High Aspect-Ratio vs. Low Aspect-Ratio

[Zipper730]

As I understand it, high aspect-ratio wings (as a rule of thumb)

• Produce more lift at low angle of attack
• Produce less drag due to vortex-generation at the tips (wing body interference might theoretically be lower as well due to less wing being affected)
• Produce more lift for their wing-area
• Are more subject to flexing loads and have higher T/C ratios

As I understand it, low aspect-ratio wings (as a rule of thumb)

• Operate better at high airspeed
• Operate better at higher angle of attack
• Experience less gust-response at low-speeds
  
• Often require less flexibility
• Often can be designed more easily with a low T/C-ratio

I've noticed, however that there are cases were there were exceptions to these rules such as the following

High Altitude

• Flight at altitudes of 25000 to 35000 feet, at Mach numbers around 0.45 to 0.65 seems to favor a wing of moderate aspect-ratio with a high taper-ratio than a high aspect-ratio wing: The Spitfire, Mosquito, Hornet, and P-38 Lightning* seem to be good examples of this.
• Turning-performance at speeds from 0.75 to 0.90, and altitudes of around 40000-50000-feet seems to favor large wings with low/moderate aspect-ratio, often with moderate to substantial taper-ratio: The Canberra, Valiant, Vulcan, Victor, F-102, and F-106 all seem to conform to this.

I would guess the difference has to do with the fact that taper-ratios play a role in vortex strength as does aspect-ratio, lower aspect-ratio wings are thinner which tends to favor high-mach operation, and the longer root-chord might facilitate wing-body blending schemes.

Am I onto something?

 

[pbehn]

Am I onto something?

Possibly, I think a little more reading is required.

 

[Zipper730]

You know, sometimes it's nice to know where to go to be told where to get information: However, if a person has information, it's preferable to just give the person the information rather than relaying a person in circles.

 

[pbehn]

You know, sometimes it's nice to know where to go to be told where to get information: However, if a person has information, it's preferable to just give the person the information rather than relaying a person in circles.

Zipper your endless quest for a simple almost one word answer never stops. Ask yourself if the turning performance was high on the list of priorities for the Valiant Victor Vulcan and Canberra.

You cannot take one out of the hundreds of different parameters of air plane design and then choose WW2 piston engined fighters and bombers plus post war jet fighters and bombers to prove or disprove your theory.

To answer your question you need to be expert on all aspects of aircraft design AND how changes in knowledge and technology and materials have affected each era of design. Some of todays frontline fighters can cruise at supersonic speeds and are fundamentally unstable requiring a computer to keep them flying. This could not possibly be conceived by the designers of the Spitfire Mosquito and P38 who were just running into problems of compressibility, mach tuck etc.

 

[Zipper730]

Zipper your endless quest for a simple almost one word answer never stops.

I wouldn't say a one word answer. I figure a few sentences, a paragraph or so is fine.

Ask yourself if the turning performance was high on the list of priorities for the Valiant Victor Vulcan and Canberra.

Well, they were designed to maneuver well at high altitude. The Canberra was designed to be a jet-mosquito...

You cannot take one out of the hundreds of different parameters of air plane design and then choose WW2 piston engined fighters and bombers plus post war jet fighters and bombers to prove or disprove your theory.

It wasn't exactly a theory... it was more a personal observation that seemed to have a touch of fact to it.

I was basically curious on why aspect ratio's benefit on low speed performance tapers off with altitude most of the time (the B-47 and U-2 are an exception to this).

 

[pbehn]

I wouldn't say a one word answer. I figure a few sentences, a paragraph or so is fine.
Well, they were designed to maneuver well at high altitude. The Canberra was designed to be a jet-mosquito...
It wasn't exactly a theory... it was more a personal observation that seemed to have a touch of fact to it.

I was basically curious on why aspect ratio's benefit on low speed performance tapers off with altitude most of the time (the B-47 and U-2 are an exception to this).

To discuss all different parts of the f104 design and its positives and negatives would be a very long essay at least.
Jet Mosquito is a simplistic handle, the Canberra was a light medium bomber and high altitude recon aircraft. The U2 was so specialized it is was barely a practical aircraft, It operated at the very limits of flight where maximum speed and stall speed are almost the same

 

[Zipper730]

To discuss all different parts of the f104 design and its positives and negatives would be a very long essay at least.

I didn't say anything about the F-104...

