Fighter Generations

[Kim Margosein]

I've heard the term "fifth generation fighter" mentioned a few times here. Please, could someone briefly define generations 1 through 5 with perhaps an example or two of each?

Kim Margosein

 

[SOC]

First off, bear in mind that I am using the definitions I've used professionally with the USAF. So, a European or Chinese designer might use different criteria.

Here we go:

GEN 1: MiG-15, F-86
-subsonic jet fighters

GEN 2: F-100, MiG-21, F-102
-supersonic jet fighters
-limited AAM carriage
-radar introduced

GEN 3: MiG-23, F-4, Mirage F-1, MiG-25
-limited look-down/shoot-down performance
-introduced BVR AAM carriage

GEN 4: F-15, F-16, MiG-29, Su-27, F-14
-BVR AAM carriage
-advanced digital avionics introduced
-look-down/shoot-down weapon systems are common

GEN 5: F-22A, F-35
-stealth
-integrated advanced avionics

4.5 GEN aircraft are 4th GEN fighters modified and incorporating 5th GEN features, such as advanced avionics or weapon systems. Examples here are the Su-35, EF-2000, and Rafale.

Here's a decent overview:

http://www.aerospaceweb.org/question/history/q0182.shtml

 

[smurf]

Thanks for these explanations, but I must be getting old. I remember when swept wings were a huge advance on (real?) first generation (jet) fighters like Meteors. You actually got sonic bangs. A few people might even remember biplanes!

 

[overscan (PaulMM)]

Occasionally US sources call the F-16 a 3rd generation aircraft, with F-22 being 4th generation. This is because the US went very quickly to BVR AAMs so the 2nd/3rd generation as shown above were compressed into one.

 

[AeroFranz]

It all depends on what you define "generation" as.
Chronologically?
As having markedly different characteristics from predecessors?
It doesn't necessarily have to mean "has more gizmos", or for that matter "is better".
It does however imply (at least in my mind) that other designs would follow in the same philosophy, otherwise it's not so much a generation as a single aberration.
So if you started seeing new designs embodying the characteristics that set the -39 apart, then yes, it would be the first of a new generation.

 

[Dreamfighter]

Which characteristics set the 39E so apart that it is a next generation? The software-enhancements, the somewhat larger range and payload compared with the 39C, the affordability and it's ability to attain 1.2M in supercruise?
Personally I would use the term "6th generation" for completely new designs with technical advancements (software-wise but also aerodynamics, propulsion, signature-reduction, etc) over the present generation. Imo Gripen-E is rather 4.75 generation, not even 5 like F-22, F-35, T-50 and J-20.
And I don't think evolved designs like Gripen 39E are THE future of fighterdesign, if the US wouldn't be able to find the money to develop and produce their F/A-XXs and NGADs, then surely the Chinese will and military aviation-advancement will proceed overthere. For us here in Europe, well that's another matter I guess, Gripen-E (and perhaps a Super Typhoon in a sweet dream?) might indeed be the future of our domestically made manned fighters.

 

[GTX]

The generally accepted view of the Jet Fighter "Generations" is as follows (courtesy of David Cenciotti):

Generation 1: Jet propulsion
Generation 2: Swept wings; range-only radar; infrared missiles
Generation 3: Supersonic speed; pulse radar; able to shoot at targets beyond visual range.
Generation 4: Pulse-doppler radar; high maneuverability; look-down, shoot-down missiles.
Generation 4+: High agility; sensor fusion; reduced signatures.
Generation 4++: Active electronically scanned arrays; continued reduced signatures or some “active” (waveform canceling) stealth; some supercruise.
Generation 5: All-aspect stealth with internal weapons, extreme agility, full-sensor fusion, integrated avionics, some or full supercruise.
Potential Generation 6: extreme stealth; efficient in all flight regimes (subsonic to multi-Mach); possible “morphing” capability; smart skins; highly networked; extremely sensitive sensors; optionally manned; directed energy weapons.

The attached image also gives some examples against each.

Sure there might be some to-ing and fro-ing between some elements but not that much.

Using this sort of information as a guide, the Saab Gripen NG probably best fits as either a Generation 4+ or Generation 4++.

 

[Avimimus]

Potential Generation 6: moderate stealth; efficient in subsonic flight regimes; reduced development costs; reduced maintenance costs; higher fuel efficiency; highly networked; extremely sensitive sensors; optionally manned; directed energy weapons.

