KNOWLEDGE TESTING

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(Note: There are 69 questions in total).

1 What is the main purpose of Dynamic Positioning?

A   To leave the positioning of the vessel to the computers in order that the operators on the bridge can be relieved of tedious work and focus on more important bridge responsibilities
B   To increase the accuracy of positioning
C   To increase operational safety
2 There are six degrees of freedom on a vessel afloat, three of which can be controlled by a Dynamic Positioning system. One of these three does not depend on the input of a position reference system. Which is it?

A   Surge
B   Sway
C   Yaw
3 What is the purpose of a Vertical Reference Sensor?

A   To measure the GPS antenna height
B   To measure the vessel displacement
C   To measure the pitch, roll (and heave) motions of the vessel
4 What single component is the most essential part of a DP system?

A   Navigation radar system
B   Wind sensor
C   The compass
5 What is the nominal accuracy of a modern DGPS system?

A   Less than 0.1 meters
B   Less than 1 meters
C   Less than 10 meters
6 What has a major negative effect on sound propagation in water when using an Acoustic Position Reference system?

A   Seabed topography
B   Water pressure
C   Thruster activity
7 When making a move under DP control it is recommended to make the move at a low speed. What is the main reason for this?

A   The position reference systems' filtering process is not able to cope at high speeds
B   The wind sensor will add the vessel speed to the true wind speed, thus giving an erroneous wind force
C   The reduction in transverse thruster efficiency creating a risk of losing heading control
8 When is it advisable to deselect the wind sensor?

A   When a helicopter is about to land on your vessel.
B   When moving from one position to another under DP control
C   When thunderstorms are in the vicinity
9 What is the main advantage of a triple redundant DP system?

A   Up to 3 DP operators may operate the DP system simultaneously
B   A dramatic increase in the Mean Time Between Failure (MTBF) rating.
C   You may leave one or two system(s) switched OFF, thus avoiding unnecessary wear and tear.
10 What is a Fanbeam system?

A   A microwave positioning reference system
B   An ultrasonic positioning reference system
C   A Laser positioning system
11 A DP system fitted with two gyrocompasses, both are enabled and one is in use by the DP system. The system suddenly alerts you that there is a heading difference between the two compasses. What would you do?

A   Immediately switch over to the other compass
B   Call the for assistance to check out the compasses and wait for the report
C   Compare the two compass readings with the standard (magnetic) compass, to decide which one is giving the correct heading and switch to it.
12 What is a vessel model?

A   100% accurate description of a vessel’s motions
B   A computer algorithm that calculates thruster set point signals.
C   A mathematical description of how the vessel reacts to the forces acting upon it (stimulus).
13 Most modern DP systems have a built in Trainer. What would be one of the requirements to enter the Trainer mode?

A   Ensure DP is in control of the thrusters
B   Ensure DP system is in Stand By Mode
C   Ensure a DP system is in active control of vessel positioning
14 What is required to enable Auto heading while in Joystick mode?

A   Position Reference System input
B   Wind Sensor input
C   Compass input
61 The Coanda effect causes

A   an increase in net thrust by the Bernoulli lowering of pressure on the downstream side of the hull.
B   a decrease in net thrust from change in momentum as propeller wash curves upward on downstream side of the hull.
C   a sometimes dangerous pulsating force from interaction of the propeller blades and the hull.
62 Fixed speed, variable pitch propellers

A   are inherently more efficient at generating thrust at all power levels.
B   are least efficient at full thrust.
C   lose up to thirty percent of full thruster power at low thrust.
63 For a given fixed-pitch propeller, thrust is directly proportional to:

A   Propeller speed.
B   Shaft input power.
C   Shaft torque.
64 One of the main functions of the Power Management System is to:

A   Prevent blackouts.
B   Reduce operator workload.
C   Reduce engine loads.
70 The purpose of wind feed forward is to hold closer position by

A   anticipating the wind force and correcting for it
B   measuring the wind force and providing an opposing thrust
C   providing an opposing thrust calculated from drag coefficients
71 The thrust required to hold vessel position against a wind of ten knots is 12,000 pounds ~ 53.38 kN. Considering wind only, and from the same direction, what thrust would be required at 60 knots?

