Which of the following is a recognised root cause of DP drive-off incidents, as identified in IMCA incident reporting?

A. Drive-offs are always caused by power management system failures

B. A failure of the thruster controller causing a thruster to go to maximum demand in a single direction, or a DP software fault generating an erroneous heading/position correction output

C. All drive-offs are caused by operator error — the DPO selected the wrong setpoint

D. Drive-offs only occur when transitioning between DP modes

A. A drive-off occurs during manual joystick mode; a drift-off only occurs in DP auto mode

B. A drift-off is always slower than a drive-off

C. A drive-off occurs when a thruster malfunction or DP system error actively propels the vessel away from position against the operator's intent; a drift-off occurs when power or thrust is lost and the vessel moves passively under environmental forces

D. They are two terms for the same event — the vessel leaves its position in both cases

A. Because drive-offs only occur in bad weather when the vessel is already at risk

B. Because a drift-off always results in a controlled shutdown, whereas a drive-off does not

C. Because thruster power is being applied in the wrong direction, accelerating the vessel toward (or away from) the structure — the vessel gains speed rapidly and the DPO has very little time to stop it before impact

D. Because drift-offs are automatically detected by the DP system and corrected; drive-offs are not