Learjet 60 - System Test Switch-Mach Trim Function

Pilot's Manual
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Learjet 60
SYSTEM
TEST SWITCH-MACH TRIM
FUNCTION
The rotary-type
SYSTEM TEST switch on the center instrument
panel
is used to test the Mach
trim system and the Mach trim monitor
while
the aircraft is on
the ground . In flight, the switch is
used to resyn-
chronize the system
if the Mach trim monitor
has disengaged the sys-
tem . The test
function is initiated by
rotating the switch to MACH
TRIM and then
depressing the switch
PRESS TEST button . When the
aircraft is on
the ground and the test sequence
is initiated, the test
switch inserts a
signal that causes the
horizontal stabilizer to trim in
the nose-up direction . Since
there is no corresponding
airspeed
change, the Mach trim
monitor senses a Mach/horizontal
stabilizer
position error,
disengages Mach trim, and
illuminates the MACH
TRIM light . In flight,
depressing the PRESS TEST button
will
resyn-
chronize the
Mach
trim
system to the horizontal stabilizer
position
and Mach existing
when the PRESS TEST button
was depressed .
5-10
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PM-123
Original