decays to zero as the charge on capacitor C621
current in signal winding number 2. The magnetic
field of this current is in opposition to the
reaches the potential on the collector of transistor
Q603. When engine RPM changes, a change
magnetic field of the signal current in winding
in the collector voltage of transistor Q603
number 1. This stops the servomotor. As the
proportional to the change in tachometer gene-
anticipator capacitor continues to charge to its
rator frequency occurs. This causes capacitor
new peak value, the current in signal winding
number 1 decays to zero. The feedback potenti-
C621 to change its charge at the rate in which the
tachometer generator frequency is changing. This
ometer is still applying voltage to signal winding
produces a current in signal winding number 1.
number 2. This results in a leading voltage to the
The current size varies at the rate at which the
servomotor control winding that returns the
motor to its original position. This position
engine is varying offspeed. Its direction is such
corresponds to a zero-volt feedback potentiometer
that the amplified signal in the servo-bias assembly
position. In retarding the throttle lever very
control winding drives the servomotor in a
rapidly, the peak voltage will overcome the reverse
direction to dampen the drift in engine RPM.
Speed-error signals in signal winding number 1
bias on diode CR620. This will limit the signal
value to prevent overcompensation toward a flat
from the speed-derivative circuit cancel in the
blade pitch. For an increase in engine power, the
same manner as anticipation signals from the
capacitor discharges. This causes a current in the
anticipation circuit cancel.
T h e speed-derivative and power lever
opposite direction in signal winding number 1,
which results in a temporary resetting toward
anticipation circuits are much more sensitive
increased pitch. The amount of reset in either case
to engine RPM changes than the mechanical
depends on the rate at which the lever moves.
governor flyweight speeder spring. The governing
action of the flyweight and speeder spring
Mechanical stops in the speed-bias servo assembly
limit speed resets to plus 10 and minus 10 percent
improves the mechanical governor's response to
regardless of the applied signal. Furthermore, stops
changes in power lever settings and engine RPM.
in the propeller control valve housing linkage
reduce the limits to plus 6 and minus 4 percent.
Synchrophaser Mode
In adding synchrophasing to normal governing
LIMITING ENGINE TRANSIENT SPEED
mode, the master switch selects either engine 2 or
CHANGES. --The speed-derivative circuit in the
3 as the master engine (fig. 5-18). With master
synchrophaser (fig. 5-19) senses changes in engine
RPM and produces output signals, which dampen
engine selection, relays energize, removing dummy
loads from signal winding number 2 of all
the engine RPM changes. The speed-derivative
magnetic modulators, except the master channel
circuit does this by translating the frequency
modulator. Also, the outputs of the speed-error
changes received from one phase of the tach-
ometer generator into signal voltages. The
and phase-error circuits of each synchrophaser
magnitudes of the signal voltages vary at the rate
channel (except the master) are taken from ground
the tachometer generator frequency changes. The
and connected to signal winding number 2 of their
respective modulators. While the slave engines are
signal voltage goes to signal winding number 1
in synchrophasing mode, the master engine
of the magnetic modulator, where it is summed
remains in normal governing mode. Essentially,
and sent to the push-pull amplifier. After
pulses from the master engine form into sawtooth
amplification, the signal goes to the servomotor
waves and are compared to pulses from each of
control winding. The servomotor adjusts the
the slave engines in the slave channel sampling
speeder spring tension, which begins a change in
circuits. If slave pulses are not in phase with the
propeller pitch, thus dampening the change in
master pulse (sawtooth), error detection occurs
engine RPM.
in the respective synchrophaser channel. The
The action of the speed-derivative circuit is
errors then go to signal winding number 2 of the
further described as follows: The voltage
channel magnetic modulator. Here, they are
produced on the collector of transistor Q603 is
summed with any error signals that exist in signal
proportional to the output frequency of the
winding number 1. The result of the error signals
tachometer generator. When engine RPM is
is amplified and fed to the control winding of the
constant, the voltage on the collector is constant
respective speed-bias servomotor. This alters the
and capacitor C621 charges through resistor R634
tension of the slave governor speeder spring,
and signal winding number 1 of the magnetic
correcting for engine speed differences and
modulator. Current in signal winding number 1
