caused by the movement of the spoilers or
flaps. This mode is only functional when the
trim selector switch is in the PRI position
and the autopilot is not engaged.
Trim commands from either CWTS will have
priority over the configuration trim commands.
Mach Trim
Mach trim is a fully automatic system installed
to increase longitudinal stability and maintain
consistency in “stick” pressures throughout the
airspeed envelope.
The #1 IC-600 performs all the computational
aspects for Mach trim and signals the primary
trim actuator to apply trim as necessary.
Airspeed information provided by the ADCs
is used by the IC-600 in computing the trim
requirement.
The pitch trim selector must be in the PRI po-
sition for Mach trim to be functional and the
autopilot must be disengaged for the Mach
trim to become active. If the autopilot is en-
gaged, it performs the pitch trim function
using the secondary trim actuator and the
Mach trim is in a passive mode.
Mach trim automatically becomes active at
.725 M
I
. Nose up trim will be applied as Mach
increases and nose down as Mach decreases.
Mach trim is interrupted whenever the manual
trim is activated. The system resynchronizes
to function about the new horizontal stabilizer
position when manual trim is released.
If the IC-600 detects a fault within the Mach
trim system, a “MACH TRIM FAIL” message
is posted on the CAS (Table 15-1). The
“MACH TRIM FAIL” CAS will be white when
the speed of the aircraft is below Mach Trim
Off M
MO
and amber above Mach Trim Off
M
MO
.
Mach Trim Off M
MO
is 0.76 MI at 23,400 feet
and increases proportionately to 0.78 M
I
by
42,000 feet.
When the “MACH TRIM FAIL” message is
posted, the Overspeed cue on the airspeed in-
dicator will also adjust to indicate the Mach
Trim Off M
MO if the autopilot is not engaged.
If the autopilot is engaged, the Overspeed cue
will remain at 0.81 M
I
.
Primary Trim Electrical Power
Electrical power for primary pitch trim is
provided by the L Essential bus. The circuit
is protected by the TRIM - PRI PITCH cir-
cuit breaker located in the FLIGHT group on
the pilot’s circuit breaker panel. DC electri-
cal power to the #1 IC-600 is required for pri-
mary pitch trim, except for primary bypass
trim.
Secondary Pitch Trim
General
Secondary pitch trim is electrically indepen-
dent 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 (Figure 15-13).
The autopilot also uses the secondary trim ac-
tuator 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.
Secondary Manual Trim
The dual-segment SEC trim switch is located
on the center pedestal (Figure 15-14). 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 white “SEC PITCH
TRIM” CAS message is displayed.
The secondary pitch trim actuator has a self
monitor function. It performs a power-up check
and if any faults are detected, a white “SEC
TRIM FAULT” message is posted on the CAS,
however, secondary trim operates normally
(Table 15-1).
15-17
FOR TRAINING PURPOSES ONLY
LEARJET 45 PILOT TRAINING MANUAL
FlightSafety
international
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