# Why was the Spitfire's elliptical wing almost uncopied by other aircraft of World War 2?

The Spitfire was one of the most successful designs of its day, with flying qualities of a similar standard to the other best designs of the era. In its decade of production from 1936 it grew bigger, stronger and faster.

Yet there seems to be almost no appetite from any of the major aircraft-manufacturing powers to emulate its most iconic feature. In fact, there is only one mass-produced aircraft of that time with an elliptical wing, the American P-47 Thunderbolt. Nothing German or Japanese, and nothing more from the British either.

In a period where every manufacturer was trying to gain every last bit of advantage, it seems odd that a prime design feature attracted so little appetite to copy.

There are good explanations here on the aerodynamics or performance of the elliptical wing. Why is it so rare when it demonstrably works so well?

Source

• Note that even Spitfires were manufactured in "clipped wing" variants during the war which had the wingtips squared off. This was to improve the low altitude speed and roll rate, which is an important factor in air combat but not so much in other types of aviation. – llama Apr 26 '19 at 18:06
• Note that the your link about performance contains in the accepted answer: " Both weight and stall characteristics of elliptical wings are less than optimum; the low induced drag coefficient is bought with higher structural mass and, consequently, lift." – Vladimir F Apr 27 '19 at 6:30
• Interesting article on Air & Space. – BillDOe Apr 27 '19 at 20:21

Interestingly, I couldn't find an answer to this question on the website, but I've found an answer of Peter Kämpf on Quora. He brings forth the same arguments I wanted to mention, so I'll repeat them here.

Elliptical wings are very good - aerodynamically. If you want to minimize induced drag for a given lift requirement, you end up with an elliptical wing.

But a plane is not only aerodynamics. You also have to consider:

• Weight, an elliptical wing is not structurally efficient, and will lead to a higher weight, which leads to higher lift requirements which will lead to more induced drag, even with a very efficient wing.
• Controllability, where and how the wing stalls determines if you're able to recover from a stall. Elliptical wings stall tip first, leading to bad stall behavior.
• Manufacturability, a fully elliptical wing is very hard to make, with its double curves. This will make the wing more expensive.

If you include these factors, you'll see that you'll end up with a compromise. If you use wing taper (which is somewhat close to the aerodynamic optimal shape) but much easier to make and much lighter you'll see that you'll end up with a better design overall.

An analysis of how the design of a wing changes if you include the structural requirements was done by Jones and can be found here.

• The real killer was having to make compound stamping dies for the LE wing skins. The P-47 got a lot of the way there by making just the TE eliptical, allowing just straight bent leading edges. Overall, the Spit, like the Merlin had the typically British characteristic of very high parts count, of components being made from 5 pieces where an American aircraft would make them from one or two. Fuselage formers made from numerous little bits, etc. – John K Apr 26 '19 at 12:30
• "Elliptical wings are very good - aerodynamically. If you want to minimize induced drag for a given lift requirement, you end up with an elliptical wing." That is incorrect. – Lysistrata Apr 26 '19 at 14:26
• If you go tons faster, you minimize induced drag. Few people comprehend 300 mph wind force, and they were already on their way to 400 mph. The thinking behind this type of wing simply was superseded by newer design requirements focused on the leading edge and compressability. They did get one thing right though, they made it thin, and the Spitfire line lasted until the 1950s. – Robert DiGiovanni Apr 26 '19 at 16:56
• Should "recover from a wing" perhaps have been "... from a spin"? – hmakholm left over Monica Apr 26 '19 at 18:41
• @RoiMaison. It is regurgitating the old myth that elliptical planforms produce elliptical pressure distributions. They don't. And I wish people would stop propagating that nonsense. – Lysistrata Apr 27 '19 at 17:46

Well the short answer is the elliptical wing was used on a lot more aircraft than this article lets on.

