Viper variants: Unusual F-16s

The F-16, the best designed fighter jet of the 20th century, has proved an excellent aircraft to modify, build upon and generally mess around with. Here are some of the unlikely Vipers that have flown over the last forty years, we have also cheated to include some unofficial clones that cheekily borrowed a little F-16 DNA. 

Diverterless supersonic inlet ‘Bump Rider’ (1996) 

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Jet engines cannot handle supersonic airflow, which considering fighters go at twice the speed of sound is a problem. So the airflow is slowed down before it enters the engine. There are various ways to do this and they are heavy, require maintenance and tend to be highly visible to enemy radars. The diverterless supersonic inlet, however, is an elegant and clever solution.

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It is simply a bump that slows down the airflow, while also blocking enemy radar’s view of the engine compressor face (a highly reflective surface). It was used on the F-35 Lightning with and achieved a 30% weight saving over the traditional solution. I’m not (necessarily) saying that Chinese designers stole the idea, but have a look at the Chengdu J-10B/C,  CAC/PAC JF-17 Thunder, Chengdu J-20, Shenyang FC-31 and Guizhou JL-9.

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General Dynamics F-16XL ‘Hyper Viper’

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The leading edge of Concorde’s wing reduces in sweep as it runs from the fuselage to the wingtip. The reason being that a traditional delta wing, like that of the Mirage III has pretty ropey low-speed handling qualities. The XL began life as an effort to see if technologies from supersonic transport, such as the cranked delta, could benefit military aircraft.  The first of two F-16XLs flew in 1982 and the results were dramatic: there was a 25% improvement in maximum lift-to-drag ratio in supersonic flight and an 11% while in subsonic flight. Compared to a regular F-16 the ride was smoother at high speeds and- somewhat surprisingly – at low altitudes. The baseline F-16 was already the longest-legged fighter in USAF, but the fuel was could now be increased by a hefty 82%. The F-16XL could carry twice the ordnance weight of the F-16 and deliver it 40% further.

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Before the XL had flown, USAF had launched the Enhanced Tactical Fighter to replace the F-111. USAF essentially wanted a fighter-bomber capable of deep air interdiction missions without fighter or jammer support. Something based on the F-16XL could clearly be a strong contender and so General Dynamics entered the fray, eventually losing out to the F-15E. The XL lost, as unlike the F-15E it varied a great deal from the aircraft it was based on and would likely have incurred greater development costs. The larger more powerful twin-engined aircraft was also seen as more survivable and future-proof.

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This 1990s Sukhoi study shares an, at least superficially, similar wing shape to the F-16XL.

The aircraft then went to work for NASA, exploring the use of holed laminar flow wings. The intention was to explore whether these laser-cut holes could suck turbulent airflow over the wing, restoring laminar flow.  Around this time the second XL, which was a two-seater, was re-engined with the monstrous -229. With this new engine it accidentally achieved supercruise (reaching and sustaining supersonic speed without recourse to afterburner) getting to Mach 1.1. After various research for NASA in support supersonic transport research, including sonic boom characteristics and engine noise,  the XLs ceased flying in 1999.

Unusual F-4 Phantom IIs here

Lockheed F-16U ‘The Delta Belter’ (1991)

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In the early 90s the United Arab Emirates was after a fighter with a long range and a large weapon load, capable of mounting attacks deep into Iran. General Dynamics, which had just been absorbed into Lockheed, came up with a strong concept – a delta F-16. A cranked ‘arrowhead’ delta wing had been tested on the F-16 already and had boosted fuel capacity by up to 82%. GD’s new delta F-16 would use a cropped wing design it had developed for the ATF effort that led to the F-22. The UAE was willing to pay for development on the condition that USAF purchased a wing’s worth of F-16Us. This was an offer USAF could not agree to as devotion to JSF (later F-35) was sacrosanct and the lower risk F-16U threatened to steal funding, and possibly the security of the whole JSF effort . Others were afraid of the F-16U too. Aerospace reporter Bill Sweetman noted that prominent members of the Eurofighter consortium believed the aircraft would have ‘killed’ the Typhoon. If it had been built it is likely the F-16U would have been an extremely capable aircraft  that would have dented the eurocanard’s global sales severely.

