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Why Creating a Unique Aircraft Design is Difficult

Mod Squirrel  2.2 years ago

I’m sure you’ve seen it or though about it before. Why does X aircraft look like Y aircraft even though they were made by completely different countries?
I’ll throw a few examples your way:


J-20 and Mig 1.44


F-22 and SU-57


T-4 and XB-70


B-1 and TU-160

Now you’d be forgiven for thinking one was a copy of another.

Background

Now, in every aircraft company are a series of talented engineers which work as a team to draft, design test and manufacture an aircraft. Each aircraft part is specifically designed with a purpose, from the airframe to the grommets and bolts. Most of these processes and technologies are closely guarded from said companies. So, counterintuitively, it seems odd that not only companies within a country, but also outside of a country can create such similar aircraft designs when a lot of the designs, systems, etc are so closely guarded by official secrets, non-disclosure agreements, etc.

Now, while copying in the aviation industry does exist (TU-4 is a perfect example of this), the reality can, and often is a lot more complex than it first seems.


TU-4 was a reverse engineered B-29

The J-20 and Mig 1.44

Some have simple explanations. For example, the J-20 isn’t a copy of the Mig 1.44 (contradicting what many websites would have you believe) as its origins can be traced back to 1971 with the development of the J-9 with the image below being a wind tunnel test model of a proposed twin engine design for the J-9:

J-9 Wind Tunnel Test Model

However, other explanations are a lot more complex.

Understanding Aircraft Design

To understand why other designs like the TU-160 and B-1 along with the F-22 and SU-57, etc look so similar we need to investigate the origins of the aircraft developed.

The first step in aircraft development is to acknowledge a problem in the industry. A gap that other existing aircraft have issues filling. In the case of the B-1 and TU-160 it’s high speed bomb delivery and with the SU-57 and F-22 it’s radar evasion in air superiority. Once the inadequacy in operational capability has been determined, specifications need to be set in place to establish what the final product should be able to do in order to fill in the operational deficiency as efficiently and effectively as possible.

Note: I have oversimplified the examples below to better illustrate the point.

B-1 and TU-160

In the case of the TU-60 and B-1 it was to:

  • Fly at supersonic speeds
  • Carry a payload of around 50,000kg
  • Have a short take off distance to increase operational availability

So how do you design a plane in the 1970s that can achieve those specs? Well, one way of helping hit all three of those requirements is to use variable geometry wings. These are also large and heavy aircraft and need a serious amount of power to push them to those supersonic speeds. So, 2 turbojets aren’t going to cut it, so 4 turbofans/turbojets are a lot more practical. Unfortunately, you can’t fit 4 jets in a fuselage that has space taken up by a bomb bay and a swing-wing mechanism, so you must mount them underneath the aircraft. Unfortunately, the exhaust is now in line with where the horizontal stabilisers will be, which isn’t a great idea, so you opt for a cruciform tail design.

As you can see it’s very easy to end up with a convergence of aircraft design when the specifications and technological limitations at the time dictate a large amount of what the finished product will look like.

F-22 and SU-57

In the case of the F-22 and SU-57 it was to:

  • Have a long range.
  • Have stealth characteristics.
  • To contend with and defeat other aircraft.

Long story short the aircraft will need the following features in order to fulfil the specs above:

  • No right angles (especially exterior angles as they reflect radar.)
  • Use Parallel surfaces to reduce radar cross section. Also known as “planform alignment”:


Planform Alignment on an F-22

  • Use 2 engines for greater power and cover distances faster than a single engine (can also equate to greater range.)
  • Store internal weapons such as missiles internally to improve stealth.
  • Twin tail (a single tail means an exterior 90 degree angle is created. The image below better illustrates the issue with right angles on an aircraft.)


The Effect of Right Angles on Radar

Again, the specifications the aircraft must live up to limit what the product looks like. If two countries set similar specifications for a product, the results from both companies will naturally look very similar due to a convergence of design.

The Bigger Picture

Take airliners as an example. There’s only so many designs you can make for a short-range jet that carries 150 passengers.

737 (Top) and A320 (Bottom)

Of course, these things aren’t just limited to aviation, or human inventions. To see how wide the phenomenon extends, we can look at convergent evolution. The Shark, Dolphin and Ichthyosaur are perfect example of a problem being solved with the same solutions, despite evolving on separate timelines. Reptiles, mammals and fish came up with the same solution to a very similar problem through this convergence to the point where an uneducated person might assume these were just variations of the same species.

In this case, the solutions to living efficiently in water were:

  • Aerodynamic body to reduce drag
  • Pectoral fins for steering
  • Dorsal fin for stability
  • Tail with a wide surface area at the tip for propulsion


Convergent Evolution in Reptiles, Mammals and Fish

Conclusion

While there are undoubtable copies of things out there, such as the T-4 mentioned earlier, two things looking similar doesn’t necessarily mean they are a copy, but rather a convergence established by limitations derived from a predetermined specification.

In reality, having 2 designs or looking so similar despite having different origins is a reinforcement that the design used for said object is very good for its application, meaning that the similar products are likely highly capable at performing the task they were designed for.

Next Post: Engine Types: Part 1

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  • Profile image
    3,888 Thunderhawk

    Very informative

    3 months ago
  • Profile image
    18.5k NexusGaming

    @KnightOfRen yes (kind of)

    10 months ago
  • Profile image
    40.1k KnightOfRen

    @NexusGaming
    finding post a year late gang RISE UP!!

