C
IRRUS
D
ESIGN
S
ECTION
7: A
IRPLANE
AND
S
YSTEMS
SR20
F
LIGHT
I
NSTRUMENTS
P/N 11934-005
7-19
“earth”. The pitch scale on the attitude display is graduated in 5° incre-
ments. Chevrons appear on the pitch scale at extreme pitch attitudes. The
MD302 Standby Attitude Module is electrically driven. A red X indicates
the attitude display is absent due to exceedance of internal rate sensors, loss
of airspeed, or other reasons. Redundant circuits paralleled through diodes
supply DC electrical power to the unit.
All Serials:
28 VDC for the standby attitude indicator is supplied through the 5-amp
STDBY ATTD A circuit breaker on ESS BUS 1 and the 5-amp STDBY
ATTD B circuit breaker on MAIN BUS 1.
Airspeed Indicator
Primary airspeed data is provided by the Air Data Computer and is shown
as a vertical tape along the upper left side of the PFD. The airspeed scale is
graduated with major tick marks at intervals of 10 knots and minor tick
marks at intervals of 5 knots. Speed indication starts at 20 knots, with 60
knots of airspeed viewable at any time. The actual airspeed is displayed
inside the black pointer. The pointer remains black until reaching the
never-exceed speed (V
NE
), at which point it turns red. Color coded bars are
provided to indicate flap operating range, normal operating range, caution
range, and never-exceed speed. Speeds above the never-exceed speed,
appear in the high speed warning range, represented on the airspeed tape
by red/white “barber pole” coloration. Calculated true airspeed is displayed
in window at the bottom edge of the airspeed tape. Airspeed trend is also
displayed as a bar along side of the airspeed tape.
Standby Airspeed Indicator
Serials w/o MD302 Standby Attitude Module:
The standby airspeed indicator is mounted on the LH bolster panel and
displays indicated and true airspeeds on a dual-scale, internally lit precision
airspeed indicator installed in the pilot's instrument panel. The instrument
senses difference in static and Pitot pressures and displays the result in
knots on an airspeed scale. A single pointer sweeps an indicated airspeed
scale calibrated from 40 to 220 knots. The 'zero' index is at the 12 o'clock
position. A sub-scale aligns true airspeed with the corresponding indicated
airspeed when the altitude/temperature correction is set in the correction
window. A knob in the lower left corner of the instrument is used to rotate
the pressure altitude scale in the correction window to align the current
pressure altitude with the outside air temperature.
Serials w/ MD302 Standby Attitude Module:
The MD302 Standby Attitude Module is mounted on the LH bolster panel
and displays the current Indicated Airspeed (IAS). The instrument senses
difference in static and pitot pressures and displays the result in knots in the
Airspeed Window. The Airspeed Window/Pointer sweeps the indicated
Reissue A
