On 27 November 2006, a Beechcraft King Air 200 aircraft, registered VH-XDB and carrying two crew and six passengers, was on a flight from Mount Hale to Perth, Western Australia. Shortly after commencing the decent into Perth airport, the right engine failed catastrophically.
An engineering examination of the failed Pratt and Whitney Canada PT6A-41 turboprop engine was performed and revealed that the first-stage 'sun' and 'planet' gear set within the propeller reduction gearbox had decoupled from the power turbine. The decoupling allowed the power turbine to overspeed, which resulted in destruction and shedding of the turbine blades. Several blade fragments punctured the outer gas generator case.
A metallurgical examination of the failed first-stage gear set revealed that a mismatch in service histories between the sun gear and planet gears was the most likely contributor to the failure. The engine manufacturer had been alert to the occurrence of reduction gearbox distress due to gear mismatching at overhaul.
Following this incident, the aircraft operator initiated a review of their system of maintenance with respect to monitoring of life-limited engine components, for all PT6A engines in their fleet.
|Date:||27 November 2006||Investigation status:||Completed|
|Time:||1800 WST||Investigation level:||Complex - click for an explanation of investigation levels|
|Location:||93km N of Perth Airport|
|State:||Western Australia||Occurrence type:||Engine failure or malfunction|
|Release date:||24 June 2009||Occurrence class:||Technical|
|Report status:||Final||Occurrence category:||Incident|
|Highest injury level:||None|
|Aircraft manufacturer||Beech Aircraft Corp|
|Type of operation||Air Transport Low Capacity|
|Damage to aircraft||Minor|
|Departure point||Mt Hale. WA|