27 terms starting with A.
- Able Seaman (AB)
Certified deck rating with a minimum of 18 months sea service, competent in watchkeeping, mooring, and cargo handling.
- Abrasive Blast Cleaning
Surface preparation by abrasive grit; standards Sa 1, Sa 2, Sa 2.5, Sa 3 per ISO 8501.
- Aframax
Crude tanker 80,000-120,000 DWT — historically the AFRA (Average Freight Rate Assessment) midpoint; now the most common medium-haul crude size.
- AFS Convention
International Convention on the Control of Harmful Anti-Fouling Systems on Ships (2001).
- AIS Aid to Navigation (AIS-AtoN)
AIS station fitted on a buoy/light/synthetic mark broadcasting position and identity for ECDIS/radar overlay.
- AIS Class A
The mandatory AIS transponder fitted on SOLAS ships transmitting vessel data at regular intervals and responding to interrogations.
- AIS Class B
A lower-power AIS transponder used by smaller non-SOLAS vessels, transmitting position and identity data at reduced reporting rates.
- AIS-SART (AIS Search and Rescue Transmitter)
Survival-craft device that broadcasts AIS Class A position reports when activated, with an MMSI beginning 970, enabling rescuers to plot its position on AIS displays.
- AIS-SART
Survival craft locator that transmits a synthetic AIS Class A signal pattern to nearby ship and aircraft AIS receivers.
- Ammonia as Marine Fuel
Carbon-free fuel under development for two-stroke engines; key challenges are toxicity, NOx, and ammonia slip.
- Anchor Handling Tug Supply (AHTS)
Offshore vessel that handles MODU anchors during rig moves and supplies installations with deck cargo, mud, water, fuel.
- Anchor Handling Tug Supply Vessel (AHTS)
An offshore support vessel designed to tow and position mobile drilling rigs and handle anchors in deepwater operations.
- Anchor Handling Tug Supply Vessel (AHTS)
OSV that anchors and tows mobile offshore units and supplies rigs; high bollard pull and stern A-frame.
- Anchor Watch
Continuous bridge / deck watch monitoring position, swing, and chain tension to detect dragging.
- Anchorage
A designated area with suitable holding ground where a vessel anchors to wait for a berth, tide, or clearance.
- Anemometer
An instrument for measuring wind speed, with the cup anemometer and sonic anemometer being the most common types aboard ships.
- Angle of Loll
The angle at which a vessel with negative initial stability comes to rest on her side as she cannot return to upright.
- Angle of Vanishing Stability
Heel angle at which the GZ righting arm becomes zero — beyond which the ship will capsize.
- Annual Survey
A classification inspection conducted each year to confirm that a vessel's hull and equipment remain in a satisfactory condition.
- Antifouling Coating
Hull coating slowing or preventing biofouling; modern systems are silicone-based (foul-release) or copper/zinc biocidal.
- articulated tug-barge (ATB)
Tug rigidly locked into a purpose-built notch barge via a specialised coupling, operating as a single integrated unit while retaining separate vessel registration.
- Automatic Identification System (AIS)
VHF transponder system that automatically broadcasts vessel identity, position, course, and speed to nearby ships and shore stations.
- Autonomous Underwater Vehicle (AUV)
Untethered, programmable underwater vehicle for survey work — typically hydrographic, environmental, or military.
- Auxiliary Engine (AE)
A diesel generator engine providing electrical power for shipboard systems independent of the main engine.
- Azimuth
The angular bearing of a celestial body measured clockwise from true north, used to check compass error.
- Azimuth Stern Drive Tug (ASD)
Harbour/escort tug with two stern-mounted azimuth (Z-drive) thrusters giving 360° thrust direction.
- Azimuth Thruster
A propulsion unit that can rotate 360 degrees, providing both thrust and steering without a conventional rudder.