The investigation report by the Australian Transport Safety Bureau (ATSB) on an incident involving in-flight Propeller separation from a Saab 340, registration VH-NRX, about 19 km from Sydney on 17 March 2017.
It is reported that the right propeller assembly detached in-flight during the Regional Express (REX) flight from Albury to Sydney, with 16 passengers and three crew on board. The aircraft landed safely at Sydney.
ATSB findings reported that,
The engine manufacturer’s preliminary metallurgical analysis of the fractured shaft has identified that fatigue cracking in the propeller main shaft originated within a dowel pin bore that was located on the forward face of the propeller flange from the propeller reduction gearbox (PGB). Their analysis indicates that the initiation of fatigue cracking within the hub flange may be associated with a combination of factors that include:
• the accumulation of significant operational hours for each propeller reduction gearbox
• the development of pitting corrosion damage within the dowel pin bore and at the front face of the propeller flange
• progressive wear and subsequent surface damage of the hub flange at stress-critical regions surrounding the dowel pin.
The ATSB advises that those responsible for the operation and maintenance of SAAB 340 and EADS CASA CN-235 aircraft fitted with the GE Aviation CT7 engine type variants 5A2, 7A1, 9B, 9C, and 9C3 should note the facts presented in this preliminary report with a view to addressing any risks to their own operation.
For full report: ATSB : http://www.atsb.gov.au/publications/investigation_reports/2017/aair/ao-2017-032/