NTSB Identification: BFO93IA070.
The docket is stored on NTSB microfiche number 50237.
Scheduled 14 CFR operation of USAIR
Incident occurred Friday, May 07, 1993 in PITTSBURGH, PA
Probable Cause Approval Date: 11/03/1993
Aircraft: FOKKER F28-MK-0100, registration: N867US
Injuries: 1 Minor,50 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.

SHORTLY AFTER TOUCHDOWN AT MEMPHIS, TN, A SEVERE VIBRATION WAS FELT BY THE FLIGHTCREW IN THE COCKPIT. THE FLIGHTCREW THOUGHT THE VIBRATION WAS GENERATED BY THE RIGHT MAIN GEAR SO THEY HAD MAINTENANCE PERSONNEL CHECK THE RIGHT MAIN GEAR. NO ANOMALIES WERE NOTED. THE FLIGHT CONTINUED TO PITTSBURGH, PA, AND SHORTLY AFTER TOUCHDOWN, THE LEFT MAIN GEAR COLLAPSED. POST INCIDENT EXAMINATION OF THE LEFT MAIN GEAR REVEALED THAT TWO SPACERS IN THE TORQUE LINK ASSEMBLY WERE FOUND TO HAVE BEEN IMPROPERLY INSTALLED. THE INVESTIGATION ALSO REVEALED THAT DURING RE INSTALLATION OF THE TORQUE LINKS AND SHIMMY DAMPER AT THE LAST MAINTENANCE CHECK, THE TWO SPACERS WERE INSTALLED IN REVERSE OF THEIR NORMAL POSITIONS. ACCORDING TO FOKKER, REVERSAL OF THE TWO SPACERS WOULD RESULT IN AN UNDAMPED FREE PLAY BETWEEN THE UPPER AND LOWER TORQUE LINK RESULTING IN OSCILLATIONS IN THE LATERAL MODE OF THE LANDING GEAR. REVIEW OF USAIR'S AIRCRAFT MAINTENANCE MANUAL, SUPPLIED BY FOKKER, REVEALED THAT THE TWO SPACERS THAT WERE INCORRECTLY INSTALLED ON THE INCIDENT AIRPLANE WERE NOT DESCRIBED BY DIMENSIONS OR VERBIAGE.

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

THE IMPROPER INSTALLATION OF THE SPACERS BY THE MECHANIC AND THE UNCLEAR INFORMATION SUPPLIED FROM THE MANUFACTURER AND OPERATOR REGARDING THE INSTALLATION OF THE SPACERS.

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