Rabu, 15 Desember 2010

Lockheed F-117 Nighthawk


The Lockheed F-117 Nighthawk is a stealth ground attack aircraft formerly operated by the United States Air Force. The F-117A's first flight was in 1981, and it achieved initial operating capability status in October 1983.[1] The F-117A was "acknowledged" and revealed to the world in November 1988.[4]
A product of the Skunk Works and a development of the Have Blue technology demonstrator, it became the first operational aircraft initially designed around stealth technology. The F-117A was widely publicized during the Persian Gulf War of 1991.
The Air Force retired the F-117 on 22 April 2008,[2] primarily due to the fielding of the F-22 Raptor[5] and the impending fielding of the F-35 Lightning II.
RoleStealth attack aircraft
National originUnited States
ManufacturerLockheed Corporation
Lockheed Martin
First flight18 June 1981
Introduced15 October 1983
Retired22 April 2008[2]
Primary userUnited States Air Force
Number built64 (5 YF-117A, 59 F-117A)
Unit costUS$42.6 M (flyaway cost)
US$111.2 M (total program)
Developed fromLockheed Have Blue

Development

In 1964, Pyotr Ya. Ufimtsev, a Soviet/Russian mathematician, published a seminal paper, "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 a radar return is related to the edge configuration of an object, not its size.[7] Ufimtsev was extending theoretical work published by the German physicist Arnold Sommerfeld.[8][9][10] Ufimtsev demonstrated that he could calculate the radar cross-section across a wing's surface and along its edge. The obvious conclusion was that even a large airplane could be made stealthy by exploiting this principle. However, the airplane's design would make it aerodynamically unstable, and the state of computer technology in the early 1960s could not provide the kinds of flight computers which allow aircraft such as the F-117, and B-2 Spirit to stay airborne. However, by the 1970s, when a Lockheed analyst reviewing foreign literature found Ufimtsev's paper, computers and software had advanced significantly, and the stage was set for the development of a stealthy airplane.

Senior Trend

F-117A painted in "Gray Dragon" experimental camouflage scheme.
The F-117 was born after combat experience in the Vietnam War when increasingly sophisticated Soviet surface-to-air missiles (SAMs) downed heavy bomber flights.[12] It was a black project, an ultra-secret program for much of its life, until the late 1980s.[13] The project began in 1975 with a model called the "Hopeless Diamond"[14][15] (a wordplay on the Hope Diamond due to its appearance). In 1977 Lockheed produced two 60% scale models under the Have Bluecontract. The Have Blue program was a stealth technology demonstrator that lasted from 1976 to 1979. The success of Have Blue led the Air Force to create the Senior Trend[16][17] program which developed the F-117.
The decision to produce the F-117A was made on 1 November 1978, and a contract awarded to Lockheed Advanced Development Projects, popularly known as the Skunk Works, in Burbank, California.[18] The program was led by Ben Rich. Rich called on Bill Schroeder, a Lockheed mathematician, and Denys Overholser, a computer scientist, to exploit Ufimtsev's work. They 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.[11][19][20]
The F-117 first flew in June 1981, only 31 months after the full-scale development decision. The first production F-117A was delivered in 1982, operational capability was achieved in October 1983.[21] The Air Force denied the existence of the aircraft until 1988, when a grainy photograph was released to the public. In April 1990 two were flown into Nellis Air Force Base, Nevada, arriving during daylight and visible to a crowd of tens of thousands. Five Full Scale Development (FSD) aircraft built and were designated "YF-117A".[22] A total of 59 production F-117s were delivered through July 1990.[23]
F-117 taxiing.
As the Air Force 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."[1] The aircraft maintenance statistics are comparable to other tactical fighters of similar complexity. Logistically supported by Sacramento Air Logistics Center, McClellan AFB, California, the F-117A was kept at the forefront of technology through a planned weapon system improvement program located at USAF Plant 42 at Palmdale, California.
Several of the F-117s were painted with a gray camouflage pattern in an experiment to determine the effectiveness of the F-117's stealth during daylight conditions. 2004 and 2005 saw several mid-life improvement programs implemented on the F-117, including an avionics upgrade.

