Embraer EMB145 Operation Manual page 2004

FLIGHT CONTROLS
AIRPLANE
OPERATIONS
MANUAL
PITCH TRIM SYSTEM
GENERAL
Pitch trim is accomplished by an electrically-actuated movable
horizontal stabilizer. The system may be either automatically or
manually commanded. In both cases, the pitch trim signal is sent to
the Horizontal Stabilizer Control Unit (HSCU) channels, which after
processing it, command the electric motor in the Horizontal Stabilizer
Actuator (HSA).
SYSTEM COMPONENTS
Horizontal Stabilizer Control Unit (HSCU)
The Horizontal Stabilizer Control Unit (HSCU) is located in the rear
electronic compartment at the rear fuselage. It incorporates two
identical control channels, main and backup. These channel
operations are totally independent from each other. If the pitch trim
main channel is inoperative, the horizontal stabilizer can still be
commanded through the backup channel.
The HSCU controls the trimming rate (in degrees/second) based upon
the airplane airspeed. The trimming rate reduces as the airspeed
increases. The HSCU also checks the stabilizer surface position.
When the Takeoff Configuration Check Button is pressed, if the
surface is not within the takeoff green band limits, an aural warning
message is sounded to the crew.
Horizontal Stabilizer Actuator (HSA)
The Horizontal Stabilizer Actuator (HSA) consists of an
electromechanical actuator driven by two DC motors. One of the
motors is driven by the main control channel of the Horizontal
Stabilizer Control Unit (HSCU) and the other motor is driven by the
backup channel of the HSCU. Only one motor will be driven at a time.
Page Code
5 01
2-13-10
REVISION 38