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IC trim functions (IC controller/monitored primary trim, configuration
trim, and Mach trim) are all disabled in this case. When in bypass trim,
the primary trim actuator operates at only two speeds (high or low).
The speed depends on flap position. Dual flap position inputs are provided
to the actuator electrical box to maintain redundancy. If the flap
signals do not agree, the rate of trim function is limited to slow speed.
Both flap signals must agree and must indicate flaps are greater than 3°
for the actuator to operate at a high rate. When the flaps are up (<3°),
primary bypass trim will be at a slow rate. The primary trim actuator
continues to monitor for uncommanded trim and incorrect trim direction
in the bypass trim mode. It also monitors for the correct trim speed
based on flap position. If it detects a failure in any of these areas, primary
trim is disabled and a fail CAS is displayed.
The following CAS illuminations are specific to the primary pitch trim:
CAS Color Description
PRI TRIM FAIL Amber The primary pitch trim system has failed.
PRI TRIM FAULT White The Integrated avionics Computer (IC)
detects a fault in the primary pitch trim
system.
Pilot’s Manual
5-18 PM-126A
SECONDARY PITCH TRIM
Secondary pitch trim is electrically independent of the primary trim,
configuration trim, and Mach trim. In the event of primary trim failure,
secondary pitch trim is available as a backup means of trimming the
airplane in the pitch axis. The autopilot also uses the secondary trim actuator
as a normal means of trimming in the pitch axis. The autopilot
can use the secondary trim actuator with the trim selector in the PRI or
SEC position.
The dual-segment SEC trim switch (Figure 5-4) is located on the center
pedestal. Manual activation of secondary trim requires that the pitch
trim selector be in the SEC position and that both segments of the
spring-loaded SEC switch be moved at the same time. When SEC position
is selected, a CAS is displayed.
The secondary pitch trim actuator has a monitor function similar to the
primary actuator. It performs a power-up check and if any faults are detected,
a fault is displayed on the CAS, however, secondary trim operates
normally. The secondary trim actuator also monitors for
uncommanded trim, trim in wrong direction, and incorrect trim rate. If
any of these malfunctions are detected, a fail annunciation is posted on
CAS and the secondary actuator is disabled. The IC has no control or
monitor functions for manual secondary trim.
The following CAS illuminations are specific to the secondary pitch
trim:
Electrical power for the secondary pitch trim system is provided from
the R ESS BUS and is protected by the TRIM-SEC PITCH circuit breaker
located on the copilot’s circuit breaker panel (FLIGHT group).
CAS Color Description
SEC TRIM FAIL Amber Secondary pitch trim has failed.
SEC PITCH TRIM White Secondary pitch trim is selected by the crew.
SEC TRIM FAULT White A pitch trim actuator (secondary) fault is
detected.
Pilot’s Manual
PM-126A 5-19
AUTOPILOT PITCH TRIM
When the autopilot is engaged, it can drive the horizontal stabilizer
trim to alleviate elevator servo loading. The autopilot pitch trim function
is contained in the #2 IC autopilot processor. When elevator servo
current exceeds a predetermined threshold for a given period of time,
this is considered to be a steady state error and trim will run. As the
trim runs, the horizontal stabilizer is re-positioned and the air load on
the elevator primary servo is reduced. When this load falls below the
threshold level, trim stops running.
Whenever the autopilot is engaged, #1 IC trim functions, which includes
config/Mach trim, drop off-line. The autopilot commands pitch
trim based on elevator servo current demand and airspeed. Autopilot
pitch trim engagement is controlled by the autopilot engage logic. An
autopilot engage signal is provided to the horizontal trim actuator. If
the autopilot is disengaged as a result of a monitor trip, the aural tone
alert will sound until the MSW switch is pushed. A red AP will also be
displayed on the PFDs and flash for five seconds and then go steady.
The #2 IC monitors for uncommanded trim, trim direction, and incorrect
trim rate. If the actuator detects one of the above faults, a CAS is
displayed.
The following CAS illumination is specific to the autopilot pitch trim:
TRIM-IN-MOTION INDICATION
A trim-in-motion potentiometer is installed on the secondary trim actuator.
When the autopilot energizes the secondary trim actuator for
more than 2 to 3 seconds, a series of audible clacker sounds is transmitted
　
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