The Aerodynamics of the Spitfire

[PatMc]

**LINK** I came across this today whilst looking for something else (it's raining) & although I've only scanned through it thought it might be interesting. Probably more for the technically minded geeks than for WW2 fighter pilot fantasists.

Edited By PatMc on 10/08/2019 16:55:43

[Peter Miller]

Alittle while ago I read a book about Smith who actually did most of the developement work on all the marks of Spitfires.

In he states that when Mitchell was asked about whether they should go for the ellipticeal wing plan form he said "I don't care what shape it is so long as you can get the guns in"

[i12fly]

Like Peter, I too have read a book about Joe Smith; "Spitfire's Forgotten Designer". Excellent book. Whilst Mitchell was clearly an excellent designer the Spitfire was a team effort and many of Mitchell's good ideas came from other people. The elliptical wing concept came from a chap called Shenstone and detail design came from Alf Faddy. They really deserve some credit as Mitchell had to be persuaded to use it.

The team that developed and tested the basic prototype model, ironing out all the issues and produce the excellent fighter it became, then kept the design current to compete with the opposition fighters was led by Joe Smith.

Smith doesn't appear to get the credit he deserves, he was a true team leader and innovator, coordinating a brilliant team of engineers and had to work very hard to get the Spitfire into production -it was a pilot's dream aeroplane and a production engineer's nightmare. Similar to Mitchell, Smith basically worked himself to death and died at an early age, struck down with cancer. In the words of Eric Winkle Brown "he gave his all to his country, to his company , to the Fleet Air Arm, and to the RAF - with scant reward".

[Colin Leighfield]

There appeared to be a co-incidence of rare talent and foresight in the design of the Spitfire. Mitchell had certainly grasped the importance of thin wing sections for high speed flight earlier than most. His ability to choose a talented team and clearly direct them in the achievements of his objectives was remarkable, the reported light hearted comments made about the reasons for choosing the elliptical wing (actually two semi-ellipses) are certainly true but it would be a mistake to take them at face value. There was a deeper understanding than that. The combination of that shape, thin section and progressive wash-out resulted in a plane that proved in tests by the High Speed Flight post-War to have a significantly higher limiting Mach number than any of the later “laminar flow” winged fighters and indeed than the early jets, including the semi-swept wing Me262. Also, it was discovered that the efficiency of the wing increased with altitude, which must have been a factor in that as late as the Korean War it was the Spitfire PRXIX that was used for clandestine PR flights over mainland China. The superior level speed of the P51B, C and D with similar Merlin engine to the Spitfire VII, VIII and IX was found by the North American development team to be due to the very low drag of the cooling system, worth 35 mph and the laminar flow wing didn’t really work, similar to the experience with the Spiteful that truthfully wasted years for Supermarine and Smith and resulted in the mediocre Attacker. As Jeffrey Quill told Smith, it would have been a b****y sight better plane with a Spitfire wing. Almost certainly true, particularly with the re-engineered 20 series version that was stiffened to the degree that aileron reversal couldn’t happen until beyond 800 mph. In 1944 there was close collaboration between North American and Supermarine, when Ed Schmued came over and worked with the Spitfire team for about three months. The outcome of that was a reduction in the weight of the P51 by 600 lbs and the P51H, also a proposal for a version of the Spitfire VIII with a P51 type cooling system that would have been really interesting. It didn’t go ahead because it was late in the war and jets were on the way.

Joe Smith was the right man at the right time for the Spitfire and we owe him a great debt. He wasn’t an inspirational designer though and his later works never achieved the greatness of the Spitfire. Mitchell left us a remarkable legacy, but his loss was a tragedy and he could have achieved so much more. A massive loss to British aeroplane design and advancement. However it would be hard to imagine a better legacy than the Spitfire, it is remarkable how even now so many people know what it is and recognise it. Magical inspiration.

[Former Member]

[This posting has been removed]

[J D 8]

+ 1 on the above.

