NTSB Identification: SEA91FA261.
The docket is stored on NTSB microfiche number 46321.
Accident occurred Wednesday, January 16, 1991 in WALLA WALLA, WA
Probable Cause Approval Date: 03/09/1993
Aircraft: BEECH 35, registration: N3081V
Injuries: 2 Uninjured.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

THE PLT RPRTD THAT DRG DSCNT, AT ABOUT 150 KTS, TURBULENCE WAS ENCTRD & THE RUDDER PEDALS BEGAN SHAKING UNCONTROLLABLY ALONG WITH THE WHOLE ACFT, MAINLY THE EMPENNAGE. PULLING BACK ON THE CONTROL COLUMN & PUSHING ON THE RUDDER PEDALS CAUSED THE SHAKING TO SUBSIDE. A LANDING WAS MADE WITHOUT FURTHER INCIDENT. ALTHOUGH THE AFT FUSELAGE SKIN WAS WRINKLED, THE ACFT CONTINUED TO BE FLOWN FOR SVRL MONTHS. A SUBSEQUENT INSPN DISCLOSED THAT ALL 4 CORNERS OF THE AFT FUSELAGE BULKHEAD WERE CRACKED. THE STATIC BALANCE OF EACH RUDDERVATOR WAS MEASURED & FOUND TO BE EXCESSIVELY TAIL HEAVY. ALSO, BOTH RUDDERVATOR TRIM TABS HAD BEEN INSTALLED IMPROPERLY, RESULTING IN FREE PLAY AT THE HINGE LINE. NO LEAD BALANCING WASHERS WERE FOUND IN EITHER RUDDERVATOR COUNTERWEIGHT HOUSING. THE THICKNESS OF PAINT ON THE RUDDERVATORS EXCEEDED THE MANUFACTURER'S FACTORY ACCEPTANCE CRITERIA.

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

IMPROPER STATIC BALANCE OF THE RUDDERVATORS FOLLOWING REBUILDING/REPAINTING, WHICH RESULTED IN EMPENNAGE FLUTTER. IMPROPER INSTALLATION OF THE TRIM TABS AND AN ENCOUNTER WITH TURBULENCE WERE RELATED FACTORS.

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