Hawker Siddeley P.1200 ‘Kingston Rudeboy’

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This isn’t really a F-16 but is worthy of inclusion in this list.

In the mid 1970s, the British company Hawker Siddeley developed a concept for a medium-weight fighter for the Royal Air Force strongly influenced by the US’ F-16. This series of ‘P.1200’ concepts came from the company’s Kingston division. Though considerably larger than the F-16, most of the P.1200 designs featured a similar air intake, canopy, leading edge root extensions and general wing configuration.

Strangely the P.1202 design was offered with either two RB.199s or a single RB.431. The RB.199 was then in development for the Tornado, but as experience would show with the ADV, it was not a suitable fighter engine; it was tailor-made for the low-level regime and was a poor performer at the medium and high altitudes that an air superiority fighter needs to operate in. The RB.431  study was essentially a Pegasus with reheat and no vectored thrust nozzles, though powerful it again seems an odd choice for a supersonic fighter.

The initial design, from November 1975,  featured a canard layout with square shoulder-mounted intakes, similar to the later Saab Gripen. Further designs utilised a conventional tail and dorsal intakes. Internal armament for the early P.1200 designs was two 27-mm Mauser cannon. Air-to-air armament was expected to be AIM-9 Sidewinders and SkyFlash medium-range missiles. In the secondary air-to-ground role it could have carried four bombs in a low-drag recess.

By 1977 the aircraft had become even more strongly influenced by the F-16. Both single and twin vertical fin configurations were tested. The twin-tailed P.1202 pictured above, would have had superior high alpha performance to the F-16, and given a suitable engine, would have made a formidable dogfighter.

 

Mitsubishi F-2  ‘Mamushi moshi’ (1995)

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Notably, the F-2 was probably the first operational fighter to carry an AESA radar. Note the distinctive clipped shape of the tailplane.

If Japan’s desire to keep its aerospace industrial base alive is an expensive vanity project, then a prime example is the F-2. It’s a pretty average F-16 in capability, yet costing around four times per unit! Still, with its fantastic paintjob the F-2 is the most attractive member of the Viper family. The US negotiated an exceptionally aggressive technology transfer agreement whereby the US benefits from any unique tech that Japan develops for the F-2. The F-2 has a larger wing than the F-16, more composites in the structure and a stronger (more conventionally braced) canopy. The wing, and indeed the F-2 itself, was based on the Agile Falcon, a proposed low cost complement to the ATF programme that led to the F-22.

Unusual F-4 Phantom IIs here

Whereas the Mitsubishi F-1 was essentially an unlicensed pirate copy of the Jaguar (an aircraft JASDF had assessed in detail), Mitsubishi did not dare the same approach with the US. One of the most expensive aircraft in the world, it is at least a real looker. It could also be argued that the F-2 kept the Japanese aerospace industry technologically relevant – something vital to Japan’s ambitious new fighter, the nascent F-3.

Lockheed Martin built 40% of the F-2. Comapred to a baseline F-16C, the F-2 has a larger nose, more internal fuel, greater wingspan and wing area, with two more hardpoints. It may be the only F-16 with 13 hardpoints, making an eight air-to-air missile load-out conceivable. It would appear to have the largest radar array of any F-16 variant — and Japan has recently upgraded their AESA.

F-16 VISTA MATV ‘Hasta la VISTA’ (1992)

The most manoeuvrable jet America ever produced was the F-16 Variable stability In-flight Simulator Test Aircraft (VISTA) — a project started to investigate future fighter technologies that later went on to include a radical new control technology.  Fitted with an Axisymmetric Vectoring Exhaust Nozzle (AVEN) 3D-vectored thrust nozzle and a flight control system able to handle the extreme nature of post-stall supermaneuverability, the VISTA could fly in seemingly impossible ways.  The multi-axis thrust vectoring (MATV) engine nozzle made active control of the aircraft in a post-stall situation possible, with extremely dramatic results.

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The three best Western dogfighters ever flown. From left to right, F-18 HARVX-31, and F-16 MATV.  Much of the VISTA effort was primarily about replicating the control system and handling of other aircraft. It was converted for the MATV then presumably converted back — and used to test the F-22 and X-35 flight control software.

