Lockheed F-117A General
Aircraft
F-117A Nighthawk
Type
Modern Stealth Fighter
Crew
1
Unit Cost
US$ 122 million
Main Operator
United States Air Force
Click here for all pictures of the F-117A currently available

Lockheed F-117A Program Milestones
Maiden Flight
February 2, 1974
Production Start
1976
Introduction
August 17, 1978
First User
USAF


Lockheed F-117A Aircraft Dimensions
Wing Span
43 feet 4 inch (13.20 m)
Length
69 feet 9 inch (20.08 m)
Height
12 feet 9.5 inch (3.78 m)
Wing Area
780 square feet

Lockheed F-117A Weights
Empty Weight
29,500 lb (13,380 kg)
Loaded
52,500 lb (23,800 kg)
Maximum Take-off Weight
N.A.

Lockheed F-117A Powerplants
2 x GE F404-F1D2 turbofans
10,600 lbf

Lockheed F-117A Radius & Performance
Combat Radius
N.A
Ferry Radius
N.A. - Air Refueling Capability
Service Ceiling
69,000 feet (20 km)
Maximum Speed
Mach 0.92 (617 mph)
Maximum Rate of Climb
N.A.
Thrust to Weight
0.40
Wing Loading
65 lb/square feet


Accidents
Only one F-117 has been lost in combat. During the Kosovo War, on March 27, 1999, a F-117A with callsign "Vega 31" was downed by a Serbian improved Neva-M missile. According to several NATO generals, Serb air defences found that they could detect the aircraft with their radars operating on unusually long wavelengths. This meant that the aircraft was visible on the radar for short periods of time. The pilot survived the crash and was later rescued by United States Air Force Pararescue personnel. It was believed that the wreckage was handed over to the Russians in order to inspect the remains in order to compromise the then 25-year-old US stealth technology. Since the wreckage was not destroyed by the US, it can still be seen today at the Museum of Aviation in Belgrade.

Lockheed F-117A "Nighthawk"
The Lockheed F-117A Nighthawk is the world's first operational stealth ground attack aircraft and is solely operated by the United States Air Force. The aircraft first flew in 1981, and it achieved Initial Operational Capability status in October 1983. It is the unique design of the F-117A that provides exceptional combat capabilities. It is roughly the size of the F-15 Eagle and is powered by two General Electric GE F404 turbofan engines and has quadruple redundant fly-by-wire flight controls. Air refuelable, it supports worldwide commitments and adds to the deterrent strength of the United States Air Force.

The F-117A is able to carry a wide variety of weapons and is equipped with sophisticated navigation and attack systems integrated into a state-of-the-art digital avionics suite that increases mission effectiveness and significantly reduces pilot workload. In order to take advantage of the unique capabilities of the F-117A, detailed planning for missions into highly defended target areas is accomplished by an automated mission planning system.

United States Air Force Lockheed F-117A
United States Air Force Lockheed F-117A
United States Air Force Lockheed F-117A
Click for a large image
Click for a large image
Click for a large image

Lockheed F-117A "Nighthawk" Design
The actual design of the F-117A is, off-course, a well kept secret. Apart from its unique geometry, the aircraft has some impressive in-house technology. First of all, it was the first aircraft ever to incorporate stealth technology and is made available by using the method of geometrical optics, which essentially says that an impinging ray (beam) is reflected at an angle equal to the incident angle relative to the normal to the reflecting surface. This means that the wavelength must be much smaller than the dimensions of the reflecting flat surface and it is clear that the F-117A is able to defeat mid to high band microwave radars. In order to achieve this, the designers found a way to reflect impinging radar beams away from the radar by breaking the area of the airframe into flat facets. This basically explains why the external geometry does not contain any curved edges. The straight edges contained in the F-117A's design reflect in directions given by the above described rule. By arranging all edges to be straight and all areas to be flat, the designers could ensure that most microwave energy is reflected away from the aircraft at angles which are determined by the instantaneous orientation of the airframe relative to the searching radar. As the frontal RCS is of greatest importance tactically, the edges and surfaces of the airframe about the frontal aspect are all arranged at shallow angles with respect to an impinging wave.

This results into both a weak radar return a and a continuously scintillating one, which causes problems in many target tracking systems. By shaping in clever way, the RCS of the airframe was decreased significantly. Besides this the cockpit canopy windows were coated with an electrically conductive layer and the inlets were covered by a fine mesh grill, with holes smaller than the wavelength of the victim radars. Good reflectors such as the cockpit interior and engine fan faces are thus hidden away.

Furthermore, the canopy edges, weapon bay, undercarriage doors and FLIR bay have serrated edges since electrical discontinuities associated with panel edges and control surfaces at angles close to normal to frontal aspect beams could also make a measurable contribution to frontal RCS. From this it is obvious that shaping has thus been the principel RCS reduction technique used in the F-117A design. Besides shaping, radar absorbent materials were used for some panels and radar absorbent coating over the area of the aircraft.
United States Air Force Lockheed F-117A

Aerodynamic penalties incurred by the unique aircraft shape are considerable as sharp edges and flat surfaces create vortices and thus severly disturb laminar flow causing parasite drag. The wing is swept at a large angle and together with its low aspect ratio results in a shallower lift-curve slope which forces a higher nose attitude in landing configuration. This is also obvious by the high position of the canopy which in turn incurs an additional drag penalty. This is also translated into a reduction in lift on take-of, thus requiring a taller undercarriage to facilitate the required "Angle of Attack" on rotation. The highly swept wings are also poor performers at low speed, producing considerable amounts induced drag.

The design of the F-117A also affects natural stability and handling characteristics in a negative way. The swept wing configuration causes poor Dutch roll performance together with limited control effectiveness, while the rear fuselage (beavertail) contributes little to yawing stability. Just as with the General Dynamics F-16, the installment of a fly-by-wire control system and artificial stability was an absolute must for the design of the F-117A. In fact the fly-by-wire system used was derived from the Lear Astronics design which was actually fitted to the F-16. The V-tail configuration is fully movable and uses split full span trailing edge flaps.

The F-117A is powered by two GE F404-GE-F1D1 non-afterburning low bypass ratio turbofan engines. Each engine delivers 11,000 lb of thrust, with a pressure ratio of 25 and a Specific Fuel Consumption of around 0.8. How well the engines perform is unknown. An interesting aspect of the engines is the

Bombs
BLU-109
GBU-10 Paveway II
GBU-12 Paveway II
GBU-27 Paveway III
JDAM INS/GPS
geometry of the exhaust which is typical for a stealth design in that it uses a narrow horizontal slit to confine the infrared radiation pattern of the exhaust into a very narrow range of angles in elevation. In order to limit radiation to the sides because of the swept trailing edge of the exhaust, it was necessary to fit vanes to limit radiation to the sides, which also conveniently reduce the azimuth over which the exhaust can be sighted.