Lockheed F-117 Nighthawk
The Lockheed F-117 Nighthawk is an officially retired American single-seat, subsonic, twin-engined stealth attack aircraft developed by Lockheed's secretive Skunk Works division and operated by the United States Air Force. It was the first operational aircraft to be designed with stealth technology.
Work on what would become the F-117 commenced in the 1970s as a means of countering increasingly sophisticated Soviet surface-to-air missiles. During 1976, the Defense Advanced Research Projects Agency issued Lockheed a contract to produce the Have Blue technology demonstrator, the test data from which validated the concept. On 1 November 1978, Lockheed decided to proceed with the F-117 development program. Five prototypes were produced; the first of which performed its maiden flight in 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 heavily contributes to its relatively low radar cross-section of about. To minimize its infrared signature, it has a non-circular tail pipe that mixes 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 commonly referred to as the "Stealth Fighter", the aircraft was designed and employed as a dedicated attack aircraft, and indeed its performance in air combat maneuvering was less than that of most contemporary fighters. The F-117 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, thus requiring constant flight corrections via a fly-by-wire flight system to maintain controlled flight.
Even in the 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 one of 59 production F-117s was delivered on 3 July 1990. The F-117 was widely publicized for its role in the Gulf War of 1991, having flown around 1,300 sorties and scored direct hits on what the US military described as 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 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 2008, primarily due to the fielding of the F-22 Raptor. Despite the type's official retirement, a portion of the F-117 fleet has been kept in airworthy condition, and some have been observed flying since being retired from combat. It has been flown by the USAF for research and development, testing, and training purposes.
Development
Background and ''Have Blue''
In 1936, Robert Watson Watt, the British radar pioneer, noted that measures to reduce an object's radar cross-section could be used to evade radar detection. In 1962, 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 German physicist Arnold Sommerfeld. Ufimtsev demonstrated that he could calculate the RCS 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 that 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 conceived after the Vietnam War, where increasingly sophisticated Soviet surface-to-air missiles 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, remaining an ultrasecret program for much of its life. The project began in 1975 with a model called the "Hopeless Diamond". The following year, the Defense Advanced Research Projects Agency 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 mathematician and radar specialist, to exploit Ufimtsev's work. The three designed a computer program called "Echo", which made possible the design of 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, 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 Force Base, Nevada, was tasked with the operational development of the early F-117, and between 1981 and 1989, the group used LTV A-7 Corsair IIs for training, to bring all pilots to a common flight-training baseline and later as chase planes for F-117A tests.
The F-117 was secret for much of the 1980s. Many news articles discussed what they called an "F-19" stealth fighter, and the Testor Corporation produced a very inaccurate scale model. When an F-117 crashed in Sequoia National Forest in July 1986, killing the pilot and starting a fire, the USAF established restricted airspace. Armed guards prohibited entry, including firefighters, and a helicopter gunship circled the site. All F-117 debris was replaced with remains of a F-101A Voodoo crash stored at Area 51. When another fatal crash in October 1987 occurred inside Nellis, the military again provided little information to the press.
The USAF denied the existence of the aircraft until 10 November 1988, when Assistant Secretary of Defense J. Daniel Howard displayed a grainy photograph at a Pentagon press conference, disproving the many inaccurate rumors about the shape of the "F-19". After the announcement, pilots could fly the F-117 during daytime and no longer needed to be associated with the A-7, flying the T-38 supersonic trainer for travel and training, instead. In April 1990, two F-117s flew to Nellis, arriving during daylight and publicly displayed to a crowd of tens of thousands.
Five full-scale development aircraft were built, designated "YF-117A". The last of 59 production F-117s were delivered on 3 July 1990. As the USAF has stated, "Streamlined management by Aeronautical Systems Center, Wright-Patterson AFB, Ohio, combined breakthrough stealth technology with concurrent development and production to rapidly field the aircraft... The F-117A program demonstrates that a stealth aircraft can be designed for reliability and maintainability."
Designation
The operational aircraft was officially designated "F-117A". Most modern U.S. military aircraft use post-1962 designations in which the designation "F" is usually an air-to-air fighter, "B" is usually a bomber, "A" is usually a ground-attack aircraft, etc. The F-117 is primarily an attack aircraft, so its "F" designation is inconsistent with the Department of Defense system. This is an inconsistency that has been repeatedly employed by the USAF with several of its attack aircraft since the late 1950s, including the Republic F-105 Thunderchief and General Dynamics F-111 Aardvark. A televised documentary quoted project manager Alan Brown as saying that Robert J. Dixon, a four-star USAF general who was the head of Tactical Air Command, felt that the top-notch USAF fighter pilots required to fly the new aircraft were more easily attracted to an aircraft with an "F" designation for fighter, as opposed to a bomber or attack designation. Early on, one potential air-to-air mission considered for the F-117 was to hunt down the Soviet A-50 "Mainstay" airborne warning and control system. However, this was not deemed to be effective and this mission was passed to the nascent Advanced Tactical Fighter, which eventually became the F-22 Raptor.The designation "F-117" seems to indicate that it was given an official designation prior to the 1962 U.S. Tri-Service Aircraft Designation System and could be considered numerically to be a part of the earlier Century Series of fighters. The assumption prior to the revealing of the aircraft to the public was that it would likely receive the F-19 designation, as that number had not been used, but no other aircraft were to receive a "100" series number following the F-111. Soviet fighters obtained by the U.S. via various means under the Constant Peg program were given F-series numbers for their evaluation by U.S. pilots, and with the advent of the Teen Series fighters, most often Century Series designations.
As with other exotic military aircraft types flying in the southern Nevada area, such as captured fighters, an arbitrary radio call of "117" was assigned. This same radio call had been used by the enigmatic 4477th Test and Evaluation Squadron, also known as the "Red Hats" or "Red Eagles", who often had flown expatriated MiG jet fighters in the area, but no relationship existed between the call and the formal F-19 designation then being considered by the USAF. Apparently, use of the "117" radio call became commonplace, and when Lockheed released its first flight manual, F-117A was the designation printed on the cover.