NTSB Identification: SEA94LA153.
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Accident occurred Monday, June 20, 1994 in HILLSBORO, OR
Probable Cause Approval Date: 01/12/1995
Aircraft: SCHWEIZER 269C, registration: N7506A
Injuries: 2 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
WHILE EXECUTING A RUN-ON LANDING THE INSTRUCTOR FELT A 'THUMP' AND THE HELICOPTER BEGAN TO OSCILLATE LATERALLY. THE INSTRUCTOR PILOT DIAGNOSED THE PROBLEM AS GROUND RESONANCE, TOOK CONTROL OF THE AIRCRAFT FROM THE STUDENT, CLOSED THE THROTTLE, LOWERED COLLECTIVE, AND THE HELICOPTER DEPARTED THE TAXIWAY. POST CRASH EXAMINATION OF THE SKID SHOCK STRUTS REVEALED THAT ALL FOUR WERE CHARGED AT A PRESSURE LOWER THAN THAT SPECIFIED. THE MAINTENANCE HANDBOOK WARNS THAT IMPROPER SHOCK STRUT PRESSURE LEVELS MAY RESULT IN GROUND RESONANCE AND DESTRUCTION OF THE HELICOPTER.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: THE IMPROPER SERVICING OF THE SKID SHOCK STRUTS. Full narrative available
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