[Peetwo]

ATSB update REX inflight prop loss investigation -

Via ASN...

ATSB issues investigation update of Saab 340B in-flight loss of propeller incident

27 June 2017
The ATSB issued an update of their investigation into the in-flight loss of a Saab 340B propeller in March 2017.

Since the occurrence, the ATSB has been working closely with the engine manufacturer, GE Aviation, in order to establish the factors that led to cracking and fracture of the main propeller shaft from the Regional Express (REX)-operated SAAB 340B aircraft, VH-NRX.
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.
  

GE Aviation have released two service bulletins (SBs) to help understand the potential fleet risk for fatigue cracking in other CT7 PGB main propeller shafts.


More information:

• ASN Incident REX Flight 768
  
• ATSB Investigation number: AO-2017-032
  

MTF...P2