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the engine mount.
(b)
Install
upper cowling and Install screws
attaching front
baffle
to
lower
cowling.
(c)
Install bolts ln front cowling
former
that
attach
Ute upper and lower cowling section.
(d)
Install screws
ln upper
a
nd
lower cowling
at nacelle firewall.
(e)
Install bolts attaching U1e
oil
radiator to
the cowling former.
( f)
Install alr Intake duct
on
carburetor alr
intake.
(g)
Connect carburetor drain to carburetor
air
scoop.
4.4
PROPELLER AND CONTROL SYSTEM.
4.4.1
General Description - 272-101 Propeller
{Full Feathering) -
The Beech Model 272-101 propeller assem-
bly
consists
of a propeller, transmission, employing
a
governor-controlled hydraulic motor for
normal
constant-speed operation
and a manually controlled
electric
motor for quick feafuering in an emergency.
The hydraulic motor is mounted
on the
aft end
of
the
transmission case while fue electric motor is mount-
ed
on
the side
of
the case. The transmission assem-
bly
is attached
with two brackets to fue nose section
of
the
engine and
the propeller mounts on the SAE
20
spline crankshaft of
the Lycoming
GO-435-C2
engine.
The two large
external gears
on
the propeller
hub
mesh
with the
two external gears
of
fue transmission
assembly. The
transmission is
interconnected
to a
Woodward governor on
the left side
of
fue
engine
accessory
case
by two steel oil lines and to a
feathering
and
unfeathering relay
on fue
firewall by
an
electrical wiring
harness. A
conventional lever
on
the pilot's console is
linked
to
fue governor
and
to
a
feafuering switch on
the firewall.
The governor
pump
boosts
the
engine oil
pressure to approximately
500 psi
and directs
it to
either the
increase
or
decrease pitch
side
of
the
hydraulic pitch-change
motor, as
required,
simul-
taneously directing spent oil
from the
opposite
llne
back to fue engine sump
through
the
governor.
Designed internal
leakage from
the hydraulic
motor
lubricates the transmission
gear box
and drains back
to the engine sump
through
a separate line.
Forcing
the
propeller control lever past the
safety
detent to
fue
extreme aft
position
actuates
the
feafuering switch
on
the firewall which energizes the
feathering field
of fue electric motor. The hydraulic
motor assists
the electric
motor in the feafuering
direction until
the
oil pressure drops to
an
ineffective
value at about
200
engine rpm.
The
linkage
from the
propeller
control lever is so connected
that the
hydraulic feaUlering action
precedes that
of
the
elec-
tric featllering motor
by
a
fraction
of a second.
As
the featllering
is
completed,
the
fea tllering
limit
switch
breaks
the
circuit, stopping
the
electric
motor.
The
hydraulic feathering
action ls made pos-
sible
by mechanically pulling the governor pilot
va
lve
to the position where it will call
for
increased pitch,
just
as
the governor flyweights do during
an over-
speed
condition.
The mechanical
override
has no
3
effect on
the
governor operation ln the normal
constant
speed range,
but during
the
feathering
process as en-
gine speed decreases
due
to
propeller pitch
Increase,
the
override continues to direct governor
oll
to the
increase pitch
slde of
the hydraullc motor, whereas,
normal flyweight actlon would have directed thls
oll
to fue
opposite side.
Moving
the propeller control back into fue
normal
opera
ling range reverses the electric motor,
moving the blades
toward
low
pitch. At
45
degrees the
unfeatherlng limit switch breaks the
circuit,
letting
the governor and
hydraulic
motor take
over control
of
the
blade angle in the constant speed range. Since
fue
feathering limit switch closes
again
as
soon
as
the blades
leave the feathered position, the electric
m::itor
stands ready furoughout the blade-angle range
to fully
feather the propeller within 4 to 5 seconds.
Briefly,
the
transmission
changes the pitch
of
fue
blades
as follows:
when the
governor is in
the
On-speed
condition (no pitch change
is taking
place)
the
two gears (3,4 figure 4-2)
on the front
of the
transmission are turning at the same
rpm, as
are
fue
two gears (1,
2)
that
they mesh with.
When
fue governor is in
an
over-speed condition
(or under-
speed condition)
oil
pressure from the governor
is
directed to
fue
hydraulic
m
otor
on
fue rear
of the
transmission. The
oil
motor
drives
the front
gear (4)
through
a
planetary gear system, which
in turn drives
a
gear (5) for each blade, changing the pitch.
The
entire
pitch
change
oper
ation
centers
around
the
difference
in
number of teeth in
the
two gears
inside
the planetary system that drive the two gears
(3,
4)
on
fue fr
ont
of
the
transmission.
4.4.1.1
Trouble Shooting -
See
Cha
rt 4-1, Trouble Shooting 272-101
Propeller.
4.4.1.2
Removal
of
Propeller
-
Before
beginning
to
remove fue
propeller,
make
sure
the engines were stopped with
the propel-
ler in
low pitch.
NOTE
If Ule same propeller and transmission are
to
be
reinstalled wifuout disassembling either, con-
siderable
installation
time and effort can be
saved by marking the mating teeth of fue two
front gears (3, 4, figure 4-2) on the transmission
and the larger gears (1,2) that they mesh with,
before removing propeller. Use Blue Dykem
or
similar marking substance which will not
easily rub
off.
Lock together the two
front
gears
on
the transmission and also the two larger
propeller
gears
with
safety
wire to prevent
changing their relationships.
(a)
Remove cotter pin and nut from the spinner
attaching
bolt
at
point of spinner and remove
spinner.
(b)
Remove rubber cone and spacers from
propeller
reta
ining nut.
(c)
Remove
clevis
pin and loosen the hub re-
taining nut.
(d)
Tie the two external propeller gears together
Revised 1 June 1955
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