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Lockheed F-117 Nighthawk

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Lockheed's Advanced Development Projects organisation at Burbank (ADP), more commonly known as 'The Skunk Works', had stealth projects accelerated in 1977, and the Lockheed design was airborne from Groom Lake airfield, on the Nevada test range, by early 1978, flown by ADP chief test pilot Bill Park. Although only half the size of the F-117A, this aircraft's configuration was broadly similar, and by the end of 1978, Lockheed had received a USAF contract to develop a full-scale production version. It contained warranties covering the aircraft's range, weapons delivery accuracy and radar cross section.

Promising XST test results led to the development of two scaled-up YF-117A-LO prototypes which were followed by 57 production F-117As ordered in batches during the fiscal years 1980 to 1986 plus 1988. The first pre-production aircraft flew for the first time on 18 June 1981, and the first F-117A was handed over to the USAF in August 1982.

The programme was directed from AFSC's Aeronautical Systems Division (ASD) by General Richard Scofield, who later moved on to become the B-2 programme director. According to Ben Rich, head of Lockheed's ADP, the F-117A was developed in significantly less time and for less cost than comparable fighter aircraft. Using the streamlined management methods for which the Skunk Works is famous, ADP and ASD personnel "guided the programme through every step in a non-adversarial, problem-solving atmosphere". At some stage of the process, the codename Senior Trend was adopted.

 

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Although the F-117 is a radical design, every opportunity to minimise risk was taken. A number of components and systems were adopted from existing aircraft rather than designed from scratch, and this inspired programme managers to approve low rate production concurrent to full scale development. Most importantly, the quad-redundant digital fly-by-wire flight control system from the GD F-16 was incorporated. This allowed artificial stability and, therefore, much greater freedom to maximise the aircraft's shape for stealth. The ejection seat also came from the F-16, while the environmental control system was from Lockheed's own C-130 Hercules. Brake hydraulics were from the Gulfstream III business jet, while many avionics black boxes were purchased "off the shelf”. Finally, General Electric produced a non-afterburning version of the F404 designated the F1D2. This produces about 12,000 lb st (53,43 kN).

All the F-117s were manufactured at the Skunk Works' Burbank headquarters before being trucked or flown in sections to Groom Lake for final assembly and test flights. On 15 June 1981, Skunk Works' test pilot Hal Farley flew the first F-117A. This was a pre-production machine which was to crash a year later (21 June 1982) near Groom Lake while Ken Dyson was at the controls: he survived. The first aircraft destined for the customer was flying in early 1982, and deliveries to Tonopah began later that year. Lockheed received a second contract which increased the number of F-117s on order to 59, and these were completed at a rate of up to eight aircraft per year throughout the 'eighties. The last aircraft was delivered on 12 July this year, two months ahead of the original schedule. The stealth fighter has been worth $6.265 billion to Lockheed and other contractors, of which $2 billion was spent on development. These are the actual dollar amounts that have been spent over the life of the programme to date, ie, the "then-year" dollar cost. The flyaway cost per aircraft is $42.6m.

 

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The US Air Force formed the 4450th Tactical Group at Nellis AFB in 1980, and began recruiting pilots and groundcrew for the new aircraft. The pilots were nearly all drawn from the tactical fighter community (the 4450th reported direct to Tactical Air Command headquarters at Langley AFB until 1985). A minimum of 1,000 hours of mainly fighter time was required. The unit's first aircraft were 20 LTV A-7D Corsair II attack aircraft which could be flown during daylight hours, unlike the "Black Jet". They were to play an important role in maintaining pilot proficiency. In the first few years of operations, F-117 pilots were getting less than 10 hours per month in the aircraft. Despite this, an initial operational capability on the stealth fighter was achieved at Tonopah in October 1983 by the 4450th Test Squadron.

But on the night of 11 July 1986, an aircraft crashed outside the Nevada range, near Bakersfield, California, killing the pilot. In the first case, Major Ross Mulhare flew article number 792 into a hillside. Such was the extent of the security cordon thrown around the wreckage that most observers soon concluded that a stealth aircraft had crashed. Within a month, reports surfaced that about 50 "F-19 Stealth Fighters" were already fully operational at Tonopah. In fact, it was to be another three years before this number of the classified aircraft was to be in service, and the nature of the F-19 - if it exists - remains a mystery. The Pentagon has not explained the out-of sequence F-117 designation, six numerals beyond the last known previous allocation, F-111.

