French investigators believe the occurrence of dual-input situations, in which both pilots simultaneously operate the flight controls, is underestimated and should be monitored more closely.

This phenomenon had previously been associated with aircraft fitted with independent sidesticks, such as the current Airbus range, where the location of the sidestick and the absence of physical feedback means each pilot can experience difficulty perceiving the other’s actions.

But French investigation authority BEA says “several events” in recent have demonstrated that dual-input issue “also exists on aircraft with conventional flight controls”.

“The consequences can be significant,” it adds.

BEA highlights three incidents, each of which involved desynchronisation of the pilots’ control columns after the captain intervened “in the face of a danger deemed imminent”

These included an Air France Boeing 777-300ER go-around at Paris in April 2022, when the captain applied nose-down input to counter the first officer’s pitch-up command. Both pilots simultaneously acted on the controls for 53s including 12s of desynchronisation.

Just a day earlier a serious incident occurred to an Air Tahiti ATR 72 in French Polynesia, when the captain made control inputs to avert a hard touchdown during an unstable approach. BEA states that, unlike the 777, control desynchronisation on the ATR is irreversible.

BEA also refers to another ATR 72 event during descent to Sydney in February 2014. The Virgin Australia aircraft experienced a rapid increase in speed after encountering windshear, and the captain took the controls without declaring his intention – with the result that the first officer made opposite inputs, and exceeded the aircraft’s load limits.

Airbus analysis has previously identified that dual inputs can result from ‘involuntary’ and ‘comfort’ actions, which usually have limited effect, but also from ‘instinctive’ actions which are more significant.

The 777 and ATR events all arose from instinctive actions, says BEA, and desynchronisation risks following an imprecise – or perhaps unstable – trajectory.

Prevention of simultaneous piloting on certain aircraft types is based solely on the principle of announcing the assumption of control, it says.

“This principle remains fragile in dynamic and stressful situations,” it adds. “The aircraft concerned generally do not have a visual or audible alarm to alert that simultaneous actions on the flight controls are in progress.”

After the 777 incident Air France implemented monitoring for dual input on its 777s and 787s. BEA says it recorded a rate of 0.4 per 1,000 flights on 777s, a similar figure to the 0.44 on its Airbus fleet.

“The values are therefore comparable, while the reporting rate by pilots is not,” says BEA, adding that the Airbus dual-input cockpit alert “encourages reporting”.

BEA believes the frequency of such events is “underestimated” and that, to improve crew awareness, simultaneous piloting events should be monitored regardless of the flight-control configuration of the aircraft type.