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 TM 55-1925-273-10-1
OPERATOR'S MANUAL
INLAND AND COASTAL LARGE TUG (LT)
THEORY OF OPERATION
CONTROL AIR SYSTEM
GENERAL
The control air system provides dry compressed air to the throttles and transfer valves in the pilothouse control console
(figure 1, item 1) and auxiliary control stations (STARBOARD, PORT, and AFT) (figure 1, item 2) of the Large Tug (LT).
The control console and auxiliary control stations are where the commands to maneuver the vessel originate.
The major components of the control air system consist of an air dryer (figure 1, item 3), pilothouse control console (figure
1, item 1), auxiliary control stations (STARBOARD, PORT, and AFT) (figure 1, item 2), the EOS console (figure 1, item 4),
the reduction gear ratio selector, and indicator system.
AIR DRYER
The air dryer removes the moisture from the compressed air before it is supplied to the control consoles and auxiliary control
stations.
CONTROL CONSOLES
The control console is the main control station where commands originate to engage the main propulsion and the bow thruster
engine.
AUXILIARY CONTROL STATIONS
The auxiliary control stations (STARBOARD, PORT, and AFT) (figure 1, item 2) are standby control stations where commands
originate to engage the main propulsion and the bow thruster engines in place of the main control console (pilothouse) (figure 1,
item 1).
EOS CONSOLE
The EOS control console (figure 1, item 4) contains the controls for selection of reduction gear ratios and engine throttle
controls. Pneumatic valves in each console and control station provide the necessary control of the system.
REDUCTION GEAR RATION SELECTION
A selector in the EOS control console (figure 1, item 4) allows selection of the desired forward reduction gear ratio. The
reduction gear selector will be disabled whenever the throttle control is not in the center or the NEUTRAL position, or
command is at a station other than the EOS control console.
IN COMMAND INDICATORS
The pilothouse control console (figure 1, item 1) and the EOS control console (figure 1, item 4) have indicators to show
which of the five stations has command and which clutch(es) are selected. The auxiliary control stations (STARBOARD,
PORT, and AFT) (figure 1, item 2) have a single indicator to show when that station is in command.
CONTROL AIR SYSTEM OPERATION
The transfer of command to the pilothouse console (figure 1, item 1) or one of the auxiliary control stations (STARBOARD,
PORT, and AFT) (figure 1, item 2) is initiated from the EOS console (figure 1, item 4). An engine room watchstander
positions the EOS COMMAND TRANSFER control from the EOS to the REMOTE position. At the selected station, the
operator pulls up and holds the COMMAND TRANSFER plunger until air (compressed) pressure is indicated on the CON-
TROL AIR PRESSURE gauge. Once the gauge indicates air pressure, transfer is complete and all other control stations are
disabled. Transfer between the pilothouse console and an auxiliary control station is accomplished by pulling up the COM-
MAND TRANSFER plunger at the desired station until air pressure is indicated on the CONTROL AIR PRESSURE gauge
0027 00-1
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