NTSB Identification: SEA97IA051.
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Scheduled 14 CFR
Incident occurred Tuesday, January 21, 1997 in SEATTLE, WA
Probable Cause Approval Date: 06/26/1997
Aircraft: Beech 1900D, registration: N75ZV
Injuries: 7 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

While on final approach, the airplane commenced a rapid, uncommanded roll to the right when the 35-degree flap setting was selected. The flying pilot (1st officer) was able to counter the roll by applying almost full opposite aileron, during which time, he felt the aileron jam momentarily and then break free. The airplane landed without further incident. An examination revealed that the inboard, aft end of the right wing outboard flap was detached from the wing flap track. This resulted in flap asymmetry and mechanical interference with the aileron. The flap track roller bearing was seized and the flap mounting bracket was torn and separated from the bearing. The bearing outer roller was loose and could be shifted axially on the bearing outer ring. This allowed the outer roller flange to wear against and eventually tear through the flap mounting bracket. The operator was not using the most recent (revised) Beech 1900D maintenance manuals at the time of the incident and the airplane had not been subjected to a detailed inspection of the flap roller brackets, roller bearings, and attachment hardware as outlined in revised sections of the manual.

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

an axial shift of the aft flap track bearing's outer roller, resulting in erosion and failure of the flap track bracket/bearing assembly. A factor relating to the incident was: inadequate inspection of the flap roller bearing/bracket assemblies.

Full narrative available

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