Why do fighter aircraft differ?

[GC1993]

Something I've been pondering on - for you aeronautical experts.

 

Why should 2 airframes from 2 different countries designed from the same purpose differ in any way?

 

For example, America's top minds in aeronautical engineering in the late 60's and early 70's produced the Eagle to be the king of air superiority. The soviet union responded in late 70's with the flanker - also designed to be the king of air superiority. And yet - aeronautically they differ rather a lot.

 

So why are all these great minds blessed with the pinnacle of aircraft design and aeronautical knowledge, who conduct wind tunnel tests and stress test and everything else, producing aircraft that differ greatly in their airframe? If they all were as competent as each other and had the same vast knowledge and the same testing processes, surely only one airframe design would be agreed to be the best and thus be produced for all air forces that could afford it?

 

Now obviously I'm not suggesting that leading aircraft design comes only from the US and Russia, I'm simply using them as comparison in this context because of their differences for the same job:

Eagle/Flanker

B1/TU-160

Raptor/PAK FA

 

Why does internationally known aeronautical design knowledge available to most leading countries still produce different results?

Edited April 24, 2014 by GC1993

[cichlidfan]

Possibly because there is more than one way to skin a cat. Also, giving different priorities/budgets to different aspects of the design goals would produce different results.

[4c Hajduk Veljko]

Why should 2 airframes from 2 different countries designed from the same purpose differ in any way?

Because of the different tactical objectives.

 

For example, America's top minds in aeronautical engineering in the late 60's and early 70's produced the Eagle to be the king of air superiority. The soviet union responded in late 70's with the flanker - also designed to be the king of air superiority. And yet - aeronautically they differ rather a lot.

F-15 is designed to fight BVR battle deep into the opponent territory, relying on its own powerful radar. Flanker is designed to defend territory in CAC, relying on a GCI data link and EOS, because powerful ground based jammers render radars useless.

[Kuky]

Different mindset of what each country/military expect from their hardware and how to operate it... many different things come into play:

 

- how cheap you want it to be - how much you can afford or are willing to spend on it

- how easy conversion you want your pilots to switch from one plane to another

- what conditions is the plane to be operating in

- how far you need it to go (big country needs planes to fly longer and further)

- how self reliant is the plane/pilot need to be (does he need or have ground support... what terrain (friendly or enemy) is he going to be fighting over)

- how easy is the maintenance to be or techs to be trained

- how much and what kind of weapons it needs to carry

- what is the purpose of the plane (what is most likely mission to be flying)

- etc etc etc, many many things ate taken into consideration

 

Also unless one man copies exactly the other, no 2 people/brains will think the same and their products will differ :)

[stokerel]

There is no such thing as a perfect design in engineering. Every project is a sum of compromises made to achive a certain goal.

That's why there is no single perfect way of doing something, just like everything else in life.

[Bucic]

1. Slight differences in priorities leading to significant design differences.

2. Past design experience, e.g. it would be hard to convince the French against delta wing.

3. Available resources. Again, see point #1.

 

Example:

Both sides design an air superiority fighter. One side prefers fixed engine inlets and doesn't care about rearward cockpit visibility. The other prefers the opposite. Result. Completely different airframe.

Edited April 24, 2014 by Bucic

[Sharpe_95]

Well its a basic answer at the highest level but becomes more and more technical the further you go into the weeds. Some BASIC points to consider:

 

-While all aircraft might be designed as a 'fighter plane' or 'bomber' - bear in mind these are top level requirements and each country that designs a 'fighter aircraft' will still have many other top, middle, lower and macro requirements - all of which creates variance in design.

 

- No one country has access to all the same technology - this again creates variance in design.

 

- No aircraft are designed at the same time, this effects access to technology.

 

- You can make an aircraft do broadly the same thing in many different ways that effect it's cost, service costs, through life costs etc (remember that the acquisition cost is ALWAYS much lower than the through life cost thus designing aircraft that reduce through life costs can be a major priority in aircraft design.

 

- Evolution of potential threats. If a country decides it needs the next generation of shiny shiny, it's generally because it's old design is running out of service life and/or because there is a perceived capability gap (in the near to long term future) that the aircraft is trying to fill.

 

- Evolution of enemy aircraft mean you have to design something to counter it. This applies to design of radar, wings, power etc etc. A good example is the A10c. An aircraft that was admittedly designed around its gun, with engines that were highly efficient to meet a need for longer loiter times over the target with straight wings to allow better stability at low speeds, well armoured against ground threats and with a large ordnance capacity.

 

- Cost, it governs all things.

