Editing Lockheed F-117 Nighthawk (section)

=== Stealth ===
{{main|Stealth aircraft}}

The F-117 has an RCS around {{Convert|0.001|m2|sigfig=3|abbr=on}}.<ref name="richardson" /> Among the penalties for stealth are subsonic speeds to prevent frame heating, heat on the engine inlet and outlet prevent certain thrusting maneuvers, a very low [[Aspect ratio (wing)|wing aspect ratio]], and a high [[sweep angle]] (50°), needed to deflect incoming radar waves to the sides.<ref name=":0" /><ref name="richardson36"/><ref name="richardson51"/> With these design considerations and no [[afterburner]], the F-117 is limited to subsonic speeds. Additionally, to maintain its low observability, the F-117 was not equipped with radar; not only would an active radar be detectable through its emissions, but also an inactive radar antenna would also act as a reflector of radar energy.<ref>{{cite web |last= Holloway |first= Don |date= March 1996 |title=Stealth Secrets of the F-117 Nighthawk |url= https://www.historynet.com/stealth-secrets-of-the-f-117-nighthawk-mar-96-aviation-history-feature.htm |access-date= 19 January 2022 |website= Historynet.com |publisher= HistoryNet}}</ref> Whether it carries any radar detection equipment remained classified as of 2008.<ref name=":0" />

Its [[faceting|faceted]] shape (made from two-dimensional flat surfaces) resulted from the limitations of the 1970s-era computer technology used to calculate its RCS. Later [[supercomputer]]s made subsequent aircraft like the [[B-2 bomber]] made use curved surfaces while maintaining stealth possible, through the use of far more computational resources to perform the additional calculations.<ref name="rich4" /> The radio-wave absorbing materials<!-- (RAM) --> covering the F-117 weighed almost one ton and were held in place by glue.<ref>{{Cite web |date=August 17, 2021 |title=Stealth Aircraft Technology in the F-117 Nighthawk and Beyond |url=https://www.aerospaceutah.org/stealth-aircraft-technology-in-the-f-117-nighthawk-and-beyond/ |access-date=December 16, 2024 |website=Hill Aerospace Museum}}</ref> The gaps between the sheets are filled with a kind of [[putty]] material called "butter".<ref name=":0" /><ref name="crickmore 2728">Crickmore and Crickmore 2003, pp. 27-28.</ref>

An exhaust plume contributes a significant [[infrared signature|infrared (IR) signature]]. The F-117 reduces IR signature with a noncircular [[exhaust system|tail pipe]] (a slit shape) to minimize the exhaust cross-section and maximize the mixing of hot exhaust with cool, ambient air.<ref name="crickmore 1516">Crickmore and Crickmore 2003, pp. 15-16.</ref> The F-117 lacks afterburners, because the hot exhaust would increase the infrared signature, breaking the [[sound barrier]] would produce an obvious [[sonic boom]], and surface heating of the aircraft skin would also increase the IR footprint. As a result, its performance in [[air combat maneuvering]] required in a [[dogfight]] would never match that of a dedicated fighter aircraft; this was unimportant in the case of the F-117, since it was a dedicated attack aircraft.<ref name="history" />

[[Passive radar|Passive (multistatic) radar]], [[bistatic radar]], and especially [[multistatic radar]] systems detect some stealth aircraft better than conventional [[monostatic radar]]s, since first-generation stealth technology (such as the F-117) reflects energy away from the transmitter's [[Line-of-sight propagation|line of sight]], effectively increasing the RCS in other directions, which the passive radars monitor.<ref name="Bistatic Radar Sets">{{cite web |url=http://www.radartutorial.eu/05.bistatic/bs04.en.html |title=Bistatic Radar Sets |publisher=Radartutorial.eu |access-date=16 December 2010}}</ref>