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INTRODUCTION
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, and was the first operational aircraft to be designed around stealth technology. The maiden flight of the Nighthawk happened in 1981 and the aircraft achieved initial operating capability status in 1983.The Nighthawk was shrouded in secrecy until it was revealed in 1988.
The F-117 was born after combat experience in the Vietnam War when increasingly sophisticated Soviet surface-to-air missiles (SAMs) downed heavy bombers. It was a black project, an ultra-secret program for much of its life, until it was revealed in November 1988. The project began in 1975 with a model called the “Hopeless Diamond”. The following year, the Defence 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 C130. By bringing together existing technology and components, Lockheed built two demonstrators under budget, at $35 million for both aircraft.
STEALTH TECHNOLOGY
Stealth technology is also termed as LO technology (low observable technology) is a sub-discipline of military tactics and passive electronic counter measures which cover a range of techniques used with personnel, aircraft, ships etc, to make them less visible to radar , infrared, sonar and other detection methods. It corresponds to military camouflage for these parts of the electromagnetic spectrum.
The concept of stealth is to operate or hide without giving enemy forces any indication as to the presences of friendly forces. This concept was first explored through camouflage by bending into background visual clutter. As the potency of detection and interception technologies have increased over time, so too has the extent to which the design and operation of military personnel and vehicle have been affected in response. Some military uniforms are treated with chemicals to reduce their infrared signature. A modern stealth vehicle is designed from the outset to have a chosen spectral signature. The degree of stealth embodied in particular design is chosen according to predicted capabilities of projected threats.
Stealth aircraft has to be stealthy in six disciplines:
1. Radar
2. Infrared
3. Visual
4. Acoustic
5. Smoke
6. Contrail
Some of them are explained as follows:
1) Infrared
To achieve infrared stealth, the exhaust gas is cooled to the temperature where the brightest wavelengths it radiates are absorbed by atmospheric carbon dioxide and water vapors, dramatically reducing the infrared visibility of the exhaust plume.
2) Visual
The simplest technology is visual camouflage, the use of paint or other material to color and break up the lines of the vehicle or person. Most stealth aircraft use matte finish
3) Acoustic
Acoustic stealth plays a primary role in submarines as well as for ground vehicles. Early stealth observation aircraft used slow turning propeller to avoid being heard by enemy troops below. Stealth aircraft that stay subsonic can avoid being tracked by sonic boom
There are two different ways to create invisibility:
1) The airplane can be shaped so that any radar signals it reflects are reflected away from the radar equipment.
2) The airplane can be covered in materials that absorb radar signals
GENERAL CHARCTERSTICS
1) Crew = 1
2) Length = 65 ft 11 in (20.09 m)
3) Wingspan = 43 ft 4 in (13.20 m)
4) Height = 12 ft 9.5 in (3.78 m)
5) Wing area = 780 ft² (73 m²)
6) Empty weight = 29,500 lb (13,380 kg)
7) Loaded weight = 52,500 lb (23,800 kg)
8) Power plant =2 × General Electric F404-F1D2 turbofans,10,600 lbf (48.0 kN)each
Performance
1) Maximum speed = Mach 0.92 (617 mph, 993 km/h)
2) Cruise speed = Mach 0.92
3) Range = 930 NM (1720 km)
4) Service ceiling = 70,000 ft
5) Wing loading = 65 lb/ft² (330 kg/m²)
6) Thrust/weight = 0.40
CHAPTER 4
F-117 VARIANTS
The different versions of F-117 nighthawk are as follows:
1. F-117B/YF-117B
2. F-117C
3. F-117N (II)
4. A/F-117X
F-117 COMPONENTS
5.1 F-117 ENGINE
The F-117A is powered by two low-bypass F404-GE-F1D2 turbofan engines from General Electric. The rectangular air intakes on both sides of the fuselage are covered by gratings, which are coated with radar-absorbent material.
The wide and flat structure of the engine exhaust area reduces the infrared and radar delectability of the aft section of the engine. The two large tail fins slant slightly outwards to provide an obstruction to the infrared and radar returns from the engine exhaust area
5.2 F-117 COCKPIT
The cockpit has a Kaiser Electronics head-up display (HUD) and the flight deck is equipped with a large video monitor, which displays the infrared imagery from the aircraft's onboard sensors. The cockpit has a full-colour moving map developed by the Harris Corporation. The fly-by-wire system is supplied by BAE Systems Aircraft Controls.
5.3 F-117 WEAPONS
The aircraft can carry a range of tactical fighter ordnance in the weapons bay, including BLU-109B low-level laser-guided bomb, GBU-10 and GBU-27 laser-guided bomb units, Raytheon AGM-65 Maverick and Raytheon AGM-88 HARM air-to-surface missiles.
In January 2004, an F-117 successfully released a JDAM (JDAM) 2,000lb bomb for the first time. The integration of JDAM and other precision-guided weapons on the F-117 is coupled with the block II software upgrade and achieved initial operating capability (IOC) in 2006.
Nighthawk stealth fighter design
The surfaces and edge profiles are optimised to reflect hostile radar into narrow beam signals, directed away from the enemy radar detector. All the doors and opening panels on the aircraft have saw-toothed forward and trailing edges to reflect radar.
The aircraft is mainly constructed of aluminium, with titanium for areas of the engine and exhaust systems. The outer surface of the aircraft is coated with a radar-absorbent material (RAM). The radar cross-section of the F-117 has been estimated at between 10cm² and 100cm².
The F-117A has four ailerons on the inboard and outboard trailing edge of the wing. The V-shaped tail, which controls the yaw of the aircraft, acts as a flying tail, which means that the whole surface acts as a control surface. The ailerons do not act as flaps to reduce the rate of descent for touchdown, so the landing speed of the F-117A is high, at about 180mph to 190mph, and a drag parachute is used.
ADVANTAGES AND DISADVANTAGES
7.1 ADVANTAGES
1. The primary mission of the aircraft is to penetrate dense threat environments and attack high-value targets
2 It can fly up to 70,000ft which is beyond the range of SAM(surface to air missile)
3 Due to its unique design It cannot be detected by radar system
4 It can attack its target with high accuracy from any range
5 It has high flying range up to 1700 km
6 Can carry up to 25,000 kg
7.2 DISADVANTAGES
1. High cost thus only used by some countries
2. Weapon carrying capacity is low
3. Lack of air to air missile
CHAPTER 8
APPLICATION
1. The wing's F-117As led the attack against Panama on December 21, 1989 during Operation Just Cause. Pinpoint bombing stunned and disrupted the Panamanian infantry at Rio Hato and paved the way for US paratroopers to land and eventually overcome the Panamanian opposition
2. During the Gulf War in 1991, the F-117A flew approximately 1,300 sorties and scored direct hits on 1,600 high-value targets in Iraq over 6,905 flight hours
3. the F-117 made up 2.5% of Coalition tactical aircraft in Iraq and they attacked more than 40% of the strategic targets
CONCLUSION
1. Flying USAF’s F-117A stealth fighter is a lesson in psychology rather than aerodynamics. It requires the pilot to abandon human senses completely and allow electronic instruments to work in their absence
2. The resulting unusual shape of the F-117A is the end product of the low-observables goals set for the aircraft at the program's beginning. Not surprisingly, it provided the aerodynamic and stability and control engineers with a significant challenge
3. The development of the F-117A avionics systems continues to be an ever-evolving program of changes, upgrades, and improvements