Editing Runway (section)

==Sections==
There are standards for runway markings.<ref>[http://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentid/1022266 FAA AC 150/5340-1L – Standards for Airport Markings] pages 13 and following</ref>

[[File:Runway diagram.svg|700px|center]]

* The '''runway thresholds''' are markings across the runway that denote the beginning and end of the designated space for landing and takeoff under non-emergency conditions.<ref>{{webarchive |url=https://web.archive.org/web/20140207222155/http://128.173.204.63/courses/cee4674/cee4674_pub/markings_airports_rev.pdf |date=7 Feb 2014}}</ref>
* The '''[[runway safety area]]''' is the cleared, smoothed and graded area around the paved runway. It is kept free from any obstacles that might impede flight or ground roll of aircraft.
* The '''runway''' is the surface from threshold to threshold (including displaced thresholds), which typically features threshold markings, numbers, and centerlines, but excludes blast pads and stopways at both ends.{{Anchor|blastpad}}
* '''Blast pads''' are often constructed just before the start of a runway where [[jet blast]] produced by large planes during the takeoff roll could otherwise erode the ground and eventually damage the runway. 
* '''Stopways''', also known as overrun areas, are also constructed at the end of runways as emergency space to stop planes that overrun the runway on landing or a [[rejected takeoff]].
** Blast pads and stopways look similar, and are both marked with yellow [[Chevron (insignia)|chevrons]]; stopways may optionally be surrounded by red runway lights. The differences are that stopways can support the full weight of an aircraft and are designated for use in an aborted takeoff, while blast pads are often not as strong as the main paved surface of the runway and are not to be used for taxiing, landing, or aborted takeoffs.<ref name="AC 150/5300-13B">{{cite web |url=https://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentID/1040834 |title=AC 150/5300-13B - Airport Design |access-date=15 April 2023 }} FAA Advisory Circular 150/5300-13B</ref> An '''[[engineered materials arrestor system]]''' (EMAS) may also be present, which may overlap with the end of the blast pad or stopway and is painted similarly (although an EMAS does not count as part of a stopway).<ref name="AC 150/5300-13B"/>
[[File:Runway diagram, Blast pad.png|700px|center]]
* '''[[Displaced threshold]]s''' may be used for taxiing, takeoff, and landing rollout, but not for touchdown. A displaced threshold often exists because of obstacles just before the runway, runway strength, or noise restrictions making the beginning section of runway unsuitable for landings.<ref>Pilot's Handbook of Aeronautical Knowledge FAA-H-8083-25A, p. 306</ref> It is marked with white paint arrows that lead up to the beginning of the landing portion of the runway. As with blast pads, landings on displaced thresholds are not permitted aside from emergency use or exigent circumstance.
[[File:Runway diagram, Displaced threshold.png|700px|center]]
* '''Relocated thresholds''' are similar to displaced thresholds. They are used to mark a portion of the runway temporarily closed due to construction or runway maintenance. This closed portion of the runway is not available for use by aircraft for takeoff or landing, but it is available for taxi. While methods for identifying the relocated threshold vary, a common way for the relocated threshold to be marked is a ten-foot-wide white bar across the width of the runway.<ref>{{Cite PHAK|year=2016|chapter=14|page=5}}</ref>
* '''Clearway''' is an area beyond the paved runway, aligned with the runway centerline and under the control of the airport authorities. This area is not less than 500&nbsp;ft and there are no protruding obstacles except for threshold lights provided they are not higher than 26 inches. There is a limit on the upslope of the clearway of 1.25%. The length of the clearway may be included in the length of the [[Runway#Declared distances|takeoff distance available]].<ref>US Federal Aviation Regulations, FAR Part 1, Definitions and abbreviations</ref> For example, if a [[Runway#Pavement|paved]] runway is {{convert|2000|m|ft}} long and there are {{convert|400|m|ft}} of clearway beyond the end of the runway, the takeoff distance available is {{convert|2400|m|ft}} long.  When the runway is to be used for takeoff of a large airplane, the [[Maximum Takeoff Weight#Maximum permissible takeoff weight or maximum allowed takeoff weight|maximum permissible takeoff weight]] of the airplane can be based on the takeoff distance available, including clearway.  Clearway allows large airplanes to take off at a heavier weight than would be allowed if only the length of the paved runway is taken into account.