A problem with an electronic system prompted a Jetstar flight crew to make flawed manual calculations and exceed safety limits as they took off from Sydney.
They also failed to retract the landing gear when required, doing so after realizing it was the source of a buffeting noise.
A newly-released report by the Australian Transport Safety Bureau found that a Jetstar crew was preparing for a flight from Sydney to Melbourne in September 2018 when they experienced problems with the electronic system used to calculate take-off performance.
They reverted to a back-up procedure and calculated the information manually but in doing so inadvertently calculated take-off speeds that were too high and failed to identify them by independent verification and cross-checking.
This resulted in an incorrect pitch rate and acceleration that was higher than anticipated.
This result was a flap overspeed, an event where the aircraft exceeds a speed safety limit that could result in damage to the flap system.
“The aircraft did not rotate to the correct pitch attitude and the pilot monitoring did not alert the pilot flying of this,’’ the report said.
“However, he called ‘speed, speed’ in an attempt to assist the pilot flying manage the airspeed, to which the pilot flying reduced the engine power in response, rather than increasing the aircraft pitch.
“The action of reducing the engine power was taken when the aircraft was below the safe altitude above ground.
“The landing gear would normally be retracted by the flight crew as soon as the aircraft had a positive rate of climb.
“In this case, the crew did not retract the landing gear when required.
“Climbing through 2,800 ft, they identified that the landing gear was still extended while troubleshooting the source of a buffeting noise.
“They then immediately selected the gear to ‘UP’ without first checking the aircraft speed, resulting in a landing gear retraction overspeed event.”
Jetstar subsequently distributed a safety summary of the event to the wider pilot community and highlighted the importance of “reasonability and accuracy checks” as well as consulting the company procedure manuals in the event of issues with electronic systems.
“This incident highlights the importance of independent validation and cross-check by the flight crew, in particular for performance speeds and aircraft weight,” the ATSB said in its safety message.