The goal of this post is to show with simple use cases, how SyMAP technology performs real time predictive maintenance of airbus aircraft flight control system (FCS)
We start by presenting with Figure 1, flight control surfaces and 3 axes used by FCS, including roll axis, pitch axis and yaw axis. We show 3 use cases of SyMAP focusing on 3 primary surfaces: ailerons, spoilers and elevators.
Each surface is controlled by one or two actuators and each actuator is connected to one or two primary or secondary computers . For example, on Figure 2 , the left inband aileron is controlled by two actuators: one conventional actuator which is active during normal operation , and one EHA (Electro-Hydrostatic Actuator) which is damping during normal operation. The conventional actuator is connected to primary computer P1 and secondary computer S2, and to the backup control module (B) of computers. EHA is connected to primary computer P2 and secondary computer S2. Flight control surfaces are controlled as follows. A computer receives order from human pilot or auto-pilot, it computes a surface deflection order and send it to SV (Servo Valve) of conventional actuator or MDE (Motor Drive Electronic) of EHA. The feedback LVDT (Linear Variable Differential Transformer) gives the piston rod position of the actuator and computer fulfils the “inner” control loop.
Figure 2 shows how SyMAP can predict two successive faults related to one aileron (the left inband aileron) and propose two preventive actions to crew members in order to avoid that aircraft undergoes these failures even for a few moments. Conventional actuator of the left inband aileron is powered by green hydraulic system of the aircraft and EHA is powered by the alternative electrical current E2. When the green hydraulic power is lost, there is a protection mecanism which activates the EHA . But this protection mecanism takes few moments to make the reconfiguration. More over it is not always availaible since it can be faulty also. During these few moments, the aircraft undergoes the failure, i.e., the left inband aileron is no longer available and, the control of the aircraft along the roll axis during a turn becomes more complicated and therefore dangerous.
SyMAP is able to predict at time t, the green hydraulic lost at time t+T1, and propose to crew members to activate the EHA at time t+t1 such that t1 is between t and T1, but t1 is very close to T1. Doing so, SyMAP gives to pilot, the possibility to avoid that aircraft undergoes green hydraulic lost and left inband aileron lost during the small moment during which the protection mechanism inhibits the conventional actuator and activates the EHA. In the case where the protection mecanism is also faulty, SyMAP acts as a fault tolerance system of this protection mecanism.
Figure 2 also shows that, SyMAP can combine two predictions and propose an appropriate prevention action. Based on prediction 1 (green hydraulic lost) and prediction 2 ( E2 electrical source lost), i.e., the two actuators of the left inband aileron will be damping, so SyMAP propose right inband aileron inhibition to maintain aircraft equilibrium according to roll axis. Note that, in this use case , prevention actions will help crew members to avoid some consequences of green hydraulic lost or E2 electrical source lost, but SyMAP can also go beyond FCS to research and propose a preventive action in the hydraulic system or in the electrical system in order to avoid green hydraulic lost or E2 electrical source lost. Figure 3 and Figure 4 respectively show other SyMAP similar failure predictions related to left spoiler 7 and left inband elevator.