SAFETY REPORT: Faulty bolts on RFDS plane caused engine failure.
Source: PerthNow
A NUMBER of failed bolts inside a gearbox caused the engine of a Royal Flying Doctor Service (RFDS) plane with four people on board to stop, an investigation has found.
A single-engine RFDS Pilatus PC-12 aircraft was on a medical evacuation flight from Derby to Kununurra, in WA, on January 29 this year when the pilot heard a loud humming and whining noise.
The pilot turned back to the Derby aerodrome, in the state's north, after an engine warning light lit up about 56km after take-off.
An oil quantity light then lit up 11km from Derby before the pilot reported the engine had failed and put in a MAYDAY call.
She glided the plane to land safely at Derby and no one was hurt.
An RFDS spokeswoman said the pilot did everything right.
"She did everything by the book and brought her in safely to land," the spokeswoman said.
A preliminary report into the incident by the Australian Transport Safety Bureau (ATSB) said a subsequent inspection confirmed the engine propeller reduction gearbox had seized.
"The investigation found that a number of first-stage reduction gearbox carrier bolts had failed," the report said.
"As a result, the engine manufacturer has reviewed a number of issues relating to engine overhaul practices and has recommended withdrawal from service of an engine from one aircraft in the Australian fleet for examination."
The engine, was examined at an approved workshop of Canadian aircraft engine manufacturers Pratt & Whitney, under the supervision of the ATSB.
An examination of the propeller gearbox found four of six bolts had failed due to fatigue cracking which had led to gear damage.
Pratt & Whitney had issued a 2008 service difficulty advisory about the fractured carrier bolts when it advised there had been more than 20 fractures of the gearbox carrier bolts, the ATSB said.
The company told the ATSB there had been 27 gearbox failures between 2000 and 2010 because of the bolt distress on engines.
"Of the 27 reported gearbox failures, 15 resulted in in-flight shutdowns,"
the ATSB report said."All of the failure events had occurred after engine overhaul, with no events associated with new production engines."
New overhaul procedures were introduced by Pratt & Whitney in January 2009.
The engine in the RFDS plane had its last overhaul in May 2007, the ATSB said.
The ATSB investigation is continuing to determine the level of risk to aircraft with similar engines.
Source: http://www.perthnow.com.au/news/western ... 5867850107
