Incident Overview
On 4 October 2009, at 1257 EST, a SAAB 340B aircraft, registered VH-SBA, experienced a failure of the left engine during initial climb out from Wagga Wagga Aerodrome, New South Wales, Australia. The aircraft was operating a regular scheduled flight to Melbourne, Victoria. The flight crew observed abnormally high indications of the left engine inter-turbine temperature, conducted the non-normal checklist, shut down the left engine, and returned to the aerodrome without further incident.
Aircraft and Engine Details
The aircraft, serial number 340B-311, was built in Sweden in 1992. It is a twin-engine turboprop fixed-wing regional airliner with a tricycle-type landing gear. The left engine was a General Electric Company model CT7-9B, serial number 785210.
Inspection Findings
Subsequent inspection of the left engine revealed internal damage, specifically to the 1st stage compressor blisk airfoil section (blade). The engine was disassembled and examined under the supervision of a representative of the UK Air Accidents Investigation Branch (AAIB) on behalf of the Australian Transport Safety Bureau (ATSB).
Observations included:
- All compressor blades were mechanically damaged.
- The 1st stage compressor blisk had four blades broken off at approximately mid-span, while the others had tip damage and diameter reduction apparently from impact and trapping of debris.
- The four failed 1st stage blades had fracture faces that appeared similar to each other.
Further metallurgy examination of the failed blades from the 1st stage blisk was performed in the UK. That examination confirmed that the four failed blades on the 1st stage blisk of the compressor showed a fatigue mechanism related to the failure.
Occupants and Injuries
There were 34 passengers and 3 crew members on board. No injuries were reported.