Navigation light
{{Short description|Lights on a vessel, aircraft or spacecraft giving information on its position, heading, and status}}
{{redirect|Position light|the railroad signals|North American railroad signals#Position light signals}}
{{Use British English|date=July 2022}}
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A navigation light, also known as a running or position light, is a source of illumination on a watercraft, aircraft or spacecraft, meant to give information on the craft's position, heading, or status.{{cite book |title=A Dictionary of Aviation |first=David W. |last=Wragg |isbn=9780850451634 |edition=first |publisher=Osprey |year=1973 |page=200}} Some navigation lights are colour-coded red and green to aid traffic control by identifying the craft's orientation. Their placement is mandated by international conventions or civil authorities such as the International Maritime Organization (IMO).
A common misconception is that marine or aircraft navigation lights indicate which of two approaching vessels has the "right of way" as in ground traffic; this is never true. However, the red and green colours are chosen to indicate which vessel has the duty to "give way" or "stand on" (obligation to hold course and speed). Consistent with the ground traffic convention, the rightmost of the two vehicles is usually given stand-on status and the leftmost must give way. Therefore a red light is used on the (left (port)) side to indicate "you must give way"; and a green light on the (right (starboard)) side indicates "I will give way; you must stand on". In case of two power-driven vessels approaching head-on, both are required to give way.
=Basic lighting=
Watercraft navigation lights must permit other vessels to determine the type and relative angle of a vessel, and thus decide if there is a danger of collision. In general, sailing vessels are required to carry a green light that shines from dead ahead to 2 points ({{frac|22|1|2}}°) abaftabaft: to the rear/closer to stern/'aft' the beam on the starboard side (the right side from the perspective of someone on board facing forward), a red light from dead ahead to two points abaft the beam on the port side (left side) and a white light that shines from astern to two points abaft the beam on both sides. Power driven vessels in addition to these lights, must carry either one or two (depending on length) white masthead lights that shine from ahead to two points abaft the beam on both sides. If two masthead lights are carried then the aft one must be higher than the forward one.
Small power-driven vessels (under {{convert|12|m}}) may carry a single all-round white light in place of the two or three white lights carried by larger vessels, they must also carry red and green navigation lights. Vessels under {{convert|7|m}} with a maximum speed of less than {{convert|7|kn}} are not required to carry navigation lights, but must be capable of showing a white light.{{Cite web |title=Amalgamated International & U.S. Inland Navigation Rules: Part C - Lights and Shapes |url=https://www.navcen.uscg.gov/navigation-rules-amalgamated |access-date=July 18, 2022 |website=United States Coast Guard Navigation Center}} Hovercraft at all times and some boats operating in crowded areas may also carry a yellow flashing beacon for added visibility during day or night.
=Lights of special significance=
In addition to red, white and green running lights, a combination of red, white and green mast lights placed on a mast higher than all the running lights, and viewable from all directions, may be used to indicate the type of craft or the service it is performing. See "User Guide" in external links.
- Ships at anchor display one or two white anchor lights (depending on the vessel's length) that can be seen from all directions. If two lights are shown then the forward light is higher than the aft one.
- Boats classed as "small" are not compelled to carry navigation lights and may make use of a hand-held flashlight.
See also
Notes
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References
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External links
{{commons category|Navigational lights}}
- {{webarchive |url=https://web.archive.org/web/20210509130706/https://www.glamox.com/upload/2015/11/20/aqua-signal_user-guide-navigation-lightsl_2015-16.pdf |date=May 9, 2021|title=Navigation Lights User Guide}}
{{Aircraft components}}
{{Artificial light sources}}
Category:Aerospace engineering