 

- Imagine all aircraft were all the same, wars would be a really unhealthy place to be. Ask any military tactician what he prefers: a noble honourable fight or the ability to sneak up behind someone and shoot them in the back without being seen or in range and they will normally take the latter. The modern aircraft that resembles this metaphor is the B2 Spirit Stealth bomber. The price of which makes F35 look like a basement bargain.

 

- Everything is about trade off and balance. Otherwise you would be in a situation similar to the one noted above where everything is the same - which is not a desirable military situation. War, and the evolution of military kit and doctrine is evolutionary not revolutionary (to use the academic use of the terms not the military terms). One thing counters another that is then countered by something else and so on. Or something new pops up and you have to figure out how to fight the new threat. An example here is the evolution of stealth tech which (in Russia) has (allegedly) been countered by the SA20/21/23 system. Now something will need to be designed to defeat those SAM systems and so on.

 

These are just some minor high level points tapped out on my mobile. But if you read up on the development of a selection of aircraft on say Wikipedia (quick and easy place to start from) you will start to see common themes in how aircraft are designed that will help answer your question of why all aircraft are not a like.

 

Taking the example you give (F15 vs flanker) some basic points to ponder:

a) Soviet Strategy was to fly many cheap(er) solutions at less numerous technologically superior enemy (by doctrinal design without getting into the classic and childishly oversimplified bun fight over which aircraft is best).

b) US doctrine relied heavily on the promise of BVR radar guided combat. Soviet design relied slightly less on BVR combat and where it did it was often achieved through thermal not radar guidance (although both were possible IRST leaves no RWR trace, like TWS).

c) Soviet tech was often less efficient but more rugged than US tech. (Slightly off topic but have you ever noticed how Russian aircraft wings have a tendency to sag a lot more than other non Russian designs of similar size?).

 

It's a good question that will continue to plague people like me and other people that work in defence acquisition from now until the end of time.

 

Regards,

-Sharpe

Edited April 25, 2014 by Sharpe_95

[EtherealN]

These are just some minor high level points tapped out on my mobile.

 

You typed that wall on a mobile? Wow, I've met my match! :D

 

c) Soviet tech was often less efficient but more rugged than US tech.

 

I don't know if this is apokryphal or not, but I remember a story about that MiG-25 that defected to Japan; the americans were surprised to find that it's avionics and computation systems still relied on vacuum tubes - very basic, energy inefficient, less serviceable etc. BUT with an advantage: in a nuclear battlespace, it's a lot less susceptible to damage from the EMP's associated with nuclear blasts.

 

An illustrative difference that might be telling is if we compare a small american fighter like the F-16 with the Swedish JAS-39, the latter has a very different aerodynamic configuration. (Though early in the project SAAB did consider both F-18 and F-16-style configurations.) One of the reasons for this is that the Swedish doctrinal requirement was for a fighter that could operate from roads (the doctrine was that in event of war, combat jets leave the air bases and disperse to "war bases" all over the country, essentially straight stretches of road along the highways with revetments and such hidden next to it). The canard design helped in allowing rediculously short runways in compliance to that without the need of heavy reverser gear as in the JA/AJ-37. (Sadly though, it also removed the awesome ability to parallell park a fighter jet...)

 

(The canard design also helped with other things, of course. But as an example.)

 

For a country like the US, that capability is fairly pointless given their doctrine. So what is a "plus" for Sweden would at best be neutral for the US. Similarly, Sweden does not need long range, since it's a relatively small country that has no real commitments to project force outside of our borders, so while a large fuel tank would be almost essential for the US (plus aerial refueling capability), both of those are at best neutral for Sweden. And both come with added weight, which can negatively affect performance. (Aerial refueling was implemented in the C/D revision, though, and the E/F will be getting bigger tanks, but that is in part due to export considerations but also partly changes being done in our air defense doctrine, with deployments to other countries becoming more relevant - for example Libya and potentially Iceland.)

 

An analogy could be in automobiles: for most people, a normal sedan and an SUV really does just do the same thing - transports you to and from work. But depending on where you live, the SUV might be useful (for example here, we have a lot of snow in winter, and the plows might not have reached your area yet when you need to go to work). If you're in a city, the sedan probably gets the same job done but with better economy. But the job they're asked to do is the same, just in different circumstances.

 

And in jet fighter design, there's a LOT of circumstances, all the way from technology to materiel availability to doctrine and let's not forget - politics. If sweden had been a NATO member, it would be a fair bet that the 39 either wouldn't have gotten made at all (rather 16's or 18's would have been purchased, or perhaps joined the Eurofighter programme), and even if the 39 was made you bet it would have had bigger tanks and aerial refueling from the start even if that slightly lowered performance.