...or you can go with the Sukhoi interview a while back and say: Spaceplane!!

If it hasn't happened yet we don't really know what the future holds.

P.S. There is the interesting issue about whether to define Generation 5 via the 1990s F-22 ADF... or something more flexible. Arguably, it is better to use the Russian's for a coherent definition (as they tend to develop missiles and radar at the same time as new airframes so definitions based on their development programs tend to be more 'coherent'). Then I'd also ask - should we treat the Euro-Canards as their own generations?

 

[F-14D]

Maybe he isn't defining generation by being defined by performance and or capability alone, but by philosophy (I didn't want to use the cliche "new paradigm"). In other words, the next "generation" is a different direction. For example, if we could build reliable A2A missiles that were hypersonic, extremely accurate multi-mode guided, capable of 100 g turns, ranges from 500 yards to 120 nm yet were small and light enough that you could hang bunch on an aircraft the next "generation" of fighters wold be more concerned with powerful sensors, long endurance and sustained speed to get on station than what we are presently expecting the F-22 replacement to be. Ditto if a practical long range airborne rapid-fire multi-shot directed energy weapon could be fielded. Then the next "fighter" might be a 747 sized a/c with an enormous radar and mutli-spectral sensors.

Maybe he's saying that the "6th generation" will be a/c with the general performance of what they expect to encounter, sensors and avionics up to the task but not necessarily a major leap ahead in every area. OTOH, it would be not a bank-breaker, would be robust and among its advanced concepts would be ease of maintenance and much lower cost of ownership. This would be a change in direction. After all, the F-22 and -35 aren't promising they'll require less maintenance or cost less to operate than their predecessors, so this would be a change in direction.

he could have just said "next" generation, but "6th" is so much more provocative

 

[LowObservable]

About right, F-14D.

The Cenciotti chart is not very valuable, let alone generally accepted. The Russians invented the 5th-gen label (as any fule kno) and it made some sense for them because of their centralized planning and development. They also tried to forget about their crappy straight-wing fighters, quite understandably.

1 - MiG-15/17
2 - MiG-21/Su-7/Su-9
3 - MiG-23/Su-15
4 - MiG-29/Su-27
5 - T-50

Simples! However, this ignores a lot of aircraft (Yak-28P, Tu-128, MiG-25/31) that are outliers.

The point is that if there is really a generational structure, it involves evolution to match the environment: conflicts, missions, threats, technical and economic, to name but a few. As the most-new post-2000 program in the West, JAS 39E was born into a different world from the one in which the "Gen5" philosophy originated.

 

[Mike Pryce]

Was the MiG 19 deliberately excluded by the Russians? Surely supersonic ability counts as a 'generational' advance?


Cenciotti puts it with the Phantom. Not sure I would.


Of course, it's all PR tripe, but SAAB could also have a bash at their own generations: 21/21R/Tunnan/Lansen/Draken/Viggen/Gripen (6 or 7 there already).

 

[sferrin]

IMO:

1st Gen: Earliest jets. Meteor, Me262, XP-59, F-80

2nd Gen: Swept wing, range-only radar (maybe), earliest gudied missiles. Mig-15, F-86, F-89, CF-100, Mig-19, Javelin

3rd Gen: Supersonic speed, PD radar, 2nd gen guided missiles. Mig-23, F-4, Mirage III

4th Gen: LD/SD radars, renewed emphasis on manueverability and visibility, afterburning turbofans. Mirage 2000, Tornado ADV, F-Teen, Su-27

5th Gen: All aspect stealth, the role of avionics, sensors, and networking taking a MUCH larger role in aircraft effectiveness, HMCS/HOBS. F-22, F-35, J-20.

Thing is, in the 1980s (yes the generation thing was talked about back then - it isn't a Lockheed Martin marketing invention) "next generation" (which, one would presume, meant the next aircraft being developed) would be: F-22, Typhoon, Rafale, Mig-2000. To lump them together though is misleading (to say the least) so. . .who knows? It's not an exact science (obviously). And there are a lot of aircraft that don't really fit neatly in there.

 

[LowObservable]

If anyone can find a citation (we've been through this before) to numbered fighter generations before 2000, and not in reference to Russia, please produce it.

Books in the shed somewhere don't count.