The following all used an elliptical wing and there are others too:

• German Heinkel 112 fighter
• German Heinkel 111 bomber
• German Heinkel 70
• US P35
• US P43
• Italian Reggiane 2000
• Japanese Aichi D3A "Val" dive bomber
• British Hawker Tempest
• I've never heard of any of those. And I doubt I'd have ever heard of a Spitfire if it didn't have "its most iconic feature" inside it, the Rolls-Royce Merlin – Mazura Apr 27 '19 at 3:11
• @Mazura He 111 and Tempest are very well known aircraft. He 111 was the main German bomber nd an important target of Spitfires. And although RR Merlin is well known too, it is hardly the reason to know Spitfire unless you are an aviation engines geek (i.e. Lancasters and Mosquitos would have to be much more famous than they are.). – Vladimir F Apr 27 '19 at 6:22
• Thanks but I suggest that's quite a broad definition of both elliptical and mass-produced. – Party Ark Apr 27 '19 at 8:39
• I wouldn't describe the P43 as elliptical wing – Notts90 supports Monica Apr 27 '19 at 9:18
• @PartyArk How do you define elliptical that you find the answer uses a broad definition? – Vladimir F Apr 27 '19 at 19:35

Short answer: Elliptical wings are too expensive to manufacture. A trapezoid wing with a defined geometric or aerodynamic twist can get very close to an elliptical lift distribution (optimal lift distribution over the wingspan, therefore the primary goal of the wing design).

• Welcome to Aviation.SE! Adding some sources by editing your answer would really improve your answer. – dalearn Apr 26 '19 at 14:09
• Just like houses that aren't made out of rectangles; harder to make, and thus more expensive. – Mazura Apr 26 '19 at 22:34

A lot of planes still use elliptical wings - sort of.

What the maths tell us is that the most efficient wing configuration for a given wing span should have an elliptical lift distribution*. The most obvious way to implement this is to make your wings elliptical.

But aircraft designers learned from the experience of manufacturing the Spitfire that elliptical wings are more difficult to manufacture leading to increased cost and manufacturing time.

So later in the war when resources became tight and everyone assumed that they were racing the Germans to build better, faster planes designers deliberately chose to use straight wings to ease production and reduce costs. The P51 Mustang was designed this way.

But we have learned that making your wing elliptical isn't the only way to have elliptical lift distribution. To get elliptical lift distribution you can:

• Make your wing more elliptical
• Add washout to tune lift distribution along the wing
• Change airfoil profile from root to tip to change lift distribution
• Do any combination of the above (eg. washout + rounded tips)

So a lot of planes still use elliptical wings. Especially when fuel economy is one of the main driving design objective. It's just that they don't look elliptical.

* note: There is evidence that this may not be accurate. It is true that if you fix your wingspan the maths will output an elliptical distribution but if you fix your weight (ie. lift at cruise) the most efficient distribution turns out to be something else (something bell shaped) but you end up needing to extend your wingspan

• This is too imprecise to be useful. What maths are you talking about? Do you have any citations (from reputable sources) to back up your statements? – Lysistrata Apr 30 '19 at 13:39
• @Lysistrata THE standard maths when calculating lift distribution: Prandtl's lifting line theory (google "lifting line theory") – slebetman Apr 30 '19 at 16:52
• Thanks. Lifting line theory is particularly inaccurate near the wing tips. It is a very poor choice for wings with aspect ratios as small as those of the Spitfire. – Lysistrata May 2 '19 at 3:17

The main drawback of the Spitfire's elliptical wing was the the amount of labour required to build it. Overall the Spitfire required about five times as many man-hours to build as the nearest German equivalent, the Messerschmitt Bf 109.

• That's very interesting - do you have a source for the 5x man-hours? – Party Ark Apr 28 '19 at 12:34
• 13,000 man hours for the Spitfire compared with 4000 for the Bf 109 would be 3.25 times as many man hours, but the actual figures would have varied during the period of several years in which both aircraft were in production. – J. Southworth May 3 '19 at 16:24
• One internet source quotes figures of 15,200 man hours for the Spitfire, 10,000 for the Hurricane and 6000 for the Bf 109 in early 1940, also a variable figure of between 2000 and 10000 man hours for the different models of the Bf 109. – J. Southworth May 3 '19 at 16:43