NTSB Identification: CHI97IA074.
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Scheduled 14 CFR operation of MESA AIRLINES (D.B.A. UNITED EXPRESS )
Incident occurred Monday, February 24, 1997 in RAPID CITY, SD
Probable Cause Approval Date: 01/30/1998
Aircraft: de Havilland DHC-8-311, registration: N430AW
Injuries: 45 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.
The captain said that he engaged the airplane's autopilot while passing through 10,000 feet mean sea level (msl). About 10 minutes later, the crew noticed illumination of a 'PITCH MISTRIM, TRIM NOSE DOWN' annunciator light. The captain attempted to trim the airplane using the manual elevator trim, but it would allow only limited movement. The crew declared an emergency, returned to Rapid City, and landed the airplane without further incident. A postincident inspection of the aft fuselage compartment revealed that one of the two master links (which held the chain and cable assembly to the electric elevator trim system) had come apart. The chain had subsequently entangled itself in the elevator trim cables. Further examination revealed that the 'C' clip (which snaps to the two posts of the master link base plate and held the master link cover plate in place) was missing.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: a missing 'C' clip, which resulted in the master link coming apart, allowing the electric elevator trim chain and cable to become entangled in the elevator trim cables. Full narrative available
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