RUDDER TRAVEL LIMITING The rudder travel limiting system modifies control inputs to the servo controls, to vary rudder travel in relation to airspeed (Vc). Limitation is such that the maximum deflection which can be achieved by the rudder remains lower than the deflection which would induce limit loads on the structure, throughout the flight envelope.
The system is composed of: • A variable stop unit consisting of an articulated lever operated by an electro-mechanica]. actuator, end a transducer unit detecting lever position. These items are all mounted on a frame assembly located downstream of the differential between the AP and yaw damper actuators. • Two control and monitoring computers designated FLC (Feel and Limitation Computer). • One RUD TRAVEL control panel, one PITCH FEEL & RUD TRAVEL maintenance panel and five electrical power supply circuit breakers.
The variable stop lever is operated by an electric actuator which consists basically of • Two AC motors, supplied with 26 V ,400 Hz • A single reducting gear actuated by both motors, which are rigidly connected. • A nut/screw system, driven by means of a torque limiter • Mechanical end of travel stops • A torque limiter provided to protect the reduction system from any abrupt jamming of the output shaft, particularly when it reaches the mechanical stop.
The actuator is servo controlled and is monitored through a transducer unit driven by variable stop lever movement. The transducer unit, comprising two inductive transducers is identical to the one used in the spoiler control system.
In the event of a rupture or disconnection of an actuator attachment a retention rod limits actuator movement to prevent it from jamming the variable stop lever. A spring returns the lever to the ‘low speed' position where full control deflection (÷ 30°) is possible.
Feel and limitation computer contains the circuitry required for two functions : Rudder travel limiting and pitch feel.
The FLC is a digital computer comprising two different computation channels: • Rudder travel limiting/pitch feel control channel • Rudder travel limiting/pitch feel monitor channel.
Safety of the systems is ensured by control and monitor channel programs which are intentionally different
Monitoring of digital computations which are performed by control and monitor channels with the same input data, achieved by comparison between the results of both channels, by mean of analog comparators.