The Australian Transport Safety Bureau has determined that an RV-7A broke-up in mid-air because the airframe was overstressed after the pilot flew into IMC.
RV-7A VH-XWI was lost on 23 April 2021 south of Charters Towers on a private VFR flight from Winton to Bowen in Queensland. The pilot, the sole person on the aircraft, was killed in the crash.
VH-XWI was part of a four-plane touring group that was headed to Bowen; three flying IFR and XWI restricted to VMC.
The weather en route was considered to be adverse for VFR flight, and the flight path revealed manoeuvres consistent with the pilot trying to remain visual, including instances when the aircraft was likely not under control overhead Catumnal Station.
The ATSB believes the aircraft stalled at that time, resulting in the pilot recovering only 50 feet above the ground.
The pilot headed back towards Winton before later resuming a track for Bowen.
The recorded altitude on the resumed Bowen track varied between 10,000 feet and 500 feet, with sudden changes of bank angle, high rates of descent and large changes in airspeed recorded in the last minutes before the break-up.
The ATSB believes the pilot re-entered IMC and became spatially disoriented, leading to a loss of control that resulted in the airframe speed limitations being exceeded and the tail separating in flight due to rudder flutter.
Data recovered from the Dynon Skyview indicated a maximum speed during the last seconds of the flight of 224 knots. The Vne for the RV-7A is 200 knots.
“The ATSB found that the pilot departed Winton with a high risk of encountering adverse weather conditions along the planned route,” said ATSB Director Transport Safety Dr Mike Walker.
“There were no operational reasons for the pilot to continue the flight to Bowen, and the pilot probably had a self-imposed motivation or pressure to continue the flight.
“The ATSB urges VFR pilots to avoid flying into deteriorating weather by conducting thorough pre-flight planning to ensure you have alternate plans in case of an unexpected deterioration in the weather, and to pro-actively decide to turn back, divert or hold in areas of good weather.”
Pilots of the accompanying aircraft told the ATSB the weather had been discussed among the group before departing Winton, with one pilot offering to return to pick up the pilot of the RV-7A if the weather was not good enough for VFR.
The ATSB was not able to determine why the pilot decided to resume the flight to Bowen after initially losing control over Catumnal Station.
The full investigation report is available on the ATSB website.