Aviation safety investigations & reports

Overspeed and pitch up resulting in cabin crew injury involving Boeing 737, VH‑VUE, 42 NM ESE Adelaide Airport, South Australia, on 13 September 2017

Investigation number:
AO-2017-092
Status: Completed
Investigation completed
Phase: Final report: Dissemination Read more information on this investigation phase

Final Report

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What happened

On 13 September 2017, the crew of a Boeing 737, registered VH-VUE and operated by Virgin Australia, were flying a scheduled passenger flight from Melbourne, Victoria to Adelaide, South Australia. Shortly before top of descent, air traffic control instructed the crew to perform a high-speed descent. The crew commenced descent with the first officer as pilot flying and the autopilot engaged, and intended to target a descent speed of 320 kt, which was higher than the normal descent speed of 280 kt.

During the descent, the first officer attempted to manage airspeed fluctuations by using changes in the autopilot modes and reductions in the target airspeed. As the aircraft descended through around 17,000 ft, the tailwind affecting VUE decreased suddenly and significantly. The reduction in tailwind caused the indicated airspeed to increase and approach the maximum operating speed limit of 340 kt.

The captain responded to the sudden increase in airspeed by abruptly pulling back on the control column, causing the autopilot to disconnect. The resulting control forces caused sudden changes to the aircraft’s pitch attitude and vertical acceleration. Two cabin crew who had been standing in the rear galley were injured, with one sustaining serious injuries.

What the ATSB found

The ATSB found that a sudden reduction in tailwind caused the airspeed to increase towards the maximum operating speed. The safety implications associated with this event related to the captain’s sudden control inputs to prevent an overspeed, and the consequent effects of vertical acceleration on the aircraft and its occupants. Although there was a resulting one knot overspeed from the sudden speed increase, it was not by an amount that required any structural inspections to ensure the ongoing airworthiness of the aircraft, according to the guidance provided by the aircraft manufacturer.

Even though the autopilot was operating correctly, when the aircraft was approaching and exceeding the maximum operating speed, the captain’s perception was that the autopilot was not controlling the aircraft and that urgent intervention was necessary. However, the captain did not follow the normal procedure for taking over control of pilot flying duties. The large pitch control inputs made by the captain were probably influenced by the captain’s perception of urgency.

The ATSB also found that the captain was highly concerned about avoiding an overspeed. This was partly because of a perception that Virgin Australia were also concerned about overspeed and wanted to avoid overspeed events, and partly because of a perception that minor overspeeds had significant implications for the safety of the aircraft. These factors contributed to how the captain responded to the sudden increase in airspeed towards the maximum operating speed.

The crew identified the risk of overspeed earlier in the descent, but did not discuss how they would manage that risk. This reduced the pilots’ ability to effectively respond to the overspeed situation, and probably contributed to the rapid, reflexive nature of the captain’s control inputs.

What's been done as a result

Virgin Australia have updated the training and information provided to pilots about overspeed and overspeed recovery. The intent of these actions was to reinforce the correct overspeed recovery technique, and to provide a greater opportunity for pilots to understand the negative safety implications of manual inputs to correct a minor overspeed. These actions have included an animation showing pilots mishandled and correct overspeed recoveries, and an update to manuals which explains that the 737 has been flight tested at speeds above VMO.

Virgin Australia have also changed procedures for ground handling staff when responding to requests from emergency services.

Safety message

During this accident, the pilots accepted and targeted an air traffic control instruction to conduct a high-speed descent. Due to increased kinetic energy and reduced margins to placard speed limits, high-speed descents involve a higher level of risk, including increased risk of harm due to abrupt control input. Pilots are entitled to decline air traffic control instructions where they do not perceive they can safely comply.

This accident highlights the challenges pilots face when responding to sudden or unexpected situations. There will often be a reduction in safety when pilots perceive a situation is urgent and when they make decisions rapidly and reflexively. In these situations, pilots may not be able to effectively process information or make good decisions.

Wherever possible, pilots should take the opportunity provided in an earlier stage in flight to identify risks and take steps to reduce the likelihood of a critical situation developing. Potential threat identification and planning for their management should also involve considering, as a multi-person crew, what the implications of a perceived risk might be, and how to respond if the threat does develop. By taking steps in an earlier stage in flight, pilots can improve their ability to respond effectively to threats. The Federal Aviation Administration Aeronautical Decision Making material provides pilots with accessible guidance on these concepts.

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The occurrence

Context

Safety analysis

Findings

Safety issues and actions

Sources and submissions

Appendices

General details
Date: 13 September 2017   Investigation status: Completed  
Time: 1659 CST   Investigation level: Defined - click for an explanation of investigation levels  
Location   (show map): 78 km ESE Adelaide Airport   Investigation phase: Final report: Dissemination  
State: South Australia   Occurrence type: Control issues  
Release date: 30 September 2020   Occurrence category: Accident  
Report status: Final   Highest injury level: Serious  

Aircraft details

Aircraft details
Aircraft manufacturer The Boeing Company  
Aircraft model 737-8FE  
Aircraft registration VH-VUE  
Serial number 34167  
Operator Virgin Australia Airlines  
Type of operation Air Transport High Capacity  
Sector Jet  
Damage to aircraft Nil  
Departure point Melbourne, Victoria  
Destination Adelaide, South Australia  
Last update 30 September 2020