internal shaft of the actuator and the associated pushrods and bellcranks without
powered assistance. More pilot force is required, but full movement of the flight
controls is attainable.
The autopilot is interfaced with the primary flight controls through electric servos
to move parallel cable linkages to the hydraulic actuators. Each flight control
surface has a Linear Variable Displacement Transducer (LVDT) that provides an
electrical signal proportional to flight control surface displacement from neutral.
The LVDT signal provides feedback to the autopilot for positioning the flight
controls, and also communicates control surface position for display on systems
and synoptic windows through interface with the Modular Avionics Units (MAUs).
The description of the Digital Automatic Flight Control Systems (autopilot) makes
up the entire content of Section 2B of this manual, and for that reason is not
covered in this Section. However, for the convenience of the reader, a tabulation
of the Crew Alerting System (CAS) messages associated with the autopilot is
included below.
The elevators and ailerons have trim tabs to position the flight controls with
aerodynamic forces to moderate the amount of physical effort to maintain the
control surfaces in the desired steady-state condition. The rudder is not equipped
with a trim tab, but instead has a mechanical trim input to reset the neutral
position of the rudder. The mechanical trim uses the hydraulic actuator to project
the rudder slightly into the windstream in the desired direction to compensate for
induced yaw.
The secondary flight controls and functions are:
• Wing flaps - enhance wing lift characteristics
• Flight and Ground Spoilers - reduce wing lift and add overall drag
• Movable horizontal stabilizer - aligns the elevator with aircraft angle of
attack
• Yaw damper - uses the autopilot rudder servo to moderate aircraft heading
oscillation
Some functions of the secondary flight controls are integrated with the operation
of the primary flight controls and other functions mutually complement the
operation of other secondary controls.
• As flaps extend, moving the wing center of lift aft, a downward pitch
moment is created - the moveable stabilizer automatically compensates for
the pitch moment by trimming downward. The opposite movement occurs
as flaps are retracted and the nose of the aircraft pitches up.
• When ailerons are used, flight spoilers on the downward wing activate to
increase roll rate and provide yaw into the turn. Ground spoilers decrease
ground roll distance during landings and aborted takeoffs.
• The yaw damper provides a degree of turn coordination for aileron roll
commands, provided wing flaps are not selected to more than thirty
degrees (30°).
Safety features incorporated into the flight controls system include:
• A stick shaker warning and a stick pusher stall prevention actuator.
• A gust lock that prevents damage to flight controls while the aircraft is
secured on the ground.
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS2A-27-00
Page 2
August 14/03
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