Service difficulty report · Turbine Wheel

Difficulty date
May 29, 2008
Submitted
July 16, 2008
Operation
General aviation
Engine
Allsn 250C20B
Part
Turbine Wheel
Part number
23073853
Part serial
X151927
Condition
Failed
Location
Engine
Part time
1,036 hours
Stage of operation
IN
How discovered
V
Nature of condition
O
Precautionary procedure
K

As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.

What was found

TURBINE ASSY RECEIVED FOR REPAIR DUE TO METAL IN OIL. UPON DISASSEMBLY, IT WAS NOTED THAT THE 1ST STAGE TURBINE WHEEL BLADES WERE MISSING PIECES OF BLADE MATERIAL. THE APPARENT IMBALANCE OF THE GP ROTOR ASSY PRODUCED BY THE MISSING BLADE PIECES CAUSED THE GP STATOR SEAL TO FRACTURE. ONE PORTION OF THE STATOR SEAL BEGAN TO ROTATE WITH THE NR 8 BEARING OUTER RACE. THE DOWNSTREAM PORTION OF THE STATOR SEAL BELOW THE FRACTURE REMAINED STATIONARY AND THE GRINDING BETWEEN THE STATIONERY PORTION OF THE SEAL AND THE ROTATING PORTION APPEARS TO BE THE SOURCE OF THE METAL. THE TURBINE WHEEL BLADE TIPS APPEAR TO HAVE FAILED DUE TO HOT - CORROSION SULFIDATION AS DEFINED IN MFG CSL-1210. SOME DOWNSTREAM PORTIONS OF THE TURBINE GAS PATH WERE DAMAGED BEYOND REPAIR BY IMPACT OF THE FAILING WHEEL BLADE PIECES. (K)