACCIDENT AIRPLANE WAS OBSERVED TO SUDDENLY ROLL INVERTED DURING FINAL APPROACH AND DESCEND INTO THE GROUND. INVESTIGATION OF THE WRECKAGE SHOWED A BENDING OVERLOAD FAILURE OF THE EXTERNAL THREADED STEM TYPE ROD END BEARING ATTACHED TO THE PISTON OF EACH WING FLAP HYDRAULIC ACTUATOR. THE EXPERIMENTAL RACING AIRPLANE WAS ORIGINALLY BUILT AND FLOWN WITHOUT WING FLAPS. THE WING FLAPS WERE ADDED BY THE PILOT/OPERATOR AT A LATER DATE.
NTSB Probable Cause
A BENDING OVERLOAD FAILURE OF THE WING FLAP CONTROL RODS AND REMEDIAL ACTION BY THE PILOT WAS NOT POSSIBLE. FACTORS IN THE ACCIDENT ARE THE INADEQUATE DESIGN OF THE WING FLAP SYSTEM BY THE PILOT/OPERATOR MANUFACTURER AND HIS LACK OF TOTAL EXPERIENCE IN TYPE OF AIRCRAFT.
Full Narrative
THE ACCIDENT AIRPLANE WAS OBSERVED TO SUDDENLY ROLL INVERTED DURING FINAL APPROACH AND DESCEND INTO THE GROUND. INVESTIGATION OF THE WRECKAGE SHOWED A BENDING OVERLOAD FAILURE OF THE EXTERNAL THREADED STEM TYPE ROD END BEARING ATTACHED TO THE PISTON OF EACH WING FLAP HYDRAULIC ACTUATOR. THE EXPERIMENTAL RACING AIRPLANE WAS ORIGINALLY BUILT AND FLOWN WITHOUT WING FLAPS. THE WING FLAPS WERE ADDED BY THE PILOT/OPERATOR AT A LATER DATE.
Flight
Event TypeAccident
Event Time12:30 MDT
Nearest AirportPierre Municipal (0nm)
Runway0
Flight Plan FiledNone
Aircraft FireNo
Aircraft ExplosionNo
Aircraft
AircraftBoland/Poe Tsunami
Tail NumberNX39JR
Aircraft CategoryAir
DamageDestroyed
OperatorJohn Richard Sandberg
Operating RulePart 91
Engines1
Engine TypeReciprocating
Engine DetailsRolls-Royce · V-1650-7 · Reciprocating · 3000
Seats1
People & Injuries
Injury Summary1 injury (1 fatality)
Fatal1
Serious0
Minor0
Uninjured0
Total1
Crew 1Age 59 · Second Class
Conditions
ConditionsVMC
LightDaylight
Wind310° @ 20 kt, gusting 28 kt
Visibility45 sm
CeilingNone
Temperature / Dew Point68 F / 28 C
Altimeter30.00 inHg
Observation Time18:32
Weather SourceWFAC