Wings Level And Heading Hold Mode - Honeywell SPZ-8000 Maintenance Manual

it also drives the dc tach generator through mechanical
coupling (represented by a dotted line). The tach generator
provides a rate feedback signal that serves two functions.
First, it
acts as a damping term when
summed with the
lateral command input to the pulse width command limiter.
This helps to stabilize aileron position and minimize
excessive aileron travel.
Second, the rate feedback signal is integrated to obtain
position feedback, gain adjusted and summed with the
steering command. When these signals are equal, the aileron
is in the proper position to satisfy the steering command.
As the aircraft responds, roll attitude and roll rate
information provided by the IRS, are summed with the
steering command. This allows the feedback position signal
to drive the aileron back to its original position.
As the steering command is satisfied and diminishes in size,
the roll attitude signal becomes dominant and provides a
command to move the aileron in the opposite direction, to
return the aircraft to a wings level attitude. The servo
loop
follow up would be identical to that just discussed.
If the summation of command and roll attitude are not
exactly equal, the difference between the two signals is
sent to the command rate taker. The signal is changed to
rate, and summed with tach generator rate feedback. The
summing of these two signals is then integrated to obtain
position data and summed with the steering command. This
boost helps eliminate flightpath or attitude standoffs.
3. B. (7) (g) ~ Wings Level and Heading Hold Mode
If
the autopilot is engaged and no flight director
mode has
been selected, then a zero roll command becomes the desired
steering command. This zero command is routed through the
following:
. Rate Limiter
. Bank Angle Limiter
. Roll Hold Switch
. First Summation Point
. Second Summation Point
At the second summing point, roll attitude provided by the
IRS is added to the command. Since the command is zero, the
summing point's output is an attitude displacement signal
that is rate limited, acceleration limited, and summed with
roll rate, provided by the IRS.
This attitude signal is now routed to the aileron servo
drive as discussed in paragraph 3.B.(7)(g)~.
22-14-00
Page 298.98
Aug 15/91
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