Jet Mosquito is a simplistic handle

It was simplistic, but the fact is the Canberra was kind of designed to do the high altitude bomber/reconnaissance role that the DH Mosquito was designed for: Presumably this would include a good g-load and good turning rate at altitudes

The U2 was so specialized it is was barely a practical aircraft

That's true

 

[pbehn]

I didn't say anything about the F-104...

My bad (tired eyes) but same for f102 and f106 delta wings solve some problems and uncover others

It was simplistic, but the fact is the Canberra was kind of designed to do the high altitude bomber/reconnaissance role that the DH Mosquito was designed for: Presumably this would include a good g-load and good turning rate at altitudes
That's true

The defence of both the Mosquito and Canberra was based on height and speed you cannot bet on out turning a fighter he can just keep you turning until his mates turn up or you run out of fuel. By the time the Canberra was in service SAMs had entered the game too. I have read of a Mosquito being able to avoid an Fw190 by going into a shallow but high speed dive, at those speeds the Mosquito had slightly better control and was able to survive until the FW 190 ran out of fuel or ammo. That is desperation stuff though.

 

[Zipper730]

The defence of both the Mosquito and Canberra was based on height and speed you cannot bet on out turning a fighter he can just keep you turning until his mates turn up or you run out of fuel. By the time the Canberra was in service SAMs had entered the game too. I have read of a Mosquito being able to avoid an Fw190 by going into a shallow but high speed dive, at those speeds the Mosquito had slightly better control and was able to survive until the FW 190 ran out of fuel or ammo.

Getting into a protracted turning match with a fighter would be foolish, but a few quick moves would sometimes shake a plane lose high altitudes particularly when aircraft were still subsonic. The Mosquito could not only pick up speed faster, it actually could turn better at altitudes of 22,000 feet or better. As for dive performance, in a book on the Mosquito, there was a statement about traversing a remarkable distance while descending (if I did my math right I think it was over Mach 0.86, but they could have had a stiff tailwind).

As for SAMs: The USSR didn't seem to have a SAM until 1956, and the SA-2 until 1959

 

[pbehn]

Getting into a protracted turning match with a fighter would be foolish, but a few quick moves would sometimes shake a plane lose high altitudes particularly when aircraft were still subsonic. The Mosquito could not only pick up speed faster, it actually could turn better at altitudes of 22,000 feet or better. As for dive performance, in a book on the Mosquito, there was a statement about traversing a remarkable distance while descending (if I did my math right I think it was over Mach 0.86, but they could have had a stiff tailwind).

As for SAMs: The USSR didn't seem to have a SAM until 1956, and the SA-2 until 1959

The first thing that happens when you turn is that you slow down and lose altitude. The second thing is that you start going back where you came from.

 

[Shortround6]

I wouldn't say a one word answer. I figure a few sentences, a paragraph or so is fine.

As Pbehn has noted and I am expanding on, some of these subjects have had entire books written on them, and often sizable chapters in books that try to cover more than one area or aircraft design. This is more than even a long essay.
Trying to cut it to a short paragraph or a couple of sentences means leaving out a lot of "stuff" than can lead to wrong conclusions, or at least leave out a number of negative characteristics while highlighting a few positive ones.

You also have to be able to actually build certain structures and not just theorize about them.

One of the highest aspect ratio wings to see use on a powered aircraft

the Hurel-Dubois HD-31 form about 1953, from some angles it can look rather distorted by the camera angle

Please note the extent of the under wing bracing as the wing was NOT stiff enough on it's own. Trying to play with limits of structural design at the same time as exploring aerodynamic limits can get you in trouble real quick.

As one problem with high aspect ratio wings goes, they are slower in roll response than lower aspect ratio wings.
So even if your high aspect ratio wing gives you better turning ability once you have rolled to the desired bank angle the shorter aspect ratio plane can either see you starting to bank and roll into his turn quicker and cut the corner a bit or if being pursued can bank one way and then other before the slower rolling plane can follow.

This is a generality, size and placement of ailerons, mechanical advantage in control system or powered ailerons can greatly affect actual results. One reason trying to compare jets and piston aircraft gets very complicated, only a few piston powered planes had powered flight controls (and like the late P-38s, often only one powered system) while jets were increasingly given powered flight controls for all three axis.

