the switches reads PROP GOV TEST. Each switch
controls test circuits for the corresponding propeller.
In the test position, the switches are used to test the
function of the corresponding overspeed governor.
Refer to Chapter 8, for test procedure. Propeller test
circuits are protected by one 5-ampere circuit
breaker placarded PROP GOV located on the over-
head circuit breaker panel (fig. 2-26).
2-46. PROPELLER SYNCHROPHASER.
Operation. The propeller synchrophaser
automatically matches the RPM of the right propel-
ler (slave propeller) to that of the left propeller (mas-
ter propeller) and maintains the blades of one pro-
peller at a predetermined relative position with the
blades of the other propeller. To prevent the right
propeller from losing excessive RPM if the left pro-
peller is feathered while the synchrophaser is on, the
synchrophaser has a limited range of control from
the manual governor setting. Normal governor oper-
ation is unchanged but the synchrophaser will con-
tinuously monitor propeller RPM and reset the gov-
ernor as required. A magnetic pickup mounted in
each propeller overspeed governor and adjacent to
each propeller deice brush block transmits electric
pulses to a transistorized control box installed for-
ward of the pedestal. The right propeller RPM and
phase will automatically be adjusted to correspond
to the left. To change RPM, adjust both propeller
controls at the same time. This will keep the right
governor setting within the limiting range of the left
propeller. If the synchrophaser is on but is unable to
adjust to the right propeller to match the left, the
actuator has reached the end of its travel. To
recenter, turn the switch off, synchronize the propel-
lers manually, and turn the switch back on.
Control Box. The control box converts any
pulse rate differences into correction commands,
which are transmitted to a stepping type actuator
motor mounted on the right engine cowl forward
support ring. The motor then trims the right propel-
ler governor through a flexible shaft and trimmer
assembly to exactly match the left propeller. The
trimmer, installed between the governor control arm
and the control cable, screws in or out to adjust the
governor while leaving the control lever setting cons-
tant. A toggle switch installed adjacent to the syn-
chrophaser turns the system on. With the switch off,
the actuator automatically runs to the center of its
range of travel before stopping to assure normal
function when used again. To operate the system,
synchronize the propeller in the normal manner and
turn the synchrophaser on. The system is designed
for in-flight operations and is placarded to be off for
take-off and landing. Therefore, with the system on
and the landing gear extended, the master caution
lights will illuminate and a yellow light on the cau-
tion/advisory annunciator panel, PROP SYNC ON,
c. Synchroscope. The propeller synchroscope,
provides an indication of synchronization of the
propellers. If the right propeller is operating at a
higher RPM than the left, the face of the synchro-
scope, a black and white cross pattern, spins in a
clockwise rotation. Left, or counterclockwise, rota-
tion indicates a higher RPM of the left propeller.
This instrument aids the pilot in obtaining complete
synchronization of propellers. The system is pro-
tected by a 5-ampere circuit breaker placarded
PROP SYNC, located on the overhead circuit
breaker panel (fig. 2-26).
2-47. PROPELLER LEVERS.
Two propeller levers on the control pedestal (fig.
2-7), placarded PROP, are used to regulate propeller
speeds. Each lever controls a primary governor,
which acts to regulate propeller speeds within the
normal operation range. The full forward position of
the levers is placarded TAKEOFF, LANDING AND
REVERSE - and also HIGH RPM. The full aft posi-
tion of the levers is placarded FEATHER. When a
lever is placed at HIGH RPM, the propeller may
attain a static RPM of 2,000 depending upon power
lever position. As a lever is moved aft, passing
through the propeller governing range, but stopping
at the feathering detent, propeller RPM will corre-
spondingly decrease to the lowest limit. Moving a
propeller lever aft past the detent into FEATHER
will feather the propeller.
2-48. PROPELLER REVERSING.
Do not move the power levers into
reverse range without the engine running.
Damage to the reverse linkage mecha-
nisms will occur.
Propeller reversing on unimproved sur-
faces should be accomplished carefully to
prevent propeller erosion from reversed
airflow and, in dusty conditions, to pre-
vent obscuring the operators vision.