to signal winding number 2 of the magnetic
a series capacitor, giving the voltage a 90-degree
modulator. The electric brake has clutch-
phase shift from the aircraft power source.
Appropriate signals to the modulators cause
controlled input and output shafts. The output
clockwise or counterclockwise rotation of the
shaft drives a lever, which biases the speeder
motor because of phase difference in the speed
spring in the propeller governor. Energizing
the clutch decouples the two shafts, locking
bias motor windings. The use of the two
the output shaft and leaving the input shaft free
signal windings in the modulators, along with
appropriate relay switching, permits the two
to turn.
modes of synchrophaser operation.
The synchrophaser. The synchrophaser has
four channels, which correspond to the aircraft's
four engines. Figure 5-18 is a schematic of the
OPERATIONAL MODES
synchrophaser. For explanation purposes, only
The normal governing mode provides im-
two channels (one slave channel and one master
proved engine response to transient RPM changes.
channel) are shown. Each channel has a push-pull
In this mode, the synchrophaser receives signals
power amplifier feeding the control winding of
its corresponding servomotor in the speed-bias
from the power lever anticipation potentiometers
and the engine tachometer generators. Signals
servo assembly. Magnetic modulators using dc
from these result in a temporary resetting of the
control current furnish a phase and amplitude
mechanical propeller governor. This resetting
controlled ac signal to the push-pull amplifier
adjusts for power lever changes and engine speed
input. The synchrophaser changes all signal inputs
changes, thus limiting engine overspeeds or
to dc voltages proportional to the error before
under speeds.
they are applied to the modulator. The modu-
lators are the signal summing devices for the two
The synchrophasing governing mode synchro-
operational modes of the synchrophaser.
nizes engine speeds, regulates propeller phase
angles, and maintains the limiting features of the
The magnetic modulators function on a core
normal governing mode. In the synchrophasing
saturation basis. Each modulator consists of a dc
governing mode, one engine (2 or 3) is the master.
bias winding, a 400-Hz excitation winding, and
The master engine operates in normal governing
two control windings (signal winding number 1
mode, while the other three engines (slaves) follow
and signal winding number 2). With no signals
changes in speed or phase of the master within
applied elsewhere, the 400-Hz excitation vohage
preset limits.
appears as a 400-Hz output of negligible ampli-
tude due to the bias winding current. Any current
in either or both signal windings will change the
Normal Governing Mode
output.
In normal governing mode, the propeller
The size of the signal windings current controls
governor switch is in the NORMAL position
the amplitude of the output; the current direction
and the power lever switch closes, providing
controls the phase of the output. Thus, current
reference voltages to the servomotors. The
from pin 10 to 9 in winding number 2 and current
from pin 8 to 7 in winding number 1 of any
synchrophase master switch is OFF and the PROP
RESYNCH switch is in NORMAL. All relays are
modulator produces a voltage 180 degrees out of
de-energized, resulting in the speed and phase
phase from the excitation voltage. Current in the
error circuits being grounded. Each phase- and
opposite direction in the signal windings produces
speed-error signal side of every magnetic modu-
an in-phase voltage. Simultaneous currents
lator signal winding number 2 (pin 10) ends on
flowing in opposite directions in the two signal
windings produce a signal that is the algebraic sum
a dummy load (fig. 5-18) within the synchro-
phaser. The other side (pin 9) connects to the
of the two signals. Then, the modulator produces
feedback circuit in the speed-bias servo assembly.
a 400-Hz signal, which is either in phase or 180
The controlling signals go to signal winding
degrees out of phase with the excitation voltage.
number 1 (pin 8) of each modulator. All channels
This signal is amplified and fed to the servomotor
function identically while in the normal governing
control winding. The 400-Hz voltage in the
mode.
reference winding of the servomotor goes through
