Vacuum System - Cirrus DESIGN SR20 Information Manual

Section 7
Airplane Description
static pressure source is selected, refer to Section 5 airspeed
calibration and altitude for corrections to be applied.

Vacuum System

The airplane vacuum system provides the vacuum necessary to
operate the attitude gyro and directional gyro. The system consists of
an engine-driven vacuum pump, an electric vacuum pump for backup,
two vacuum switches, two annunciators, a vacuum manifold, a vacuum
regulator, vacuum system air filter, and the vacuum-driven instruments
(including a suction gauge). The backup portion of the system
operates automatically to provide vacuum for the instruments should
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.
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.
7-62
• Note •
Cirrus Design
P/N 13999-002 Info Manual
September 2011
SR20