Learjet 60 - Pitch Trim; Pitch Trim Selector Switch

Lexqet60
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Pilot's
Manual
PITGH
TRIM
Pitch trim is accomplished by repositioning the horizontal stabilizer to
the
desired trim setting through actuation of the horizontal stabilizer
pitch trim actuator
. The actuator is a dual-motor, screwiack-type actua-
tor . The primary motor is
operated by the aircraft primary pitch trim
system and the Mach trim system . The secondary motor
is operated by
the aircraft
secondary pitch trim system and the autopilot . A speed con-
troller in the primary
pitch trim system changes primary pitch trim rate
as a function of horizontal stabilizer trim
position . The speed controller
allows high trim rates when the aircraft is
trimmed for takeoff or
approach
and low trim rates when the aircraft is trimmed for cruise
. A
trim speed monitor is
incorporated into the speed controller to alert the
crew of a trim speed error . The primary and
secondary pitch trim sys-
tems
are electrically independent and mode selection is made
through
a selector switch .
Primary pitch trim is pilot controlled through trim
switches on each control wheel .
Secondary pitch trim is pilot controlled
through a switch on the pedestal . Emergency interrupt
is provided for
both systems through the Control Wheel Master switches (MSW) . Hor-
izontal stabilizer
trim position is displayed onan indicator mounted in
the center instrument panel below the
landing gear lever . Primary pitch
trim control circuits operate on 28 VIDC supplied through
the 3-amp
PRI PITCH
TRIM circuit breaker on the pilot's circuit breaker panel .
Secondary pitch trim control circuits operate on 28 VDC supplied
through the 10-amp
SEC PITCH TRIM circuit breaker on the copilot's
circuit breaker panel . Both the primary
and secondary pitch trim sys-
tems are operative during EMER BUS mode .
PITCH TRIM
SELECTOR SWITCH
The PITCH TRIM selector
switch, located on the pedestal trim control
panel, provides primary and secondary
mode selection for the aircraft
trim systems . The switch has
three
positions : PRI, OFF, and SEC . When
me switch is set
to PRL a ground path is provided for the primary pitch
trim system control circuits
and trim changes are accomplished
through
the control wheel trim switches . When the switch
is set to SEC,
a ground
path is provided for the secondary pitch trim system control
circuits and trim changes
are accomplished through the pedestal NOSE
DN-OFF-NOSE UP switch .
When the switch is set to the OFF position,
both pitch trim electrical control circuits are isolated from
the aircraft
electrical system
. The Mach trim system is inoperative with the PITCH
TRIM selector switch in the
OFF or SEC positions . The autopilot is
inoperative with the PITCH TRIM
selector switch in the OFF position .
PM-123
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5-11
Change 4