NTSB Identification: CHI85IA032.
The docket is stored on NTSB microfiche number 27668.
Scheduled 14 CFR UNITED AIRLINES
Incident occurred Saturday, October 27, 1984 in CHICAGO, IL
Probable Cause Approval Date: 08/30/1994
Aircraft: McDonnell Douglas DC-10-30, registration: N1852U
Injuries: 276 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 TAKEOFF, THE FLIGHT CREW HEARD A NOISE FROM THE RIGHT SIDE OF THE AIRCRAFT, WHICH SOUNDED LIKE AN ENGINE COMPRESSOR STALL. THE #3 ENGINE WAS SHUT DOWN & THE CREW MADE AN UNEVENTFUL LANDING AT THE DEPARTURE AIRPORT. PIECES OF COWLING FROM THE RIGHT ENGINE FELL IN A RESIDENTIAL AREA, BUT DID NO DAMAGE. TEARDOWN OF THE ENGINE REVEALED THAT TURBINE BLADES ON THE FIRST STAGE LOW PRESSURE TURBINE WHEEL HAD BROKEN OFF & HAD PENETRATED THE ENGINE CASE & CORE COWL DOORS. FURTHER INVESTIGATION REVEALED THAT 2 STUD BOLTS (SADDLE BOLTS) HAD PULLED OUT FROM STRUT BOSSES 2 & 3 IN THE TURBINE MID FRAME (TMF), WHICH PLACED AN ADDITIONAL LOAD ON STRUT BOSSES 1 & 4. EVENTUALLY, THE 1 & 4 SADDLE BOLTS PULLED LOOSE & ALLOWED THE NOZZLE SUPPORT FLANGE TO SHIFT REARWARD. THIS SHIFT ALLOWED THE NOZZLE SEGMENTS TO COME IN CONTACT WITH THE LOW PRESSURE TURBINE & RESULT IN THE FAILURE. THERE WAS INDICATION THAT UNAUTHORIZED REWORK HAD BEEN ACOMPLISHED ON THE SADDLE BOLTS BEFORE OWNER (UNITED AIRLINE) HAD PURCHASED THE AIRPLANE FROM ANOTHER (LAKER) AIRLINE.

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

TURBINE ASSEMBLY,NOZZLE RETENTION..FAILURE,TOTAL

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

MAINTENANCE..IMPROPER..OTHER MAINTENANCE PERSONNEL



Index for Oct1984 | Index of months