The aircraft has demonstrated a sustained angle of attack of 86 degrees, and a transient angle of attack of 180 degrees (meaning the aircraft could fly backwards). The degree to which thrust-vector control is tactically applicable remains hotly debatable, though it can allow for dramatic and unexpected last-ditch missile shots. The argument against TVC’s use in air combat points to the perilously low-levels of energy the post-stall aircraft suffers, the weight and complexity of the nozzle and the ability of modern fighters to cue high off-boresight missiles with a helmet or on- or off-board sensor. Essentially why move the whole aircraft a head movement or  sensor on another aircraft could tell the missile which portion of sky to target.

The VISTA also pioneered voice control (something already explored to some degree with the British EAP) and the virtual HUD, both of which would be used on the F-35 Lightning II. Today no Western fighters use 3D TVC, though the Russian Su-30, Su-35S and Su-57 do.

 

Mikoyan MiG-33/35 ‘F-16ski’ (1981)

Because it’s interesting, let’s  bend the rules again and include another aircraft that is not an F-16. In the 1980s, the Mikoyan design bureau tinkered with a simple, single-engine warplane similar in concept to the original version of Lockheed’s F-16 lightweight fighter. Like the F-16A, the new Soviet plane would be simple, manoeuvrable and inexpensive.

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The Project 33 design, sometimes – and perhaps erroneously – referred to as the MiG-33 or MiG-35, featured a single Klimov RD-33/93 afterburning turbofan, two of which power the larger and more complex MiG-29. According to a 1988 report in Jane’s Defense Weekly, Project 33 was “seen as a complementary combat aircraft to the powerful MiG-29.” Where the MiG-29 boasts some multirole and beyond-visual-range capability, the Project 33 was a short-range, point-defence fighter. Here was a MiG-21 for the 1980s – an ideal fighter for friendly states on a budget.

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Mikoyan didn’t get very far with Project 33, as Soviet leadership apparently preferred to devote the USSR’s resources to more sophisticated aircraft. But Project 33’s DNA perhaps survives to some extent in the Chinese-made FC-1 export fighter.
Mikoyan reportedly sold the Project 33 design to China after it became clear there would be no Soviet market for the plane. China folded elements of Project 33 into the FC-1, which itself evolved from the joint U.S.-Chinese Super 7 light fighter, work on which collapsed following the 1989 Tiananmen Square massacre. In a weird sort of aerospace-design convergence, the Super 7 had also drawn inspiration from the F-16.
Powered by a single RD-33/39-powered FC-1, the FC-1 (also known as the JF-17) today is one of Pakistan’s most important fighters, serving alongside…you guessed it… F-16s.

– David Axe  War is Boring

Unusual F-4 Phantom IIs here

General Dynamics F-16 SFW (Swept Forward Wing) Windscreen Viper’ (1980)

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You can do anything with an F-16: Stick a delta wing on and you’ve got a long-range attack aircraft (F-16XL), change the landing gear you can make a decent naval fighter (V-1600). So why not make a forward swept wing demonstrator? In 1976, DARPA (Defense Advanced Research Projects Agency) awarded funds to General Dynamics, Rockwell and Grumman under the Forward-Swept Wing Program. The engineers at General Dynamics, of course, suggested fitting a FSW to their F-16. In 1981 DARPA decided to opt instead for the Grumman X-29 based on the F-5/F-20, a decision many said was due to the F-16s over -representation in upcoming DARPA test programmes. In the end the X-29A featured a load of F-16 components, including an adapted form of its fly-by-wire system.

Vought/General Dynamics 1600 series ‘Sea Viper’ (1973)

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The F-16 won the USAF Light Weight Fighter contest in the early 1970s, so it made sense – in terms of commonality and economy of scale – to suggest a version for the Navy. The Navy wanted a replacement for the F-4 and A-7 that was smaller and cheaper than the F-14 Tomcat. Having no carrier aircraft experience, General Dynamics teamed up with Vought to offer the 1600.

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It would have differed from the early F-16 in several ways, including a beefier undercarriage and the ability to use AIM-7 Sparrow missiles. The Navy decided against it in 1975, preferring the twin-engined F/A-18 (based on the Northrop F-18L) offered by McDonnell Douglas.

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  1. Pingback: Viper variants: Unusual F-16s — Hush-Kit – ianwattsblog

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