DPO Operation & Vessel Maneuvering 2 — Questions and Answers
Question 1: When executing a DP approach to a fixed platform in current-dominated conditions, the operator should align the vessel so that:
- The bow points directly into the current
- The vessel's most powerful thrusters face the dominant force (Correct answer)
- The stern faces the platform for quick departure
- The vessel drifts naturally alongside the platform
Correct answer: The vessel's most powerful thrusters face the dominant force
Orienting the vessel so its most powerful thrusters oppose the dominant environmental force maximizes station-keeping capacity and control authority.
Question 2: During a DP operation, the operator notices the vessel's actual heading deviating consistently from the DP-commanded heading. The FIRST action should be to:
- Switch to manual heading control immediately
- Check gyrocompass inputs and verify sensor validity (Correct answer)
- Increase thruster output to compensate
- Initiate an emergency DP disconnect
Correct answer: Check gyrocompass inputs and verify sensor validity
A persistent heading deviation often indicates a sensor input problem; verifying gyrocompass validity before taking control action prevents compounding the issue.
Question 3: What is the primary purpose of performing a 'consequence analysis' on a DP vessel before operations?
- To calculate the vessel's total fuel consumption for the operation
- To determine which thruster failures would cause the vessel to lose position (Correct answer)
- To assess the financial risk of equipment damage during the operation
- To calculate the maximum speed achievable in current conditions
Correct answer: To determine which thruster failures would cause the vessel to lose position
Consequence analysis simulates thruster failure scenarios to determine which single or combined failures would cause loss of position, informing the required DP class.
Question 4: A DP vessel is operating in 'DP2' mode. Which statement about redundancy is correct?
- Any single failure may cause loss of position but not sinking
- Any single failure must not result in loss of position or heading (Correct answer)
- Two simultaneous failures are acceptable without loss of position
- Redundancy only applies to power systems, not thruster systems
Correct answer: Any single failure must not result in loss of position or heading
IMO DP Class 2 (DP2) requires that any single failure of active components or systems must not cause loss of position or heading.
Question 5: During a vessel approach, the DP operator uses the 'joystick mode' rather than fully automatic DP. This mode differs from auto-DP because:
- Joystick mode uses GPS only, while auto-DP uses all position reference systems
- The operator provides manual force commands while the DP system allocates thrust (Correct answer)
- Joystick mode disables all thruster feedback loops entirely
- Auto-DP is faster to respond than joystick mode in all conditions
Correct answer: The operator provides manual force commands while the DP system allocates thrust
In joystick mode the operator commands forces and moments directly, but the DP system still handles thrust allocation among individual thrusters.
Question 6: What effect does a strong tidal current have on DP vessel operations near a fixed structure?
- It reduces power consumption as the vessel rides the current
- It can create suction and bank effects, complicating position keeping (Correct answer)
- It has no effect if the DP system is in fully automatic mode
- It only affects vessels with azimuth thrusters, not tunnel thrusters
Correct answer: It can create suction and bank effects, complicating position keeping
Strong tidal currents near fixed structures can generate hydrodynamic interaction forces such as suction and bank effects that the DP system must compensate.
Question 7: When a DP vessel is operating in 'auto-heading' but not in 'auto-position', the operator must:
- Manually monitor and adjust heading using the rudder only
- Manually control surge and sway while the DP maintains heading automatically (Correct answer)
- Disengage all thrusters not related to heading control
- Switch to full manual control because partial DP modes are not permitted
Correct answer: Manually control surge and sway while the DP maintains heading automatically
In auto-heading only mode, the DP system manages heading via thruster allocation while the operator manually controls the vessel's position in surge and sway.
DPO Operation & Vessel Maneuvering 2
When executing a DP approach to a fixed platform in current-dominated conditions, the operator should align the vessel so that: