Wednesday, July 31, 2013

Lockheed F-117 Nighthawk

Lockheed F-117 Nighthawk

The Lockheed F-117 Nighthawk is a single-seat, twin-engine stealth ground-attack aircraft formerly operated by the United States Air Force (USAF). A product of Lockheed Skunk Works and a development of the Have Blue technology demonstrator, the F-117 was the first operational aircraft to be designed around stealth technology. The maiden flight for the type was conducted in 1981, and it achieved initial operating capability status in October 1983.[1] The F-117 was "acknowledged" and revealed to the world in November 1988.[4]
The F-117 was widely publicized for its role in the Persian Gulf War of 1991. It was commonly referred to as the "Stealth Fighter", although it was a strictly ground-attack aircraft. The F-117 also saw combat in Yugoslavia; during which the only aircraft of the type to be lost in combat was shot down by a surface-to-air (SAM) battery on 27 March 1999. The Air Force retired the F-117 on 22 April 2008,[2] primarily because of the fielding of the F-22 Raptor[5] and the impending introduction of the multirole F-35 Lightning II.[6] Sixty-four F-117s were built, 59 of which were production versions with five demonstrators/prototypes



Background and Have Blue

Main article: Lockheed 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 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 and logical conclusion was that even a large aircraft 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 Lockheed analyst Denys Overholser found Ufimtsev's paper, computers and software had advanced significantly, and the stage was set for the development of a stealthy airplane.[11]
Aircraft parked inside an open hangar
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 bombers.[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 because of its appearance). 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".[16] 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.[16] By bringing together existing technology and components, Lockheed built two demonstrators under budget, at $35 million for both aircraft, and in record time.[16]
The maiden flight of the demonstrators occurred on 1 December 1977.[17] Although both aircraft were lost during the demonstration program, test data 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-117A, under the program code name "Senior Trend".[18][19]

Senior Trend

The decision to produce the F-117A 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.[20] The program was led by Ben Rich, who called on Bill Schroeder, a Lockheed mathematician, and Denys 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.[11][21][22]
The first YF-117A, serial number 79-0780, made its maiden flight from Groom Lake, Nevada on 18 June 1981,[23] 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.[8][24] 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 publicly displayed to a crowd of tens of thousands. Quote: "Shortly after I arrived in Las Vegas to work at the Dunes, the USAF announced a static display of two aircraft for a one day open house at Nellis AFB."[25] Five Full Scale Development (FSD) aircraft were built, designated "YF-117A".[26] The last of 59 production F-117s were delivered on 3 July 1990.[24][27]
F-117 flight demonstration
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]

Designation

The operational aircraft had the official designation of "F-117A".[28] 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, including the Republic F-105 Thunderchief and General Dynamics F-111 Aardvark.
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. Soviet fighters obtained by the United States via various means under the Constant Peg program[29] 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", 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 (i.e., the Air Force "dash one" manual for the aircraft), F-117A was the designation printed on the cover.[30]
A televised documentary quoted a senior member of the F-117A development team as saying 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 ("B") or attack ("A") designation.[31]



Design

Closeup view of the nose of a black jet, emphasizing the many angled-surfaces
Front view 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 General Dynamics F-16 Fighting Falcon, McDonnell Douglas F/A-18 Hornet and McDonnell Douglas 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 (0.269 sq ft).[32] Among the penalties for stealth are lower engine power thrust, due to losses in the inlet and outlet, a very low wing aspect 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-accuracy inertial 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, two BLU-109 penetration bombs, or two Joint Direct Attack Munitions (JDAMs), a GPS/INS guided stand-off bomb.
The F-117A's faceted shape (made from 2-dimensional flat surfaces) resulted from the limitations of the 1970s-era computer technology used to calculate its radar cross-section. Later supercomputers made it possible for subsequent planes like the B-2 bomber to use curved surfaces while staying stealthy, through the use of far more computational resources to do the additional calculations needed.[34]

