Editing Azimuth thruster (section)

==Types of azimuth thrusters==
[[File:Oued el Kebir-IMG 9346.jpg|thumb|upright|Azimuth thrusters on the tug ''Oued el Kebir'' - note the [[Kort nozzle]]s]]

There are two major variants, based on the location of the motor:{{cn|date=November 2014}}

# [[Transmission (mechanics)|Mechanical transmission]], which connects a motor inside the ship to the outboard unit by [[gear]]ing.  The motor may be [[Diesel engine|diesel]] or [[Diesel-electric transmission|diesel-electric]].  Depending on the shaft arrangement, mechanical azimuth thrusters are divided into [[L-drive]] and [[Z-drive]].  An L-drive thruster has a vertical input shaft and a horizontal output shaft with one right-angle gear.  A Z-drive thruster has a horizontal input shaft, a vertical shaft in the rotating column and a horizontal output shaft, with two right-angle gears.
# [[Diesel-electric transmission|Electrical transmission]], more commonly called pods, where an electric motor is fitted in the pod itself, connected directly to the propeller without gears. The electricity is produced by an onboard engine, usually [[Diesel engine|diesel]] or [[gas turbine]]. Invented in 1955 by [[Friedrich W. Pleuger]] and [[Friedrich Busmann]] (Pleuger Unterwasserpumpen GmbH), [[ABB Group]]'s [[Azipod]] was the first product using this technology. 

The most powerful podded thrusters in use are the four 21.5 MW Rolls-Royce Mermaid units fitted to {{RMS|Queen Mary 2}}.<ref>{{cite web| url=https://www.wartsila.com/encyclopedia/term/mermaid-propulsion-unit| title=Mermaid propulsion unit| publisher=[[Wärtsilä]]| access-date=1 February 2020}}</ref>

Mechanical azimuth thrusters can be fixed installed, retractable or underwater-mountable. They may have fixed pitch propellers or [[controllable pitch propeller]]s. Fixed installed thrusters are used for tugboats, ferries and supply-boats. Retractable thrusters are used as auxiliary propulsion for dynamically positioned vessels and take-home propulsion for military vessels.  Underwater-mountable thrusters are used as dynamic positioning propulsion for very large vessels such as [[semi-submersible]] [[drilling rig]]s and [[drillship]]s.