The Australian Transport Safety Bureau (ATSB) today said that fatigue cracking in the wing carry-through spa was responsible for in-flight wing separation on a Cessna 210 near Mount Isa.
VH-SUX was on a geological survey flight with two people on board when it crashed near Mount Isa on 26 May this year. Both people were killed in the crash.
"Evidence at the accident site indicated that the aircraft’s right wing had separated while in flight, resulting in a rapid loss of control and subsequent collision with terrain," the ATSB said.
"Subsequent technical examination confirmed the aircraft’s wing spar had fractured due to fatigue cracking, which reduced the spar’s structural integrity to the point where operational loads produced an overstress fracture."
ATSB Executive Director Nat Nagy said that the ATSB had notified the relevant National Aviation Authorities.
“The ATSB has notified the Civil Aviation Safety Authority, the US National Transportation Safety Board, the aircraft manufacturer and operator of the initial finding of fatigue cracking with the wing spar carry-through structure,” Nagy said.
"The ATSB is working closely with those parties to ensure the continued safe operation of the the aircraft type."
Fatigue cracking is most often related to the age of a metal component and happens when a small crack grows to the point that the cross-section of a component is reduced to the point where it can't carry the load imposed.
The fear of fatigue in older aircraft was one of the driving factors behind the controversial Cessna Supplemental Inspection Documents (SIDs) programs that were to have been completed for charter and aerial work by the end of July 2016. The SIDs required non-destructive testing and inspections for both primary and secondary aircraft structural components.
The ATSB has moved to differentiate this accident from two other fatal accidents involving C210s in WA and NT. Both of those accidents were attributed to over-stressing of the wings in flight.