The second fatal crash in October 1987, may have been caused by pilot fatigue. In the second, Major Michael Stewart crashed 815 into gently sloping desert terrain near Tonopah on the night of 14 October 1987. No distress calls were made and accident investigators could find no mechanical cause.  Both men were considered excellent fighter pilots. But there was little or no moonlight on either occasion and spatial disorientation may have been another factor. Despite the difficulties, the build-up continued. Tactics were constantly refined, although portions of the flying envelope were still being explored as late as 1989. A second unit, the 4451st Test Squadron, achieved operational status in January 1987, while a third unit, the 4452nd Test Squadron, was devoted to training.

After being operational for nearly six years, the US Air Force lifted, in April 1989, the veil of secrecy over the F-117 programme. The US Air Force had rotated its personnel in and out of the F117 operating unit on three-year tours throughout that time. Based at the remote Tonopah Airfield, at the edge of the Nevada Test Range, the stealth fighter was flown only at night to preserve secrecy. The USAF had spent over $295m developing the run-down Tonopah airstrip into a modern fighter base, complete with 12,000-ft (3 660-m) runway, 54 individual hangars for single aircraft and some of the most sophisticated security systems ever seen outside Fort Knox.


Officially, nothing had been said since the Pentagon's brief admission, in 1980, that stealth aircraft were being test-flown.

 

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Once the aircraft's existence had been officially acknowledged - and a single, deliberately misleading photograph released - daytime flights began and new pilots no longer had to face the prospect of soloing on the aircraft at night. There are no two-seat conversion trainers, but a ground simulator has been in use at Tonopah for the last few years, built and operated by CAE Link. Now that daytime flying was possible, the unit was able to dispense with the A-7D Corsairs, trading them for eight Northrop T-38 Talons. These are used by instructor pilots in the training squadron who can now fly 'chase' as newcomers make their first flights in the F-117. The T-38s are also used for proficiency flying, but only a quarter of the unit's pilots are dual qualified on both types. Once posted to one of the two operational squadrons, pilots begin night-flying in earnest. A combat-ready F-117 pilot still flies two-thirds of his sorties at night. He gets from 15 to 20 hours flying per month, with three to four sorties each week.

In October 1989, the F-117A unit received a regular TAC "number plate" when the 4450th Tactical Group was redesignated the 37th Tactical Fighter Wing. The three squadrons became the 415th TFS Nightstalkers (ex-4450th TS); 416th TFS Ghostriders (ex-4451 st TS) and 417th TFTS Bandits. (ex-4452nd TS). Having reported to the Tactical Fighter Weapons Center at Nellis AFB since 1985, the F-117A wing commander now takes his orders from TAC's 16th Air Force at Bergstrom AFB, Texas. In December 1989, those orders included the wing's first operational mission - against Panama during Operation Just Cause. Apart from this confirmed excursion, the unit is rumoured to have made training deployments to the UK and elsewhere.

The radar cross section (RCS) of an airframe varies greatly with the angle of observation. The wavelength of the radar is also a significant factor. The RCS of the F-117 when illuminated from certain key frontal and rear aspects may be as little as 0.1 sq ft equivalent to a medium-sized bird. Some of the energy from an air defence radar striking an F-117 is absorbed by its coating or structure, but most is reflected as 'spikes' in carefully-controlled directions. Most of these directions lead away from the transmitter/receiver in question, whether it be ground-based (eg, a SAM system) or airborne in a fighter. Those spikes of energy that are returned are very narrow.

The F-117, therefore, owes most of its extraordinary shape to the need to control these spikes. The entire fuselage surface consists of flat planes or 'facets' set in a limited number of alignments. These limitations also define the degree of sweep for both wing and V-tail, and the wingtip and trailing edge configuration. The wing and V-tail are also faceted, to a less obvious degree. No detail has been overlooked in the effort to produce an aircraft which is fully faceted. Undercarriage and bomb-bay doors, together with canopy and sensor port surrounds, all have serrated edges conforming to the required alignments. The faceting even extends to the edges where control surfaces meet the main structure. There are six control surfaces. The wing trailing edge consists of an elevon/flaperon arrangement for roll and pitch, while the all-moving tails are rudders with no influence on the pitch axis, unlike other V-tail designs.

On the F-117, the two powerplants are buried deep in the airframe and their intakes are 'guarded' against radar penetration by grilles. These grilles are made of composite material, and the grid size is an appropriate fraction of the main threat radar wavelengths. They cover a much larger intake area than those on other F404-powered aircraft. The larger area presumably compensates for the restriction in airflow to the compressor face caused by the grilles. Another compensation is evident when the aircraft is manoeuvering on the ground: auxiliary blow-in doors open in the intake area immediately aft of the grilles.

