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Summary

Summary

On 31 July 2007, a Rockwell International Aero Commander 500-S, registered VH-YJB, departed Essendon Airport, Vic. on a business flight to Shepparton that was conducted at night under the instrument flight rules (IFR). On board were the pilot and one passenger. At 1958 Eastern Standard Time, while in the cruise at 7,000 ft above mean sea level in Class C controlled airspace, radar and radio contact with the aircraft was lost when it was about 25 NM (46 km) north-northeast of Essendon.

The wreckage was found in the area of the last radar position and both occupants had been fatally injured. At the time, special weather reports for severe turbulence and severe mountain waves were current for that area. Wind speeds on the ground were reported to be 50 kts. Calculations made using the recorded radar data and forecast wind showed that the aircraft had been in cruise flight at speeds probably greater than its published manoeuvring speed, prior to disappearing from radar.

The wreckage and its distribution pattern were consistent with an in-flight breakup during cruise flight. The breakup most likely resulted from an encounter with localised and intense turbulence, or from an elevator control input, or from a combination of both. As a result of its investigation, the Australian Transport Safety Bureau reissued the publication Mountain Wave Turbulence (available for download at www.atsb.gov.au), distributed the investigation report to all Australian operators of the Aero Commander aircraft, and issued a safety advisory notice to aircraft operators and pilots. That notice encouraged aircraft operators to review their procedures to ensure an appropriate awareness amongst operating personnel of the implications for aircraft performance of the combination of aircraft weights and speed, and of the ambient conditions; in particular, when flying in, or near areas of forecast severe turbulence.

 
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