Garmin G500 Manual page 35

4.6.2 Course / NAV Selection coupling to the autopilot
When operating the autopilot in NAV mode, the deviation information from the
installed navigation sources (i.e. GPS1, GPS2, NAV1, NAV2) is switched via
the G500 PFD display. Whatever is displayed on the HSI is the NAV source the
autopilot is following. Most autopilots also use the course datum to determine
the best intercept angles when operating in NAV mode.
4.6.3 Heading Bug coupling capability to the autopilot
When operating the autopilot in HDG mode, the difference between the HDG
bug location on the HSI and the actual aircraft heading creates an error signal
which the autopilot will minimize by turning in the direction of the bug. If the
bug is turned more then 180 degrees, the autopilot may turn the airplane in the
opposite direction of the desired turn.
4.6.4 Roll Steering emulated via HDG mode
For autopilots that do not support digital GPSS signals, GPSS functionality may
be emulated by operating the autopilot in HDG mode and selecting GPSS on the
PFD. Depending on the installation, GPSS mode may be toggled via an external
switch located near the autopilot control panel, or by pressing and holding the
HDG button on the PFD. If an external switch is installed, it will be either a
toggle or push-button switch as depicted below.
If the installation uses the HDG button on the PFD, the PFD Knob Mode
Indicator is expanded to label the button function.
GPSS OFF
When GPSS is selected on the PFD, the heading bug on the HSI changes to a
hollow outline and a crossed-out heading bug appears in the PFD Knob Mode
Indicator, indicating that the autopilot is not coupled to the heading bug. The
bug is still controllable and may still be used by the pilot for reference.
AFMS, GARMIN G500 PFD/MFD SYSTEM
FAA APPROVED
AP HDG
DATUM
GPSS
HDG
(toggle switch)
AP HDG
DATUM
GPSS
OR
HDG
(push-button)
GPSS ON
190-01102-01 Rev. 9
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