The idea for a stealth aircraft like the F-117 started in 1935 when the eminent Scottish radio physicist Robert Watson-Watt was given an unusual task by the British Air Ministry. Watson-Watt, who was at that time the Director of the Radio Research Station, was asked whether it would be possible to use radio waves to create a “death ray” capable of destroying enemy aircraft?
Watson-Watt and his team quickly concluded that this wasn’t possible but noted, almost incidentally, that while they couldn’t destroy them, radio waves could be used to detect enemy aircraft.
It is probably not unreasonable to say that the memo that Watson-Watt sent to the Air Ministry in February 1935, Detection and location of aircraft by radio methods, changed air warfare forever.
By the time of the Battle of Britain in 1940, Britain had Chain Home, a linked array of radio towers on the south and east coasts of England that gave the RAF warning of the approach of enemy aircraft.
By the end of World War Two, all major combatants were using radar (radio detection and ranging) equipment. By the 1970s, radar had become so sophisticated that it could detect aircraft at extreme ranges and at virtually any altitude and in any weather.
No longer was it possible for any aircraft to approach enemy territory undetected.
That in turn led to an entirely new consideration; if a military aircraft could be created that was invisible to radar, it would have a massive advantage over defence systems and weapons that had become almost completely reliant on radar.
Skunkworks – an invisible rabbit and the Hopeless Diamond
The Lockheed Corporation created the Advanced Development Division in 1943 to address a very specific task; the creation of the first US jet fighter.
Under the direction of Lockheed’s Chief Engineer, Clarence “Kelly” Johnson, the new team was responsible for the creation of some of the most innovative aircraft designs of the next thirty years including the P-80 Shooting Star, the U-2 spy plane and the SR-71 Blackbird.
The team also gained the name under which it would become world famous; Skunkworks (named after a secret moonshine factory from the Li’l Abner comic strip).
In 1973 the Pentagon gave Skunkworks one of its most daunting challenges. Could it create a military aircraft that was invisible to radar? In 1975, five Skunkworks design engineers began work on a secret project named the Experimental Survivable Testbed (XST) program.
Within the Skunkworks, this project was identified as “Harvey,” named after the 1950 James Stewart movie in which Harvey is a rabbit who is invisible to everyone but Stewart’s character.
The technique of producing an aircraft (or anything else) that can’t be detected by radar was well understood by the early 1970s.
“Faceting”, creating a shape comprising a series of trapezoidal or triangular flat surfaces, was known to scatter radar waves, making the object virtually invisible to the radar receiver. The problem was that an aircraft constructed using only faceted surfaces would be unflyable due to instability in all three axis.
The challenge facing the Skunkworks team wasn’t just creating a faceted aircraft, but one that would actually fly.
Skunkworks designer Bill Schroeder sketched a design for an aircraft with no curved surfaces at all. Because of its odd shape, this became known within the team as the “Hopeless Diamond.” A ten-foot mock-up was created and mounted on a 12-foot pole in a remote area of the Mojave Desert. A powerful radar set was set up less than 2km away.
At first, the set could not detect the mock-up at all. Then, suddenly, it picked up a return. It was only when Skunkworks engineers looked at the mock-up through binoculars that they realised that a blackbird had landed on it.
The radar could “see” the blackbird but not the 10-foot mock-up (the mock-up proved to have a lower radar cross-section than the pole on which it was mounted!). The Hopeless Diamond was all but invisible to radar, but could it be made into a flyable aircraft?
In early 1977, Lockheed received a secret contract from the Defense Advanced Research Projects Agency (DARPA) to produce two, 60% scale, flyable prototypes of the new design.
The project was given the codename Have Blue and immediately became a black project, highly classified and known to only a few people in Lockheed and the Defense Department.
The prototypes were built in only a few months by re-using elements scavenged from existing aircraft. The General Electric J85 turbojet engines had already been used on the T-38 Talon. The undercarriage was borrowed from the A-10, the ejector seat and instruments were from the F-5 and the fly-by-wire system and flight computer were taken from the F-16.
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The semi-delta design lacked speed brakes or flaps. There was no conventional elevator, just a pair of inward-angled rudders at the rear of the fuselage which provided yaw control.
Pitch and roll control was achieved by the use of trailing-edge elevons in the inboard sections of the wings. The fly-by-wire system was essential because the new aircraft was inherently unstable on all three axis.
Even measuring airspeed was an issue; using a conventional pitot head significantly increased the aircraft’s radar signature. Both Have Blue prototypes were fitted with conventional pitot-heads that could be retracted for radar testing.
The prototypes were taken to the remote Groom Lake Test Facility in Nevada, part of the Nellis test facility so that they could be flown out of sight of civilian observers on the ground.
Flight testing proved that both aircraft were virtually invisible to most ground and air radar systems, but only if careful preparations were followed.
Both aircraft were covered in a thin skin of flexible Radar Absorbent Material (RAM) but prior to each flight, gaps around cockpit edges had to be covered with a paint-type RAM and even a single loose screw on the aircraft’s skin was found to substantially increase its visibility on radar.
These prototypes were not easy to fly and both were lost in accidents, one in June 1978 and the other in July 1979. However, stealth performance up to that point had been so impressive that a full development contract was awarded to Lockheed in November 1978 for five full-size test and 15 production aircraft.
The F-117A differed from the Have Blue prototypes in several respects in addition to size. The most noticeable external change was that the twin rudders were positioned further to the rear and angled outwards instead of inwards (the original arrangement was found to increase the aircraft’s infrared signature).
