Definitions
Stopping ability is measured by the “track reach” and “head reach” realized in a stop engine-full astern maneuver performed after a steady approach at the test speed until ahead speed in ship coordinates changes sign (i.e., vessel starts going backward).
• Track Reach is defined as a distance along the vessel’s track that the vessel covers from the moment that the “full astern” command is given until ahead speed changes sign.
• Head Reach is defined as a distance along the direction of the course at the moment when the “full astern” command was given. The distance is measured from the moment when the “full astern” command is given until the vessel is stopped dead in the water.
Track Reach Criterion
The stopping ability of the vessel is judged using a full astern crash stop maneuver. Based on IMO requirements the track reach should generally not exceed 15 ship lengths (measured along the path).
However, in the case of low-powered large displacement vessels, this value may be modified, but in no case should exceed 20 ship lengths, subject to special consideration and approval by the Bureau.
Determination of whether a vessel falls into the category of “low powered large displacement vessels” also will be done by the Bureau.
Head Reach Criterion
Head reach criterion in a form of rating is based on statistics of sea trials.
Stopping ability rating only if:
TR < 20L only for low-powered large displacement vessel
TR < 15L in all other cases
where
TR = track reach, in meters
L = vessel length, in meters
