An ATSB investigation report released today found that the pilot of a C210 flew too close to a developing thunderstorm, which resulted in the aircraft breaking up in flight.
C210N VH-TFT was on a charter flight from Gove to Katherine in the Northern Territory on Christmas Eve 2022 when it failed to arrive as scheduled. Searchers found aircraft wreckage the following day near Bulman in Arnhem Land. Both the pilot and the only passenger in the plane were killed in the crash.
Investigators found that the right wing had separated in flight after being substantially overloaded, most likely the result of coming into proximity with convective weather activity that preceded a thunderstorm.
“Weather satellite information showed the formation of a rapidly developing thunderstorm near to Bulman, during the time period the aircraft likely transited the region,” ATSB Chief Commissioner Angus Mitchell said.
“The aircraft likely entered an area of strong convective activity from the thunderstorm, subjecting it to severe turbulence and reducing visibility for the pilot.
“Why the pilot flew in close proximity to the storm could not be determined with certainty, however, it is possible that they were in the process of diverting or turning back when the break-up occurred and/or the severity of the storm was not apparent."
The Graphical Area Forecast (GAF) for the flight contained periods of low overcast, towering cumulus, thunderstorms, isolated cumulonimbus clouds from 2000 feet to above 10,000 and moderate turbulence below 10,000 feet.
ATSB investigators said the aircraft’s right wing had separated from the fuselage in flight, probably due to a combination of turbulence from the thunderstorm, airspeed above the aircraft manoeuvring speed, and control inputs.
The final report noted that it was the first time the pilot had flown during an NT wet season.
"In the context of Northern Territory aviation operations, most of the hazardous weather occurs during the wet season," the ATSB report states. "This is a period of unstable atmospheric conditions where tropical cyclones and active monsoon troughs may produce heavy rainfall for prolonged periods, squally winds, and thunderstorms."
Training in place at the operator at the time of the crash instructed pilots to avoid thunderstorms by 10 nm upwind or 20 nm downwind, but the ATSB was unable to determine if the accident pilot had applied those margins.
The full report is on the ATSB website.