While at approximately 8,000 ft after departure from Sydney, the
crew heard a loud bang from the left side of the aircraft. The
number 1 engine pressure ratio (EPR) had dropped slightly while the
compressor speed (N1), exhaust gas temperature and fuel flow
indications increased. The engine vibration level remained within
limits. A flight attendant reported seeing something entering into
or flaying around the engine intake. After discussions with ground
maintenance, the aircraft was returned to Sydney, where an
uneventful landing was made after about 50,000 kg of fuel had been
jettisoned off the coast.
Examination of the engine by the operator revealed evidence of a
bird strike. Blood was found on the engine fan exit nozzle, and the
glass-reinforced plastic of the ice impact panel was damaged. About
90 per cent of the circumference of the ice impact panel that
covered the acoustic liner aft of the fan was found to be
missing
The fan was inspected for damage and the remains of the ice
impact panel were removed. (The engine maintenance manual allows
the ice impact panel to remain damaged beyond limits or missing for
up to 125 hours, or until the next aircraft maintenance
inspection.) The EPR probes and their lines were flushed clean and
appropriate line connectors were replaced.
A subsequent engine ground run found EPR indications had
returned to normal and the engine was cleared back to line
operations.