The FFM was developed as a result of the suspected rudder hardover incidents but it does not detect a rudder hardover. The maintenance manual says it “finds opposite pressure on the A and B sides of the tandem actuator”, yet on the schematic it is shown as a “Delta P sensor” which suggests it reacts to any difference (rather than opposite force) in hydraulic pressure, much like the elevator feel diff pressure system. Either way, once triggered it starts the standby rudder PCU which should resolve the problem.