[jib]

I think 5th generation fighters have just copied the F22 and disproved your point slightly, China a getting better at making rip offs.

 

[karambiatos]

I think 5th generation fighters have just copied the F22 and disproved your point slightly, China a getting better at making rip offs.

 

only the chinese one is more of a mig1.44 made to be stealthy.

[4c Hajduk Veljko]

Yeah, all of these aircraft have wings, so it has to be a copy, because F-22 has wings too.

 

Well, similar or, exactly the same, objectives, or problems to be solved, will bring very similar, if not the same solutions. The fact is that, up to now, USA has had the most resources to come up with solutions first.

 

But, take a look little closer at PAK FA, and you will see a lots of original design solutions very different then of what's on F-22.

 

Although, they both have landing gears, thus somebody is coping that ingenious design solution, right ...

 

I think 5th generation fighters have just copied the F22 and disproved your point slightly, China a getting better at making rip offs.

 

[cichlidfan]

Yeah, all of these aircraft have wings, so it has to be a copy, because F-22 has wings too.

 

All just poor copies, as animals (or possibly plants) had wings first. :P

[whiteladder]

I think 5th generation fighters have just copied the F22 and disproved your point slightly, China a getting better at making rip offs.

 

 

Given that most these aircraft are design to be Low observable to radar they will tend to have similar design features i.e. the avoidance of 90 degree angles, blended body/wings etc.

[outlawal2]

The similarities between planes is also a function of the fact that the primary objectives are now very similar and when dealing with technology, specific shapes or design cues favor different results.. So if you want stealth, certain design attributes simply work better and this limits your options..

 

Another example is the fact that the Western countries (for whatever reason) seem to be able to build jet engines to reach a particular performance goal and they manage to keep those engines MUCH smaller than Russian or Chinese companies build. That is the reason that many of the Russian planes are much larger than American planes is the airframe has to be larger to incorporate the much larger engines. (SU-27 I am looking at YOU)

[NineLine]

"Imitation is the sincerest form of flattery."

Charles Caleb Colton

 

There is no denying that someone probably too the lead on this and did it "first", so dont get your panties in too much of a knot, they took a concept that worked and tried to improve on it... its been happening since the beginning of time in every industry... and will always happen.

 

 

Yeah, all of these aircraft have wings, so it has to be a copy, because F-22 has wings too.

 

Well, similar or, exactly the same, objectives, or problems to be solved, will bring very similar, if not the same solutions. The fact is that, up to now, USA has had the most resources to come up with solutions first.

 

But, take a look little closer at PAK FA, and you will see a lots of original design solutions very different then of what's on F-22.

 

Although, they both have landing gears, thus somebody is coping that ingenious design solution, right ...

[outlawal2]

Also keep in mind that this is a constantly moving target... Think back to WW2 where the pinnacle was arguably the P-51 Mustang or the FW 190... Those were state of the art planes and there were some similarities... And they ruled the skies...

 

Until jet engine technlogy came around and Germany stuffed a jet engine in an airframe.. THAT plane was totally different, looking nothing like previous planes and had amazing peformance that nothing at the time could match..

 

And it ruled the skies...

 

Until everyone else followed suit and built similar.. And then better planes..

It is a moving target and we are all limited by our current knowledge and technology... We couldn't build an F-22 back in 1950 due to limits in knowledge, skills, manufacturing practices, materials etc..

 

It is a constantly moving target and everyone has their own ideas, goals, limitations etc. to work thru so your end result is a wide variety of airframes used to handle the job at hand.. Some are extraordinary.. And some are junk...

 

Happens..

[4c Hajduk Veljko]

There is no denying that someone probably too the lead on this and did it "first", so dont get your panties in too much of a knot, they took a concept that worked and tried to improve on it

Sure, I agree. So, where did the concept FIRST come from? I mean the concept of stealth?

 

... its been happening since the beginning of time in every industry... and will always happen.

Absolutely. And everybody does it. However, same problem can only be solved in very similar ways. So, to just claim that all these aircraft are copies of the F-22, is plain silly. On top of that, PAK FA has some very different features, such as wider engine placement, additional control surfaces, different wing shape and angles ...

[NineLine]

Sure, I agree. So, where did the concept FIRST come from? I mean the concept of stealth?[/Quote]

 

Germany, 1940s ;)

Soon as radar became common place, the goal has been to try and counter it....

 

Absolutely. And everybody does it. However, same problem can only be solved in very similar ways. So, to just claim that all these aircraft are copies of the F-22, is plain silly. On top of that, PAK FA has some very different features, such as wider engine placement, additional control surfaces, different wing shape and angles ...

