The Australian Transport Safety Bureau (ATSB) today released the final investigation report into the fatal crash of a Cessna 210 on survey operations in 2019.
C210N VH-SUX was conducting geophysical survey operations with an attached magnetometer boom near Mount Isa in May 2019 when the starboard wing separated from the aircraft. Both the pilot and a crew member were fatally injured in the crash.
The ATSB found that a pre-existing fatigue crack in the wing carry-through spar reached a critical size during the last run, after which the wing structure was no longer capable of resisting the forces exerted on it in flight.
"Relevant components of the aircraft were subject to detailed examination at the ATSB’s technical facilities in Canberra where it was found that relatively minor corrosion near a highly-stressed location on the lower surface of the wing spar carry-through had progressed into the aluminium alloy structure, initiating a fatigue crack," the ATSB has stated.
"The crack propagated to a critical size resulting in an overstress fracture of the remaining wing carry-through structure material and separation of the right wing."
As part of the investigation, the ATSB concluded that the cyclic stresses placed on the wing of VH-SUX during the low-level survey runs was greater than the forces that would be expected at the higher level the aircraft was designed to fly at. At the time of the crash, the aeroplane was only 193 feet AGL.
The ATSB made a formal recommendation to Textron Aviation to further address the risk of fatigue cracking within the Cessna 210 carry-through structure.
Textron also issued service letters calling for one-off inspections of carry-through spars on the strutless C210 and C177 aircraft.
The US Federal Aviation Administration (FAA) issued an Airworthiness Directive 21 February 2020 requiring visual and eddy current inspections of carry-through spar lower caps on certain models of C210 along with the application of a corrosion preventative coating.
The full report is on the ATSB website.