Operational history

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, Nevada and 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 to Holloman Air Force Base, New Mexico, where it was placed under the command of the 49th Fighter Wing. This move also eliminated the Key Air and American Trans Air contract flights to Tonopah, 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.
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] Initial claims of its effectiveness were later found to be overstated. For instance it was claimed that the F-117 made up 2.5% of Coalition tactical aircraft in Iraq and they attacked more than 40% of the strategic targets;[38] this ignored the fact that only 229 Coalition aircraft could drop and designate laser-guided bombs of which 36 F-117 represented 15.7%, and only the USAF had the I-2000 bombs intended for hardened targets, so the F-117 represented 32% of all coalition aircraft that could deliver such bombs.[39] Initial reports of them hitting 80% of their targets were later scaled back to "41-60%".[40] On the first night they failed to hit 40% of the air-defense targets they were assigned, including the Air Defense Operations Center in Baghdad, and 8 such targets remained functional out of 10 that could be assessed.[41] In their Desert Storm white paper the USAF claimed that "the F-117 was the only airplane that the planners dared risk over downtown Baghdad" and that this area was particularly well defended.[42] In fact most of the air defenses were on the outskirts of the city and many other aircraft hit targets in the downtown area, with minimal casualties when they attacked at night like the F-117.[42] This meant they avoided the optically aimed AAA and infra-red SAMs which were the biggest threat to Coalition aircraft.[43]
Following its move to Holloman AFB in 1992, the F-117A and the men and women of the 49th Fighter Wing were deployed to Southwest Asia on multiple occasions. On their first deployment, with the aid of aerial refueling, pilots flew non-stop from Holloman to Kuwait, a flight of approximately 18.5 hours – a record for single-seat fighters that stands today.[1]
The F-117 was subsequently used in Operation Desert Thunder (Part of Operation Southern Watch) from 1997 to 1998, Operation Allied Force in 1999, Operation Enduring Freedom in 2001, and Operation Iraqi Freedom in 2003.

Combat loss

Main article: 1999 F-117A shoot-down
Only one F-117 (AF ser. no. 82-0806) was lost to enemy action. It was shot down during a mission against the Army of Yugoslavia on 27 March 1999, during Operation Allied Force.[44] About 8:15 pm local time, SA-3s were fired from about 8 miles (13 km) away, launched by a Yugoslav version of the Soviet Isayev S-125 "Neva" (NATO name SA-3 "Goa") anti-aircraft missile system.[44][45][46] The launcher was run by elements of the 3rd Battalion of the 250th Air Defence Missile Brigade under the command of Colonel Zoltán Dani.[47] According to Dani in a 2007 interview, his troops spotted the aircraft on radar when its bomb-bay doors opened, raising its radar signature.[48] One source states one of the missiles detonated by its proximity fuze near the F-117.[44] Dani said he 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.[46]
Canopy of F-117 shot down in Serbia in March 1999 at the Museum of Aviation in Belgrade
After the explosion, the aircraft became uncontrollable, forcing the pilot to eject.[44] The pilot was recovered a short time later by a U.S. Marine Corps combat search and rescue team.[44] Photos show that the aircraft struck the ground at low speed in an inverted position, and that the airframe remained relatively intact.[44] The Serbs invited Russian personnel to inspect the aircraft's remains, compromising the then 25-year-old U.S. stealth technology.[49] The F-117's pilot was initially misidentified. While the name "Capt Ken 'Wiz' Dwelle" was painted on the canopy, it was revealed in 2007 that the pilot was Lt. Col. Dale Zelko.[50][51]
Some American sources claim that a second F-117A was damaged during the same campaign, allegedly on 30 April;[52] the aircraft returned to base, but it supposedly never flew again.[53][54]
The stealth technology from the downed F-117 may have been acquired by Russia and China.[55]


Retirement

Though advanced for its time, the F-117's stealthy faceted airframe required a large amount of maintenance and was eventually superseded by streamlined shapes produced with computer-aided design. The Air Force had once planned to retire the F-117 in 2011, but Program Budget Decision 720 (PBD 720), dated 28 December 2005, proposed retiring it by October 2008 to free up an estimated $1.07 billion[56] to buy more F-22 Raptors.[35] PBD 720 called for 10 F-117s to be retired in FY 2007 and the remaining 42 in FY 2008, stating that other Air Force planes and missiles could stealthily deliver precision payloads, including the B-2 Spirit, F-22 and JASSM.[57]
In late 2006, the Air Force closed the F-117 formal training unit (FTU),[58] and announced the retirement of the F-117.[5] The first six aircraft to be retired made their 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."[59]
A pair of specially painted F-117 Nighthawks sporting the US flag 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 for scrapping, or dispersal to museums, most of the F-117s were retired to their original hangars at the Tonopah Test Range Airport.[44] At Tonopah, their wings were removed and the aircraft are stored in their original climate-controlled hangars.[59] The decommissioning occurred in eight phases, with the operational aircraft retired to Tonopah in seven waves beginning on 13 March 2007, and ending with the last wave's arrival on 22 April 2008.[2][44] 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. The last F-117 (AF ser. no. 86-0831) left Palmdale to fly to Tonopah on 11 August 2008.[44][60] With the last aircraft retired, the 410th was inactivated in a ceremony on 1 August 2008.[61]
Five aircraft were placed in museums including the first 4 YF-117As and some remains of the F-117 shot down over Serbia. Through 2009, one F-117 has been scrapped. F-117 AF ser. no. 79-0784 was scrapped at the Palmdale test facility on 26 April 2008. It was the last F-117 at Palmdale and was scrapped to test an effective method for destroying F-117 airframes.[44]
Although officially retired, the F-117 fleet remains intact, and photos show the aircraft carefully mothballed.[44] F-117s have been spotted flying in the Nellis Bombing Range as recently as 2010.[62]

