Engine Start/Stop Switches
LYCOMING TF40B ENGINE CONTROL
SYSTEM
The function of the TF40B engine start/stop
The TF40B engine control system provides
the
switches is to allow the operator to start and stop the
operator with controls and indicators to operate
the
engines from the control station. Each engine has a
START/STOP switch and an OFF/IDLE/RUN master
engines and to move the craft effectively and safely.
The
switch. The START/STOP switches send signals to the
engine control system consists of the following
five
engine sequencing units, then to the respective engine
control and indicator panels:
control box, to carry out the ordered function.
1. N1
Engine Balancing Control Potentiometers
2 . N2
3. Engine balancing
The function of the engine balancing control
4. Engine instrument
potentiometers is to control the power output of each
engine to make sure the engines are balanced.
5. Engine start
The N1 unit is the gas producer control unit. The N2
Gas Producer Controls
unit is the power producer control unit. The engine
balancing control unit is combined with the N2 unit to
The gas producer controls (Nl) are used by the
balance the power outputs of the four TF40B engines.
engineer to set the speed of the engines. These controls
T h e engine instrument panel provides an analog
are located in the engineer control station. The primary
indication of engine operating conditions. The engine
function of these controls is to allow the operator to
start panel gives the engineer or craft operator control
control the speed of the gas turbine engines and move
of the engine start and shutdown cycles.
the craft.
The controls for the TF40B engine control system
Power Producer Controls
are powered from two de power panels and by signals
from the CSEP. The N2 and engine balance control
Like the gas producer controls, the primary function
signals are combined through the CSEP. The N1 control
of the power producer controls (N2) is to allow the
signals are supplied with a positive-to-negative control
operator to control the speed of the engines. When the
voltage range from the CSEP.
operator uses the power producer controls, a signal goes
Now that you have read about the control and
to the CSEP and the correct engine control boxes to
indicator panels, let's take a look at the gas turbine
control that engine's speed.
engines and their associated controls.
Automatic Shutdown Normal/Override Switch
Gas Turbines Engines
The automatic shutdown, normal/override switch
a l l o w s the craft operator to inhibit all automatic
shutdown features of the TF40B except an overspeed
There are four direct-drive, high-speed TF40B gas
condition. This switch allows the operator to control the
turbine engines in the LCAC. Two are located on the
engines under battle conditions. This component was
port side and two are on the starboard side. The
built into the engine control system to provide maximum
two-engine assembly for each side of the craft consists
safety for LCAC personnel.
of a two-stage free-power turbine and a combination
axial/centrifugal compressor driven by a two-step
Engine Control Channel Selector Switch
axial-flow turbine. (Compare figs. 7-1 and 7-11.) Each
of these assemblies is the power source that drives the
lift fans, propellers, and forward and aft gearboxes for
The function of the engine control channel selector
that side of the craft. The lift fans and propellers are
switch is to select which CSEP will be used for engine
interconnected through the drive train by offset and
control. The operator can select the desired channel by
engine gearboxes. There is a manual clutch provided on
using the ENGINE CNTL A/B switch located on the
each power train to allow the forward engine to be
C&C keyboard. This switch provides redundancy in
disconnected from the aft engine.
case of a system malfunction or an emergency.
7-11
