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Final Report

Summary

What happened

On the evening of 9 May 2015, a Boeing B737-8FE aircraft, registered VH-YID and operated by Virgin Australia Airlines Pty. Ltd. (Virgin), was on a scheduled passenger service from Sydney, New South Wales to Adelaide, South Australia. During a high-speed descent, the crew responded to aircraft indications that they were approaching airspeeds greater than desired by extending the speed brakes. While the speed brakes were still extended, the airspeed continued to increase towards the aircraft’s maximum speed, the result of which would have been an overspeed. In an effort to prevent an overspeed, the first officer overrode the autopilot by pulling back on the control column until the autopilot entered a secondary mode known as control wheel steering‑pitch mode. This was followed immediately by an abrupt release of the control column, after which one cabin crew member sustained a minor injury.

What the ATSB found

The ATSB found that the crew selected a descent speed of 320 kt, which they routinely used for air traffic control-initiated high-speed descents. However, the increased risk of an overspeed in changing wind conditions had not been adequately considered by the crew.

The ATSB also found that, whereas Virgin’s training included a focus on the management of overspeeds, the crew had not yet completed this training. This increased the risk that the guidance provided through other sources would not be followed correctly.

Additionally, the flight crew had initiated the cabin preparation for landing earlier than usual due to the expectation of turbulence later in the descent. This likely reduced the risk of more serious injury to the cabin crew as they were in the final stages of securing the cabin than had they commenced preparations for landing at the normal time.

What's been done as a result

Prior to this occurrence, Virgin had implemented improved crew training and guidance on managing overspeeds. This included the addition of a cyclic simulator training session that focused on overspeed management on descent.

Safety message

This occurrence highlights the increased risk of overspeed when conducting high-speed descents in conditions of varying winds and any associated turbulence. Identifying and discussing the risks associated with high-speed descent increases the likelihood that crew will select a lower descent speed and/or consider the best way to deal with an impending aircraft overspeed before the descent is initiated.

The occurrence

Safety analysis

 
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