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the engine-driven vacuum pump fail. The back-up function is fully
automatic and requires no pilot action. The electric vacuum pump
operates on 28 VDC supplied through a 15-amp fuse on the airplanes
primary bus in the Master Control Unit (MCU). Electric vacuum pump
control circuits are protected by the 2-amp STANDBY VACUUM circuit
breaker on the circuit breaker panel.
• Note •
For extended ground maintenance, disable standby vacuum
pump by pulling the STANDBY VACUUM circuit breaker.
During the engine starting procedure when the battery master switch
is turned ON, the following sequence will occur:
1. The red VACUUM annunciator light will come on. The standby
vacuum pump will start and the amber AUX VAC light will come
on. After a short delay, the attitude indicator GYRO flag will go out
of view.
2. After the engine is started, the red VACUUM annunciator light will
go out. The standby pump will stop and the amber AUX VAC light
will go out.
March 2010
Information Manual 7-63
Cirrus Design Section 7
SR20 Airplane Description
INSTRUMENT
AIR FILTER
(PAPER)
FOAM
FILTER
VACUUM
REGULATOR
VACUUM
ENGINE-DRIVEN
VACUUM PUMP
ELECTRIC
(Standby)
VACUUM
PUMP
AUX VAC
N
U C T I O
S
4 6
5
ATTITUDE
GYRO
SUCTION
GAGE
DIRECTIONAL
GYRO
S
E
W
N
20 20
10
O
R
Y
G
CIRRUS
10
10 10
(CB PANEL)
15A
FUSE
MCU
2A
SR20_FM07_1017B
CHECK VALVES
VACUUM
SWITCHES
STANDBY
VACUUM
Figure 7-13
Vacuum System
March 2010
7-64 Information Manual
Section 7 Cirrus Design
Airplane Description SR20
Suction Gauge
The suction gauge, located on the far right side of the instrument
panel, is calibrated in inches of Mercury (Hg). The gauge indicates
suction available for operation of the attitude and directional gyros.
The desired suction range is 4.5 to 5.4 inches of Hg. A suction reading
out of this range may indicate a system malfunction or improper
adjustment. The attitude and directional indicators should not be
considered reliable when the suction gauge indicates out of range.
• Note •
The attitude GYRO flag will drop if the attitude indicator is not
receiving adequate vacuum for operation.
Vacuum Warning Light
Illumination of the red VACUUM warning light in the annunciator panel
indicates failure of the engine driven vacuum pump or that the
airplane's engine is not operating. A vacuum switch in the vacuum line
between the engine-driven vacuum pump and the vacuum manifold
illuminates the VACUUM warning light on low vacuum in the line. In
addition to illuminating the VACUUM warning light, the switch also trips
a relay energizing the back-up electric vacuum pump. This condition
exists whenever the BAT Master switch is on and the engine is not
operating (such as before start) or in the event the engine-driven
vacuum pump fails. The VACUUM warning light operates on 28 VDC
supplied through the 2-amp ANNUNC PWR circuit breaker on the
Essential Bus.
Aux Vac Caution Light
Illumination of the amber AUX VAC caution light in the annunciator
panel indicates that the electric (back-up) vacuum pump is supplying
vacuum. A vacuum switch in the vacuum line between the electric
vacuum pump and the vacuum manifold illuminates the light on rising
vacuum in the line. Normally, the light will be illuminated whenever
electrical power is on the airplane and the engine-driven vacuum
pump is not operating. The AUX VAC caution light operates on 28
VDC supplied through the 2-amp ANNUNC PWR circuit breaker on
the Essential Bus.
March 2010
Information Manual 7-65
Cirrus Design Section 7
SR20 Airplane Description
Stall Warning System
The airplane is equipped with an electro-pneumatic stall warning
system to provide audible warning of an approach to aerodynamic
stall. The system consists of an inlet in the leading edge of the right
wing, a pressure switch and associated plumbing, and a piezoceramic
horn behind the instrument panel. As the airplane approaches
a stall, the low pressure on the upper surface of the wings moves
forward around the leading edge of the wings. As the low pressure
area passes over the stall warning sense inlet, a slight negative
pressure is sensed by the pressure switch. The pressure switch
completes a ground circuit causing the warning horn to sound. The
warning horn provides a 94dB continuous 2800 Hz tone. The warning
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西锐20飞机信息手册 SR22 AIRPLANE INFORMATION MANUAL 1148-126(71)
