Cockpit Control Confusion

The First Officer, who was Pilot Flying (PF), called the ground crew operating the towbarless pushback vehicle connected to the A319, to state that they were cleared for pushback and engine start. The ground crew called to release the brakes and the First Officer set the PARKING BRK handle to OFF. The flight crew completed the “Before Start” checklist and a few moments after the aircraft began to move, the First Officer called out “starting engine one”. The Captain acknowledged the First Officer’s call. The First Officer then inadvertently set the PARKING BRK handle to ON causing the aircraft to abruptly stop. The sudden stop caused the nose landing gear to jump out of the tow clamp of the towbarless pushback vehicle and it became lodged on top of the vehicle platform with the nosewheel deflected at more than 90 degrees (fig.1). Two cabin crew members, who were performing the safety demonstration at the time of the incident, received minor injuries. The passengers and crew exited the aircraft using steps positioned at the rear cabin door, with no further injuries.

During the engine start sequence, the PF inadvertently set the PARKING BRK handle to ON instead of setting the ENG MODE selector to IGN/START. Both controls are located on the pedestal. The PARKING BRK handle needs to be pulled, turned in the clockwise direction to ON, and released. The ENG MODE selector also needs to be turned in the clockwise direction to IGN/START. Both controls are used in the pushback and start sequence by either: (fig.2):

• Setting the PARKING BRK handle to OFF before pushback, and setting it back to ON when pushback is complete, and then setting the ENG MODE selector to IGN/START to start the engine, or
• Setting the PARKING BRK handle to OFF before pushback, then setting the ENG MODE selector to IGN/START to start the engine during pushback, and setting the PARKING BRK handle back to ON when pushback is complete.

Many pilots position their hand on the PARKING BRK handle without making any visual check before moving it as they know very well the specific shape of the PARKING BRK handle on the pedestal and the specific action of pulling and turning to move it.

The cockpit control confusion situation described in this article occurred in normal operational conditions. Situations that cause high workload, additional stress, and cognitive overload for flight crews can lead to human errors. This is, however, not necessarily the case for cockpit control confusion incidents. In these cases, it is not due to a lack of knowledge and skills of the flight crews. In fact, even the most experienced pilots on current type can experience cockpit control confusion and so there are other contributing factors.

Humans evolved by optimizing capabilities, and when a skill is acquired and frequently used in the same environment, the human brain creates routines. This human ability for pattern seeking and automatically performing actions allows us to preserve our brain’s cognitive resources, making it possible to focus on something else when performing routine actions. For example, flight crews can often perform instantaneous monitoring of the aircraft in normal flight conditions whilst communicating with air traffic control.

Behaviors based on routines, or so-called “skill-based behaviors”, are when humans perform automatic actions with low conscious control on how they are performing them. According to aviation human factors expert, James Reason*, there are two types of skill-based errors:

• Lapses: when an action is missed
• Slips: when an action is performed incorrectly

*Reason, James. Human error. Cambridge university press, 1990.

Inadvertently using a cockpit control instead of another in normal situations is a “slip”. Although performed incorrectly, the intention of the action was correct. The momentary absence of attentional control and active thinking when performing the action caused the error and it is not related to a lack of skills or knowledge.

Cockpit control confusion situations are often encountered on the most frequently used controls, because routines are more developed on those controls. This is why cockpit control confusion is more often observed with experienced pilots performing well-known procedures.

Other contributing factors for slips are fatigue, overconfidence, and momentary distractions such as pilot preoccupation or an unexpected interruption when performing a well-known sequence of actions or a flow pattern. Anticipation of the action is also a contributing factor. For example, when a pilot habitually rests their hand on the control before activating it, this indicates that the pilot’s mind is already committed to performing the next action with that control even if a different control action is called for. This can result in the inadvertent use of that cockpit control.

There are reported cases of confusion between the expedite (EXPED) pushbutton and the approach (APPR) pushbutton (fig.3). The EXPED and APPR pushbuttons are located next to each other on the FCU panel, and they have a similar shape and action to select.

Similarly on the A220 aircraft, there are reported cases of control confusion between the autopilot (AP) pushbutton-switch and the autothrottle (AT) pushbutton-switch. For more information about this example, refer to the Safety first article on “Inadvertent Autopilot Engagement During Takeoff on A220 aircraft”.

In the case of cockpit control confusion, a pilot performs a skill without conscious control over their action, therefore, even controls with different shapes and locations in the cockpit can still be confused. For example, there are reported cases of control confusion between the landing gear lever (located on the main instrument panel) and the flaps lever (located on the pedestal).

When a control is positioned closer for the pilot to reach, then it is more likely to be subject to cockpit control confusion. For example, when PFs are in the left seat they are more likely to experience a skill-based error or slip, related to the EXPED pushbutton, because it is located on the left side of the FCU panel. When Pilots Monitoring (PMs) are in the right seat they are more likely to experience cockpit control confusion related to the flaps lever because it is located on the right of the pedestal.

The lack of attentional control and active thinking when performing the action that caused the error is not due to the lack of skills or knowledge, and therefore, cockpit control confusion or slips, cannot be mitigated by conventional training.

Changing the design of a cockpit control that is very familiar to many thousands of pilots can be counterintuitive, and it is not possible to cover all cockpit control confusion cases.

The aircraft systems are very resilient to inadvertent use of cockpit controls, pilots will react quickly to correct their error, and there is often no operational consequence. It may not seem necessary for the flight crew to report the cockpit control confusion incident, but it is important to better understand the contributing factors and identify the possible mitigations. That is why it is so important for airlines to foster a speak-up culture and just and fair policy, that encourages pilots to report such events.

Reporting cockpit control confusion events, analyzing trends, developing best practices, and raising awareness among pilots is the most effective means of prevention. Some operators have reinforced this by creating additional callouts for their flight crews when carrying out routine tasks in the cockpit.

Recognized best practices are described in the Flight Crew Techniques Manual (FCTM) of all Airbus aircraft (A300-600, A310, A320 Family, A330/A340 Family, A380, A350, A220) in the “Cockpit Philosophy” chapter.

The main recommendations for flight crews are:

• Do not rest your hands on controls.
• Do not anticipate actions by putting your hands on the controls before you need to.
• Perform a visual check on the control before using it. Even if you are focused on the PFD you should look at the controls before using them.
• Check the result of the action, which is essential.
• Break the automated loop and raise the level of active thinking and attention. Use the standard callouts and use additional callouts, if necessary.

• During the Engine Start procedure, the PF points to the ENG MODE selector and calls “ENG MODE SELECTOR” before using it.
• Before using the flaps, the PM puts their hand on the lever and calls out “Flaps” before moving the lever and calling out the flap position.
• Before using the landing gear, the PM puts their hand on the lever and calls out “Gear” before moving the lever and calling out “Up” or “Down”.

These additional callouts reduced the number of inadvertent uses of the parking brake handle instead of the ENG MODE selector, and the inadvertent flaps selection or landing gear selection, by increasing the attentional focus of the flight crew. However, the risk remains that such “attention-getters” can also become routine.

Thank you to both easyJet and KLM for their contribution to this article. With effective speak-up cultures and just and fair policies, flight crews were empowered to report several incidents that were studied to better understand the circumstances that contributed to cockpit control confusion. This allowed for more precise and targeted recommendations to reduce the risk of cockpit control confusion for all flight crews.