Auxiliary

A secondary machine, system or service that supports a vessel’s primary operation.

On a sailing vessel, “the auxiliary” commonly means an engine providing propulsion when sails are unsuitable or additional control is needed. On other vessels, auxiliary machinery includes generators, pumps, compressors, thrusters and systems serving functions other than the main propulsion plant.

Auxiliary does not necessarily mean emergency backup or smaller equipment. The role, rating and operating limits must be understood from the vessel’s design and procedures, particularly where loss of the auxiliary service affects propulsion, steering, power or safety.