F-117 Nighthawk | Stealth Attack Aircraft developed by Skunk Works

The Lockheed F-117 Nighthawk is a retired American single-seat, 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.

The F-117 was based on the Have Blue technology demonstrator. The Nighthawk's maiden flight took place in 1981 at Groom Lake, Nevada, and the aircraft achieved initial operating capability status in 1983. The aircraft was shrouded in secrecy until it was revealed to the public in 1988. Of the 64 F-117s built, 59 were production versions, with the other five being prototypes.

The F-117 was widely publicized for its role in the Persian Gulf War of 1991. Although it was commonly referred to as the "Stealth Fighter", it was strictly an attack aircraft. F-117s took part in the conflict in Yugoslavia, where one was shot down by a surface-to-air missile (SAM) in 1999. The U.S. Air Force 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 Nighthawks have been observed flying since 2009.

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.

Aircraft parked inside an open hangar
F-117A painted in "Gray Dragon" experimental camouflage scheme
The F-117 was born after the Vietnam War, where increasingly sophisticated Soviet surface-to-air missiles (SAMs) had downed heavy bombers.

General characteristics

Crew: 1
Length: 65 ft 11 in (20.09 m)
Wingspan: 43 ft 4 in (13.21 m)
Height: 12 ft 5 in (3.78 m)
Wing area: 780 sq ft (72 m2)
Airfoil: Lozenge section, 3 flats Upper, 2 flats Lower
Empty weight: 29,500 lb (13,381 kg)
Max takeoff weight: 52,500 lb (23,814 kg)
Powerplant: 2 × General Electric F404-F1D2 turbofan engines, 9,040 lbf (40.2 kN) thrust each
Performance

Maximum speed: 594 kn (684 mph, 1,100 km/h)
Maximum speed: Mach 0.92
Range: 930 nmi (1,070 mi, 1,720 km) ;
Service ceiling: 45,000 ft (14,000 m)
Wing loading: 67.3 lb/sq ft (329 kg/m2) calculated from
Thrust/weight: 0.40
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 2,000 lb (910 kg) Mk84 blast/fragmentation or BLU-109 or BLU-116 Penetrator warhead
GBU-12 Paveway II laser-guided bomb with 500 lb (230 kg) Mk82 blast/fragmentation warhead
GBU-27 Paveway III laser-guided bomb with 2,000 lb (910 kg) Mk84 blast-fragmentation or BLU-109 or BLU-116 Penetrator warhead
GBU-31 JDAM INS/GPS guided munition with 2,000 lb (910 kg) Mk84 blast-frag or BLU-109 Penetrator warhead
B61 nuclear bomb

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.

The maiden flight of the demonstrators occurred on 1 December 1977. Although both aircraft crashed 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".

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