Lockheed F-117 Nighthawk

The Lockheed F-117 Nighthawk is American twin-engine ground attack aircraft designed under the “Stealth” low observability technology program. It is intended to provide the lowest possible Radar Cross Section (RCS) as well as Infrared (IR), noise, and visual signatures, thus enhancing its survivability and ability to penetrate enemy air defenses. The Nighthawk is subsonic aircraft and has a relatively high radius of action. Its mission is to attack high-value targets in raids that depend on low-altitude flight and stealth characteristics for its defense.

The F-117 is an angular aircraft that resembles a flat arrowhead with a narrow V-tail (also called “butterfly” tail). Its shape is intended to focus incoming radar beams into a few narrow beams, greatly reducing a radar’s ability to detect the reflections. As a result, the F-117’s shape is subdivided into triangular and trapezoidal facets. The low-aspect-ratio wing is swept at approximately 67°-68° and has a sawtooth trailing edge. A low beak continues the wings continuous and severe leading-edge sweep from wingtip to nose.

The overall configuration requires continuous, active control by a Lear-Siegler digital on-board computer in a flight control system derived from that used in the F-16 Fighting Falcon.

Much of the fuselage structure (95%) is reported to be aluminum, although some elements may be made of a Dow Chemical pre-preg (fibers and resin combined) boron fiber/polymer material called Fibaloy. The surface is said to be sheathed with tiles made of a Radar-Absorbing Material (RAM), and the leading edges and nose section are heat-absorbing and nonreflective. The engines are nonafterburning derivatives of the General Electric F404 series engines that are modified to raise the bypass ratio, which contributes to reducing the IR signature and stretching the range.

The F-117 avionics include the Texas Instruments Infrared Acquisition and Designation System (IRADS), which includes FLIR, a laser designator, and Downward-Looking IR (DLIR) systems. Both the FLIR and the DLIR are mounted in turrets that are controlled by joystick-mounted buttons. The Kaiser Electronics Head-Up Display (HUD) is adapted from the F/A-18 Hornet. The mechanical SPN/GEANS Inertial Navigation System (INS) used in the B-52 Stratofortress is fitted. A “four-dimensional” (4D) navigational system was added that ensures extreme accuracy in time as well as position; autothrottles have been fitted to the engines to assist 4D navigation.

Armament is usually the Paveway II and Paveway III laser-guided bombs fitted with a BLU-109/B warhead. AGM-65 Maverick TV- or laser-guided air-toground missiles and the AGM-88 HARM antiradar missile can also be delivered as well as Sidewinder Air-to-Air Missiles (AAM).

The F-117 was first used in combat on December 20, 1989, during Operation Just Cause, the US military action that removed Panamanian leader General Noriega. The US Air Force retired the Nighthawk on 22 April 2008, primarily due to the fielding of the F-22 Raptor aircraft.

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