NTSB Identification: CHI91DTK04.
The docket is stored on NTSB microfiche number 46798.
Accident occurred Wednesday, September 25, 1991 in PIERRE, SD
Probable Cause Approval Date: 03/31/1993
Aircraft: BOLAND/POE TSUNAMI, registration: NX39JR
Injuries: 1 Fatal.

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.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

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.

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