Electronic Inclinometers and Roll Recording

An electronic inclinometer measures and records a ship’s roll angle, replacing the mechanical pendulum instrument that has been standard bridge equipment for over a century. SOLAS Chapter V Regulation 19 was amended in June 2023 to require one on container ships and bulk carriers of 3,000 gross tonnage and above constructed on or after 1 January 2026, together with a means to display and record roll motion.

The requirement exists because the mechanical instrument is unreliable in the conditions that matter. A pendulum inclinometer responds to the vector sum of gravity and lateral acceleration rather than to heel alone, so in a heavy roll it reads high. The joint investigation into the MSC Zoe container loss determined that the crew’s reports of about 30 degrees of roll came from such a reading, and that the actual maximum was about 16 degrees.

An accurate and recorded roll history matters beyond the bridge. It is the input to any check that the roll angle assumed by the lashing calculation was respected, and it is evidence after a casualty.

The full article will cover the measurement principle and why a pendulum misreads under acceleration, the carriage requirement and its application dates, the recording and display requirements, the use of roll data in cargo securing verification and casualty investigation, and the relationship to voyage data recorders.