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Insert opposite Page 3-31-
Amendment 11
This
information
supersedes
the pneumatic pressure system
adjustment
described
on
Page 3-30, 3-31
and
3-32.
PNEUMATIC PRESSURE SYSTEM
(TD-708 and after)
The pressure
system
provides filtered
air
for pressure-operated
instruments,
deice
boots, and autopilot (if
installed).
The
components
that
require
adjustment in this system are the pressure
regulator
relief
valves and the gyro instrument adjustable
orifice.
NOTE
The foam rubber filter
on
the intake side of the pressure pump, located for-
ward
of
the
rear
engine baffle,
should
be
removed
and cleaned every 100
hours of operation (or sooner if conditions
warrant).
The sealed filter
on
the
side of the pressure pump, located in the
center of each
nacelle, under the
upper nacelle access
door,
should be
replaced
every
500 hours of operation
(or sooner
if
operating in
dusty
conditions).
BASIC
PRESSURE SYSTEM (Instruments only)
The basic pressure system may be adjusted by the following procedure:
a.
Locate the pressure
regulator
relief
valve on the RH
side
of each
nacelle,
aft of
the
firewall.
b.
Tee in a test gage
(0-10
psi) on the "out" side
of
the
regulator
relief valve.
c.
Loosen the
check
nut and rotate
the
adjusting
screw clockwise to increase the pressure
and
counterclockwise to
decrease the pressure to
obtain
a
reading of
6.0 psi with the engine operating at 2200
rpm.
d.
Tighten the check nut and
remove
the test gage,
e.
Repeat the
above
procedure on
the
opposite side of the aircraft.
f.
Locate the gyro instrument adjustable orifice on the LH side of the aircraft, forward of the instrument panel, near the
top
of the
upholstery
panel. (See Figure 1.)
g.
Loosen the
check nut and rotate
the orifice body counterclockwise to increase the pressure and clockwise to decrease
the pressure to obtain a
reading of
2.5
+
.5
-0
inches
of
Hg. on the gyro pressure indicator
with
the engine operating between
600 and 650
rpm.
h.
Tighten the check nut and recheck the gyro pressure indicator
to
read in the green
arc
with the engines operating at
2200
rpm.
BASIC PRESSURE SYSTEM PLUS B5P AUTOPILOT INSTALLATION
This pressure system
may
be adjusted
by
the
following
procedure:
a.
Locate
the
regulator relief
valves
in
the
RH side of each nacelle, aft
of
the
firewall.
b.
Tee in
a
test
gage
(0-10
psi) on
the
"out" side of the
regulator.
c.
Loosen
the
check nut and
turn the
adjusting screw clockwise
to
increase the pressure
and
counterclockwise to
decrease the pressure
to
give a reading of 4.5
+
.5
-
O
psig with the engine operating at 2200 rpm and
the
autopilot ON.
d.
Tighten the
check nut.
e.
Repeat
the above
procedure
on
the
opposite side of
the
aircraft.
f.
Locate the gyro instrument adjustable orifice (see Figure 1
)
on
the
LH side of
the
aircraft,
forward
of the instrument
panel, near the top of
the
upholstery panel.
g.
Loosen the check nut and rotate the orifice
body
counterclockwise to increase the pressure
and
clockwise to decrease
the pressure to obtain
a reading
of 2.5
+
.5
-0
inches of Hg. on the gyro pressure indicator
with
the
engine
operating
between
600 and 650
rpm.
h.
Tighten the
check
nut
and
recheck
the
gyro pressure indicator
to
read in the green are with the engine
operating
at
2200 rpm.
Page 1 of 4
Issued: February, 1969
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