a total linear trim tab displacement of 6 degrees when
passing through the region.
Outside this speed region the
Mach trim function holds trim tab position. Transition to
Mach trim mode ON (via autopilot disengage, trim engage, or
manual trim switches released)
causes the Mach trim control
law to synch
such that the present trim tab position is the
correct starting point for the present Mach situation. Trim
rates are limited to tl.O degree tab/see in Mach trim
mode.
At trim engagement, the servo control is synched to command
zero rate, and the Mach trim is synched to hold present trim
position.
At trim disengagement, no synching is required.
At channel switchover, the trim is synched the
trim engagement, as described above.
When the pilot or copilot manual trim switches
the Mach trim position reference is synched to
position and the Mach trim control law remains
manual trim switch is released. The Mach trim
continues to synch for a short time afterward -
allow the trim motor to coast to a stop.
This
same as
are act
present
off unt
control
n order
Drevent
at
ve,
1 the
1aw
to
the
Mach trim from causing the trim to back up following a
manual trim input.
3. B. (8) (j) ~ Autopilot Trim - The elevator servo current is monitored by
the FZ-820 FGC.
When the current goes above a predetermined
threshold, the trim tab is moved in the opposite direction
from the elevator.
This reduces the load on the elevator
which in turn reduces the amount of current required to
drive the elevator servo.
A delay is required to prevent
trim from driving during transitory loads.
22-14-00
Page 298.126
Aug 15/91
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