The F-117A was also provided with an infrared acquisition and designation system (IRADS) and a HUD based on the system designed for the F/A-18. The twin engines were more powerful General Electric F404-GE-F1D2 turbofans.
The F-117 still wasn’t provided with flaps or speed brakes, which meant that landing speed was high (around 180 knots) and a drogue parachute was provided. The new aircraft was capable of carrying laser-guided bombs or AGM-65 Maverick and AGM-88 HARM air-to-ground missiles in its internal bomb bay.
From 1982, the 4450th Tactical Group operated the F-117A at the Tonopah Test Range, a remote and secret base in central Nevada and part of the Nellis facility. Secrecy was paramount and most flights were undertaken at night to avoid observation.
The new aircraft was given the name “Nighthawk” and the designation “F-117A,” something that has caused a degree of confusion and debate ever since. The “F” designation is generally used in the US for interceptor aircraft.
The F-117 was never intended for this role, being a light bomber capable of carrying up to 5,000 pounds (2,300 kg) of bombs in an internal bay. Why then was it given the “F” designation?
The answer seems to be that this designation was used due to the desire of the USAF to keep the very existence of the F-117A secret. Treaties then in force between the US and the Soviet Union intended to limit the numbers of nuclear-capable aircraft meant that both sides had agreed to share details of all bombers serving in their respective air forces.
This requirement did not apply to interceptors which were regarded as purely defensive. A test was carried out where an F-117A successfully launched a single air-to-air missile from its bomb bay.
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This was felt to be sufficient to identify the new aircraft to be an interceptor and thus free of the need to be declared under treaty terms.
As a result, once it became known, the F-117A was generally identified by the public and in the press as the “Stealth Fighter”, even though it was never used in or designed for that role.
The F-117A was not an easy aircraft to fly. Its inherent instability required constant input from the flight computer and the fly-by-wire system just to keep it pointing where the pilot wanted. Its twitchy, bumpy flight performance earned it the nickname “Wobbly Goblin” from the pilots who flew it.
By late 1988, the F-117A had been publicly acknowledged by the USAF and the 4450th Tactical Group was redesignated as the 37th Tactical Fighter Wing, continuing the fiction that the F-117 was an interceptor.
The F-117 was first used operationally in December 1989 when two aircraft from the 37th TFW took part in Operation Just Cause, bombing targets in Panama. The F-117 also took part in Operations Desert Shield and Desert Storm in 1990/1991.
In this conflict, F-117s flew more than 1,000 sorties against targets in Iraq, achieving an 80% success rate and suffering no combat damage.
The F-117 was the only Allied aircraft used against the heavy air defences of downtown Baghdad in the early stages of that conflict where its stealth design proved to be completely successful in evading enemy radar.
In 1999, F-117s were used in Operation Noble Anvil, the US element of the NATO bombing campaign against targets in the Federal Republic of Yugoslavia during the Kosovo War.
However, in March 1999, an F-117 was shot down by an S-125 surface-to-air missile fired by the Yugoslav Army. This was the only occasion on which an F-117 was shot down in combat. The pilot ejected safely and was rescued by USAF Pararescuemen.
In total, fewer than 65 F-117s were built. Proposals from Lockheed for the F-117 Seahawk, a version capable of operating from aircraft carriers and the F-117B, a high-performance multi-role version, were both rejected and in 2008, after 27 years in service, the F-117 was officially retired from the USAF.
It is believed that several F-117s have been stored at the Tonopah Test Range in Nevada where they could if required, be returned to service.
The main reason for the retirement of the F-117 in 2008 was another Lockheed design that entered service in 2005, the F-22 Raptor.
The F-22 Raptor uses many of the low-observable technologies first explored in the F-117 but combines them with vastly improved performance and true multi-role capability. F-22 really is a stealth fighter whereas the F-117 was a fighter in name only. Ironically, the Raptor project was also cancelled later in 2008 due to high costs.
It was replaced by the cheaper Lockheed F-35 Lightning II though that aircraft also uses stealth technology first developed for the F-117.
The truth was that the F-117 was never more than a flying test-bed for stealth technology. Its limited bomb/missile capacity made it ideal for precision strikes in a high-risk combat environment, but in Operation Desert Storm, for example, the vast majority of Allied ordnance was delivered by conventional, non-stealth aircraft that were capable of greater performance and flexibility.
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Although it received a great deal of publicity in 1991 for its part in the US air operations over Iraq and Kuwait, the truth was that the F-117 provided only a tiny element of overall Allied air power.
The F-117 did what it was designed to do with outstanding success; it proved that stealth technology worked in combat conditions. In military terms, what it achieved was very limited. This was a one-trick pony, but its distinctive appearance and innovative design made the Wobbly Goblin one of the most instantly recognizable and best-known combat aircraft of the 20th century.
- Crew: 1
- Length: 65 ft 11 in (20.09 m)
- Wingspan: 43 ft 4 in (13.21 m)
- Height: 12 ft 5 in (3.78 m)
- Empty weight: 29,500 lb (13,381 kg)
- Max takeoff weight: 52,500 lb (23,814 kg)
- Powerplant: 2 × General Electric F404-F1D2 turbofan engines, 9,040 lbf (40.2 kN) thrust each
- Maximum speed: 594 kn (684 mph, 1,100 km/h)
- Range: 930 nmi (1,070 mi, 1,720 km)
- Service ceiling: 45,000 ft (14,000 m)