NTSB Identification: ATL90IA060.
The docket is stored on NTSB microfiche number 42154.
Scheduled 14 CFR operation of EASTERN AIR LINES, INC
Incident occurred Wednesday, January 31, 1990 in LOUISVILLE, KY
Probable Cause Approval Date: 12/30/1992
Aircraft: DOUGLAS DC-9-31, registration: N8978E
Injuries: 2 Minor,71 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.

AFTER LANDING THE FLIGHT CREW NOTED A VIBRATION. LEFT MAIN GEAR TORQUE LINK APEX BOLT WAS FOUND TO HAVE VIBRATED OUT OF THE TORQUE LINK WHICH ALLOWED MAIN GEAR TRUCK TO ROTATE 360 DEGREES DURING LANDING ROLL. THE NUT HAD STRIPPED OFF OF THE BOLT. LABORATORY EXAMINATION REVEALED THAT THE TORQUE LINK ATTACHING PINS HAD EXCESSIVE PLAY. NEW & OLD APEX BOLTS WERE MEASURED. THEY FAILED TO PASS THE MOST STRINGENT QUALITY CONTROL CHECK FOR CORRECT THREAD SIZE. THE SAFETY BOARD BELIEVES THAT THE NUT STRIPPED OFF WHEN THE LOOSE TORQUE LINKS ALLOWED EXCESSIVE VIBRATION. THE UNDERSIZE APEX BOLT THREADS ALLOWED THE NUT TO SHEAR AWAY THE BOLT PIN DESIGNED TO RETAIN THE NUT.

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

THE DISABLING OF THE MAIN LANDING GEAR TORQUE LINK WHICH ALLOWED THE TRUCK TO ROTATE FREELY. THE TORQUE LINK WAS DISABLED WHEN EXCESSIVE VIBRATION WAS GENERATED BY EXCESSIVE PLAY OF THE TORQUE LINK PINS IN THEIR BUSHINGS.

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