Editing Lockheed Martin F-22 Raptor (section)

===Stealth===
[[File:F 22 raptor bomb bay display 2014 Reno Air Races photo D Ramey Logan.jpg|thumb|left|For stealth, the F-22 carries weapons in internal bays. The doors for the center and side bays are open; the six LAU-142/A AMRAAM Vertical Eject Launchers (AVEL) are visible.]]

The F-22 was designed to be highly difficult to detect and track by radar, with radio waves reflected, [[Scattering|scattered]], or [[Diffraction|diffracted]] away from the emitter source towards specific sectors, or absorbed and attenuated. Measures to reduce RCS include airframe shaping such as alignment of edges and continuous curvature of surfaces, internal carriage of weapons, fixed-geometry [[S-duct|serpentine inlet]]s and curved vanes that prevent line-of-sight of the engine fan faces and turbines from any exterior view, use of [[radar-absorbent material]] (RAM), and attention to detail such as hinges and pilot helmets that could provide a radar return.<ref name="Miller2005P25-27"/> The F-22 was also designed to have decreased radio frequency emissions, [[infrared signature]] and [[acoustic signature]] as well as [[aircraft camouflage|reduced visibility to the naked eye]].<ref>{{cite web |last=Jenn |first=D. |url=http://faculty.nps.edu/jenn/ec4630/rcsredux.pdf |title=RCS Reduction (Lecture Notes) |work=Naval Postgraduate School |date=Fall 2011 |access-date=13 March 2023 |archive-date=22 December 2022 |archive-url=https://web.archive.org/web/20221222070954/https://faculty.nps.edu/jenn/ec4630/rcsredux.pdf |url-status=live}}</ref> The aircraft's rectangular thrust-vectoring nozzles flatten the exhaust plume and facilitate its mixing with ambient air through [[vortex shedding|shed vortices]], which reduces infrared emissions to mitigate the threat of [[infrared homing]] ("heat seeking") surface-to-air or [[air-to-air missile]]s.<ref>Aronstein and Hirschberg 1998, p. 284.</ref><ref>{{cite magazine |last=Katz |first=Dan |url=https://aviationweek.com/defense/physics-and-techniques-infrared-stealth |title=The Physics And Techniques of Infrared Stealth |magazine=Aviation Week |publisher=Penton Media |date=7 July 2017 |access-date=12 April 2019 |archive-url=https://web.archive.org/web/20180814125513/http://aviationweek.com/defense/physics-and-techniques-infrared-stealth |archive-date=14 August 2018 |url-status=live}}{{subscription required}}</ref> Additional measures to reduce the infrared signature include special topcoat and [[Regenerative cooling|active cooling]] to manage the heat buildup from supersonic flight.<ref>{{cite web |url=https://www.northropgrumman.com/AboutUs/AnalysisCenter/Documents/pdfs/analogues_stealth.pdf |title=Analogues of Stealth |publisher=Northrop Grumman |date=27 April 2012 |type=analysis paper |access-date=10 April 2019 |archive-url=https://web.archive.org/web/20180219172328/http://www.northropgrumman.com/AboutUs/AnalysisCenter/Documents/pdfs/analogues_stealth.pdf |archive-date=19 February 2018 |url-status=live}}</ref><ref name="Miller2005P25-27"/>

