Controlled flight into terrain - Lake Liddell, New South Wales, on 7 December 2007, Air Tractor AT-802, VH-LIS

On 7 December 2007, the pilot of an Air Tractor Inc. AT-802 aircraft, registered VH-LIS, was conducting a test flight at Lake Liddell, NSW. The purpose of the flight was to test an experimental in-flight water collection system using skis attached to the aircraft's main landing gear.

At about 0910 Eastern Daylight-saving Time, the pilot was conducting the second test run of the day. After the aircraft skis had been in contact with the surface of the lake for 36 seconds, witnesses observed the aircraft pitching nose down, about its right main landing gear while rotating to the right. The aircraft then overturned and sank. The aircraft was substantially damaged and the pilot was fatally injured.

The investigation concluded that the right experimental ski breached the surface of the water which caused a substantial amount of drag to act on the right side of the aircraft, as a consequence, the aircraft became uncontrollable. The circumstances of this accident highlight the need for due diligence and detailed risk assessments to be performed as part of experimental test programs.

As a result of this incident, the Civil Aviation Safety Authority (CASA) has proposed amendments to Advisory Circular 21-10 - Experimental Certificates to provide:

• updated guidance information to persons applying for the issue of experimental certificates
• advice on risk management for test pilots during experimental flight testing.

In addition, the Australian Transport Safety Bureau (ATSB) issued a safety recommendation to CASA in respect of the need to consider the safety of third parties, including on the ground or water, before issuing a Special Certificate of Airworthiness.