DUAL LINEAR ACTUATORS
Three sets of dual Linear Actuators provide limited control inputs to pitch, roll
and yaw axis flight control lines in series with pilot input (see chapter 67-00).
Each set is connected to the relevant axis flight control line through a dualaction
bellcrank and an anchor spring. The bellcrank permits the Linear
Actuator displacements to be summed with the pilot inputs. The anchor
spring permits the linkage from pilot control to the Servoactuators to keep
providing mechanical connection in case a Linear Actuator disconnects from
the linkage, pilot retains manual control on the failed axis since the anchor
spring reacts to the manual input as pivot point.
Each dual Linear Actuator set incorporates two identical and independent
electrical motors, one controlled by AP 1 and one controlled by AP 2 via
dedicated digital buses (CAN Bus).
They are also called “smart” linear actuators since they include a
microprocessor to internally close the servo loop on the position command
from the on-side MAU.
Each brushless motor drives a ball-screw which displaces the flight control
line.
Each linear actuator includes an integrity centering function to protect
against runaway failure modes.
During normal operation with both Autopilots engaged, each AP outputs
50% of the computed input for an axis.
In case of single AP operation, 100% of the computed input is provided to
the on-side Linear Actuator: in this case the total authority of the control is
reduced to a half, resulting in a degradation of the system performance.