Runway excursion, VH-UZD, Thangool Aerodrome, Queensland, on 12 February 2008

On 12 February 2008, a Fairchild Industries SA227-AC (Metro III) aircraft, registered VH-UZD, was being operated on a freight service between Emerald and Thangool, Queensland with two pilots. The approach and landing into Thangool were conducted after last light in conditions of scattered low cloud and rain showers. At a speed of about 40 kts after touchdown, the aircraft suddenly veered uncontrollably to the right, departed the runway and became bogged in wet grass.

There was no damage to the aircraft or injuries to the flight crew.

The investigation determined that the runway excursion was probably a result of a directional upset at a time when the nosewheel was in castor mode. The reason for the nosewheel being in the castor mode could not be determined with certainty and may have been the result of an intermittent fault or the inadvertent failure by the flight crew to arm the system.

It was also determined that the aircraft's rate of descent during the latter stages of the approach was significantly higher than for a normal stabilised approach. In addition, the aircraft operator's stabilised approach criteria did not provide flight crew with information on maximum permitted rates of descent. The aircraft operator has advised that, as a result of the investigation, it has redefined its stabilised approach criteria.