NTSB Identification: ATL96IA053.
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Scheduled 14 CFR
Incident occurred Tuesday, February 20, 1996 in RALEIGH, NC
Probable Cause Approval Date: 02/18/1997
Aircraft: Embraer 120, registration: N129AM
Injuries: 8 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.
According to the flightcrew, during the initial climb after takeoff, an uncommanded right rudder pedal hardover occurred, during which the right rudder pedal moved to the fully depressed position. The hydraulic system was deenergized and an uneventful landing was made at the departure airport. A postincident examination of the airplane's rudder control system did not reveal any discrepancies. However, hydraulic system fluid samples were obtained and analyzed, along with an inspection, testing, and disassembly of the rudder hydraulic power control unit and the rudder actuators. As a result of the testing, contamination was found in the fluid samples from the airplane's hydraulic reservoirs and the power control unit that exceeded the maximum levels established by the airplane manufacturer's maintenance manual. The operator's FAA accepted general operating manual requires compliance with the manufacturer's maintenance manual. Additionally, the operator did not have an established procedure for periodically sampling and analyzing hydraulic fluid from airplane systems.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: The operator's inadequate progressive inspection program that did not require periodic analysis of airplane hydraulic system fluid; and the failure of the operator to comply with the airplane manufacturer's maintenance manual resulting in contamination of the airplane's hydraulic system that exceeded the maximum contamination level. Full narrative available
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