Dual Input
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Dual Input
I only thought Airbus design with un-coupled side sticks was subject to this sort of problem - but I was wrong.
Serious incident to the BOEING - 777 - 300ER registered F-GSQJ on 5 April 2022 at Paris–Charles de Gaulle.
F-GSQJ_finalreport
"The two pilots then simultaneously made inputs on the controls for 53 s. The pitch controls were desynchronized for 12 s due to opposing forces. Two brief episodes of roll desynchronization were also observed. After recovering control of the flight path, the crew carried out a new approach to runway 27R without further incident. "
"2.4 Knowledge and perception of system
The investigation revealed that crews had little knowledge of the breakout mechanisms. A certain number of pilots were aware of the existence of this system and often only associated it with a jammed control. The description of the system in the FCOM was limited to an explanation about the risk of a control jamming.
The manufacturer's and operator's documentation did not explicitly mention the effects of simultaneous actions on the controls, and this point was not covered in training. This might be explained by the fact that the flight control system on this aeroplane links the left-side and rightside controls, providing each pilot with both tactile and visual indications of the other pilot's inputs. The possibility of simultaneous inputs on the controls thus seemed to be considered marginal on aeroplanes with conventional flight controls. Operators did not seem to systematically monitor for simultaneous control inputs in their flight analyses.
However, the operator's post flight analysis showed a dual input rate of 0.4 per 1,000 flights on the Boeing 777. This rate is comparable to that reported on the operator's Airbus fleet.
The documentation provided to the pilots did not therefore allow them to reasonably envisage that, in the event of antagonistic control inputs exceeding the breakout mechanism's activation threshold, the controls would be desynchronized and the control surface would react according to the mean control positions. The behaviour of the aeroplane during this phase of simultaneous control inputs could not be anticipated.
Tests carried out on the AP0 simulator showed that pilot perception on control input response may become different during the control desynchronization phase due to altered sensitivity and nonlinear response in the controls. Some pilots who carried out the tests described it as difficult to anticipate what the other pilot was doing, while others would immediately recognize the desynchronization and call for one pilot on the controls to regain synchronization. Moreover, the FCTM warned that the jamming of controls is a difficult situation to identify.
However, the tests showed that as soon as one of the two pilots called out “you have control” and released the control, accurate pilot perception of control response returned instantly with synchronisation."
Serious incident to the BOEING - 777 - 300ER registered F-GSQJ on 5 April 2022 at Paris–Charles de Gaulle.
F-GSQJ_finalreport
"The two pilots then simultaneously made inputs on the controls for 53 s. The pitch controls were desynchronized for 12 s due to opposing forces. Two brief episodes of roll desynchronization were also observed. After recovering control of the flight path, the crew carried out a new approach to runway 27R without further incident. "
"2.4 Knowledge and perception of system
The investigation revealed that crews had little knowledge of the breakout mechanisms. A certain number of pilots were aware of the existence of this system and often only associated it with a jammed control. The description of the system in the FCOM was limited to an explanation about the risk of a control jamming.
The manufacturer's and operator's documentation did not explicitly mention the effects of simultaneous actions on the controls, and this point was not covered in training. This might be explained by the fact that the flight control system on this aeroplane links the left-side and rightside controls, providing each pilot with both tactile and visual indications of the other pilot's inputs. The possibility of simultaneous inputs on the controls thus seemed to be considered marginal on aeroplanes with conventional flight controls. Operators did not seem to systematically monitor for simultaneous control inputs in their flight analyses.
However, the operator's post flight analysis showed a dual input rate of 0.4 per 1,000 flights on the Boeing 777. This rate is comparable to that reported on the operator's Airbus fleet.
The documentation provided to the pilots did not therefore allow them to reasonably envisage that, in the event of antagonistic control inputs exceeding the breakout mechanism's activation threshold, the controls would be desynchronized and the control surface would react according to the mean control positions. The behaviour of the aeroplane during this phase of simultaneous control inputs could not be anticipated.
Tests carried out on the AP0 simulator showed that pilot perception on control input response may become different during the control desynchronization phase due to altered sensitivity and nonlinear response in the controls. Some pilots who carried out the tests described it as difficult to anticipate what the other pilot was doing, while others would immediately recognize the desynchronization and call for one pilot on the controls to regain synchronization. Moreover, the FCTM warned that the jamming of controls is a difficult situation to identify.
However, the tests showed that as soon as one of the two pilots called out “you have control” and released the control, accurate pilot perception of control response returned instantly with synchronisation."
This BEA report is also being discussed under the original thread for this incident, here:
Air France B777 control issues landing CDG
Air France B777 control issues landing CDG
