A Singapore A380 that misheard an air traffic control order to turn right and not left caused a 737 to fly too close to a smaller Dash 8 over Sydney Airport.
The ATSB investigation into the February 2020 incident said the crew of the Airbus made the mistake because they were experiencing a high workload caused by encountering a wind shear on descent.
A wind shear is a weather incident defined as a sudden change in wind velocity, which is particularly dangerous to aircraft at low altitudes, such as when approaching to land.
In response, Singapore issued a notice to its crew highlighting strategies to manage high workload situations.
The Singapore Airlines A380-841, 9V-SKQ, was operating a scheduled passenger service from Singapore to Sydney on 9 February 2020.
Its flight crew — comprising the captain as pilot flying and the first officer as pilot not flying — were briefed before and during the flight on the forecast of deteriorating weather at Sydney.
Cleared for an ILS (instrument landing system) approach to Sydney Airport’s runway 16 right, the A380 encountered wind shear while descending through about 1,000 feet.
In response, the flight crew initiated a missed approach and advised air traffic control that they were going around due to wind shear.
Air traffic control instructed the flight crew to turn right onto a heading of 270 degrees. The first officer read back the heading, however, did not include the direction of the turn, and ATC did not correct the incomplete readback. The flight crew then commenced turning the aircraft left instead of right.
Air traffic control subsequently issued a safety alert to the A380 flight crew, advised them of a Bombardier Dash 8 (DHC-8) aircraft about six nautical miles (11 kilometres) on final for runway 16 left, and instructed them to turn right and climb immediately.
Air traffic control then instructed the flight crew of the Dash 8 to make a right turn in order to maintain separation with the A380. This in turn resulted in a loss of separation between the Dash 8 and a Boeing 737, which was on approach to runway 16 right.
The minimum distance between the Dash 8 and 737 aircraft reduced to 2.6 nautical miles (4.8 kilometres) laterally and 1,300 feet (397 metres) vertically.
“The ATSB found that the A380 flight crew were likely experiencing a high workload managing a high-energy aircraft state as a result of conducting the wind shear recovery and missed approach,” said the ATSB’s acting director of transport safety, Kerri Hughes.
“This, in combination with an expectation that they would be turning left, contributed to the flight crew mishearing the ATC instruction to turn right.”
Hughes said the incident highlights the importance of readbacks to provide assurance that air traffic control instructions are correctly understood.
“The flight crew omitted the direction of the turn from their readback, which was not corrected by ATC. This was a missed opportunity to correct the misheard instruction,” she said. “This incident highlights the importance of flight crew completing full readbacks, as well as controllers correcting any readback discrepancies immediately.”
Singapore Airlines told Australian Aviation in response, “Singapore Airlines acknowledges the final report issued by the ATSB regarding an incident in Sydney on 9 February 2020.
“After an internal investigation into the incident, Singapore Airlines issued a notice to flight crew, highlighting strategies to manage high workload situations, as well as reiterating the importance of correct readbacks and acknowledgement from ATC.
“We will also share the final ATSB report with all crew for their learning and future awareness.”