The way Virgin Australia trains its rural turbo-prop pilots and the procedures it has for dealing with terrain warnings is under review by the ATSB as it continues an investigation into the conduct of a flight by one of its ATR 72s to Moranbah, Queensland, last May.
The pilots were surprised by thicker than expected cloud during the approach to the airport, and despite terrain proximity and configuration warnings, flew the 68 seat airliner down to 450 feet above the ground instead of maintaining an intended level of 1500 feet at that particular part of the flight path.
According to pilots who were asked about the update published by the ATSB today, it has ‘red flags’ all over it.
This is what the ATSB update says:
During the approach to the downwind position of the circuit, the crew observed a band of low scattered cloud and fog along the flight path. The crew reported that the cloud base appeared to be about 1,500 ft above ground level (AGL), which was their planned downwind altitude for the circuit.
As the aircraft approached 1,500 ft AGL the captain, who was the pilot flying, elected to continue descending the aircraft to remain clear of the cloud. The captain reported that, as the cloud appeared to be ‘sloped’ and he had visual reference with the ground, the aircraft could be flown visually under the cloud on the downwind leg.
It became apparent during the descent that the cloud was more extensive than expected and, in order to remain visual, the captain increased the aircraft’s rate of descent to about 1,900 ft/min until levelling below the cloud at a recorded altitude of about 450 ft AGL.
Recorded data identified that, during the descent, the aircraft’s terrain alert warning system (TAWS) activated a number of terrain proximity and aircraft configuration alerts to the crew. The crew reported that, as they were visual, the alerts were acknowledged and flight continued below the cloud base. They also reported that the height of the cloud base was difficult to judge due to the combination of the scattered cloud and the underlying fog.
Once past the low band of cloud, the aircraft was climbed to about 950 ft AGL before the captain turned the aircraft onto the base leg of the circuit. While on base, two TAWS ‘Don’t Sink’ alerts, which were based on a number of parameters including the degree of altitude loss and radio altitude, were annunciated to the crew. These alerts were acknowledged by the crew and, as the aircraft’s performance appeared normal, the approach was continued and the aircraft landed on runway 16.
This is an important inquiry. What has hunting for a cloud base that the pilots described as hard to judge, while ‘acknowledging’ but not acting on terrain, sink rate or configuration alerts, got to do with the safety culture of a major Australian airline?
The history of air crashes is full of incidents like this but where the ground found the airliner before it found the visibility that was being looked for.
The investigation is continuing and will include a review of the:
- operator’s standard operating procedures and pilot training relating to the conduct of approaches
- operation and performance of the TAWS
- operator’s management of TAWS alerts.
It is anticipated that the investigation report will be released to the public no later than April 2014.