Ground proximity warning events on the Lockhart River Runway 12 RNAV (GNSS) non-precision approach

During the Australian Transport Safety Bureau investigation into the accident at Lockhart River, Qld on 7 May 2005, involving the Metro 23 aircraft registered VH-TFU, it was established that it was possible to receive ground proximity warning system (GPWS) warnings while conducting the Runway 12 RNAV (GNSS) non-precision approach, even when the aircraft was on the correct profile and track. After several reports of crews receiving such warnings, an investigation into the potential safety implications of these 'nuisance' warnings' was commenced. It was found that nuisance warnings could condition flight crews to ignore the warnings in order to complete the approach procedure, rendering the warning system ineffective in preventing controlled flight into terrain.

The safety issue identified as a result of this investigation related to the generation of 'nuisance' GPWS warnings while conducting the Runway 12 RNAV (GNSS) non-precision approach at Lockhart River. Airservices Australia have commenced designing a revised approach using new approach design criteria, and the Civil Aviation Safety Authority has undertaken to flight validate the revised approach when available.