Compared to previous stealth designs, the F-22 is less reliant on RAM, which are maintenance-intensive and susceptible to adverse weather conditions, and can undergo repairs on the flight line or in a normal hangar without climate control. The F-22 incorporates a ''Signature Assessment System'' which delivers warnings when the radar signature is degraded and necessitates repair.<ref name="avweek_20070107" /> While the F-22's exact RCS is [[Classified information in the United States|classified]], in 2009 Lockheed Martin released information indicating that from certain angles the airplane has an RCS of 0.0001 m<sup>2</sup> or −40 [[Decibel#Radar|dBsm]] – equivalent to the radar reflection of a "steel marble"; the aircraft can mount a [[Luneburg lens]] reflector to mask its RCS.<ref name="f22-paris">{{cite web |last=Fulghum |first=David A. |url=http://aviationweek.com/awin/f-22-raptor-make-paris-air-show-debut |title=F-22 Raptor To Make Paris Air Show Debut |archive-url=https://web.archive.org/web/20160819132737/http://aviationweek.com/awin/f-22-raptor-make-paris-air-show-debut |archive-date=19 August 2016 |work=Aviation Week |date=4 February 2009 |access-date=15 February 2009}}</ref><ref>{{cite web |last=Lockie |first=Alex |url=https://www.businessinsider.com/f-35-luneberg-radar-cross-section-russia-estonia-2017-5 |title=This strange mod to the F-35 kills its stealth near Russian defenses—and there's good reason for that |work=Business Insider |date=5 May 2017 |access-date=15 February 2020 |archive-date=24 August 2020 |archive-url=https://web.archive.org/web/20200824190211/https://www.businessinsider.com/f-35-luneberg-radar-cross-section-russia-estonia-2017-5 |url-status=live}}</ref> For missions where stealth is required, the [[availability|mission capable rate]] is 62–70%.{{refn|"... noting that Raptors are ready for a mission around 62 percent of the time, if its low-observable requirements are met (DAILY, 20 November). Reliability goes up above 70 percent for missions with lower stealth demands."<ref>{{cite news |last=Butler |first=Amy |url=http://aviationweek.com/awin/usaf-chief-notes-f-22s-are-needed-defends-capabilities |title=USAF Chief Defends F-22 Need, Capabilities |archive-url=https://web.archive.org/web/20160819052137/http://aviationweek.com/awin/usaf-chief-notes-f-22s-are-needed-defends-capabilities |archive-date=19 August 2016 |work=Aviation Week |publisher=McGraw Hill |date=17 February 2009 |access-date=31 August 2011}}</ref> |group= N}} Beginning in 2021, the F-22 has been seen testing a new chrome-like surface coating, speculated to help reduce the F-22's detectability by infrared tracking systems.<ref>{{cite web | url=https://theaviationist.com/2021/12/10/f-22-with-a-mirror-like-coating/ | title=This Video Provides Another Look at the F-22 Raptor Covered with a Mirror-Like Coating | date=10 December 2021 | access-date=13 March 2023 | archive-date=30 January 2023 | archive-url=https://web.archive.org/web/20230130102155/https://theaviationist.com/2021/12/10/f-22-with-a-mirror-like-coating/ | url-status=live}}</ref><ref>{{cite web | url=https://theaviationist.com/2022/03/19/second-chrome-f-22-raptor/ | title=There's Now a Second 'Chrome' F-22 Raptor Flying with Mirror-Like Coating at Nellis AFB | date=19 March 2022 | access-date=13 March 2023 | archive-date=12 December 2022 | archive-url=https://web.archive.org/web/20221212195536/https://theaviationist.com/2022/03/19/second-chrome-f-22-raptor/ | url-status=live}}</ref>

[[File:Lockheed Martin F-22A Raptor (09-4191) arrives at the 2016 RIAT Fairford 7Jul2016 arp.jpg|thumb|Front fuselage detail of an F-22]]
The effectiveness of the stealth characteristics is difficult to gauge. The RCS value is a restrictive measurement of the aircraft's frontal or side area from the perspective of a static radar. When an aircraft maneuvers it exposes a completely different set of angles and surface area, potentially increasing radar observability. Furthermore, the F-22's stealth contouring and radar-absorbent materials are chiefly effective against high-frequency radars, usually found on other aircraft. The effects of [[Rayleigh scattering]] and resonance mean that [[low-frequency radar]]s such as [[weather radar]]s and [[early-warning radar]]s are more likely to detect the F-22 due to its physical size. These are also conspicuous, susceptible to [[Clutter (radar)|clutter]], and have low precision.<ref>Ralston, J; Heagy, J; et al. [http://apps.dtic.mil/dtic/tr/fulltext/u2/a359931.pdf "Environmental/Noise Effects on UHF/VHF UWB SAR".] {{Webarchive|url=https://web.archive.org/web/20150102110548/http://www.dtic.mil/dtic/tr/fulltext/u2/a359931.pdf |date=2 January 2015}} ''dtic.mil'', September 1998. Retrieved 2 January 2015.</ref> Additionally, while faint or fleeting radar contacts make defenders aware that a stealth aircraft is present, reliably vectoring interception to attack the aircraft is much more challenging.<ref>Plopsky, Guy and Fabrizio Bozzato. [https://thediplomat.com/2014/08/the-f-35-vs-the-vhf-threat/ "The F-35 vs. The VHF Threat."] {{Webarchive|url=https://web.archive.org/web/20141226203753/https://thediplomat.com/2014/08/the-f-35-vs-the-vhf-threat/ |date=26 December 2014}} ''The Diplomat'', 21 August 2014.</ref><ref>{{cite book |author=Grant, Rebecca |title=The Radar Game: Understanding Stealth and Aircraft Survivability |publisher=[[Mitchell Institute]] |date=September 2010 |url=https://higherlogicdownload.s3.amazonaws.com/AFA/6379b747-7730-4f82-9b45-a1c80d6c8fdb/UploadedImages/Mitchell%20Publications/The%20Radar%20Game.pdf |access-date=28 April 2019 |archive-url=https://web.archive.org/web/20161203095318/https://higherlogicdownload.s3.amazonaws.com/AFA/6379b747-7730-4f82-9b45-a1c80d6c8fdb/UploadedImages/Mitchell%20Publications/The%20Radar%20Game.pdf |archive-date=3 December 2016 |url-status=dead}}</ref>