Cessna SKYMASTER 336 1964 - UNFEATHERING SYSTEMS; MAINTENANCE

accomplished
in
the field.
Repairs to
governors
are
classed
as propeller
major repairs
in FAM
18, which
also defines
who may accomplish
such repairs.
12-10.
REMOVAL.
a.
Remove
cowling and
baffles
as required
for
access.
b. If
an optional
unfeathering
system
is installed,
place propeller
control in high rpm
position.
c. Disconnect propeller
control from
governor.
d. If an optional
unfeathering system
is installed,
release
accumulator
pressure,
then disconnect
ac-
cumulator
hose
from governor
fitting.
e. Remove
nuts
and washers
securing
governor
and pull governor
from mounting
studs.
f.
Remove gasket between
governor and engine
mounting pad.
12-11. INSTALLATION.
a.
Wipe governor and
engine mounting pad
clean.
b. Install a new gasket, with the raised surface of
the screen away from the engine pad.
c. Position governor
on mounting studs,
aligning
governor splines with splines in engine, and install
mounting
washers and nuts.
Do not force spline
en-
gagement. Rotate engine crankshaft and splines will
engage smoothly when aligned.
d. If an optional unfeathering system is installed,
connect accumulator hose to governor, and recharge
the accumulator.
e. Connect governor control to governor arm. If
rod-end adjustment
was not disturbed, it
should not
be
necessary to rig the
control. Check rigging
and
adjust as
required.
Refer
to paragraph
10-55.
f. Reinstall baffles
and cowling removed
for access.
HIGH
-SPEED
STOP SCREW
LOCK NUT
GOVERNOR ARM
rant. Refer to paragraph 10-55.
e. Tighten
the lock
nut on the
high-speed
stop screw.
f. Reinstall
baffles and cowling
removed for access.
12-13. UNFEATHERING
SYSTEMS.
12-14.
Each optional
unfeathering
system
consists
of
a nitrogen-charged
accumulator,
mounted
on the
engine mount,
a special
governor,
and
a hose run-
ning between the governor
and the accumulator.
The
governor
contains
a spring-loaded
check
valve which
is unseated
while the
propeller
control is
in any po-
sition
except "FEATHER,"
thus
permitting
governor-
pressurized
oil to flow
to and from
the accumulator.
When the
propeller control is
moved to "FEATHER"
position,
the check
valve
is seated
and oil under
governor
pressure is trapped
in the accumulator
and
hose. As
the propeller
control
is moved
from
the
"FEATHER" position,
the trapped pressurized
oil
flows back
through the
governor
to the propeller
to unfeather it.
12-15. MAINTENANCE.
CAUTION
Always release
system pressure
by placing
propeller
control in high rpm
position, and
release
accumulator
pressure through
the
filler
valve, before disconnecting
hose be-
tween accumulator
and governor
or
remov-
ing accumulator.
a. Place
propeller control
in the
high rpm
position
before
charging the accumulator
to prevent the
possi-
bility of oil under
pressure being trapped
in the ac-
cumulator.
b.
Although the accumulator
will function properly
when charged
with
air, nitrogen
gas is recommended
to minimize corrosion.
c.
Either too much pressure
or not enough pressure
in the accumulator
will reduce
efficiency of the un-
feathering system.
With a normal
amount of friction
within the propeller,
optimum pressure
is approxi-
mately 110
psi. A range
of 100-125
psi is acceptable.
d. Always check
that the filler valve
does not leak
after charging an accumulator.
Figure 12-3.
High
Rpm
Stop Adjustment
12-12.
HIGH
RPM STOP
ADJUSTMENT.
a.
Remove
engine cowling
and baffles
as necessary
for access.
b. Loosen
lock
nut on high-speed
stop screw.
c. Turn the screw
in to decrease maximum
rpm
and out to increase
maximum rpm. One full
turn of
the
stop screw
causes a
change of
approximately
25
rpm.
Also
see the
"Note"
at the
end
of paragraph
12-4.
d.
Make propeller
control
adjustments
as required
for
full travel
and proper
cushion at the
control
quad-
12-8