Inadvertent rudder trim input led to VA 737 in-flight upset

[33kft]

The ATSB have just released a report into an incident on 6 Sep 2023 involving VA aircraft VH-YQR, which resulted in a Minor injury to cabin crew. A summary from the ATSB press release and link to the report is below.

A pilot of a Virgin Australia Boeing 737 inadvertently input full left rudder trim when they intended to activate the flight deck door switch, resulting in an in-flight upset and a cabin crew member sustaining a minor injury, an ATSB investigation report details.

The incident occurred as the aircraft was approaching cruise altitude on a September 2023 flight from Brisbane to Melbourne, when the flight crew received a call from a cabin crew member requesting entry to the flight deck.

After completing security procedures, the captain, who was pilot monitoring, visually identified the flight deck door switch, then reached across to activate it.

“As they reached for the switch, the captain looked up from the switch to the flight deck door, and then inadvertently grasped and activated the rudder trim control instead,” ATSB Chief Commissioner Angus Mitchell said.

In-flight upset involving Boeing 737-8FE, VH-YQR, 143 km west of Ballina/Byron Gateway Airport, New South Wales, on 6 September 2023 | ATSB

www.atsb.gov.au

 

[Quickstatus]

It is not so different to the YT691 crash where the pilot pulled the propellor feather lever rather than the flaps level, especially when they are adjacent to one another, peripherally, appear similar and the muscle action is similar - pulling in the same direction for example.

There is something similar in anaesthesia delivery systems.
There is an oxygen knob and a nitrous oxide knob - they are adjacent to one another.
There have been mistakes where the nitrous oxide (laughing gas) knob is turned instead of the O2 knob - such that no oxygen is given despite a belief that the patient is receiving oxygen. Subsequently due to these errors, additional measures were instituted such as making the knobs different in colour, diameter and tactile feel. Also the nitrous cannot be turned to 100% nitrous oxide (meaning 0% oxygen) because a failsafe gear will also turn the oxygen knob when the nitrous oxide knob is turned such that the minimum O2 can never be less than 21%. And then there are oxygen sensors which alarm when O2 levels fall below a minimum. And a final failsafe alarm which does not rely on power but oxygen pressure -when oxygen pressure drops off (meaning no oxygen supply is below critical levels, the alarm will sound.

Similarly, drug vials can look similar and there have been numerous wrong drug given because the wrong vial was used because they appeared the same and next to another similar vial of a different drug despite the label being not the drug. That is why the potassium chloride (can stop the heart) vial is printed in red whereas the saline vial is in green (cannot stop the heart), and they are kept in completely separate locations.

Medical gas cylinders have unique pin indexing systems which are supposed to prevent it being connected to non matching gas systems. CO2 and nitrous oxide cylinders cannot be connected to O2 gas lines for example or vica versa. Though there have been examples of people cutting the hardened steel pins so they do connect - it is possible with enough effort to make a square peg fit into a round hole.

Many car accidents have been caused by people pressing on the accelerator rather than the brake.

Human error happens and will continue to happen, and it is not always the pilot/dr/nurse fault. More often than not, there are other systemic factors at play which create the latent conditions in which these errors can happen - to the extent that the operator can look at the knob and think it is something else other than what it is.