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The Lockheed F-117 Nighthawk is a retired American single-seat, subsonic twin-engine stealth attack aircraft developed by Lockheed's secretive Skunk Works division and operated by the United States Air Force (USAF). It was the first operational aircraft to be designed with stealth technology. Work on what would become the F-117 was commenced in the 1970s as a means of countering increasingly sophisticated Soviet surface-to-air missiles (SAMs). During 1976, the Defense Advanced Research Projects Agency (DARPA) issued Lockheed with a contract to produce the Have Blue technology demonstrator, the test data from which validated the concept. On 1 November 1978, it was decided to proceed with the F-117 was made on 1 November 1978. A total of five prototypes would be produced; the first of which performed its maiden flight during 1981 at Groom Lake, Nevada. The first production F-117 was delivered in 1982, and its initial operating capability was achieved in October 1983. All aircraft were initially based at Tonopah Test Range Airport, Nevada. The aircraft's faceted shape (made from two-dimensional flat surfaces) heavily contributes to its relatively low radar cross-section of about 0.001 m2 (0.0108 sq ft). To minimise its infrared signature, it has a non-circular tail pipe that mixing of hot exhaust with cool ambient air and lacks afterburners; it is also restricted to subsonic speeds as breaking the sound barrier would produce an obvious sonic boom that would increase both its acoustic and infrared footprints. While its performance in air combat maneuvering was less than that of most contemporary fighters, it was strictly an attack aircraft despite being commonly referred to as the "Stealth Fighter". For this reason, it is equipped with integrated sophisticated digital navigation and attack systems, targeting being achieved via a thermal imaging infrared system and a laser rangefinder/laser designator. It is aerodynamically unstable in all three aircraft principal axes and thus requires constant flight corrections via a fly-by-wire (FBW) flight system to maintain controlled flight. Even years following its entry to service, the F-117 was a black project, its existence being denied by USAF officials. On 10 November 1988, the F-117 was publicly acknowledged for the first time. Its first combat mission was flown during the United States invasion of Panama in 1989. The last of 59 production F-117s were delivered on 3 July 1990. The F-117 was widely publicized for its role in the Gulf War of 1991, having flown approximately 1,300 sorties and scored direct hits on what the US called 1,600 high-value targets in Iraq. F-117s also participated in the conflict in Yugoslavia, during which one was shot down by a surface-to-air missile (SAM) in 1999. It was also active during Operation Enduring Freedom in 2001 and Operation Iraqi Freedom in 2003. The USAF retired the F-117 in April 2008, primarily due to the fielding of the F-22 Raptor. Despite the type's official retirement, a portion of the fleet has been kept in airworthy condition, and F-117s have been observed flying since 2009. Development Background and Have Blue In 1964, Pyotr Ufimtsev, a Soviet mathematician, published a seminal paper titled Method of Edge Waves in the Physical Theory of Diffraction in the journal of the Moscow Institute for Radio Engineering, in which he showed that the strength of the radar return from an object is related to its edge configuration, not its size. Ufimtsev was extending theoretical work published by the German physicist Arnold Sommerfeld. Ufimtsev demonstrated that he could calculate the radar cross-section across a wing's surface and along its edge. The obvious and logical conclusion was that even a large aircraft could reduce its radar signature by exploiting this principle. However, the resulting design would make the aircraft aerodynamically unstable, and the state of computer technology in the early 1960s could not provide the kinds of flight computers which would later allow aircraft such as the F-117 and B-2 Spirit to stay airborne. By the 1970s, when Lockheed analyst Denys Overholser found Ufimtsev's paper, computers and software had advanced significantly, and the stage was set for the development of a stealth airplane. The F-117 was born after the Vietnam War, where increasingly sophisticated Soviet surface-to-air missiles (SAMs) had downed heavy bombers. The heavy losses inflicted by Soviet-made SAMs upon the Israeli Air Force in the 1973 Yom Kippur war also contributed to a 1974 Defense Science Board assessment that in case of a conflict in Central Europe, air defenses would likely prevent NATO air strikes on targets in Eastern Europe.It was a black project, an ultra-secret program for much of its life; very few people in the Pentagon knew the program even existed. The project began in 1975 with a model called the "Hopeless Diamond" (a wordplay on the Hope Diamond because of its appearance). The following year, the Defense Advanced Research Projects Agency (DARPA) issued Lockheed Skunk Works a contract to build and test two Stealth Strike Fighters, under the code name "Have Blue". These subscale aircraft incorporated jet engines of the Northrop T-38A, fly-by-wire systems of the F-16, landing gear of the A-10, and environmental systems of the C-130. By bringing together existing technology and components, Lockheed built two demonstrators under budget, at $35 million for both aircraft, and in record time. Undersecretary of Defense for Research and Engineering William J. Perry was instrumental in shepherding the project.The maiden flight of the demonstrators occurred on 1 December 1977. Although both aircraft crashed during the demonstration program, test data gathered proved positive. The success of Have Blue led the government to increase funding for stealth technology. Much of that increase was allocated towards the production of an operational stealth aircraft, the Lockheed F-117, under the program code name "Senior Trend". Senior Trend The decision to produce the F-117 was made on 1 November 1978, and a contract was awarded to Lockheed Advanced Development Projects, popularly known as the Skunk Works, in Burbank, California. The program was led by Ben Rich, with Alan Brown as manager of the project. Rich called on Bill Schroeder, a Lockheed mathematician, and Overholser, a computer scientist, to exploit Ufimtsev's work. The three designed a computer program called "Echo", which made it possible to design an airplane with flat panels, called facets, which were arranged so as to scatter over 99% of a radar's signal energy "painting" the aircraft.The first YF-117A, serial number 79-10780, made its maiden flight from Groom Lake ("Area 51"), Nevada, on 18 June 1981, only 31 months after the full-scale development decision. The first production F-117A was delivered in 1982, and operational capability was achieved in October 1983. The 4450th Tactical Group stationed at Nellis Air.... Discover the Alan Hlad popular books. Find the top 100 most popular Alan Hlad books.