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 propellers 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 propeller 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
constant. A toggle switch installed adjacent to the
synchrophaser 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
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 caution/advisory annunciator
panel, PROP SYNC ON, will illuminate.
Synchroscope. The propeller synchroscope,
propellers. If the right propeller is operating at a higher
RPM than the left, the face of the synchroscope, a black
and white cross pattern, spins in a clockwise rotation.
Left, or counterclockwise, rotation indicates a higher RPM
of the left propeller. This instrument aids the pilot in
obtaining complete synchronization of propellers. The
system is protected by a 5-ampere circuit breaker
placarded PROP SYNC, located on the overhead circuit
breaker panel (fig. 2-27).
2-48. PROPELLER LEVERS.
Two propeller levers on the control pedestal (fig. 2-
8), 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 position 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 correspondingly decrease to the lowest
limit. Moving a propeller lever aft past the detent into
FEATHER will feather the propeller.
2-49. PROPELLER REVERSING.
Do not move the power levers into
reverse range without the engine
running. Damage to the reverse
linkage mechanisms will occur.
Propeller reversing on unimproved
surfaces should be accomplished
erosion from reversed airflow and,
in dusty conditions, to prevent
obscuring the operator's vision.
To prevent an assymetrical thrust
condition, propeller levers must be
in HIGH RPM position prior to
The propeller blade angle may be reversed to
shorten landing roll. To reverse, propeller levers must be
positioned at HIGH RPM (full forward), and the power
levers are lifted up to pass over the IDLE detent, then
pulled aft into REVERSE setting. One yellow caution
caution/advisory annunciator panel, alerts the pilot not to
reverse the propellers. This light illuminates only when
the landing gear handle is down, and if propeller levers
are not at HIGH RPM (full forward). This circuit is
protected by a 5-ampere circuit breaker, placarded
LANDING GEAR RELAY, located on the overhead circuit
breaker panel (fig. 2-27).
2-50. PROPELLER TACHOMETERS.
Two tachometers on the instrument panel register
propeller speed in hundreds of RPM (fig. 2-30). Each
indicator is slaved to a tachometer generator unit
attached to the corresponding engine.