On September 29, 1984, a Boeing 747-200B (registration N613US) was involved in an aviation accident near Seattle, WA. Investigators recorded the probable cause as: Turbine stator support structure weakened by sulfidation due to exhaust gases escaping through an inspection port; failure of the port allowed contact with the turbine blades, resulting in blade escape and subsequent imbalance. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During climbout at 4000 ft MSL, an aircraft experienced a #2 engine failure with an explosive sound and N1 dropping to 30%. The aircraft returned to Seattle for an uneventful landing. Investigation found sulfidation weakened the turbine stator support through an inspection port failure, causing blade escape and imbalance.
Incident
During climbout, passing through 4000 feet MSL, the aircraft experienced a failure of the #2 engine. The crew reported hearing an explosive sound followed by a drop in fuel flow, with N1 speed decreasing to 30% RPM on the #2 engine. The aircraft returned to Seattle for an uneventful landing.
Investigation
The engine exhaust tail cone and numerous turbine blades were located in a rural area approximately 11 miles south of the airport. Investigation revealed that the turbine stator support structure had been weakened by sulfidation, a result of exhaust gases escaping through an inspection port.
Findings
Failure of the inspection port allowed contact with the turbine blades, leading to blade escape and subsequent imbalance. The sulfidation of the support structure was identified as the underlying cause of the port failure.
Probable cause
Turbine stator support structure weakened by sulfidation due to exhaust gases escaping through an inspection port; failure of the port allowed contact with the turbine blades, resulting in blade escape and subsequent imbalance.
What happened in the 29 Sept 1984 Boeing 747-200B accident near Seattle, WA?
During climbout at 4000 ft MSL, an aircraft experienced a #2 engine failure with an explosive sound and N1 dropping to 30%. The aircraft returned to Seattle for an uneventful landing. Investigation found sulfidation weakened the turbine stator support through an inspection port failure, causing blade escape and…
What aircraft was involved and where did it happen?
The accident on 29 Sept 1984 involved a Boeing 747-200B, registration N613US, at Seattle, WA.
What was the probable cause of the accident?
Turbine stator support structure weakened by sulfidation due to exhaust gases escaping through an inspection port; failure of the port allowed contact with the turbine blades, resulting in blade escape and subsequent imbalance.
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