Boeing 747-438, VH-OJU
EXECUTIVE SUMMARY
An Australian registered Boeing 747-438 aircraft operating a
regular passenger transport flight sustained the failure of an
engine shortly after takeoff from Los Angeles, USA. The engine was
subsequently shut-down and the aircraft returned for an uneventful
landing.
The failed engine was a Rolls Royce RB211-524G2-T model.
Preliminary inspection by the operators maintenance personnel found
evidence of extensive internal mechanical damage within the
high-pressure compressor section of the engine and as a result,
returned the engine to Australia for inspection and overhaul.
The Australian Transport Safety Bureau examined the engine
following its disassembly into primary modules. The engine had
failed as a result of the liberation of a single blade from the
first-stage high-pressure compressor section. That failure
subsequently precipitated a titanium metal fire within the
compressor, extensively damaging the following stages and rendering
the engine inoperative.
The engine manufacturer has attributed three previous failures
of RB211 high-pressure compressors to the loss of blades from the
first-stage rotor. The blade losses were all associated with
fatigue cracking of the dovetail root connection. The manufacturer
identified uneven centrifugal loads on the blade roots as a
significant factor in the development of blade cracking; possibly
exacerbated by 'patchy' root friction and minor mechanical
imperfections in the critical blade root transition region.
Evidence from the current investigation indicated the nature of
the failure to be very similar to the previously reported
events.