Pitch Channel Functional Operation - Honeywell SPZ-8000 Maintenance Manual

Honeywell #.#!r.cE
3. B.
(8)
Pitch Channel Functional Operation
(a)
~~li~~tlD~ rector Pitch Attitude Hold
Mode (See Figure 260,
.
The pitch attitude hold mode is the basic vertical flight
director mode. It is activated when a flight director roll
mode is selected without an accompanying pitch mode and is not
annunciated on the PFD. The pitch command on the PFD provides
the pilot with a pitch reference corresponding to the pitch
attitude existing at the moment the roll mode was selected.
This pitch reference may be changed with the TCS button located
on the pilot's and copilot's control wheel.
The reference pitch attitude may also be changed as a function
of the pitch wheel on the PC-880 Turn Pitch Controller when the
autopilot is engaged. (Refer to discussion in paragraph
3.B.(8)(i)~.) Prior to the mode being operative, IRS pitch
attitude information is applied to a summation pfit and then
routed through a closed [PITCH HOLD + (AP ENG TCS NO VERT
F/D MODE)] switch to the input of a synchronizer. The output
of the synchronizer is of opposite polarity to the pitch
attitude signal, and therefore the two signals cancel each
other. This results in a zero signal out of the summation
point.
When only a lateral fligmdirector mode is selected, the
[PITCH HOLD + (AP ENG
TCS NO VERT F/D MODE)] switch opens.
This clamps the synchronizer output as a reference for the
pitch hold mode. As long as the pitch attitude of the aircraft
remains unchanged, there will be no command to drive the pitch
cue on the PFD. If the aircraft deviates from the reference
attitude established at mode engagement, an error signal
corresponding to the difference between the actual aircraft
attitude and the reference attitude will drive the pitch flight
director cue in the proper direction to fly the aircraft back
to the pitch reference attitude.
As the aircraft responds to the command, the error signal
diminishes and the flight director pitch cue on the PFD returns
to center.
The pitch reference signal is limited to +20, -15 degrees and
then routed to Figure 260, sheet 7, and is processed as
discussed in paragraph 3.6.(8)(i).
Lift compensation is provided to hold the aircraft's nose up in
a turn commanded through the autopilot. Roll attitude from the
IRS is routed to a block where the cosine of the bank angle is
subtracted from one. The resultant output will be routed to
the pitch autopilot to keep the nose of the aircraft up during
the turn maneuver. The lift compensation function is inhibited
during the FLCH mode of operation.
22-14-00
Page 298.109
Aug 15/91
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