A   432,000 pounds ~ 1,922 kN
B   360,000 pounds ~ 1,601 kN
C   144,000 pounds ~ 641 kN
72 At full rated thrust a fixed pitch variable speed thruster will produce about 30 pounds ~ 133.4 N of thrust per shaft horsepower. At half of rated thrust, the same thruster will produce about

A   15 pounds ~ 67 N per horsepower
B   30 pounds ~ 133 N per horsepower
C   42 pounds ~ 187 N per horsepower
73 Underwater Acoustic transmission is not hampered by

A   Rain
B   Solar prominences
C   Schools of fish
74 Acoustic reception is not damaged by

A   Bubbles in the water
B   Thruster noise
C   Snow
75 Acoustic reception is not obscured by

A   Waves
B   Coriolis impingement
C   Wind
76 Long base line acoustic position is determined by

A   Round trip time to multiple transponders in an array
B   Phase shift between elements in a single transducer
C   Difference in time of arrival of signal at separately mounted hydrophones
77 Ultrashort base line acoustic position is determined by

A   Round trip time to multiple transponders in an array
B   Phase shift between elements in a single transducer
C   Difference in time of arrival of signal at separately mounted hydrophones
78 Short baseline acoustic position is determined by

A   Round trip time to multiple transponders in an array
B   Phase shift between elements in a single transducer
C   Difference in time of arrival of signal at separately mounted hydrophones
79 How many Global Positioning Satellites are above the horizon at any time?

A   Approximately 12
B   Approximately 10
C   Approximately 6
80 How many Global Positioning Satellites are required to fix a position at sea?

A   1
B   3
C   4
81 Cumulus coud thunder storms can drop cold air and generate surface winds in excess of

A   40 knots
B   60 knots
C   80 knots
82 A Gulf of Mexico Eddy Current is a spin off from

A   The Gulf Stream
B   A tropical depression
C   A hurricane
83 In a DP control system, the controlled degrees of freedom are

A   Combined by the model
B   Controlled independently
C   Pitch, roll, and yaw
84 In a DP control system, the controlled degrees of freedom are

A   Surge and sway
B   Surge, sway, and yaw
C   Pitch, sway, and heading
85 Multipath can be a problem for both acoustic and satellite position sensing by

A   Confusing the distance and/or direction from the source through reflection
B   Creating a shorter than correct path for the signals
C   Causing the system to listen to the wrong signal source
86 What task does the Thruster Allocation Logic perform?

A   Allocates thrusters to generators that have sufficient power available
B   Monitors available generator power and divides it among online thrusters equally
C   Distributes the required force among active thrusters
87 What is a thruster exclusion zone

A   An area under the vessel where thrusters cannot be installed because of noise and geometry
B   Azimuth sectors within which thruster output is significantly limited to prevent noise and/or inflow degradation of other thrusters
C   Certain operating conditions in which thrusters are not allowed to be run, such as coming into shallow water to dock the vessel
88 What is thruster modulation

A   Significant frequent variations in thruster load
B   In order to resist noisy power circuits, thruster commands are encoded, or “modulated” to ensure accuracy over the long distance from DP to the thruster.
C   Thruster modulation is the technique of modulating, or smoothing out thruster commands so that power plant load is less “peaky”
89 Explain the effects if a thruster drive fails such that thruster output falls to 50% of commanded output on a thruster that is pushing the vessel to STBD (assume that this DP system does not use RPM feedback for control purposes)

A   Initially the vessel will move off location to PORT. The resulting position deviation causes the control system to correct the error by pushing harder with the remaining thrusters to STBD. After a few minutes the DP system will calculate an increased force from STBD.
B   Initially the vessel will move off location to PORT. The resulting position deviation causes the control system to correct the error by pushing harder with the remaining thrusters to STBD. After a few minutes the DP system will calculate an increased current from PORT.
C   No effect, the DP system control will increase the other thrusters to compensate. No errors will be introduced. The calculated force will remain unchanged.
90 Which of the following statements is most true about a controllable pitch fixed RPM thruster.

A   Starting currents are very high, power consumption is about 25% at zero thrust, and certain types of control failures may cause the thruster to run at 100%.
B   Starting currents are minimal, power consumption is about zero at zero thrust, and almost all control failures cause the thruster to shut down.
C   Starting currents usually require an extra engine online, power consumption is constant regardless of RPM, and all failure modes shut down the thruster.
91 Which of the following statements is most true about a fixed pitch variable speed thruster

A   Starting currents are very high, power consumption is about 25% at zero thrust, and certain types of control failures may cause the thruster to run at 100%.
B   Starting currents are small, power consumption is about zero at zero thrust, and most control failures cause the thruster to shut down.
C   Starting currents usually require an extra engine online, power consumption is constant regardless of RPM, and all failure modes shut down the thruster.
92 Which fixed pitch thruster configuration would cause the least power load

A   One thruster running at 90% of rated thrust
B   Two thrusters running at 45% of rated thrust each
C   Six thrusters running at 15% of rated thrust each
93 Which fixed pitch thruster configuration would produce the least noise effects on the acoustic position reference system

A   One thruster running at 90% of rated thrust
B   Two thrusters running at 45% of rated thrust each
C   Six thrusters running at 15% of rated thrust each
94 Which thruster configuration would produce the most thrust.

