Introduction
In September 2021, two separate incidents involving Virgin Australia Boeing 737 aircraft occurred at Darwin Airport, Northern Territory. On both occasions, flight crews planned and conducted displaced threshold approaches to runway 11, even though no displacement existed for that runway at the time. The opposite end, runway 29, had a displaced threshold due to ongoing works.
Incident Details
On 3 September 2021, a Boeing 737-8FE (registered VH-YIS) was operating a flight from Melbourne to Darwin. During the pre-flight briefing, the crew misinterpreted a NOTAM, believing that runway 11 had a displaced threshold. They subsequently planned the VOR-T displaced threshold approach. Air traffic control cleared them for the non-displaced VOR-Z approach, but the crew proceeded with their original plan and landed 1,153 meters into the runway.
On 19 September 2021, a Boeing 737-81D (registered VH-YFC) operated a flight from Brisbane to Darwin. Its crew similarly misinterpreted the NOTAM, concluding that both ends of runway 11/29 were displaced. They planned the VOR-T approach for runway 11, intending to await further information from the ATIS. They landed 932 meters into the runway.
Investigation Findings
The ATSB found that the flight crew of VH-YIS misinterpreted the NOTAM during pre-flight briefing, which led them to believe runway 11 was displaced. They continued the planned displaced threshold approach despite being cleared for the non-displaced approach by ATC. The crew omitted the suffix "Zulu" in their readback, and ATC did not request a correct readback, missing an opportunity to identify the error.
Similarly, the crew of VH-YFC misinterpreted the NOTAM, concluding both ends were displaced. The Flight Crew Operational Notice (FCON) used by the crew of VH-YIS stated that thresholds were displaced at separate times and directed them to refer to NOTAM. An updated FCON for VH-YFC provided information that only runway 29 was displaced, but the crew did not realize that the reduced length of runway 11 was due to works at the upwind end.
Both crews also misinterpreted the Darwin Airport recorded information (ATIS), which only referenced the runway in use (runway 11) and its reduced length but did not mention a displacement. No attempt was made to contact ATC for clarification on either occasion.
Safety Actions
After the first incident, Virgin Australia updated its Flight Crew Operational Notice to reflect that the Darwin Airport runway 11 works had been completed. After the second occurrence, the notice was further modified to specifically highlight the displaced thresholds.
Conclusion
Operational information in a NOTAM can have critical importance for flight planning and conduct. Misinterpretation can significantly affect flight safety. Correct and complete readback of ATC clearances is important to confirm understanding and provide a defense to detect and correct errors. When uncertainty exists about runway conditions, flight crews are encouraged to seek clarification from air traffic control.