Variants

F-117N "Seahawk"

In the early 1990s, Lockheed proposed an upgraded, carrier capable variant of the F-117 dubbed the "Seahawk" to the U.S. Navy as an alternative to the canceled A/F-X program. The unsolicited proposal was received poorly by the Department of Defense, which 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".[63][64] 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 AMRAAM air-to-air missiles.[63][65]
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 multi-mission aircraft, rather than just an attack aircraft.[65] 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 Royal Air Force.[66] This renewed F-117N proposal was also known as the A/F-117X.[67] Neither the F-117N or the F-117B were purchased by any party



Notable accidents

  • F-117, Air Force Serial Number 79-0785, was lost on 20 April 1982 during takeoff on its maiden flight. The cause was incorrect assembly following a major design change to the flight control computer's inputs sequence, which differed from that of previous aircraft. As a result, the aircraft went out of control on takeoff, and crashed. Pilot Robert L. Riedenauer was unable to eject in time, and was seriously injured, requiring eight months of hospitalization and was forced to retire from flying. The battered airframe was taken to Skunk Works plant at Burbank, California for use as a functional engineering testbed for component testing.[44]
  • F-117, AF Ser. No. 80-0792, was lost on 11 July 1986 near Bakersfield, California. The aircraft suffered a controlled descent into terrain, and was destroyed on impact. The pilot, Maj Ross E. Mulhare, was killed in the crash. The cause was determined to be spatial disorientation.[44]
  • F-117, AF Ser. No. 85-0815 was lost on 14 October 1987. The aircraft suffered a controlled descent into terrain, and was destroyed on impact about 100 miles north of Nellis Air Force Base, just east of Tonopah. The pilot, Maj Michael C. Stewart, was killed in the crash. The cause was determined to be spatial disorientation.[44]
  • F-117, AF Ser. No. 82-0801, Perpetrator was lost on 4 August 1992. The aircraft crashed approximately eight miles northeast of Holloman Air Force Base, and was destroyed on impact. The pilot, Capt John B. Mills, 416th FS, ejected safely. The cause was determined to be an improperly installed bleed air duct.[44]
  • F-117, AF Ser. No. 86-0822, was lost on 10 May 1995. The aircraft suffered a controlled descent into terrain, and was destroyed on impact approximately seven miles south of Zuni, New Mexico on the Zuni Indian Reservation. The pilot, Capt Kenneth Levens, was killed in the crash. The cause was determined to be spatial disorientation following autopilot failure.[44]
  • F-117, AF Ser. No. 81-0793, was lost on 14 September 1997 during an airshow at Martin State Airport / Warfield Air National Guard Base in Baltimore, Maryland. The aircraft suffered a catastrophic wing failure, resulting in the port wing completely separating from the fuselage. The aircraft was destroyed on impact. The pilot ejected safely. The cause was determined to be missing wing bolts.



Nicknames

The aircraft's official name is "Night Hawk",[74] however the alternative form "Nighthawk" is frequently used.
As it prioritized stealth over aerodynamics, it earned the nickname "Wobblin' Goblin" due to its alleged instability at low speeds; according to F-117 pilots, the nickname is undeserved.[75] "Wobblin' (or Wobbly) Goblin" is likely a holdover from the early Have Blue / Senior Trend (FSD) days of the project when instability was a problem. In the USAF, "Goblin" (without wobbly) persists as a nickname because of the aircraft's appearance. During Operation Desert Storm, Saudis dubbed the aircraft "Shaba", which is the Arabic word for "Ghost".[76]

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. Also visible, to the right of the USAF roundel, is a radar reflector that is usually installed when not on combat operations.
Data from USAF National Museum,[1] U.S. Air Force[77]
General characteristics
Performance
Armament
  • 2 × internal weapons bays with one hardpoint each (total of two weapons) equipped to carry:
  • Bombs:
    • GBU-10 Paveway II laser-guided bomb with 2000lb Mk84 blast/fragmentation or BLU-109 or BLU-116 Penetrator warhead
    • GBU-12 Paveway II laser-guided bomb with 500lb Mk82 blast/fragmentation warhead
    • GBU-27 Paveway III laser-guided bomb with 2000lb Mk84 blast-fragmentation or BLU-109 or BLU-116 Penetrator warhead
    • GBU-31 JDAM INS/GPS guided munition with 2000lb Mk84 blast-frag or BLU-109 Penetrator warhead
    • B61 nuclear bomb[78]
 From Wikipedia

 

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