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 TM 55-1905-223-24-6
p. Hydraulic Motors. (FIGURE 1-17). Two identical reversible hydraulic motors drive the right and left
steering gear assemblies. Piping to the motors is configured to operate both motors in parallel from a common
control valve. The motors drive identical gear assemblies which engage opposite arcs of the bevel gear and
therefore turn in opposite directions.
q. Disk Brakes. (FIGURE 1-17). A disk brake between each hydraulic motor and the associated steering
gear mechanically applies friction to the motor shaft whenever hydraulic pressure is below the threshold of the
load holding valve. During normal steering, this brake is disengaged. At all other times, it is engaged.
r. Oil Evacuation Pump. (FIGURE 1-18). This semi-rotary hand pump allows the removal of lube oil and
hydraulic fluid from enclosures that cannot be drained by gravity. The pump is bolted to one leg of the
framework supporting the motor/pump assembly.
1-9. Safety, Care and Handling. Safety precautions must be observed at all times while performing
maintenance. General WARNINGS and first-aid data appear in the front of this manual. Review all safety
information before starting any task. Carefully read through an entire maintenance procedure before performing
any maintenance function. Make sure the task can be done safely. All WARNINGS, CAUTIONS, and NOTES
are of great importance to your personal safety and the safety of the equipment.
Section III. PRINCIPLES OF OPERATION
1-10. General. The bowthruster waterjet is a propulsion and steering system located at the bow and used in
combination with the ship's twin screws and twin rudders to give the LCU added maneuverability. A high volume
jet pump driven by the bowthruster diesel engine is the propulsion element. Throttling the engine increases or
decreases the thrust force. Twin hydraulic steering motors point the jet nozzle to any desired relative bearing. This
controls thrust direction.
Displacement of seawater in a given direction generates an equal recoil force in the opposite direction. This
directional recoil force moves the bow of the LCU as needed. Local control of the waterjet is provided in the
bowthruster room. A manual control handle on the valve assembly steers the waterjet clockwise or
counterclockwise, depending on which way the handle is moved. A thrust direction indicator identical to the one on
the pilot house console is mounted on the cover of the rudder angle transmitter. These controls allow a local
operator to steer the waterjet on orders from the pilothouse.
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