NTSB Identification: BFO88FA036.
The docket is stored on NTSB microfiche number 39449.
Scheduled 14 CFR PIEDMONT AVIATION
Accident occurred Thursday, April 14, 1988 in CHARLESTON, WV
Probable Cause Approval Date: 10/01/1991
Aircraft: FOKKER F28 MK 4000, registration: N110UR
Injuries: 8 Minor,54 Uninjured.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

THE ACFT WAS AT FLIGHT LEVEL 310, WHEN THE NO. 2 ENGINE FIRST STAGE TURBINE DISC SEPARATED, CAUSING AN UNCONTAINED ENGINE FAILURE. TURBINE DEBRIS PENETRATED THE FUSELAGE STRUCTURE & CAUSED DEPRESSURIZATION. THE PLT MADE AN EMERGENCY DESCENT & LANDED AT CHARLESTON, WV, WHICH WAS ABOUT 50 MILES AWAY. THE INVESTIGATION REVEALED SEVERE RUBBING & MELTING OF THE LOW PRESSURE TURBINE INTERSTAGE SEAL & SEPARATION OF THE DRIVE FLANGES CONNECTING THE LP1 & LP2 TURBINE DISCS. ROLLS-ROYCE REPAIR SCHEME XRS 3505 DESCRIBES A PROCEDURE FOR REPAIR OF THE INTERSTAGE SEALS. HOWEVER, IN REPLACING THE SEALS, THE REPAIR FACILITY USED MACHINING REFERENCE SURFACES WHICH DIFFERED FROM THOSE IN THE REPAIR SCHEME. ROLLS-ROYCESUBSEQUENTLY AMENDED XRS 3505 TO MAKE IT MORE TOLERABLE TO RUBBING OR MISASSEMBLY OF THE LOW PRESSURE TURBINE SEAL. ALL OF THE FIRST CLASS SECTION & TWO CABIN SECTION PASSENGER OXYGEN MASKS FAILED TO DEPLOY.

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

ENGINE AND AIRFRAME FAILURE WERE CAUSED BY THE THE SEPARATION OF THE FIRST STAGE LOW PRESSURE TURBINE DISK. THE DISC INTERSTAGE SEAL WAS INSTALLED INADEQUATELY, RESULTING IN RUBBING BETWEEN THE SEAL AND DISK, CAUSING FAILURE OF THE DISK. INADEQUATE PROCEDURE BY MAINTENANCE PERSONNEL ARE A CONTRIBUTING FACTOR.

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