Mitsubishi Aircraft Int MU-2B-30, VH-UZB

The aircraft was operating a night freight operation from
Brisbane to Sydney. While cruising at flight level (FL) 130 in
visual conditions, the crew reported a loud bang and the right
engine suddenly ran down. When the crew were about to feather the
propeller, the blades were found to be already in the feathered
position, and one of the blades was missing. As the aircraft
handling was normal, and after considering a diversion to
Bankstown, the pilot in command elected to continue to Sydney due
to the availability of emergency services, which were placed on
standby. The aircraft subsequently made a safe approach and landing
on runway 34L.

A post-flight inspection revealed substantial damage to the
engine and its mountings. The rear turbine bearing oil supply line
had failed and the subsequent loss of oil pressure had resulted in
the propeller auto-feathering. The right wingtip fuel tank
attachments were loose and the fuel tank could be moved by
hand.

The propeller blade had failed about 96 mm from the blade butt.
An analysis of the failure surface determined that the failure was
the result of fatigue. Fatigue cracking had initiated at the end of
the blade pilot tube bore in the region of smallest section
thickness on the thrust side of the blade. The cracking did not
appear to be associated with any discrete mechanical or corrosion
damage.

The propeller is overhauled every 3,000 hours. The last overhaul
was in November 1994, 790 hours prior to the accident. During the
overhaul the blade pilot tube bore was inspected using the dye
penetrant inspection process as required by Airworthiness Directive
AD/PHZL/48. Examination of the fracture surface features and an
assessment of the rate of crack growth indicated that a region of
fatigue cracking, approximately 12 mm in length and 6 mm in depth,
was present at the time of the overhaul. However, compounds
containing calcium had contaminated this region, reducing the
ability of the dye to penetrate the cracks.