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 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

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

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

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 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

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

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