    10 months ago
  • Profile image
    18.5k NexusGaming

    @BaconAircraft um the j-31 is closer to the f-35
    it actually looks like a chinese bootleg of the f-35 with f-22 engines
    [basically kind of like this, except

    10 months ago
  • Profile image
    18.5k NexusGaming

    @Squirrel You put "Tu-60" when in reality it's actually Tu-160. There was never a Tu-60 of any sort.
    I also found another site that has the same error

    @KnightOfRen Moderators can see deleted posts and comments

    10 months ago
  • Profile image
    40.1k KnightOfRen

    @Squirrel
    How did you comment on my forum? I removed it to disable more backlash.

    1.2 years ago
  • Profile image
    40.1k KnightOfRen

    Interesting read. This has taught me alot.

    1.2 years ago
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    Very informative, especially for this engineer wannabe. I knew about most of these cases, but it’s always good to get more information on this.

    2.2 years ago
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    40.4k MrVaultech

    I've been noticing this for years, primarily in building planes in SP. I've found theres really only so many ways you can strap wings and engines to a round fuselage before you start scrapping designs because it looks too similar to an existing one, even when making attempts to not have them similar.
    I'm at least glad I'm not the only one noticing this, since I've never seen it said on SP before.

    2.2 years ago
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    129k RAF1

    Very well done post. I have had a lot of trouble explaining this concept to many people, but you hit the nail on the head with this.

    +7 2.2 years ago
  • Profile image
    Mod Squirrel

    @GINGER01 yeah, I have a few more posts like this one in mind.

    +1 2.2 years ago
  • Profile image

    @Blue0Bull of what really defines a aircraft is really a aircraft but its not
    to define a aircraft or which is not but
    its very complex

    2.2 years ago
  • Profile image
    8,196 12ocketguy

    You nailed right on the head. There is only so many ways an aircraft can be shaped for stealth or reentry cough shuttle cough I like these types of posts. You got any more in mind?

    2.2 years ago
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    13.0k Botfinder

    The Su-57 has its similarities to the F-22, but the more noticeable difference is that the Su-57 is alot bigger than the F-22.

    Length of the Su-57 is about 70' while the F-22 is about 62'

    +3 2.2 years ago
  • Profile image
    70.8k Blue0Bull

    @Squirrel I can get behind that.

    +2 2.2 years ago
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    tHe J-2o i5 a CoP y oF tH3 F 2 2 An D f3 5

    +3 2.2 years ago
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    12.5k HNL47

    This is exactly the kind of info we need in forum section thank Demi-God 🙌

    +3 2.2 years ago
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    Mod Squirrel

    @Blue0Bull The YF-23 was a bit of a wild card and looks the way it does because they emphasised stealth over manoeuvrability, although I'd argue it still looks quite similar to the F-22. I mainly chose the SU-57 and F-22 as an example because a lot of people like to claim the SU-57 is a copy of the F-22 and they're both stealthy aircraft with an emphasis on manoeuvrability.
    .
    Obviously, there are variations within the classifications, for example the J-20 doesn't really look anything like the SU-57 and that's mainly because of the configuration difference. There are some interesting stealth concepts out there, but they never got built because they didn't fit the requirements, were too expensive, were being developed during a transitional stage in the industry, etc.
    .
    I personally don't think Sukhoi took inspiration from Lockheed for its design. At least not to the extent that some people imply. They were on a budget and played it safe with a traditional surface configuration from the tried and tested SU-27. It was a natural progression for them. Sukhoi would be risking their financial stability otherwise, they don't have the history of canard configuration that the likes of SAAB and Chengdu have and likely didn't have the budget to try out weird tail designs like Northrop did. If they went with something with a 1st gen stealth look, they'd ruin any chance of air superiority with the poor drag characteristics. Realistically, the only configuration they could have opted for is a delta wing or a 3 surface layout and a three surface layout would only add to the cost due to increased complexity (again Sukhoi was on a budget. They didn't have the good old soviet union throwing money at them because it no longer existed).
    .
    In reality, even with the standard control layout the SU-57 looks a lot different to the F-22 and employs a slightly different philosophy with again, emphasis on agility. The intakes are mounted differently, the weapons bays are in completely different locations, the SU-57 engines are mounted at an outward angle and don't have stealthy nozzles, it has extra weapon bays at the wing root, the wing and tail angles are completely different, etc. If anything, once you get into the specifics, and the SU-57 is a just a completely different aircraft to the F-22 in terms of design, with the only real visual similarities being a stealthy profile and a standard flight surface layout

    +3 2.2 years ago
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    70.8k Blue0Bull

    Lockheed F-22A and Sukhoi Su-57 are in my personal opinion a bad example. There are many twin engine stealth aircraft designs that look completely different than the F-22A but still are just as or more effective in terms of stealth. Look at the YF-23 or various designs and concepts designed by Boeing, Lockheed, Northrop, BAE, and various other companies that designed stealth fighter aircraft (designed, but not always built).
    .
    .
    I do think that Sukhoi took some inspiration from Lockheed's F-22A since there are way more options for stealth design...
    .
    .
    Fun forum to read and you made allot of good points.

    +7 2.2 years ago
  • Profile image
    28.0k ChiChiWerx

    Form follows function.

    +5 2.2 years ago
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    @FreeRangedLemon
    dolphins ichthyosaurs Sharks are an example of aerodynamics as they have streamlined bodies to reduce drag on water

    2.2 years ago
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    Yep the soviets copied the design of the concorde but they put some changes on it

    2.2 years ago
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    40.0k Awsomur

    Them greedy plane companies have done tooken erry’ aeroplane design!

    +8 2.2 years ago