In a stealth aircraft, the cockpit transparency must also prevent radar energy from penetrating to the interior. It does so by shape (divided into five flat sections) and content (a conductive coating is laminated to the plexiglass to provide an effective barrier). To protect the ports in the nose and under the forward fuselage through which the aircraft's two primary sensors view, a different solution was required. Here, unwanted electromagnetic energy is kept at bay by a screen mesh, which evidently does not interfere with the transmission of laser and infrared energy.

Apart from faceting, the F-117 also gains stealthiness from the almost complete absence of surface discontinuity. Apart from the faceted pitot heads projecting from the pointed nose, all the other protuberances usually associated with a combat aircraft are either eliminated by removal or retraction. There are no external weapons pylons or fuel tanks. Anti-collision lights are displayed on training missions, but removed and the gaps faired over before combat. Some other lights which remain have special lenses which reduce their radar return. Aerials for radio and IFF transmissions are retractable - strict radio silence is observed during combat missions. This super-smooth finish, therefore, eliminates the possibility of a discontinuity returning radar energy to the receiver, either directly from a corner type of reflection, or indirectly through the phenomenon known as 'creep'. This consists of a certain amount of radar energy flowing around any surface that it strikes until reaching a discontinuity from which it is reflected.

Large fairings aft of the national insignia in the mid-fuselage area, and foot-long cylinders extending beneath the fuselage immediately aft of the undercarriage are radar reflectors which are carried when the aircraft is operating in controlled airspace so that air traffic control radars can actually track the "Black Jet”.

Contrary to some of the early speculation, the F-117 is not a "plastic" aircraft. During the Have Blue era the all composite Windeck Eagle light aircraft was modified and tested by Lockheed for stealth potential as the YE-5A. But the problem of shielding the remaining metal parts (engine, hydraulics, undercarriage) remained, although the YE-5A did contain internal radar absorbent material (RAM) for this purpose. In the mid 'seventies, composite manufacturing technology had not matured sufficiently for it to be a viable option for the construction of a combat aircraft. The Skunk Works decided that the primary structure of their stealth fighter could be aluminium, although extensive use would be made of RAM inserts and coatings. Significant progress has been made in the manufacture and deployment of RAM since Lockheed's first, failed attempt to use it successfully on the U-2 in 1956. The heavy weight and limited durability of RAM coatings made them unsuitable for application to airborne vehicles in those days. Also, the range of frequencies at which they were effective was limited.

"Stealth technology does not involve a single technical approach, but rather a complex synthesis of many. Even if I were willing to describe it to you, I could not do it in a sentence or even a paragraph". Thus spoke the US Under Secretary of Defense for Research and Engineering, Bill Perry, when the stealth programme was first unveiled in 1980. In addition to radar signature reduction, therefore, the F-117 is also designed to present minimal infrared, acoustic, electromagnetic and visual signatures.

The engine exhaust slots are about six feet (1,83 m) wide and divided by vanes into 12 separate ports. They are shielded from the ground by an upturned lip - the rearward extension of the fuselage. This lip has a somewhat jagged edge and is believed to consist of ceramic tiles for greater dispersion of heat. Even before reaching the slots, exhaust from the non-afterburning F404s is already cooled by mixing with a proportion of cool air, which enters the intake, but by-passes the compressor face, before these unusual outlets promote further rapid mixing with ambient air. The exhaust plume therefore presents only a negligible infrared target for heat-seeking missiles. The buried engine and its inlet/exhaust configuration also serve to reduce jet noise the F-117 is noticeably quieter in an overhead pass than other combat aircraft.

It carries no radar or active jamming system. Navigation is by inertial platform targeting and attack is performed by passive means alone: FLIR and laser. As for visual signature, the F- 117 employs no exotic technology to defeat the power of observation. It goes to war under cover of darkness.

The pilot has no rearward visibility whatsoever from the cockpit: "it feels like you are flying at the tip of a spear," said one F-117A pilot. The thrust to weight ratio is no better than 0.5, and wing loading is 55 lbs/ sq ft. It is capable of high subsonic speed only. Stealth fighter pilots say that it handles like an F-15 or F-16.

There are no curved surfaces and the underside is completely flat. The prismatic forward fuselage is actually taller at 12 ft 5 in (3,78 m) than the highly swept V-tail, which extends the aircraft's length to 65 ft 11 in (20,09 m). An uncompromised and highly swept-back wing leading edge allows a 43 ft 4 in (13,21 m) span. Maximum gross weight is officially stated to be 52,500 lb (23814 kg) - slightly more than the F/A-18, which has similar dimensions.

