Editing Airfield traffic pattern (section)

== Layout ==
[[Image:Airport Traffic Pattern from AIM 4-3-2.svg|thumb|upright=1.35| Standard traffic pattern. Fig. 4-3-2 from FAA AIM.]]
[[Image:Airport Traffic Pattern with Upwind Leg.svg|thumb|upright=1.35| Components of a traffic Pattern. Fig. 4-3-1 from FAA AIM.]]
Traffic patterns can be defined as left-hand or right-hand according to which way the turns in the pattern are performed. They are usually left-hand turns because most small airplanes are piloted from the left seat (or the senior pilot or [[pilot-in-command]] sits in the left seat), and so the [[aviator|pilot]] has better visibility out the left window. Right-hand patterns will be set up for parallel [[runway]]s, for noise abatement, or because of ground features (such as terrain, towers, etc.). In the US, the non-standard (i.e. right-hand) patterns are noted in the Airport/Facilities Directory or on a [[sectional chart]]; in other countries they may be indicated in that nation's similar document, e.g. Canada Flight Supplement. Unless explicitly indicated otherwise, all traffic patterns at [[non-towered airport]]s are to the left.  The direction of the pattern may be indicated by a [[traffic pattern indicator]] in the aerodrome's [[signal square]].

In the United States, the [[Code of Federal Regulations]] CFR 91.126 a. (2) requires helicopters to avoid the flow of fixed wing aircraft.<ref>{{cite web|url=http://www.ecfr.gov/cgi-bin/text-idx?node=14:2.0.1.3.10#se14.2.91_1126|title=eCFR — Code of Federal Regulations}}</ref>

Because the [[active runway]] is chosen to meet the wind at the nearest angle (with take-offs and landings upwind), the pattern orientation also depends on wind direction. Patterns are typically rectangular in basic shape, and include the runway along one long side of the rectangle. Each leg of the pattern has a particular name:<ref name="FAA AIM 4-3">{{Cite book
 |author=Federal Aviation Administration 
 |author-link=Federal Aviation Administration 
 |contribution=4-3-2.c Airports with an Operating Control Tower 
 |contribution-url=http://www.faa.gov/air_traffic/publications/ATpubs/AIM/Chap4/aim0403.html 
 |access-date=2011-03-07 
 |title=Aeronautical Information Manual: Official Guide to Basic Flight Information and ATC Procedures 
 |place=Washington, DC 
 |date=11 February 2010 
 |edition=Change 1 (26 August 2010) 
 |url=http://www.faa.gov/air_traffic/publications/ATpubs/AIM/ 
 |publisher=[[Federal Aviation Administration]] 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20090712031134/http://www.faa.gov/air_traffic/publications/ATpubs/AIM/ 
 |archive-date=12 July 2009 
}}</ref>

* ''Upwind leg''. A flight path parallel to and in the direction of the landing runway. It is offset from the runway and opposite the downwind leg.
* ''Crosswind leg''. A short climbing flight path at right angles to the departure end of the runway.
* ''Downwind leg''. A long level flight path parallel to but in the opposite direction of the landing runway. (Some{{who|date=March 2011}} consider it to have "sub-legs" of early, mid and late. Certainly a plane giving a position report of "mid-downwind" can be visually located easily.)
* ''Base leg''. A short descending flight path at right angles to the approach end extended centerline of the landing runway.
* ''[[Final approach]]''. A descending flight path in the direction of landing along the extended runway centerline from the base leg to the runway. The last section of the final approach is sometimes referred to as ''short final''.
* ''Departure leg'', ''Initial'',<ref name=CASA.gov.au>{{cite web|title=CAAP 166-1(1): Operations in the vicinity of non-towered (non-controlled) aerodromes|url=http://www.casa.gov.au/wcmswr/_assets/main/download/caaps/ops/166-1.pdf#23|publisher=Australian Government Civil Aviation Safety Authority (CASA)|access-date=11 April 2013|pages=23|archive-url=https://web.archive.org/web/20130410160959/http://casa.gov.au/wcmswr/_assets/main/download/caaps/ops/166-1.pdf#23|archive-date=2013-04-10|url-status=dead}}</ref> or ''Climb out''. The climbing flight path along the extended runway centerline which begins at takeoff and continues to at least 1/2 mile beyond the runway's departure end and not less than 300 feet below the traffic pattern altitude.

The names of the legs are logical and based on the relative wind as seen looking down a runway facing into the wind. An aircraft flying ''upwind'' heads into the wind, flying ''crosswind'' heads across the wind, flying ''downwind'' heads in the direction of the wind just like blown smoke.

While many airfields operate a completely standard pattern, in other cases it will be modified according to need. For example, [[military aviation|military airfields]] often dispense with the crosswind and base legs, but rather fly these as circular arcs directly joining the upwind and downwind sections.