Elliptical Wings

[GrauGeist]

I've always been curious about the advantages of the elliptical wing on certain fighter aircraft over the Moderate or High Taper wings.

How well would the Spitfire performed, for example, if it had been given a different wing planform.

This of course, could be asked of the P-47 as well.

Only three fighter aircraft of WWII had the Elliptical wing, the Spitfire, the P-47 and the He280 which all had excellent handling characteristics for thier designs.

 

[fastmongrel]

Dont forget the Hawker Tempest

 

[GrauGeist]

Ahh right, the Tempest as well!

Didn't they change the Typhoon's wing to the elliptical design to accomodate the armament more than flight performance when it became the Tempest?

I will admit that I am not all that well versed in British aircraft :/

 

[swampyankee]

An elliptical lift distribution provides the least amount of induced drag for a given span; the easiest way to produce an elliptical lift distribution is to have an elliptical planform and no twist. Usually, designers do not use elliptical planforms as the difficulty in manufacture is not worth the small reduction in induced drag: careful selection of taper and twist will get quite close to an elliptical lift distribution, at least in a range of lift coefficients. Incidentally, the wing on the Spitfire has an elliptical planform but it also has washout, so it does not have an elliptical lift distribution. The reason for the elliptical wing is to provide more internal volume outboard, to accommodate landing gear and armament.

There were many ww2-era fighters with excellent handling that did not have elliptical planforms, e.g., the Hellcat, P-36, P-40, and Hurricane.

 

[drgondog]

An elliptical lift distribution provides the least amount of induced drag for a given span; the easiest way to produce an elliptical lift distribution is to have an elliptical planform and no twist. Usually, designers do not use elliptical planforms as the difficulty in manufacture is not worth the small reduction in induced drag: careful selection of taper and twist will get quite close to an elliptical lift distribution, at least in a range of lift coefficients. Incidentally, the wing on the Spitfire has an elliptical planform but it also has washout, so it does not have an elliptical lift distribution. The reason for the elliptical wing is to provide more internal volume outboard, to accommodate landing gear and armament.

There were many ww2-era fighters with excellent handling that did not have elliptical planforms, e.g., the Hellcat, P-36, P-40, and Hurricane.

True - The elliptical wing planform provides minimum Induced Drag for a given span over trapezoidal/tapered wing - as you noted.

All so called elliptical wings, by necessity for low speed performance handling qualities, required LE twist to provide aileron authority as the inboard sections stalled out at high CL, but the twist only changed the shape of the elliptical like lift distribution to a small degree - and less than a trapezoidal wing planform.

Curiously the FW 190 wing had LE Twist from root to 80% semi span - then zero twist thereafter which is the dominant suspected reason for such nasty high speed stall behavior... as the 'up wing' (Higher relative AoA and higher drag side) stalled first.

The Spitfire wing is The classic example of large chord/thin section ratio which was more optimal for critical delay of onset mach characteristics at high speed - yet provided a sufficiently deep inner chord height to allow wheel and armament internally. The Mustang had a fatter wing but the NACA 45-100 airfoil had its max T/C at approximately 45% of chord (versus 24% for the Spit IIRC), making the velocity gradient smaller and achieving almost the same benefit in onset mach divergence/drag rise.

Offhand - There is no reason that I can think of where handling qualities improve in favor of an elliptical wing as wing stiffness, aileron size and controls design are entirely independent of wing planform whereas reduction in induced drag affects performance only where CL/CDmax is crucial and meaningful?

 

[GrauGeist]

Ok, stupid question here...

Actually two:
1) suppose the Spitfire was designed with a Moderate Taper wing, how would this have effected it's performance?

2) would the Elliptical wing have been a benefit to the P-51 or a hinderance?

 

[drgondog]

A Mustang with the Spitfire wing and span would have had as much drag (nearly-except for radiator) as the Spit... not worth consider not only for drag reasons but also wing volume for fuel

Remember, with same engine the Mustang was 30 mph faster while carrying 1000+ pounds more weight - and the wing parasite drag comparisons dominate.

The Spit with a Trapezoidal wing?

1. The T/C ratio has to be enough to permit the gear and guns to be installed - doable with say, a Mustang plan form. If the same area is desired it seems that the trapezoidal wing must have a similar root dimension to maintain the same T/C ratio - suggesting that the span of the wing must be a little shorter to permit a .2 to .3 taper for tip chord to maintain same equivalent area. That implies smaller Aspect Ratio creating more induced drag.