(Not sure where the MiG-19 fell. I suspect with the -15/-17... in any event, it was a retrospective issue with the Russians as well.)

 

[Reaper]

The generally accepted view of the Jet Fighter "Generations" is as follows

published by John A. Tirpak in Air Force Magazine

 

[sferrin]

If anyone can find a citation (we've been through this before) to numbered fighter generations before 2000, and not in reference to Russia, please produce it.

Books in the shed somewhere don't count.

Too bad.

Here's one from 1990 (albeit they split it a bit differently):
http://www.airpower.au.af.mil/airchronicles/apj/apj90/win90/1win90.htm

Following is a list of the generations, typical aircraft in each generation, and some of the definingcharacteristics of these aircraft.

1. High subsonic (1943-50): Me 262, Meteor, P-80, Vampire, Yak-15, MiG-9, Saab J-21, F-84 straightwing, F9F straightwing, Ouragan, Venom. Little aerodynamic difference from the last generation of propeller-driven fighters. First- and second-generation turbojets; wood, fabric, and all-metal construction; optical gunsights; straight wing and straight tail. Mechanical control systems. Primitive ejection seats. Mach 0.75-0.85.

2. Transonic (1947-55): F-86, F-84 sweptwing, F9F sweptwing, MiG-15/17, Hunter, Mystère TV. Second-generation turbojets; radar gunsights; swept wings; generally have adjustable horizontal stabilizers. Early hydromechanical flight control systems. Mach 0.90-1.05.

3. Early supersonic (1953-60): MiG-19, F-100, F-8. Swept wings, all-moving tails, radar gunsights, introduction of air-to-air missile armament. Third-generation turbojet engines. Early stability augmentation technology. Generally adaptable for both air-to-air and air-to-ground missions. Mach 1.3.

4. Supersonic (limited purpose) (1955-70): F-104, early model MiG-21, EE (BAC) Lightning, early model Mirage III. Supersonic aerodynamics, especially area ruling; fourth-generation turbojets; radar for search and fire control. Overreliance on -air-to-air missiles based on unrealistic expectations. Mach 2.0.

5. Supersonic (multirole) (1958-80): F-105, F-4, late-model MiG-21, late-model Mirage III, F-5, F-111, Mirage V, Su-24, MiG-23/27, Jaguar, Mirage Fl, Kfir. Refined supersonic aerodynamic design, including canards and variable geometry wings; fourth- and fifth-generation engines; stability augmentation; mixed-gun air-to-air missile (AAM) armament; terrain-following radar for low-level high-speed flight; radar search and fire control; infrared sensors; heads up displays (HUD); laser ranging and targeting; wide range of air-to-surface missiles, bombs, and rockets, including precision-guided munitions. Mach 1.4-2.5.

6. Supersonic multirole, high efficiency (1974-present): F-14, F-15, F-16, F-18, Mirage 2000, Tornado, MiG-29, Su-27. Combined the characteristics of the fifth-generation fighters with advances in propulsion, radar (multiple target track-while-scan, look-down/shoot-down), sensor, and electronic flight control technology to generate highly maneuverable, highly agile aircraft that can be swing-roled for air-to-air and air-to-ground missions. Fifth- or sixth-generation gas-turbine engines; engine thrust-to-weight ratios in excess of one; ability to attain supersonic speeds without afterburning; sustained high-G flight, and controllability below 70 knots at angles of attack exceeding 70 degrees. High degree of energy efficiency. Mix of cannonand missile armament, coupled with diverse air-to-ground weaponry. Mach 1.8-2.5.

 

[overscan (PaulMM)]

By that list the F-22 is at least "Gen 7"


The Chinese refer to J-20 as 3rd Generation, which it is, in their context.


The whole thing is pretty meaningless.

 

[GTX]

 

[sferrin]

By that list the F-22 is at least "Gen 7"


The Chinese refer to J-20 as 3rd Generation, which it is, in their context.


The whole thing is pretty meaningless.

It's useful from a historical perspective as it shows how techology and emphasis has changed over time.

 

[sublight_]

Ditto if a practical long range airborne rapid-fire multi-shot directed energy weapon could be fielded. Then the next "fighter" might be a 747 sized a/c with an enormous radar and mutli-spectral sensors.

That is what I was thinking. If we get to the point where a platform can vaporize all incoming threats, will it look like an F15 or more like Next Gen Bomber?

