Editing Thrust reversal (section)

==Operation==
[[File:Thrust levers of a Boeing 747-8.jpg|thumb|Reverse thrust levers forward of the main levers, seen on a [[Boeing 747-8]]]]
In most cockpit setups, reverse thrust is set when the thrust levers are on idle by pulling them farther back.<ref name="Airplane handbook2011" /> Reverse thrust is typically applied immediately after touchdown, often along with [[Spoiler (aeronautics)|spoiler]]s, to improve deceleration early in the landing roll when residual [[aerodynamic lift]] and high speed limit the effectiveness of the brakes located on the landing gear. Reverse thrust is always selected manually, either using levers attached to the [[thrust lever]]s or moving the thrust levers into a reverse thrust 'gate'.

The early deceleration provided by reverse thrust can reduce landing roll by a quarter or more.<ref name="MacIsaacLangton2011 Propulsion" /> Regulations dictate, however, that an aircraft must be able to land on a runway without the use of thrust reversal in order to be certified to land there as part of [[airline|scheduled airline]] service.

Once the aircraft's speed has slowed, reverse thrust is shut down to prevent the reversed airflow from throwing debris in front of the engine intakes where it can be ingested, causing [[foreign object damage]]. If circumstances require it, reverse thrust can be used all the way to a stop, or even to provide thrust to push the aircraft backward, though [[Pushback (aviation)|aircraft tug]]s or [[towbar]]s are more commonly used for that purpose. When reverse thrust is used to push an aircraft back from the gate, the maneuver is called a [[powerback]]. Some manufacturers warn against the use of this procedure during icy conditions as using reverse thrust on snow- or slush-covered ground can cause slush, water, and runway deicers to become airborne and adhere to wing surfaces.<ref>{{cite web |url=http://www.boeing.com/commercial/aeromagazine/articles/2010_q4/2/ |title=Safe Winter Operations |publisher=Boeing Corp |access-date=2014-09-28 |archive-date=2019-07-24 |archive-url=https://web.archive.org/web/20190724075906/http://www.boeing.com/commercial/aeromagazine/articles/2010_q4/2/ |url-status=live }}</ref>

If the full power of reverse thrust is not desirable, thrust reverse can be operated with the throttle set at less than full power, even down to idle power, which reduces stress and wear on engine components. Reverse thrust is sometimes selected on idling engines to eliminate residual thrust, in particular in icy or slick conditions, or when the engines' [[jet blast]] could cause damage.{{Citation needed|date=July 2013}}

===In-flight operation===
[[File:C17 Reverse Thrust.JPG|thumb|right|A [[vortex]] made visible as powerback is used on a [[Boeing C-17 Globemaster III]]]]
Some aircraft, notably some Russian and [[Soviet aircraft]], are able to safely use reverse thrust in flight, though the majority of these are propeller-driven. Many commercial aircraft, however, cannot. In-flight use of reverse thrust has several advantages. It allows for rapid deceleration, enabling quick changes of speed. It also prevents the speed build-up normally associated with steep dives, allowing for rapid loss of [[altitude]], which can be especially useful in hostile environments such as combat zones, and when making steep approaches to land.{{Citation needed|date=July 2013}}

The [[Douglas DC-8]] series of airliners has been certified for in-flight reverse thrust since service entry in 1959. Safe and effective for facilitating quick descents at acceptable speeds, it nonetheless produced significant aircraft buffeting, so actual use was less common on passenger flights and more common on cargo and ferry flights, where passenger comfort is not a concern.<ref>{{Cite web|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19950022395.pdf|title=NASA Technical Reports Server (NTRS)|date=June 1995|last1=Hamid|first1=Hedayat U.|last2=Margason|first2=Richard J.|last3=Hardy|first3=Gordon|access-date=2017-07-07|archive-date=2020-02-01|archive-url=https://web.archive.org/web/20200201022240/https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19950022395.pdf|url-status=live}}</ref>

The [[Hawker Siddeley Trident]], a 120- to 180-seat airliner, was capable of descending at up to 10,000&nbsp;ft/min (3,050&nbsp;m/min) by use of reverse thrust, though this capability was rarely used.

The [[Concorde|Aerospatiale-BAC Concorde]] supersonic airliner could use reverse thrust in the air to increase the rate of descent.  Only the inboard engines were used, and the engines were placed in reverse idle only in [[subsonic flight]] and when the aircraft was below {{cvt|30,000|ft|m}} in altitude. This would increase the rate of descent to around {{cvt|10,000|ft/min|m/min}}.{{Citation needed|date=January 2010}}

The [[Boeing C-17 Globemaster III]] is one of the few modern aircraft that uses reverse thrust in flight. The Boeing-manufactured aircraft is capable of in-flight deployment of reverse thrust on all four engines to facilitate steep [[Tactical descent|tactical descents]] up to 15,000&nbsp;ft/min (4,600&nbsp;m/min) into combat environments (a descent rate of just over 170&nbsp;mph, or 274&nbsp;km/h). The [[Lockheed C-5 Galaxy]], introduced in 1969, also has in-flight reverse capability, although on the inboard engines only.<ref>{{cite web|url=http://foxtrotalpha.jalopnik.com/what-it-is-like-to-fly-the-americas-biggest-jet-the-ga-1727650088|title=What It's Like To Fly America's Biggest Jet, The Gargantuan C-5 Galaxy|first=Tyler|last=Rogoway|website=jalopnik.com|date=31 August 2015|access-date=3 April 2018|archive-date=1 February 2020|archive-url=https://web.archive.org/web/20200201013735/https://foxtrotalpha.jalopnik.com/what-it-is-like-to-fly-the-americas-biggest-jet-the-ga-1727650088|url-status=live}}</ref>

The [[Saab 37 Viggen]] (retired in November 2005) also had the ability to use reverse thrust both before landing, to shorten the needed runway, and taxiing after landing, allowing many Swedish roads to double as [[Highway strip|wartime runways]].

The [[Shuttle Training Aircraft]], a highly modified [[Grumman Gulfstream II]], used reverse thrust in flight to help simulate [[Space Shuttle]] aerodynamics so astronauts could practice landings. A similar technique was employed on a modified [[Tupolev Tu-154]] which simulated the Russian [[Buran (spacecraft)|Buran]] space shuttle.{{Citation needed|date=July 2013}}