Thus - if same airfoil, with same T/C, and same area with less AR - the only design performance impact would seem to be slightly more Induced drag for the trapezoidal wing. If you put a Mustang wing with same area on the Spit you should get a.) same or slightly less climb rate, poorer turn, slightly less dive speed but b.) better speed, better roll than any Spit except for clipped wing. This Spit could go to Berlin(Lower wing Profile drag and fuel tanks in wing) and be as effective or moreso than all original Spit in air combat.

 

[davebender]

He-112B

 

[davebender]

 

[Clayton Magnet]

Also the Re.2005, albiet only semi eliptical.

 

[davebender]

I suspect that higher production cost is a significant disadvantage.

He-112B was more expensive then Me-109. P-47 was one of the most expensive single engine aircraft produced by anyone during WWII.

 

[wuzak]

P-47 was one of the most expensive single engine aircraft produced by anyone during WWII.

Don't think that was just down to the wing Dave.

Lots of aluminium required for that beast.

 

[Shortround6]

I suspect that higher production cost is a significant disadvantage.

He-112B was more expensive then Me-109. P-47 was one of the most expensive single engine aircraft produced by anyone during WWII.

Was that because of the elliptical or in spite of it?

As a general rule the cost of a plane can be estimated by the weight, exceptions do happen but the heaviest single engine fighter should be the most expensive IF everything else is the same. This is NOT a surprise.

The P-47 used one of the largest, most expensive engines used in a single engine plane.

The P-47 used one of the largest, most expensive propellers used in a single engine plane.

The P-47 used one of the most complicated armament setups of any singe engine fighter.

The Ducting for the turbo was not easy to manufacture or install.

The people making the wings were NOT handed a pile of aluminium sheets and pairs of tinsnips and told to start making wing edge panels. Tooling was set up for production rates of hundreds of aircraft per month. With proper tooling an elliptical wing is no more difficult to make than a straight wing. And in fact, much of the rear of the elliptical shape is in the ailerons.

See: http://www.mnbigbirds.com/images/3 Views/P47/expld.jpg

Or any decent 3 view drawing.

 

[Aozora]

I suspect that higher production cost is a significant disadvantage.

He-112B was more expensive then Me-109. P-47 was one of the most expensive single engine aircraft produced by anyone during WWII.

More than likely the He 112 was more expensive than the 109 because the 109 was mass-produced whereas the He 112 was almost hand-built in small numbers. Had Heinkel been able to mass produce the He 112 no doubt costs would have been lower. As well as that, even with the redesign of the He 112 B series, the entire structure was still more complex than that of the 109.

 

[nuuumannn]

Although not a fighter, let's not forget the beautifully elegant He 70 Blitz.

I remember an incident when at a place I used to work at there was a P-47 that no longer flew and was on undercarriage supports. We had to move it and I was placed under one of the tailplanes and used my back to arch up and lift the back end off the tail wheel supports, but the guy under the opposite tailplane got out early, which meant I had the full weight of a P-47's back end land on my back!

 

[Aozora]

Although not a fighter, let's not forget the beautifully elegant He 70 Blitz.

I remember an incident when at a place I used to work at there was a P-47 that no longer flew and was on undercarriage supports. We had to move it and I was placed under one of the tailplanes and used my back to arch up and lift the back end off the tail wheel supports, but the guy under the opposite tailplane got out early, which meant I had the full weight of a P-47's back end land on my back!

Owwww! I take it you went down with a Thud?

 

[nuuumannn]

Owwww! I take it you went down with a Thud?

Yep, sure did. Ended up prostate on the hangar floor a bit winded but not too worse for wear.

 

[Zipper730]

It seems the only American aircraft designers that used elliptical wings that I can think of was Seversky/Republic -- at least that I can readily think of -- anybody know of any others?

 

[Glider]

Ok, stupid question here...

Actually two:
1) suppose the Spitfire was designed with a Moderate Taper wing, how would this have effected it's performance?

2) would the Elliptical wing have been a benefit to the P-51 or a hinderance?

The Supermarine Spiteful was effectively a Spitfire fitted with a mid chord wing and the first was simply that, a Spit XIV with the new wing. The performance was significantly increased to about 480mph, but at the cost of slightly worse handling issues around the stall. These were considered acceptable but development was basically dropped as the RAF recognised that the Jet fighter was the way forward

An aside but back in the day I used to have a share in a Discus glider and this had an elliptical wing. It was very popular as its performance was extremely good winning a number of championships, but it was a very safe design allowing inexperienced pilots to fly it without difficulty. An ideal combination

 

[GrauGeist]

It seems the only American aircraft designers that used elliptical wings that I can think of was Seversky/Republic -- at least that I can readily think of -- anybody know of any others?

Technically speaking, the P-35 had a semi-elliptical wing, like the He280.