 

[Dreamfighter]

If anyone can find a citation (we've been through this before) to numbered fighter generations before 2000, and not in reference to Russia, please produce it. Books in the shed somewhere don't count.

Both terms "4th generation fighter" and "5th generation fighter" were used long before the turn of the century, and are not invented with regard to the Russian Suchoi T-50 or such.

As you say quotes from "books" don't count as proof, maybe quotes from "magazines" are allowed? :
(the internet was not yet very common in the first half of the 90s, and certainly not in the 80s right )


I just pulled 2 magazines, dating from the 2nd half of the 1990s out of the piles here:



French Magazine "Air Fan N. 223 Bourget Special", JUIN (June) 1997, article "dossier Raptor" by author René J. Francillon, pages 45 - 53;

On page 46 the terms "quatrième génération" (translation: "fourth generation") and "cinquième génération" (translation: "fifth generation") are used in bold as paragraph-titles.

Quote from the text on pages 46-47:


"Cinquième génération

Alors que l'aviation militaire russe et l'US Navy on choisi la voie plus conservatrice de l'évolution (Su-27, Su-30, Su-35, Su-37 pour l'une et Hornet, Super Hornet pour l'autre), et que la France, quatre de ses voisins membres de l'Otan et la Suède se sont engagés sur celle plus risquée de la quatrième génération (Rafale, Eurofighter 2000 et Gripen). l'US Air Force a franchement mis le paquet en se lançant directement dans le développement d'un chasseur de la cinquième génération destiné à succéder à son F-15."

I'll translate;

Fifth generation

Whereas the Russian airforce and the US Navy have chosen a more conservative path of evolution (Su-27, Su-30, Su-35, Su-37 and Hornet, Super Hornet respectively), and whereas France and four of it's neighbouring members of NATO and Sweden have engaged themselves for the more risky fourth generation (Rafale, Eurofighter 2000 and Gripen), the US Air Force has given itself completely into directly launching the development of a fifth generation fighter, destined to succeed it's F-15.





There was sometimes a somewhat different interpretation of "4th generation" back then (it is meanwhile about 15 to 20 years ago), especially with European authors who sometimes considered the Eurocanards as a completely new generation, whereas we now tend to call them rather 4.5th generation.
The (French) author of this artcile describes Rafale, Typhoon and Gripen as 4th generation and apparantly regards the US teenseries and Russian Su-27 and MiG-29 as 3.5th generation fighters.



French Magazine "Science & Vie Nr. 207 Hors Série Aviation 99", JUIN (June) 1999, article "Chasseurs futurs polyvalents et invendables" by author Jean-Louis Prome, pages 141-147;

Quote from page 142:

"...les Rafale, Typhoon, Gripen ou F/A-18E/F tentent de répondre à l'étappe suivante. Ces appareils, dits de quatrième génération, sont entièrement polyvalents."

translation:
"... the Rafale,Typhoon, Gripen or F/A-18E/F try to answer the next step. These aircraft, to say the fourth generation, are completely multirole."

 

[Dreamfighter]

 

[LowObservable]

Thanks, DF - I wonder where Francillon picked that up from?

 

[LowObservable]

I asked for non-Russian citations before 2000. I did not know of any (although there are Rand accounts that use the Russian terminology in the later 1990s) and none was produced in previous discussions. Yours was, as they say, nonresponsive because it listed seven generations, not including the F-22.


Does the Francillon article define the first, second and third generations?

 

[Dreamfighter]

I asked for non-Russian citations before 2000. I did not know of any (although there are Rand accounts that use the Russian terminology in the later 1990s) and none was produced in previous discussions. Yours was, as they say, nonresponsive because it listed seven generations, not including the F-22.

[font=verdana, arial, helvetica, sans-serif]I believe the post you are answering to, has disappeared ...
[/font]

Does the Francillon article define the first, second and third generations?

No, just the fourth and fifth generations are mentioned. The topic of this article was purely about the (then) newest jets and the YF-22/F-22 in particular, not about older aircraft.

 

[sferrin]

I asked for non-Russian citations before 2000. I did not know of any (although there are Rand accounts that use the Russian terminology in the later 1990s) and none was produced in previous discussions. Yours was, as they say, nonresponsive because it listed seven generations, not including the F-22.

