On 10 May 2013, at about 2000 Eastern Standard Time, a Sunstate Airlines Bombardier DHC‑8‑402 aircraft, registered VH‑QOD (QOD), departed Townsville on a scheduled passenger flight to Cairns, Queensland.
About 20 minutes into the flight, the aircraft was in the cruise at FL 180 and flying in clear air when the aircraft encountered light turbulence. The captain immediately switched on the seat belt sign. A second later, the aircraft encountered abrupt severe turbulence.
The autopilot disconnected and the captain, as pilot flying, assumed manual control of the aircraft. The flight crew reduced the speed of the aircraft to below the turbulence penetration speed. The turbulence event lasted about 10 seconds, during which time the aircraft climbed about 400 ft above the cruising altitude. The flight crew then re-engaged the autopilot and returned the aircraft to the assigned level.
The weather radar did not show any significant weather for the entire flight. Both members of the cabin crew were standing when the aircraft encountered the turbulence and impacted the roof before falling to the floor. Both sustained head injuries and one was knocked unconscious.
The aircraft landed in Cairns about 20 minutes later, without further incident and the cabin crew were transferred to hospital.
In this event, all passengers were seated with their seat belts fastened, even though the seat belt sign had been switched off earlier. The fact that none of the passengers were injured highlights the benefits of keeping your seatbelt fastened during the flight.
Cabin crew are at greater risk of injury during turbulence encounters as they are moving around the cabin and not seated with a seat belt fastened.