MINNEAPOLIS, MN, USA
N409AA
MCDONNELL DOUGLAS DC-9-82
THE AIRCRAFT LANDED UNEVENTFULLY AFTER THE RIGHT ENGINE FAILED DURING A DESCENT. THE SHUTDOWN OCCURRED AFTER FAILED ANTIROTATION PINS ALLOWED GAS LOADS TO DRIVE NORMALLY STATIONARY THIRD STAGE VANE CLUSTERS IN THE LOW PRESSURE TURBINE AREA. ROTATION OF THE CLUSTERS IN THEIR CHANNEL ALLOWED THE CLUSTERS TO MACHINE THEMSELVES OUT THROUGH THE LOW PRESSURE TURBINE CASE. EVIDENCE INDICATES THAT 23 OF THE 44 THIRD STAGE VANE ANTI-ROTATION PINS RUPTURED FOLLOWED BY FRACTURE OF THE REMAINING PINS FROM SHEAR OVERLOAD. THE PIN STRESS RUPTURE WAS THE RESULT OF BENDING STRESSES ON THE VANE PINS FROM VANE TWIST & PIN MATERIAL CREEP. A DESIGN TASK WAS INITIATED IN 1986 TO PROVIDE A MORE DURABLE PIN AND IN MAY 1987 P&W RELEASED A NEW MATERIAL, INCO 901 NON-STEPPED, ANTI-ROTATION PIN, PN 803995, TO REPLACE THE PN 599714 TINIDUR PIN.
Source: NTSB Aviation Accident Database
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