[font=verdana, arial, helvetica, sans-serif]I believe the post you are answering to, has disappeared ...
[/font]

Does the Francillon article define the first, second and third generations?

No, just the fourth and fifth generations are mentioned. The topic of this article was purely about the (then) newest jets and the YF-22/F-22 in particular, not about older aircraft.

So what we have then is verifiable proof that the concept of aircraft generations existed outside of Russia well before 2000, and is not simply a Lockheed Martin marketing gimmick. Let's hope that puts an end to the matter.

 

[Dreamfighter]

Done a bit more digging today, before the pile of 1990s-magazines must go back in the (magazines-)closet.
(collecting stuff is fun, until you've to find back things while still having space to walk around in the room : )

The following is from the German magazine "Flug Revue", august 1996. It is about the fourth generation and the Gripen, and it describes the Gripen as the first European fighter of the fourth generation; "erstes europäisches Kamfflugzeug der vierten Generation". The Gripen-photo with yellow title "Die Vierte Generation" ("the fourth generation") is from pages 42 & 43.

 

[J.A.W.]

'The Illustrated History of Aircraft' (1977) edited by Brendan Gallagher.

Page 102 has the heading,

' The Soviet second generation',

& goes on,

'What had the Russians been up to since the mid 1950's?'

 

[overscan (PaulMM)]

I asked for non-Russian citations before 2000. I did not know of any (although there are Rand accounts that use the Russian terminology in the later 1990s) and none was produced in previous discussions. Yours was, as they say, nonresponsive because it listed seven generations, not including the F-22.

I believe the post you are answering to, has disappeared ...

Does the Francillon article define the first, second and third generations?

No, just the fourth and fifth generations are mentioned. The topic of this article was purely about the (then) newest jets and the YF-22/F-22 in particular, not about older aircraft.

So what we have then is verifiable proof that the concept of aircraft generations existed outside of Russia well before 2000, and is not simply a Lockheed Martin marketing gimmick. Let's hope that puts an end to the matter.

Noone was arguing that the concept of aircraft generations was new. The question is whether the concept of the F-22 being the "fifth generation" existed prior to 2000. It did.


I believe the first mention of "fifth generation fighter" was late 1994 in reference to the MiG 1.42. A non-scientific search of flightglobal.com archive confirms this (e.g. Uncle Roger's question here - http://www.flightglobal.com/pdfarchive/view/1994/1994%20-%203078.html?search=fifth-generation%20fighter) Roughly, the generations are MiG-15, MiG-21, MiG-23/25, MiG-29/31, 1.42. MiG-19 seems to be ignored as well as the MiG-9 but neither were truly mainstream.


Mikoyan thought the 5th generation was characterised by the "3 S's" of stealth, supercruise, supermanouverability. Mikoyan should have applied for the trademark on "fifth generation fighter" because they seem to have popularised the term in relation to the 1.42.


Russian, as LowObservable says.


Ironically, the 1.42 wouldn't meet sferrin's definition of a fifth generation fighter due to insufficient stealth and inadequate sensors, which neatly makes the point that the 5th generation as defined by Lockheed Martin is "whatever features are possessed by our products".


Which makes my point - its a meaningless bullshit marketing term.

 

[sferrin]

This is what LowObservable asked for,

"If anyone can find a citation (we've been through this before) to numbered fighter generations before 2000, and not in reference to Russia, please produce it.

Books in the shed somewhere don't count. "

I responded with a cite from 1990 giving him exactly what he asked for. Nothing more, nothing less. Pretty straight forward.

 

[GTX]

Which makes my point - its a meaningless bullshit marketing term.

If you want to call it a "marketing term" it has been extremely successful since it is in common usage in industry and in the word's air forces and not simply in relation to Russian aircraft or the F-35. Moreover, the term has been extended into the world of gas turbines. For example, engines such as the Jumo 004 are referred to as Gen 1; RR Avon commonly thought of as Gen 2; TF30 Gen 3; F404 Gen 4; F414 Gen 4.5 and F135 Gen 5. Of course just as with the fighters themselves, there is a bit of dispute over what classifies which and as I am sure you can imagine, a bit of crossover between Generations in some cases. Never-the-less, the use of the generations term is there.

Therefore, I would not call it "a meaningless bullshit marketing term".