Designation

The operational aircraft had the official designation of "F-117A".[24] 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. (Examples include the F-15, the B-2, and the A-6.) The F-117 is primarily a ground-attack aircraft so its "F" designation is inconsistent with the DoD system, but it is an inconsistency that has been repeatedly employed by the U.S. Air Force with several of its ground attack aircraft since the late 1950s (i.e., F-105, F-111, etc.).
Lockheed F-117.ogg
F-117 flight demonstration
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 designation F-19 as that number had not been used. However there were no other aircraft to receive a "100" series number following the F-111. Captured Soviet fighters were given F-series numbers for their evaluation by U.S. test 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 "Red Hats/Red Eagles" unit that often had flown expatriated MiGs in the area, but there was no relationship to the call and the formal F-19 designation then being considered by the Air Force. Apparently, use of the "117" radio call became commonplace and when Lockheed released its first flight manual ("dash one"), F-117A was the designation printed on the cover.[25]
A televised documentary quoted a senior member of the F-117A development team as saying that the top-notch fighter pilots required to fly the new aircraft were more easily attracted to an "F" plane, as opposed to a "B" or "A" aircraft.[26]

[edit]F-117N “Seahawk”

In the early 1990s, Lockheed proposed an upgraded, carrier capable variant of the F-117 dubbed the “Seahawk” as an alternative to the canceled A/F-X program. The unsolicited proposal was received poorly by the Department of Defense, who had little interest in the single mission capabilities of such an aircraft, particularly as it would take money away from the Joint Advanced Strike Technology program (which evolved into the Joint Strike Fighter). The new aircraft would have differed from the land based F-117 in several ways, including the addition “of elevators, a bubble canopy, a less sharply swept wing and reconfigured tail".[27][28] The “N” variant would also be re-engined to use General Electric F414 turbofans instead of the older General Electric F404s. Furthermore the aircraft would be optionally fitted with hardpoints, allowing for an additional 8,000 lb (3,600 kg) of payload, and a new ground attack radar with air-to-air capability. In that role the F-117N could carry AIM-120 AMRAAMair-to-air missiles.[27][29]
After being rebuffed by the Navy, Lockheed submitted an updated proposal that included afterburning capability and a larger emphasis on the F-117N as a multimission aircraft, rather than just an attack aircraft.[29] In efforts to boost interest, Lockheed also proposed an F-117B land-based variant that shared most of the F-117N capabilities. This variant was proposed to both the US Air Force and the RAF.[30] This renewed F-117N proposal was also known as the A/F-117X.[31] Neither the F-117N or the F-117B were purchased by any party.

[edit]Design

The front side of an F-117
The F-117 is shaped to deflect radar signals and is about the size of an F-15 Eagle. The single-seat Nighthawk is powered by two non-afterburning General Electric F404 turbofan engines, and has quadruple-redundant fly-by-wire flight controls. It is air refuelable. To lower development costs, the avionics, fly-by-wire systems, and other parts are derived from the F-16 Fighting Falcon, F/A-18 Hornet and F-15E Strike Eagle. The parts were originally described as spares on budgets for these aircraft, to keep the F-117 project secret. The F-117 Nighthawk has a radar signature of about 0.025 m2.[32]
F-117 with its canopy opened
Among the penalties for stealth are lower engine power thrust, due to losses in the inlet and outlet, a very low wingaspect ratio, and a high sweep angle (50°) needed to deflect incoming radar waves to the sides.[33] With these design considerations and no afterburner, the F-117 is limited to subsonic speeds.
The F-117A is equipped with sophisticated navigation and attack systems integrated into a digital avionics suite. It carries no radar, which lowers emissions and cross-section. It navigates primarily by GPS and high-accuracyinertial navigation. Missions are coordinated by an automated planning system that can automatically perform all aspects of an attack mission, including weapons release. Targets are acquired by a thermal imaging infrared system, slaved to a laser that finds the range and designates targets for laser-guided bombs.
The F-117A's split internal bay can carry 5,000 lb (2,300 kg) of ordnance. Typical weapons are a pair of GBU-10, GBU-12, or GBU-27 laser-guided bombs, twoBLU-109 penetration bombs, or two Joint Direct Attack Munitions (JDAMs), a GPS/INS guided stand-off bomb.

