RAZAIR
‐
A1
‐
METRO
‐
III
‐
AFM
‐
001
1
‐
37
PNEUMATIC
SYSTEMS
The
pneumatic
system
provides
the
bleed
air
manifold
with
hot
compressed
air
for
use
by
associated
systems.
The
pneumatic
system
consists
of
a
bleed
air
system
and
vacuum
system.
Both
engines
provide
air
to
the
manifold,
but
either
engine
is
sufficient
to
maintain
all
required
system
functions
during
single
engine
operation.
BLEED
AIR
SYSTEM
The
engines
provide
bleed
air
pressure
to
the
following
airplane
systems:
Engine
and
Nacelle
anti
‐
icing.
Air
Conditioning.
Hydraulic
reservoir.
Suction
control
(Vacuum
pump).
Door
seal.
Window
defog.
Deice
boot.
The
flight
crew
monitors
system
operation
with
associated
suction,
pressure
and
warning
devices
in
the
cockpit.
VACUUM
SYSTEM
The
vacuum
system
uses
bleed
air
pressure
to
operate
a
vacuum
pump.
The
system
supplies
the
necessary
suction
for
operation
of
a)
the
vacuum
instruments,
b)
the
suction
phase
of
the
deice
boots,
and
c)
control
of
the
pressurization
system.
An
amber
LOW
SUCTION
warning
light
illuminates
if
the
suction
drops
below
limits.
The
suction
indicator
on
the
instrument
panel
is
direct
‐
reading
and
does
not
require
electrical
power.
HYDRAULIC
SYSTEM
The
main
hydraulic
system
is
pressurized
by
two
engine
‐
driven
pumps,
one
on
each
engine.
The
system
provides
pressure
for
actuation
of
the
landing
gear,
flaps
and
nose
wheel
steering.
Two
warning
lights
on
the
annunciator
panel
warn
of
low
pump
pressure
or
pump
failure.
Supply
fluid
to
the
engine
‐
driven
pumps
passes
through
shutoff
valves
controlled
by
two
HYDR
SHUT
OFF
switches
on
the
center
pedestal.
These
switches
are
normally
in
the
OPEN
position
are
and
CLOSED
only
in
the
event
of
fire
or
engine
shutdown
in
flight.
If
either
of
the
switches
is
moved
to
the
CLOSED
position,
an
amber
L
HYD
or
R
HYD
light
will
illuminate.
A
single
HYD
PRESS
indicator
serves
both
hydraulic
systems.
The
indicator
always
displays
the
higher
value
of
the
two
systems.
Fig.
64
Suction
indicator.
