On 28 May 2008, a Boeing Company 737-5U3 (737) aircraft, registered PK-GGE was being operated on a scheduled passenger transport service from Jakarta, Republic of Indonesia to Perth, WA. The flight was conducted under the Instrument Flight Rules (IFR) and Perth Airport was affected by low cloud, rain showers and reduced visibility during the aircraft's arrival.
Shortly after clearing the flight crew to make an instrument landing system (ILS) approach to runway 21, the approach controller assessed that the required separation between landing aircraft was not going to be maintained and cancelled the approach clearance. The controller instructed the crew to maintain 2,500 ft, which was the radar minimum vector altitude (MVA) in that area, and to expect radar vectors for an ILS approach to runway 24. Subsequently, while being radar vectored, two-way communication between the controller and the crew ceased.
The late notice change of approach and landing runway represented a significant increase in workload for the crew, and the investigation concluded that the crew probably inadvertently deselected the approach radio frequency soon after being issued a radar vector for the amended approach and landing.
The crew did not follow the published loss of communication procedure, which resulted in the aircraft operating below the published 25 NM (46 km) minimum safe altitude and below the relevant MVA in instrument meteorological conditions (IMC) for just over 1 minute. There were no warnings or alerts from the aircraft's enhanced ground proximity warning system (EGPWS) during the flight, and the aircraft was not less than 1,421 ft above terrain during the loss of communication.
As a result of this incident, the aircraft operator undertook a number of safety actions. Those actions sought to enhance the operator's operations into Australia, and to review the procedures in the case of a communications failure with air traffic control.