It is also much the same story with computer development and the ideas of Alan Turing for which he is rightly recognised.

However it was Tommy Flowers and other former GPO team members who built the electronic Colossus and made it work. I think there is a street/road named after him somewhere.

[Josip Vrandecic -Mes]

What a pleasure to read Colin's comment...

 

PatMc thanks so much.

Edited By Josip Vrandecic -Mes on 11/08/2019 10:28:55

[Alan Gorham_]

Posted by J D 8 on 11/08/2019 09:15:41:

+ 1 on the above.

It is also much the same story with computer development and the ideas of Alan Turing for which he is rightly recognised.

However it was Tommy Flowers and other former GPO team members who built the electronic Colossus and made it work. I think there is a street/road named after him somewhere.

It is an interesting parallel indeed...Maybe it's human nature to latch onto one person's name in association with great advances.

The housing built at the site of the GPO research station in Dollis Hill is called Flowers Close.

[Former Member]

[This posting has been removed]

[Nigel R]

Nice post Colin.

I guess any successful project needs a champion (Mitchell) and a talented team behind them (led by Smith).

"The superior level speed of the P51B, C and D with similar Merlin engine to the Spitfire VII, VIII and IX was found by the North American development team to be due to the very low drag of the cooling system"

The P51 cooling setup used "waste" heat to provide a small amount of thrust. Working very much like a ramjet, with the fuel burning stage replaced by the radiator. It was a very clever piece of engineering.

**LINK**

The Spitfire system had been intended to use the same principle but did not achieve that goal. There is a transcript of a presentation by Atwood on the Mustang system here:

**LINK**

Seems the Mosquito got it about right though!

"It seems that most other contemporary airplanes attempting to take advantage of the Meredith Effect failed for one reason or another to combine an efficient duct system with a properly designed and regulated exit-closing mechanism and did not develop the energy recovery inherent in the Meredith method. They generally used 10 percent or more of their power available at high speed to overcome cooling drag. A notable exception was the DeHavilland Mosquito multi-purpose plane with the same Rolls-Royce engines and which used a wing leading edge radiator mounting with a short and direct inlet duct"

[Colin Leighfield]

Thanks for all of the interesting comments chaps, it is always good to be able to share what we know with each other, I still learn new things every day.

[Colin Leighfield]

Nigel R, good one. I was aware of the reports from Lee Atwood, he presented on this to the RAeS post war and it is described in Ken Delve’s book on the Mustang. I don't think that many people realise just how close the Spitfire and P51 were. Despite the difference in wing shape and section/thickness, the key dimensions such as wing span, area, aspect ratio etc, are practically identical, not a co-incidence. The proposed Spitfire VIII with the properly developed Meredith based P51 type cooling system would certainly have had similar level speed to the P51 D with better climb rate, manoeuvrability and altitude performance. Removal of the radiators from the wings to enable extra fuel combined with a higher cruising speed would certainly have given similar range, but at that stage of the war it was no longer needed.

Another interesting point is that one of Mitchell’s last contributions was the proposed four cannon version of the Spitfire in response to the RAF specification that created the Whirlwind. That had the cooling system transferred to under the fuselage to create more space in the wing and the cockpit slightly higher with raised nose profile to improve forward view. Although the proposal drawing doesn’t show a P51 type cooling system, if Mitchell had been able to continue who knows where his mind would have gone on this. The Whirlwind was ordered in limited numbers because of the need to produce the Spitfire in quantity urgently and probably influenced also by the loss of Mitchell. We all love the quirky Whirlwind but for various reasons it was a road to nowhere and there is little doubt that the four cannon Spitfire as envisaged by Mitchell was the right way to go. Good as it turned out to be, the Spitfire could have been even better much earlier.

[Nigel R]

Yes the Mustang and Spit were certainly the cream of the crop and very very close indeed; a few tweaks to the Spitfire cooling could have had that top speed on a par. Like you say by then, not needed, and I guess the development interest had (or was just about to be) switched to jets anyway.