An Australian Cessna Centurion had a catastrophic failure in 2019
ATSB investigated, issued probable cause and FAA issued ADs
Recent ATSB recommendation added concern- not noted in most recent AD
In an interesting intergovernmental action, the Australian government has issued a “warning” about a defect in a US certificated aircraft.
This is actually a step in an ongoing review of a Cessna P-210. In response to the original accident, the FAA issued Docket No. FAA-2020-0156,AD 2020-03-16, requiring:
“…visual and eddy current inspections of the carry-thru spar lower cap, corrective action if necessary, application of a protective coating and corrosion inhibiting compound (CIC), and reporting the inspection results to the FAA.”
The FAA on May 11, 2021, issued a subsequent AD and requested comments on the new proposed safety requirement. The docket includes 123 comments, including a submission by EASA, but nothing from the ATSB. Some of the comments requested withdrawal of the proposed AD.
On November 23,2021 Australia Transport Safety Board issued this report—
In 2019 a Cessna P-210, a Cessna Aircraft Company T210M, registered VH-SUX and operated by Thomson Aviation, departed Mount Isa Airport for an aerial geophysical survey flight with a pilot and observer on board.
One hour and 40 minutes later, as the aircraft was flown west along a survey line about 25 km north‑east of Mount Isa Airport, the right wing separated from the aircraft. The structural failure led to a rapid loss of control and a collision with terrain. Both crewmembers were fatally injured, and the aircraft was destroyed.
The ATSB found that a pre-existing fatigue crack in the aircraft’s wing spar carry-through structure propagated to a critical size resulting in an overstress fracture of the structure and separation of the right wing.
Detailed examination of the structure found that relatively minor corrosion near a highly stressed location on the lower surface of the wing spar carry-through progressed into the aluminium alloy structure. This increased stress concentration in this area and led to initiation and growth of a fatigue crack, significantly reducing the strength of the structure.
In 1992, the aircraft manufacturer introduced a recommended continued airworthiness program, including a flight hour‑based repetitive eddy current inspection for cracking of the carry-through structure. This program included more stringent requirements for aircraft being used for low-level survey flights. However, following an assessment of historical data in 2011, the manufacturer replaced this inspection with a three-yearly visual corrosion inspection for all operation types, which was mandatory in Australia. This inspection variation significantly limited the opportunity to identify fatigue cracking within the carry-through structure of low-level survey aircraft prior to failure.
The ATSB also found that the cyclic loads induced by the low-level survey flight profile were significantly greater than those associated with the higher-level flight profile originally intended for the aircraft type. This probably increased the risk of a fatigue related structural failure.
As described in the below extensive article, the ATSB now recommends that Textron take further action.
Two observations make this ATSB pronouncement unusual: (i) curious why the Board did not submit this note to AD 2020-03-16 so that the FAA might incorporate the Australian perspective and (ii) what caused the ATSB to issue this recommendation. The release does not mention any new facts or assessments which stimulated this additional action.
Australia’s Air Transportation Board (ATSB)says a fatal crash involving a in 2019 likely would have been prevented if Cessna hadn’t relaxed inspection requirements for the wing spar carry-through structure on the aircraft eight years previously. The aircraft in question was being flown daily by a geophysical survey company when the beam broke, a wing separated, and the pilot and passenger were killed. The plane was flown a lot and racked up an average of more than 1,000 hours a year in the previous six years and that was a factor in the crash according to the ATSB.
In 1992, Cessna began requiring regular eddy current and visual inspections of the spar based on hours flown but in 2011 it determined that historical data justified changing the requirement to inspections every three years. “Had the previous flight-hour based eddy current inspection schedule remained in place, it is almost certain that the fatigue crack within the wing spar carry-through would have been detected before this accident occurred,” ATSB Chief Commissioner Angus Mitchell said. After the Australia crash, Textron, which owns Cessna, issued service bulletins requiring immediate inspections of the carry through structure and the FAA followed up with an AD but the three year schedule for subsequent inspections remained.
“The ATSB acknowledges the significant safety actions taken to date by the manufacturer and regulators as a result of this accident and the ATSB’s investigation, and notes that these measures have addressed the short-term risk of further similar failures,” said Mitchell. “Further, the ATSB welcomes Textron’s ongoing efforts to address the risk of cracking in wing spar carry-through structure of Cessna 210 aircraft used for low-level geophysical survey operations. However, the ATSB remains concerned by the indefinite nature of the manufacturer’s proposed analysis and certification program and recommends that further action be taken to address this safety issue.”
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