British Aerospace Plc BAe 146-300 , VH-EWM

While flying a coupled instrument landing system (ILS) approach to runway 35 at Canberra, the crew received a ground proximity warning system (GPWS) "terrain" warning at 470 ft above ground level. As the aircraft was in visual conditions at the time, the crew elected to continue the approach.

The crew reported that, at the time of the warning, the aircraft was established on the ILS glideslope and descending at 650 ft/min. However, the T-VASIS indicated one dot low. Immediately prior to the warning, the radio altimeter indication rapidly increased, and then decreased, apparently triggering the warning.