Cirrus DESIGN SR20 Information Manual page 184

Section 7 Cirrus Design
Airplane Description SR20
course and heading outputs provided to the autopilot to allow NAV/
LOC/GPS course tracking or to track a preset heading.
The HSI incorporates conventional warning flags. The HDG (Heading)
flag will be out of view whenever the instrument is receiving sufficient
electrical power for operation. The NAV (Navigation) flag will be out of
view when a VOR or LOC frequency is tuned in the NAV1 receiver and
a reliable signal is present. The GS (Glideslope) flag will be out of view
when an ILS frequency is tuned on the Nav 1 receiver and a reliable
GS signal is present.
The NSD-360 HSI gyro is vacuum powered and a red GYRO flag
indicates insufficient vacuum for gyro operation. 28 vdc for HSI
operation is supplied through the 2-amp HSI circuit breaker on the
Essential bus.
The NSD-1000 HSI is electrically driven and a red GYRO flag
indicates loss of electrical power. Redundant circuits paralleled
through diodes at the indicator supply DC electrical power for gyro
operation. 28 vdc for HSI and gyro operation is supplied through the 2-
amp HSI circuit breaker on the Essential bus.
Sandel 3308 Navigation Display (Optional)
The optional Sandel SN3308 Navigation Display combines the
functions of an HSI, an RMI, a full color moving map, a Stormscope (if
installed) display, GPS annunciator, and 3-light marker beacon
indicators. Compass information is derived from a remote directional
gyro and a flux detector. 28 VDC for system operation is supplied
through the 5-amp HSI circuit breaker on the Essential Bus.
The full-color display uses a rear-projection system driven by an active
matrix LCD display. A halogen lamp is the singular primary display
projection light source. A separate dimming knob for the display
brightness is provided immediately below the display.
The HSI display shows heading and navigation information in a 360°
view similar to a conventional mechanical HSI, or in an EFIS 90° ARC
view. This includes compass card, heading bug, course pointer,
course deviation bar, TO/FROM indicator, glideslope indicator, and
flags. Heading bug and course pointer settings include digital readouts
that make it easy to set precise headings and courses. Either GPS1 or
NAV1 can be selected as primary navigation sources by pressing the
NAV switch on the left side of the display. Up to two bearing pointers
7-22 P/N 13999-002 Info Manual
September 2011