A   One thruster running at 90% Yes, run fewer thrusters at higher RPM to improve power factor of rated thrust
B   Two thrusters running at 45% of rated thrust each
C   Six thrusters running at 15% of rated thrust each
95 Can a DP Operator set up DC thrusters to improve the power plant’s power factor? If so, how?

A   Yes, run fewer thrusters at higher RPM to improve power factor
B   Yes, run more thrusters at lower RPM to improve power factor.
C   No, any configuration gives the same power factor
96 Which might best help DP performance in a power limit situation?

A   Shut off thrusters until all remaining thrusters are running above 90%
B   Drop all manual or automatic thruster biasing, adjust heading for minimum thrust, adjust thruster mode so that all thrusters are working in the same direction.
C   Both A and B above
97 What is the most likely reason a DC thruster that is being commanded to run at 45% would only show 20% feedback and what effect would this have on station keeping?

A   Bad command from DP. No effect because DP would compensate.
B   Failure of the thruster drive system. Calculated forces would be incorrect.
C   Actual DP need is really 20%. No effect on DP, nothing wrong.
98 If one thruster has been running for hours at 45%, opposing the environment, still has 45% command but suddenly begins showing 20% feedback and a drop in real load, what effect should this have on positioning ability? Assume the DP system uses open loop thruster control.

A   The DP systems automatically compensates for thruster RPM so it will have no effect.
B   The vessel will initially move off setpoint away from the environment, returns but becomes somewhat unsettled until the calculated forces readjust
C   The vessel will initially move off setpont into the environment, then slowly returns while the calculated forces readjust.
99 If one thruster that is opposing the environment is being commanded at 45% and over 12 hours still runs at 45% but slowly changes to where it is only showing 20% feedback, would this affect the positioning ability? Assume the DP system uses open loop thruster control.

A   The calculated force becomes artificially larger in the direction opposite to the environmental forces but there will be no immediate effect on the DP’s ability to maintain position.
B   The vessel will slowly move off location over the 12-hour period.
C   There would be no effect at all except a prediction alarm on that thruster.
100 If one thruster is being commanded 45% but suddenly began showing 20% feedback, what immediate action should you take? Assume mild environment and plenty of spare thruster capacity is available.

A   If positioning remains stable, notify appropriate personnel to start troubleshooting the problem. Immediately remove or replace the thruster in case of instability.
B   Don’t take action unless there is a warning, alarm or inability to maintain position.
C   Take the thruster out of service immediately. Make a note in the log book and notify your relief at the change of watch not to use the faulty or suspect thruster.
101 If one thruster that is running 45% suddenly starts showing 20% feedback, what is the fastest method to troubleshoot it from DP?

A   Watch positioning ability carefully and observe calculated force while alternately enabling and disabling the thruster.
B   Compare the thruster’s load readings with other thrusters running at similar RPM.
C   You cannot troubleshoot thruster feedback from DP, call the technician.
102 Can the drive of a DC thruster exhibit a zero or near-zero power factor?

A   No, the drive has power factor of about 0.6 at all times
B   Yes, at full power the magnetic field saturates and power factor goes to zero.
C   No, the associated DC motors never stall; power factor is about 0.6 at low RPM and approaches 1.0 at full RPM.
103 At what loads do DC thruster drives exhibit their best power factor and how high should it be?

A   At full Amperage and full RPM it should achieve 0.8 or higher.
B   At low RPM DC motor drives achieve 0.8 power factor or higher.
C   Power factor of a DC thruster motor drive is about 0.6 at any RPM.
104 In general, what is a network.

A   Computers in different locations that can transfer data
B   A common set of rules for computers to use for sharing data
C   A set of devices interconnected by communication paths
105 Explain how a network works.

A   Networks transmit data in one of several standard formats along a communications path that is common to many devices. Dedicated software and hardware layers serve to make the data transfer transparent to the final devices, so that equipment from numerous manufacturers can exchange data reliably.
B   Individual wires run from a central computer to dozens of remote devices, used to carry commands to each device as needed. This “net” of wires is used to get “work” done, hence the name “network”.
C   Networks are used to translate data into formats recognizable by different devices on the network.
106 What does the term “collisions” refer to on Ethernet networks?

A   Two or more devices transmitting at the same time, so that messages “collide” at the receiver and cannot be decoded
B   Data from a device is routed to the wrong destination, so that it “collides” when it arrives.
C   A “collision” occurs when an Ethernet device attempts to transmit data at the same time that data arrives. Both packets are lost and have to be resent.
107 What is a data timeout?