 

I agree, they simply are not copies, but they copy some aspects... again you see it an just about every industry.

[OutOnTheOP]

The Horten was NOT designed to be stealth, despite the inane nattering of latter-day "experts". It was designed to be aerodynamically efficient, pure and simple. Stealth was no more a design feature of the Ho229 than it was of the Mosquito (and incidentally, any dubious stealth qualities either of them had would be due to the wooden construction more than the shape. The exposed propellers/ turbines on either would have made for plenty of return anyhow).

[NineLine]

The Horten was NOT designed to be stealth, despite the inane nattering of latter-day "experts". It was designed to be aerodynamically efficient, pure and simple. Stealth was no more a design feature of the Ho229 than it was of the Mosquito (and incidentally, any dubious stealth qualities either of them had would be due to the wooden construction more than the shape. The exposed propellers/ turbines on either would have made for plenty of return anyhow).

 

Although I agree the shape was not intentionally designed with radar avoidance in mind, they did try using radar absorbing materials to try and hide it from the radar of the day... beating radar started back then, as soon as radar started helping the other side. Modern day tests have shown that its signature would have been cut by something like 30% -35%. SO it wasnt called stealth back then... the goals were similar when dealing with radar.

[Weta43]

To the OP. The sub-text is that the constantly march through time is a big part of it...

 

For example, America's top minds in aeronautical engineering in the late 60's and early 70's produced the Eagle to be the king of air superiority. The soviet union responded in late 70's with the flanker - also designed to be the king of air superiority. And yet - aeronautically they differ rather a lot.

 

Actually, the US saw / had reports of the MiG-25 & thought that it was that fast, plus as manouverable as a fighter, and responded with the F-15 (& if you look at the F-15, it looks more like a MiG-25 than an F-4), the Russians in turn built the Mig-29 & Su-27 (off the same wind tunnel data), but each response, counter, counter the counter cycle moves through time that allows increases in the technological knowledge that goes into the design, and so each itteration benefits from new knowledge which has an effect on the design of the aircraft.

 

Until the British solved the compressibility problem, there could be no supersonic aircraft. Once they had, all aircraft could take advantage of that (& all jet fighters owe their 'all moving' elevors to that British breakthrough)

 

Any fighter before that date will look different to one after the idea disseminates.

 

Untill computers (& programmes) became powerful & sophisticated enough to do the analysis, LRO 'stealth' was not a primary concern of design. Now it is.

 

It's your standard evolutionary arms race.

[ironmarc]

You have to prioritize something, you need to make a decision on which route you will take, what you believe it's more important. And what is more important will vary from one engineer's mind to the other.

 

Forget about comparisons between Sukhoi and Boeing. That doesn't work.

 

A better example is the process of development and production of the F-15 and the F-16. Both aircraft were developed at the same time, at first they were actually competing projects.

The F-16 brings the view where energy loss, thrust, negative stability for what supposed to be improved maneuverability, were all considered more important.

The F-15 project prioritized different things, different values, that were more based on the experiences in Vietnam with the F-4 and also it was more important for them to make the F-15 be an answer to what was perceived that the soviets were doing, with their super fast interceptors.

 

Two different aircraft planned to be better at air-to-air, but differs at the routes they took, even if they tried to achieve similar things.

 

Also they need to predict what it is going to be more important in air-to-air situations in the future when they are planning on a new aircraft project.

They will take past experiences, but will try to see beyond that, and they can be wrong about their predictions even if they are the greatest minds at work.

[realtrance]

Why do fighter aircraft differ?

 

Another factor that has become increasingly important, in a world where economic warfare is slowly superseding military warfare: marketing.

 

Aircraft design now primarily has an eye on which parts of the world can be most surreptitiously destabilized by massive sales of military hardware into regions where competition for resources are most intense.

 

Making aircraft that will sell well into such markets, without breaking the banks of the countries fooled into such acquisitions against their own real interests, is the primary consideration. Marketing your aircraft as "superior" is critical, but so is "cheap to maintain." Maintenance is the real profitability center, so a careful combination of planned obsolescence plus the need for barely manageable and maximally profitable maintenance costs is critical. I'm sure there's thorough economic modeling for optimization along such lines, in corporate industries hooked into massive, decades-long contracts with governments, both for development and service.

 

This has been true of the US military since the 1970s, and no doubt will increasingly become true for the EU, Russia and the Chinese militaries as the global economic war for resources intensifies under the pressures of rapid and radical climate change.

Edited May 3, 2014 by realtrance