NSTM Chapter 562, Surface Ship Steering Systems Flashcards
The use of the steering gear while the ship is moving in the reverse direction
Astern rudder operations
On some ships, the astern speed, maximum rudder angle, or both are limited during astern operations so that the ___
Design rudder torque is not exceeded
Steering control equipment that allows the helmsman to enter a heading order for the ship, the ship maintains the heading without the need for steering with a helm wheel
Autopilot
The ordered or desired rudder angle that is input by the helmsman at the helm or differential control unit through manual operation of a helm wheel
Command angle
A condition where one rudder takes longer than a second rudder when the system is responding to a change in the command angle
Dynamic rudder split
Sometimes referred to as rudder lag
Dynamic rudder split
Components within the steering system that follow the position of the hydraulic rams or rubber stock and send a mechanical or electrical signal to the controls that is in proportion to the actual rudder position
Follow-up
The ___ provides a rudder position feedback signal to the control and nulls the pump output as the command angle is reached
Follow-up
Components of a hydraulic system that include the pump, electric motor, and other components needed to control the rudder
Hydraulic power unit
A condition where the helm angle indicator and rudder angle indicators do not display the same angle even though the rudder is not moving
Indicator split
An ___ can also occur when the rudder angle indicators do not display the same angle as the mechanical rudder angle indicator located near the rudder stock
Indicator split
A steering mode available on some ships that uses a type of joy-stick control to turn the rudder to the left or right. In this mode, the steering system does not position the rudder to an ordered angle
Nonfollow-up steering
A condition where the ram rotates slightly about its longitudinal axis as the rudder moves
Ram roll
The actual position of the rudder, measured in degrees from the zero position
Rudder angle
The average speed the rudder moves during a hard-over to hard-over rudder swing while moving ahead at the maximum rated ship speed
Rudder rate
Rudder rate is usually measured in ___
Degrees per second
A condition where the rudders of a ship do not stop at the same exact angle
Static rudder split
Different methods of operating the steering gear
Steering modes
The locations on the ship, usually the bridge and steering gear rooms, where the steering equipment can be controlled
Steering station
In breaking flanged joints, ensure that two ___ remain tight while the remainder are slacked
Diametrically opposite securing nuts or bolts
When testing after repairs, take the following precautions
Use a small-volume external pressure source for hydrostatic tests
Protect reassembled joints with spray shields or by wrapping them with polyethylene bags
Before use, subject temporary hoses to a shop hydrostatic pressure of at least ___ of the maximum pressure that the hose will be subjected during the temporary use on the ship
110%
Do not use ___ plated parts in any hydraulic unit where they may come in contact with hydraulic oil
Cadmium
Why shouldn’t cadmium-plated parts be used in a hydraulic unit where they may come in contact with hydraulic oil?
Cadmium reacts chemically with hydraulic fluid with detrimental results to system operation
___ after working with cadmium-plated tools or parts to avoid poisoning from ingestion of cadmium-contaminated food
Wash hands thoroughly
Remove oil spills or leaks as soon as possible to prevent ___
Injury from slipping and to eliminate fire hazards
The appropriate military specifications for large Navy surface ship steering systems
MIL-S-17803
MIL-S-17903
A ship is steered by the ___
Force of the water acting on the rudder as the ship moves through the water
The function of the steering system is to ___
Control the position of the rudder against the force of the water
Involves turning the rudder to a desired angle in degrees and holding the rudder in position
Rudder control
The force from the water on the rudder creates a ___ on the rudder stick
Torque
The ___ and the ___ or torque acting on the rudder stock are not constant
Magnitude
Direction
Torque varies with changes in ___ and is affected by ___
Rudder angle
Ship speed and sea state
The steering system adapts to these changes in torque by ___
Producing enough countering torque on the rudder stock to control the position of the rudder
Shows the estimated rudder torque at the maximum ship speed for a particular ship
Rudder torque curve
The basis for determining the sizes of the rudder actuator and the steering gear power units
The maximum torque value
The negative and positive regions of the rudder torque curves graph indicate the ___
Direction that the torque is applied to the rudder stock
For most ships, the rudder torque direction changes at the ___ rudder angle and at a ___ rudder angle
0
25
The rudder has a natural tendency to travel to the ___ degree position left or right of center
25
When the rudder torque is negative, the steering gear applies torque in the direction ___
Opposite the direction of rudder travel
When the rudder torque is positive, the steering gear applies torque in the direction ___
Of the rudder travel
When the ship is moving in reverse, the force of the water on the rudder tries to move the rudder ___
Away from center
The design and shape of the rudder affect the ___ acting on the rudder and steering system
Loads and torque
Instead of adding excess weight to the steering system strictly for astern operations, the ____ is limited
Maximum allowable ship speed that can be used for astern operations
When operating properly, the steering system will position the rudders to the ___
Command angle
Steering systems with new or overhauled follow-up assemblies are required to have a mechanical comparative error of not more than ___ from 0 to 5 degrees rudder angle and ____ for any rudder angle greater than 5 degrees
±1/4 degree
±1/2 degree
The comparative error requirement is based on measurements taken at the ___ and the ___
Rudder angle indicator on the mechanical differential steering stand
Mechanical rudder angle indicator on the tiller or rudder actuator
Accuracy of the steering is affected by ___ and by the ___
Lost motion in each of the gearboxes and pivot joints
Sensitivity of the pump servo control valve
Realistic accuracy requirements are a comparative error of not more than ___ from 0 to 5 degrees of rudder angle and ___ for any rudder angle greater than 5 degrees
±1/2 degree
±1 degree
An error of up to ___ is allowed when comparing the rudder angle indicated on the ship control console, or other remote electrically-operated indicators, with the mechanical rudder angle indicator in the steering gear room
2 degrees
A condition where the helm angle indicators and the rudder angle indicators do not display the same angle even though the rudder is not moving
Indicator split
Occurs when the rudder angle indicators do not display the same angle as the mechanical rudder angle indicator located near the rudder stock
Indicator split
Indicator splits can be caused by ___
Lost motion or misalignment of the follow-up mechanism or by problems with indicator calibration
Indicator splits should be corrected when they ___
Exceed the rudder position accuracy or remote rudder angle indicator accuracy requirements
Condition where the steering system positions the rudder beyond the command angle and the rudder remains in that position
Overtravel
Condition where the steering system turns the rudder beyond the command angle then reverses direction to position the rudder where it should have stopped
Overshoot
The average speed that the steering system rotates the rudder under full power and full pump output conditions
Rudder rate
Rudder rate is a design criteria for the steering system that is based on ___
The maneuvering performance requirements of the ship
When measuring rudder rate, measurement begins and ends at ___
30 degrees (or 5 degrees before hard over)
The final five degrees are not used to determine rudder rate because the steering system ___
Slows the rudder as it approaches the command angle
Measured rudder rates are approximately ____ faster when measured at the pier rather than underway
5 to 10%
Condition where one rudder takes longer than, or lags behind, a second rudder when the system responds to a change in the command angle
Dynamic rudder split
A maximum permissible rudder split should not be greater than ___
5°
Condition where the rudders of a ship do not stop at the same exact angle
Static rudder split
When the rudders are not moving, the difference between the two angles should not exceed ___ for rudder angles between 0 and 5 degrees, and should not exceed ___ for any rudder angles greater than 5 degrees
1°
2°
Two types of steering systems
Electrohydraulic systems
Electromechanical systems