Operators

 United States
United States Air Force[34]

[edit]Operational history

An F-117A during landing employing adrag-chute.
During the program's early years, from 1984 to mid-1992, the F-117A fleet was based at Tonopah Test Range Airport, Nevada where it served under the 4450th Tactical Group. Because the F-117 was classified during this time, the 4450th Tactical Group was "officially" located at Nellis Air Force Base, Nevadaand equipped with A-7 Corsair II aircraft. The 4450th was absorbed by the 37th Tactical Fighter Wing in 1989. In 1992, the entire fleet was transferred toHolloman Air Force Base, New Mexico, where it was placed under the command of the 49th Fighter Wing. The move eliminated the Key Air and American Trans Air contract flights, which flew 22,000 passenger trips on 300 flights from Nellis to Tonopah per month.
F-117 pilots called themselves "Bandits". Each of the 558 Air Force pilots who have flown the F-117 have a Bandit number, such as "Bandit 52", that indicates the sequential order of their first flight in the F-117.[35]
The F-117 has been used several times in war. Its first mission was during the United States invasion of Panama in 1989.[36] During that invasion two F-117A Nighthawks dropped two bombs on Rio Hato airfield.
F-117s in formation
During the Persian Gulf War in 1991, the F-117A flew approximately 1,300 sorties and scored direct hits on 1,600 high-value targets in Iraq[1] over 6,905 flight hours.[37] Only 2.5% of the American aircraft in Iraq were F-117s, yet they struck more than 40% of the strategic targets.[38] F-117As dropped over 2,000 tons of precision-guided munitions and struck their targets with over an 80% success rate. "Although the 37th Tactical Fighter Wing Provisional and its 42 stealth fighters represented just 2.5 percent of all allied fighter and attack aircraft in the Persian Gulf, the F-117As were assigned against more than 31 percent of the strategic Iraqi military targets attacked during the first 24 hours of the air campaign."[37] One of the missions resulted in the Amiriyah shelter massacre on 13 February 1991.
Lockheed F-117 Nighthawk.ogv
F-117 Nighthawk USAF video
It was among the only U.S. or coalition aircraft to strike targets in downtown Baghdad. Among the aircraft with which the Nighthawk shared this distinction were the F-16s which attacked Baghdad during daylight on 19 January 1991 during the "Package Q" mission—the largest single sortie flown during the war.[39]
Since moving to Holloman AFB in 1992, the F-117A and the men and women of the 49th Fighter Wing have deployed to Southwest Asia more than once. On their first trip, the crews flew non-stop from Holloman to Kuwait, a flight of approximately 18.5 hours – a record for single-seat fighters that stands today.[1]
It has since been used in Operation Allied Force in 1999, Operation Enduring Freedom in 2001 and in Operation Iraqi Freedom in 2003.

[edit]Combat losses

One F-117 has been lost in combat with the Army of Yugoslavia. On 27 March 1999, during the Kosovo War, the 3rd Battalion of the 250th Air Defence Missile Brigade under the command of Colonel Zoltán Dani,[40] downed an F-117A, callsign "Vega 31", AF serial number 82-0806, with a Yugoslav version of the Soviet Isayev S-125 'Neva' (NATO name SA-3 'Goa') anti-aircraft missile system.[41][42] According to NATO Commander Wesley Clark and other NATO generals, Yugoslav air defenses detected F-117s by operating their radars on unusually long wavelengths, making the aircraft visible to radar for brief periods. It is also possible that the aircraft was visible due to a disruption of its radar signature caused by open bomb-bay doors. This was the justification given by Colonel Dani in a 2007 interview.[43]
Canopy of F-117 shot down in Serbia in March 1999 at the Museum of Aviation in Belgrade.
Reportedly, several SA-3s were launched from approximately 8 miles (13 km) out, one of which detonated near the F-117A, forcing the pilot to eject. Though still classified, it is believed that the F-117 has no radar warning indicator, so the pilot's first indication of an incoming missile was likely seeing its flame. At this distance and combined speed the pilot had about six seconds to react before impact. According to an interview, Zoltán Dani kept most of his missile sites intact by frequently moving them, and had spotters looking for F-117s and other NATO aircraft. He oversaw the modification of his targeting radar to improve its detection.[42] The commanders and crews of the SAMs guessed the flight paths of earlier F-117A attacks from rare radar spottings and positioned their SAM launchers and spotters accordingly. It is believed that the SA-3 crews and spotters were able to locate and track F-117A 82-806 visually, probably with infra-red and night vision systems. He claimed that his battery shot down an F-16 as well.[42]
The F-117 pilot survived and was later rescued by U.S. Air Force Pararescue personnel. The wreckage of the F-117 was not promptly bombed, due to possible media fallout from news footage of civilians around the wreckage. The Serbs are believed to have invited Russian personnel to inspect the remains, compromising the then 25-year old US stealth technology.[44] The F-117's pilot was misidentified. While the name "Capt Ken 'Wiz' Dwelle" was painted on the canopy, it was revealed in 2007 that the pilot was actually Lt Col Dale Zelko, USAF.[45][46]
Some sources claim that a second F-117A was damaged during the same campaign, allegedly on 30 April.[47] Although the aircraft returned to base, it supposedly never flew again.[48][49]

