TM 55-1520-228-10
c. Droop Compensator. A droop compensator
maintains engine rpm (N2) as power demand is in-
creased. The compensator is a direct mechanical
linkage between the collective stick and the speed
selector lever on the N2 governor. Droop is defined
as the speed change in N2 rpm as power is increased
from a no-load condition. Without droop compensation,
instability would develop as engine ou tp ut is increased,
resulting in N1 speed overshooting or hunting the value
necessary to satisfy the new power condition. If N2
power is allowed to droop, othe r than m om entarily, t he
reduction in rotor speed could become critical.
d. Engine Idle Release Control. The engine idle
release is a spring loaded plunger mounted on the
switch box of the pilot collective stick (figure 2-3 and
figure 2-4). The plunger prevents the pilot from acciden-
tally retarding the throttle beyond engine idle position.
This acts as a safety feature by preventing inadvertent
engine shutdown. The plunger need not be depressed
when performing an engine start or runup; however,
the plunger must be depressed when accomplishing
an engine shutdown or when it is desired to retard the
power control below the engine idle position.
e. Governor RPM S witch. The GOV INCR/DECR
switch is mounted o n the pilot collective stick (figu re 2-3
and 2-4). The switch is a three-position momentary type
and is held in the INCR position (FWD) to increase the
power turbine (N2) speed or DECR position (AFT) to de-
crease the power turbine (N2) speed. Regulated power
turbine speed may be adjusted in flight through the op-
erating range by movement of the switch as required.
f. Gas Producer Fuel Control. The gas producer
fuel control has a bypass valve, metering valve, ac-
celeration bellows, governing and enr
ichment bellows,
manually operated cutoff valve, maximum pre ssure
relief valve, and a torque tube seal and lever assembly.
A maximum pressure relief valve is incorporated to
protect the system from excessive fuel pressure.
g. Power Turbine Governor. The power turbine
speed is scheduled by the power turbine governor
lever and the power turbine speed scheduling cam.
The c am sets a governor spring load which opposes
a speed-weight output. Overspeed protection of the
power turbine governor becomes effective at approxi-
mately 108% N2. This governing action will result in a
pulsating increase/decrease of engine power.
h. Deleted.
i. Fuel Pump and Filt er Assembly. The fuel pump
and filter assembly incorporates a single gear-type
pumping element, a low pressure barrier filter, a filter
bypass valve, and a bypass pressure regulating valve.
Fuel enters the engine fuel system at the inlet port of the
pump and passes through the low pressure filter b
efore
entering the gear element. The filt er bypass valv e
allows fuel to bypass the filter element if it becomes
clogged. The bypass return flow from the fuel c
ontrol is
passed back to the inlet of the gear element through a
pressure regulating valve which maintains the bypass
flow pressure above inlet pressure.
j. Deleted.
k. Fuel Nozzle. The fuel nozzle is a sing
le-entry
dual orifice type unit which contains an integral valve
for dividing primary and secondary flow.
l. Deleted.
Change 14 2-23
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