Lockheed F-117 Nighthawk

The first Lockheed YF-117a Nighthawk, stealth fighter made its maiden flight from Groom Lake, Nevada, on 18 June 1981. The Lockheed F-117 Nighthawk is a single-seat, twin-engine stealth attack aircraft that was developed by Lockheed’s secretive Skunk Works division and operated by the United States Air Force (USAF). The F-117 was based on the Have Blue technology demonstrator. The Nighthawk achieved initial operating capability status in 1983. It was initially 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 demonstrators/ 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; it was the only Nighthawk to be lost in combat.

The F-117 was developed following combat experience in the Vietnam War as a response to increasingly sophisticated Soviet surface-to-air missiles (SAMs). So the Air Force approached Lockheed with the stealth concept, Skunk Works Director Kelly Johnson proposed a rounded design. He believed smoothly blended shapes offered the best combination of speed and stealth. However, his assistant, Ben Rich, showed that faceted-angle surfaces would provide significant reduction in radar signature. The resulting unusual design surprised and puzzled experienced pilots; a Royal Air Force pilot, who flew it as an exchange officer while it was still a secret project, stated that when he first saw a photograph of the F-117, he was not convinced it would fly.

The project began in 1975 with a model called the “Hopeless Diamond”(a wordplay on the Hope Diamond because of its appearance). In 1976 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 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. The F-117A’s faceted shape resulted from the limitations of the 1970s-era computer technology used to calculate its radar cross-section.

The maiden flight of the demonstrators occurred on 1 December 1977. Although both aircraft were lost during the demonstration program, valuable test data proved useful. 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, code named “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. This was led by Ben Rich, with Project manager Alan Brown, Lockheed mathematician, Bill Schroeder, and computer scientist Denys Overholser. 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 with the necessary aerodynamic control being provided by computers.

The 4450th Tactical Group stationed at Nellis AFB, Nevada helped develop the early F-117 between 1981 and 1989 they 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 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, 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. The Air Force initially 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 secret “F-19”. After the announcement pilots could fly the F-117 during daytime and no longer needed to be associated with the A-7. April 1990, two F-117 aircraft were flown into Nellis Air Force Base, Nevada and displayed to the public. Five Full Scale Development (FSD) aircraft were built, designated “YF-117A” . Between 1984 and-1992, the F-117A fleet was based at Tonopah Test Range Airport, Nevada, where it served under the 4450th Tactical Group. The first production F-117A was delivered in 1982, and operational capability was achieved in October 1983

The F-117 is primarily an attack aircraft and is designed with a focus on minimal radar cross-section (RCS) rather than aerodynamic performance. Highly-stealthy, the F-117 Nighthawk isshaped to deflect radar signals and is about the size of an F-15 Eagle. The operational aircraft was officially designated “F-117A”. The public assumption was that the aircraft would likely receive the F-19 designation as that number had not been used. However, there were no other aircraft to receive a “100” series number following the General Dynamics F-111. Meanwhile Unusual military aircraft types flying in the southern Nevada area, such as captured fighters, are assigned an arbitrary radio call of “117” Which was used by the enigmatic 4477th Test and Evaluation Squadron, also known as the “Red Hats” or “Red Eagles”, that often had flown expatriated MiG jet fighters in the area. Consquently WhenLockheed 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.

The F-117 Nighthawk is powered by two non-afterburning General Electric F404 turbofan engines. It is air refuelable and features a V-tail. The maximum speed is 623 miles per hour (1,003 km/h) at high altitude, the max rate of climb is 2,820 feet (860 m) per minute, and service ceiling is 43,000 to 45,000 feet (13,000 to 14,000 m). The cockpit is quite spacious, with ergonomic displays and controls, however there is a large blind spot to the rear. It has quadruple-redundant fly-by-wire flight controls. To lower development costs, Many systems, were derived from the General Dynamics F-16 Fighting Falcon, McDonnell Douglas F/A-18 Hornet and McDonnell Douglas F-15E Strike Eagle. The aircraft is equipped with sophisticated navigation and attack systems integrated into a digital avionics suite. It navigates primarily by GPS and high-accuracy inertial navigation, however The F-117A carries no radar. Targets are acquired by a thermal imaging infrared system, slaved to a laser rangefinder /laser designator that finds the range and designates targets for laser-guided bombs. The F-117A’s split internal bay can carry 5,000 pounds (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.

Unfortunately the increased stealth capabilities of the F-117 came at a price and the F-117 is aerodynamically unstable and requires constant flight corrections from a fly-by-wire (FBW) flight system to maintain controlled flight. Engine thrust was also reduced due to losses in the inlet and outlet, due to the need to reduce Infra red signature. The F-117 has a very low wing aspect ratio, and a high sweep angle (50°) to deflect incoming radar waves to the sides. The F-117 also lacks afterburners, because the hot exhaust would increase the infrared signature, and breaking the sound barrier would produce an obvious sonic boom, as well as surface heating of the aircraft skin which also increases the infrared footprint so the F-117 is limited to subsonic speeds. A normal exhaust plume would also contribute a significant infrared signature. So The F-117 reduces IR signature with a non-circular tail pipe (a slit shape) to minimize the exhaust cross-sectional volume and maximize the mixing of hot exhaust with cool ambient air. The F-117’s performance in air combat maneuvering required in a dogfight did not match that of a dedicated fighter aircraft so it was designed to be a bomber.

F-35b lightning II

Since the F-117 entered service Stealth technology has advanced and Today Passive (multistatic) radar, bistatic and multistatic radar systems detect some stealth aircraft better than conventional monostatic radars, since first-generation stealth technology (such as the F-117) reflects energy away from the transmitter’s line of sight, effectively increasing the radar cross section (RCS) in other directions. Consequently the last of 59 production F-117s were delivered on 3 July 1990 and The F-117 was eventually retired In 2008 after the Air Force closed the F-117 formal training unit (FTU),in 2006 and announced the retirement of the F-117. 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. The F-117 has since been replaced by the F-22 Raptor and the multirole F-35 Lightning II.

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