[edit]Retirement

An F-117A parked at Langley AFB,Virginia.
Despite its productive combat service, the F-117 was designed with late 1970s technologies. Its stealth technology, while more advanced than that of any other aircraft except the B-2 Spirit and the F-22 Raptor, is maintenance intensive. Furthermore, the facet-based stealth design has been surpassed by newer technology. Program Budget Decision 720 (PBD 720), dated 28 December 2005, proposed retiring the entire fleet by October 2008 to permit buying more F-22As. PBD 720 called for 10 aircraft to be retired in FY 2007 and the remaining 42 aircraft in FY 2008 and stated there were more capable Air Force assets that could provide low observable, precision penetrating weapons capability including the B-2, F-22 and JASSM.[50] The Air Force originally planned to retire the F-117 in 2011. The Air Force later decided to retire the F-117 sooner to shift funds to modernizing the rest of the fleet.[35] This would save an estimated $1.07 billion.[51]
In late 2006, the Air Force closed the F-117 formal training unit (FTU),[52] and announced the retirement of the F-117.[53] The first six aircraft to be retired made the last flight on 12 March 2007 after a ceremony at Holloman AFB to commemorate the aircraft's career. Brigadier General David Goldfein, commander of the 49th Fighter Wing, said at the ceremony, "With the launch of these great aircraft today, the circle comes to a close — their service to our nation's defense fulfilled, their mission accomplished and a job well done. We send them today to their final resting place — a home they are intimately familiar with — their first, and only, home outside of Holloman."[54]
A pair of specially painted F-117 Nighthawks fly off from their last refueling by the Ohio Air National Guard's 121st Air Refueling Wing.
Unlike most other Air Force aircraft which are retired to Davis-Monthan AFB, the F-117s are being retired to the Tonopah Test Range Airport. At Tonopah, their wings will be removed and the aircraft will be stored in their original hangars.[54] On 11 March 2008, it was reported that the last F-117s in service would touch down on 22 April 2008 in Tonopah Test Range Airfield in Nevada, the site of the F-117's first flight.[35] The F-117 was retired during ceremonies at Palmdale and Tonopah on 22 April 2008.[2] Four aircraft were kept flying beyond April by the 410th Flight Test Squadron at Palmdale for flight test. By the beginning of August, two were remaining, and the last F-117 left Palmdale to fly to Tonopah on 11 August 2008.[55] With the last aircraft leaving for retirement, the 410th was deactivated in a ceremony on 1 August 2008.[56]


Alleged post-retirement sightings

While the F-117 was officially retired in 2007, there have been alleged sightings of the aircraft in flight since then, as recent as July 2010. Video of the alleged sightings exist, but no date appears on the video to corroborate the authenticity of the claim.[57]


Aircraft on display

[edit]Specifications

An orthographically projected diagram of the F-117A Nighthawk
An F-117 conducts a live exercise bombing run using GBU-27 laser-guided bombs.
Nighthawk's left "ruddervator" or V-tail shown
Data from USAF National Museum,[1] US Air Force[59]
General characteristics
  • Crew: 1
  • Length: 65 ft 11 in (20.09 m)
  • Wingspan: 43 ft 4 in (13.20 m)
  • Height: 12 ft 9.5 in (3.78 m)
  • Wing area: 780 ft² (73 m²)
  • Empty weight: 29,500 lb (13,380 kg)
  • Loaded weight: 52,500 lb (23,800 kg)
  • Powerplant: 2× General Electric F404-F1D2 turbofans, 10,600 lbf (48.0 kN) each
Performance
Armament
  • 2 × internal weapons bays with one hardpoint each (total of two weapons) equipped to carry:

[edit]Notable appearances in media

In the 1996 film Executive Decision a fictional, modified F-117 known as the "XF-117 Remora" is used to transfer an assault team onto a passenger aircraft inflight without being detected in order not to put any additional danger to the situation. In the film Philadelphia Experiment II a teleportation experiment sent an F-117 back in time to Nazi Germany.[citation needed]
The Omaha Nighthawks professional football team uses the F-117 Nighthawk as its logo.

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