Specifications

14 of 16 P/N 11934-S27
Section 9 Cirrus Design
Supplements SR20
All Autopilot mode selection is performed by using the mode select
buttons and VS knob on the autopilot programmer/computer in the
center console. Annunciators in the programmer/computer display
window annunciate modes. Refer to Figure 1 for an illustration of the
programmer/computer.
RDY (Ready)– Illuminates when autopilot is ready for engagement.
When the airplane’s Battery Master switch is turned on and the rate
gyro RPM is correct, the RDY annunciator will come on indicating the
autopilot is ready for the functional check and operation. The autopilot
cannot be engaged unless the RDY light is illuminated.
NAV (Heading) Mode – When HDG is selected, the autopilot will
engage the HDG mode, fly the airplane to, and hold the heading set on
the PFD. Subsequent heading changes are made using the HDG bug
knob on the PFD. For smoothest transition to HDG mode, it is
recommended that the airplane be aligned to within 10° of the selected
heading before engaging HDG. The HDG mode is also used in
combination with the NAV mode to set up a pilot selected intercept
angle to a course.
GPSS (GPS Steering) – Pressing NAV twice will cause the autopilot
to go to GPSS for smoother tracking and transitions. When GPSS is
selected, the autopilot can be switched between heading and GPSS
modes of operation. In the heading mode, the converter receives a
heading error signal from the heading bug on the Horizontal Situation
Indicator. GPSS converts this information and sends this heading error
directly to the autopilot.
In the GPSS mode, the converter receives ground speed and bank
angle digital signals that are calculated and converted to a
commanded turn rate. The turn rate is then scaled and converted to a
DC heading error signal that is compatible with the autopilot. The end
result is an autopilot that can be directly coupled to the roll steering
commands produced by the GPS Navigator, eliminating the need for
the pilot to make any further adjustments to the PFD course arrow.
REV (Reverse Course) – When REV is selected, the autopilot will
automatically execute high sensitivity gain for an approach where
tracking the front course outbound or tracking the back course inbound
is required. The APR and REV annunciators will illuminate when REV
is selected.
Revision 02: 07-18-05