Aircraft Yaw Damping System Overview

Yaw Damping

• Yaw damping is provided on some aircraft to improve directional stability and turn co-ordination.
• The hydraulic yaw damper actuator automatically compensates for yaw caused by side air-loads by generating rudder control inputs.

Yaw Control

• Yaw control is provided by a single-piece rudder actuated by three independently supplied hydraulic servo-jacks.
• The servo-jacks are signalled via interconnected pedals by a single cable run up to a spring-loaded artificial feel unit connected to the trim screw-jacks.
• The commands are transmitted by a single load path linkage fitted with a centring spring device.
• This device holds the servo-jack inputs in the neutral position should a disconnect occur.
• Rudder travel is limited as a function of air speed (CAS).
• Yaw dampening is operative throughout the whole flight envelope.
• Yaw damper commands are transmitted via a differential unit.
• Yaw stability augmentation orders are delivered by the Flight Augmentation Computer (FAC).

Gust Lock System

• The gust lock system locks the primary control surfaces in the neutral position for taxiing, parking, or mooring the aircraft.
• The system consists of forward and aft installations that are electrically connected for operation by a single lever on the flight compartment centre console.
• The forward installation locks the aileron and elevator surfaces.
• The aft installation, which includes an electrical actuator, locks the rudder.
• Each installation incorporates a weight switch controlled solenoid lock (snib).
• The snib in the forward installation prevents selecting controls LOCKED in flight.
• The snib in the aft installation prevents locking of the rudder if its associated gust lock actuator is subjected to spurious electrical signals.