NTSB Identification: SEA00IA108.
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Nonscheduled 14 CFR operation of EMERY WORLWIDE
Incident occurred Saturday, June 17, 2000 in SEATTLE, WA
Probable Cause Approval Date: 05/18/2001
Aircraft: Douglas DC-8-73, registration: N831AL
Injuries: 5 Uninjured.
NTSB investigators used data provided by various sources and may have traveled in support of this investigation to prepare this aircraft incident report.
The flight crew reported that while in cruise flight at flight level 310 (31,000 feet) they noted a loss of hydraulic fluid quantity in the aircraft's main hydraulic system reservoir. Shortly after powering the auxiliary rudder pump, the crew felt a '...chattering and feedback with the rudder pedals'. The crew also reported that the rudder momentarily deflected to the left. Post flight inspection of the aircraft's hydraulic system indicated that the auxiliary hydraulic pump was leaking fluid and that the hydraulic fluid quantity was at 'standpipe level'. Examination of the auxiliary hydraulic pump assembly revealed that the gasket located between the hydraulic pump mainframe and the AC electric drive motor, had failed. Further examination of the hydraulic pump subassembly revealed that the rate piston (part number 56909) was 'frozen' in the extended position. A frozen rate piston (in the extended position) could result in high internal case pressures capable of exceeding the manufactures specifications and the specifications of the gasket. Heavy scoring on the piston and the piston housing, with evidence of contamination were also noted.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: Auxiliary hydraulic pump leak resulting in a failure of the hydraulic system. Full narrative available
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