 

[AeroFranz]

Neither is it an effective engineering term. As you correctly mentioned, there is a lot of cross-over between generations, and aircraft do not fall neatly in categories.
I would regard the use of these terms as over simplifications which leave too much room to subjective interpretation. Who gets to decide what generation their design belongs to? I tell you who: marketeers and people who make shiny brochures with meaningless numbers and blow smoke up your skirt. Anyone tried to do competitive analysis using publicly available material? Good luck. I take whatever those people say with a grain of salt.

 

[sferrin]

Neither is it an effective engineering term. As you correctly mentioned, there is a lot of cross-over between generations, and aircraft do not fall neatly in categories.

This is true, but it will get you in the ballpark. And as GTX pointed out we've heard it cross over into other areas. AAMs for example. Bottom line though they're just general groups with common attributes. And of course marketers are going to latch onto anything they think gives them an advantage. That's not really news. The fact that LM seems to have realized this and used it to their advantage should surprise absolutely nobody. I believe it was World Air Power Journal wherein one writer compared Western fighter salesmen as "could make a hardened drug dealer look like Mother Theresa" when it came to scheming. This was in explanation for the lack of FSU fighter sales on the international market at the time.

 

[Stargazer]

Although I tend to agree with you guys that it's a fairly recent invention mainly used as a political tool/marketing ploy by the Russians and Lockheed alike, I think there is no denying that there have existed "generations" of fighters (and bombers, and transports, etc.).

Instead of relying on some obviously biased definitions, why not try and list objectively all the features that appeared in the course of fighter development, date them, then decide which ones represented a true breakthrough? Those fighters which combined a sufficient number of new features when they appeared would mark the appearance of a new "generation". I think that's pretty much what Cenciotti tried to do, albeit imperfectly as there will always be people to argue over this or that — especially if patriotic notions of "we did it first" come into the logic...

 

[GTX]

I think that's pretty much what Cenciotti tried to do, albeit imperfectly as there will always be people to argue over this or that — especially if patriotic notions of "we did it first" come into the logic...

Agreed.

 

[Thorvic]

A quick search on Flight brought up this Jan 96 Rafale advert where they call it 4th Generation.

http://www.flightglobal.com/pdfarchive/view/1996/1996%20-%200069.html

As Paul says its a marketing term B)

The trouble is now were seeing it take a human generation and half another to bring a project from definition to front line operational service which shows the process is a little bit FUBAR

 

[GTX]

As Paul says its a marketing term B)

Sorry, but it is more now. As already explained, it is used within the industry for more than simply marketing...despite what some may claim.

 

[sferrin]

A quick search on Flight brought up this Jan 96 Rafale advert where they call it 4th Generation.

http://www.flightglobal.com/pdfarchive/view/1996/1996%20-%200069.html

As Paul says its a marketing term B)

See post #10. Just because a manufacturer uses something doesn't automatically make it a "marketing term".

 

[Dreamfighter]

A quote from magazine Flight International, date March 1, 1986, article "ATF set for 1991 first flight", pages 8 and 9;

"The goal is to build an aicraft that will meet the Soviet threat from the year 2000 onwards. The problem is predicting the type of technology being produced by the Soviet Union in two generations' time. US intelligence has successfully pinned down the technology in the current MiG-29/Su-27 generation and predicts that what the Soviet Industry will be producing at the beginning of the 21st century will be what we're doing with ATF now"


There is no specific mention of "fifth generation" in this article, but they are talking about ATF being so advanced it is not only meant to beat the "Su-27/MiG-29 generation", but also match or exceed the Russian's fighter-generation to be produced in the early 21st century. When Su-27 and MiG-29 are regarded as belonging to the fourth generation, then ATF (now F-22A) surely must be a fifth generation fighter, that is pure logic I'd say?

 

[overscan (PaulMM)]

I don't think anyone is disputing that the F-22 (prototype first flight 1990, first production deliveries 2003) is a newer generation than the MiG-29 (first flight 1977, first production deliveries 1983) or that the ATF was intended to outperform the next generation of Soviet aircraft, not just the contemporary one.

 

[Dreamfighter]

A quick search on Flight brought up this Jan 96 Rafale advert where they call it 4th Generation.

An article about Rafale and 4th generation-fighters, from 1989;


http://www.flightglobal.com/pdfarchive/view/1989/1989%20-%201760.html?search=%22fourth%20generation%22