A   Data fails to arrive within the expected time frame
B   Data is received OK, but not accessed and processed within the expected time frame
C   Data packets collide and have to be retransmitted because of errors
108 How does Ethernet handle collisions

A   The devices immediately retransmit the lost data.
B   The devices resynchronize their clocks and then retransmit
C   The devices wait a random time and then retransmit.
109 Does Ethernet allow a percentage of data loss, or does it make sure all data gets through securely

A   Ethernet has a setting for allowable data loss, which is usually set to 5%
B   Ethernet doesn’t allow data loss
C   Ethernet doesn’t know or care about data loss.
110 A network hub or switch may be used in a DP system:

A   To actively monitor network traffic and determine the fastest of multiple available paths for a unit of data to reach its destination. One example is sending thruster data directly to the DP computers without incurring time delays by first passing though other remote units that aren’t involved with thruster control.
B   To combine data from several devices on a network and distribute the data in a controlled fashion to the destination devices. One example is the hubs used to link the DP computers and remote I/O.
C   To separate subsections of a network in order that data can be shared but maintain separation of unrelated devices. One example is allowing the DP system to receive data from drilling, power, or BOP networks but not allowing any unwanted data transfer from these outside systems that might crash DP.
111 TCP/IP is the protocol used on the internet and most DP networks. Which best describes TCP/IP

A   TCP or “Transmission Control Protocol” is the unique address used to identify devices on a network. TCP numbers are issued by a central authority so that manufacturers world wide each have unique numbers on their devices. IP or “Internet Protocol” is the error-correcting data transfer method used by the internet to move data between devices. TCP/IP refers to the result of both protocols.
B   TCP or “Transmission Control Priority” is used to direct data along the network. Essentially, TCP acts like a mail delivery system. TCP makes sure the data goes the right direction but doesn’t make sure that data arrives. IP or “Inspection Priority” makes sure that data is reassembled in the correct order. TCP/IP refers to the result of both protocols used to transfer data and reassemble it. Because hardware is so much faster than software, TCP/IP intentionally ignores error checking. Error checking is a performed by the network devices themselves and has nothing to do with TCP/IP.
C   TCP or “Transmission Control Protocol”, is responsible for verifying the correct delivery of data from client to server. Data can be lost in the intermediate network. TCP adds support to detect errors or lost data and to trigger retransmission until the data is correctly and completely received. IP is responsible for moving packet of data from node to node. IP forwards each packet based on a four byte destination address (the IP number). IP doesn’t make sure that the data arrives. TCP/IP refers to the result of both protocols.
112 One DP computer has a sticker on it that says “207.123.123.001”. The second computer has a sticker that says “207.123.123.002”. The remote I/O has a sticker that says “207.123.123.003”. What are these numbers and why are they important?

A   These are factory part numbers and must be included when ordering spare or replacement parts, or if installing an onboard spare. The replacement part must have the same sticker.
B   These are the IP or network addresses of the network interface circuit boards. If a device is replaced it will have a new sticker with a new address, which are unique to each device. All the other devices on the network will need to be updated to know the address of the new device.
C   These are the IP addresses of the devices. If a replacement is installed its network address must be set to the correct IP address for the other devices to be able to communicate with it.
113 Explain power factor

A   Power factor represents the ratio of real to reactive power in the power plant
B   Power factor equals generator kW divided by kVA
C   A & B
114 Two thrusters have the same power rating and same propeller diameter. One has wide blades, the other narrow blades. Which one has the higher efficiency?

A   The one with the narrow blades
B   The one with the wide blades
C   No difference
115 Two thrusters have the same power rating and propeller diameter. One has wide blades, the other narrow blades. Which is more likely to cavitate and generate noise?

A   The one with the narrow blades
B   The one with the wide blades
C   No difference
116 Two thrusters have the same power rating. One has a large propeller diameter, the other a smaller diameter. Which one generates more thrust at bollard pull ?

A   The one with the smaller diameter
B   The one with the larger diameter
C   No difference
117 At full power, in which condition does a thruster propeller generate more thrust ?

A   Bollard pull
B   Underway at 15 knots
C   No difference
118 One thruster is at 20 feet ~6.5m depth. Another is at 80 feet ~ 26m depth. Both do not cavitate. Which is more efficient?

A   The one at the lesser depth
B   The one at the greater depth
C   No difference
119 A thruster is at 20 feet ~ 6.5m depth. An identical thruster is at a depth of 80 feet ~ 26m. Which one is more prone to cavitate and generate The same magnitude of thrust noise?

A   The one at the lesser depth
B   The one at the greater depth
C   No difference
120 A thruster operates at bollard pull on one occasion, and in 4 knots current on another occasion. In both cases it works at full nominal power. At 4 knots speed does the thruster generate:

A   25% less thrust than at bollard pull
B   25 % more thrust than at bollard pull
C   The same magnitude of trust

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