The ATSB’s ongoing investigation into a Boeing 737-800 flight incident south of Canberra Airport (CBR) reveals proactive safety measures taken by the operator.
The preliminary report details the event that occurred on June 13-14, 2024. The incident in question saw an arriving Batik Air flight from Bali accidentally descend below the published minimum altitude.
The Occurrence
Batik Air’s inaugural Denpasar-Canberra flight, operated by a Boeing 737-800, departed Indonesia on the evening of June 13.
Strong tailwinds had pushed the estimated arrival time forward to just before 0600 on the morning of June 14. This was earlier than planned, and meant the aircraft would arrive before Canberra’s air traffic control services began for the day.
The crew decided to proceed without waiting for air traffic services, opting to use Canberra Airport’s common traffic advisory frequency (CTAF) upon arrival. As they descended towards Canberra in darkness, they prepared for the AVBEG 5A standard arrival route (STAR).
ATSB Chief Commissioner Angus Mitchell noted, “The crew planned to fly the STAR but didn’t request this from the air traffic controller managing the airspace.” The controller had expected the aircraft to follow the previously cleared direct route to Canberra Airport from the AVBEG waypoint.
Following their planned route, the aircraft deviated from the cleared path, tracking a series of waypoints southwest and south of the airport. The controller, who was unaware of this plan, instructed the crew to maintain 10,000 ft to avoid a restricted area near Tidbinbilla.
Descent Outside Controlled Airspace
“This instruction led to crew uncertainty about operating within or outside controlled airspace during the arrival and approach,” Mitchell explained.
After leveling at 10,000 ft, the crew requested clearance for the instrument landing system (ILS) approach. They were informed that CTAF procedures applied due to Canberra tower’s closure.
Descending outside controlled airspace, the crew found themselves above the desired flightpath. The captain initiated a holding pattern at the MOMBI waypoint to reduce altitude. During this maneuver, the aircraft descended below the minimum holding altitude of 5,600 ft. At one point the aircraft passed just 924 ft above terrain.
A Canberra Tower controller preparing for duty observed the low-flying aircraft and attempted to contact the crew on CTAF without success. Simultaneously, the Canberra Approach controller issued a safety alert about the aircraft’s low altitude.
The crew, now visual with the runway, continued their approach and landed safely.
Safety Actions Following the Incident
Following the occurrence, Batik Air implemented several safety actions.
The Canberra Airport flight crew briefing document was revised to include more detailed information. This included holding requirements and guidance for adherence to lowest safe altitude requirements.
Internal flight crew notices were also issued to highlight the importance of a comprehensive approach briefing, adherence to air traffic control instructions and altitude awareness. Details of the Canberra incident were also disseminated to all flight crew. The airline then conducted a special flight crew briefing with event details and lessons.
Batik Air also adjusted the flight schedule for the Denpasar to Canberra flight (ID6015) to ensure that arrivals occur during Canberra Tower and Approach air traffic control operating hours.
Conclusion
The investigation will now examine Batik Air’s procedures, training, and route implementation processes, as well as air traffic control procedures and training.
Mitchell concluded, “While our final report is pending, we’ve noted the operator’s proactive safety actions. This has included revised airport briefing documentation, crew notices on non-controlled airspace procedures, and rescheduled flights to align with air traffic control hours.”
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