The F117 is a one-mission airplane: the night attack of critical, high leverage targets with pinpoint accuracy. The aircraft carries "a sophisticated INS" which appears to be the prime means of navigation. Satellite navigation using GPS is a possibility, if a small, conformal antenna has been fitted. The two large turrets housed in recesses in the nose and under the cockpit contain combined infrared and laser targeting sensors. They are known as the FLIR and DLIR (Downward-Looking Infra Red) respectively, and are wide field of view sensors. The digital avionics suite is said to be "state-of-the-art", and based upon those in the F/A-18 which has three CRTs surrounding an information control panel and a HUD.

The weapons payload is not very great - perhaps 5,000 lb/2 270 kg - since all ordnance is carried internally in a bomb bay measuring some 16 ft (4,9 m) in length and 6 ft (1,83 m) in width. "Smart” bombs appear to be preferred: two laser-guided Mk 84 Paveway II 2,000-pounders. The imaging infrared guidance version of the GBU-15 (also based on the Mk 84) may also be an option. A submunitions dispenser designated BLU-109 is also mentioned as F-117 ordnance.

The F-117 apparently does straight and level attacks at 5,000 ft. The F-117 would conduct an attack mission cruising at an economical 20,000 ft (6 100 m) or more, it descends when approaching the target area, but only as low as necessary for the FLIR to perform satisfactorily. The DLIR's function is to continue the imaging and designation of the target as the aircraft passes overhead. Compared with conventional low-level attacks, the F- 117 method allows targets to be detected at greater range, allows the pilot to retain broader situational awareness, and gives a more vertical bomb impact (enhancing accuracy and penetration).

The aircraft's first combat mission to Panama was an inconclusive demonstration of its capability. The decision to employ F-117s in Operation Just Cause was a strange one. Unlike the Libyan raid, for which the F-117 was also available, there were no air defence fighters, radars or SAMs to contend with. USAF commanders said that the F-117 was chosen simply because it was considered more capable than any other available aircraft for the precision nightime delivery of 2,000-1b (907-kg) bombs. Six aircraft made a 5,200-naut mile (9 650-km) round trip from Tonopah, with multiple aerial refuellings. There were two sets of targets, each to be attacked by a pair of aircraft (the other two aircraft were backups). In the event, the ground commander called for only one target to be attacked: two F-117s were each to drop a 2,000-lb bomb in fields some 150 ft (46 m) from two army barrack blocks at Rio Hato. These were intended to disorient the occupants and distract their attention from a parachute landing of US forces which would closely follow the bomb drop.

The lead pilot was to deliver his bomb near the barracks to the left of the flight path. Number two was to use the first bomb hit as a reference point to drop his bomb near to the right barracks. But during the approach to Rio Hato, the lead pilot determined that the prevailing left-to-right wind over target might cause debris and smoke from his bomb to obscure the right barracks. He therefore announced that he was switching his attack to the right barracks, and that number two should adjust accordingly and attack the left barracks. Since the barracks were obscured by low cloud, the pilots were not able to acquire them through the FLIR or DLIR until they descended into the clear with a short distance to run. At this stage, the lead pilot apparently mistook the left barracks for the right barracks. His bomb actually achieved the required accuracy, against the target that he had originally nominated for himself. But his number two was still working to Plan B, and he therefore offset his bomb to the left of the first explosion, and missed the target area by almost 1,000 ft (305 m).

Production of 59 F-117As ended with final delivery on 12 July 1990. By July 1997 the Lockheed company set-up then included Lockheed Martin Skunk Works which undertook advanced, secret and innovative design/development, work including support and improvement of the F-117.

In January 1991 with the Gulf conflict and a major proportion of the USAF fleet (42 out of the surviving 54) were eventually based in Saudi Arabia with 415th Tactical Fighter Squadron 'Nightstalkers', the 416th TFS 'Ghostriders' and the 417th Tactical Fighter Training Squadron 'Bandits', all comprising the 37th Tactical Fighter Wing, one of whose aircraft dropped the very first bomb of Operation Desert Storm on 17 January 1991.

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F-117A Nighthawk
Engines: 2 x General Electric F404-GE-F102 non-afterburning turbofan, 5400kg / 24 kN
Length: 65 ft 11 in (20.3 m)
Height: 12 ft 5 in (3.78 m)
Wingspan: 43 ft 4 in (13.2 m)
Wing area: 105.9 sq.m / 1139.90 sq ft
Empty weight est: 13.381 kg (29,500 lb)
Max take-off weight: 23814 kg / 52500 lb
Max level speed Mach 0.98 / 1.040 km/h (656 mph)
Service ceiling: 15,240m (50,000 ft)
Range: 1663 nm / 3080 km
Cruise speed: 0.9M
Air refuelling: yes
Armament: Internal 2268 kg (5,000 lb)

Unit Cost: US$45 million.
Crew: One.

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Lockheed F-117 Nighthawk

 

 

 


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