 

[pbehn]

It should always be borne in mind that the aircraft has to do a job. The HD-31 was a prototype airliner. I flew one time on a similar plane the Short Skyvan. London to Leeds-Bradford then to Teesside. The total journey time was 2 hrs 45 mins and from descent to Leeds and take of then landing at Teesside the whole time was in cloud or turbulence the thing was all over the place and half the passengers were physically sick. The pilot did great job of two cross wind landings in about 45 minutes but it is a civilian plane, there were pensioners and women with children on board, absolute chaos. I myself had just had 3 months in Saudi Arabia and had enjoyed a few beers in a Heathrow bar, bad mistake.
air ecosse skyvan pics - Google Search:

The next time I took the train, which got me home an hour earlier in comfort with a nice breakfast.

 

[XBe02Drvr]

I flew one time on a similar plane the Short Skyvan.

Our airline had a pair of Shorts SD30s, big brother of the Skyvan, and I rode in them occaisonaly, even getting an hour of stick time on a ferry flight. What a pig! Waddled like an obese goose, and had to replenish barf bag supplies after every leg. To make matters worse, the fuel tank vents were upstream of the cabin intakes, so there was the everpresent aroma of kerosene to add to the residual hint of stomach acid. I thought I had an iron stomach, but I almost lost it a couple times.
Cheers,
Wes

 

[swampyankee]

High aspect ratio will produce lower induced drag; this will tend to improve sustained turn performance, rate of climb, ceiling, and lift/drag in comparison to a low-aspect ratio wing; a high aspect ratio will tend to be heavier, may have less internal volume, will be more responsive to gusts, and may have a poorer aileron response. If the wing is swept, high-aspect ratio wings tend to be more susceptible to pitch-up.

Picking an aspect ratio is a balancing act. For piston-engined fighters, it was a trade-off between structural weight, internal volume, sustained turn rate, service ceiling, and rate of climb.

 

[John Frazer]

It seems to be a myth at least for very low aspect ratio (below 3-1) that they produce very high drag due to wing-tip vortices.
The Vought V-173 perpetuated this.
See the Arup S-2 and S-4 of the early-mid 1930s. Very near 1-1 aspect ratio, all-wing little round things with a bulge for the pilot and a tailfin (S-4 had a tail-plane up on the fin)

Both planes flew for several seasons on airshow circuits (see youtubes of them). Several pilot,. No accidents. A couple of versions each.
They did not exhibit high drag at "low-A" cruise. As little all-wings, they were slippery. Stable and responsive, very difficult to stall, impossible to spin.

As very low aspect ratio planes, they had the trick of being able to fly at silly slow speeds, and very high almost 35 degree "A". S-2 was ~780 pounds with a 37hp engine, 90+kts cruise, and astonishing 23kts landing speed.

See NASA studies of the '90s Wainfan "Facetmobile". Low aspect ratio unitary wing-body.
Low aspect ratio planes can stay aloft at such low speeds at very high "A", because of the enormous wing-tip vortices that develop at high-A. They wrap around and keep airflow from the leading edge over the top of the wing from detaching. Called "vortex lift", it is not present at normal flight.

Charles Zimmerman worked for NACA and was with the team that saw the S-2 perform an impresssive showing.
It was after this that his dream of a twin-rotor VTOL hovering toy gelled and took the low aspect-ratio discoid shape.
When the Navy decided to look into such planes for a STOL fighter, for some reason they let Zimmerman and Sikorsky & Vought build his silly flappy-prop parody of the Arup. For some reason, they were under the misapprehension that it would suffer high drag from the wing-tips, so he used his twin-rotor hovering design with the props counter-rotating to counter the wing-tip vortices.
Later tests with simple 2-blade normal props rotating the opposite direction (*with* the wing-tip vortices) showed almost no change in performance.
They don't have high drag at cruise, so it did not need the huge silly flapping props and the gearing system that killed the follow-on XF5U. In low-speed landing, high-A flight, you wouldn't want to counter the wing-tip vortex lift if you could.
We can call the V-173 and XF5U "Zimmerman's folly" or how the Navy threw away a fighter like the Bearcat but with greater range, speed and payload, and 40kt landing speed.

See also the Boeing model 396 proposal for a Navy flapjack fighter test plane. A simple straightforward study of the Arup planes, it would have led to their phenomenal fighter with the 28 cylinder 4-row radial engine and contra-props at the nose.

The advent of the jet age didn't kill the Navy flapjack. For one thing, they continued flying piston-prop planes until the '70s. The Skyraider and the S-2/C-1/E-1 series were mid-'40s designs.
If the Boeing flapjack had flown, the Arup planform would have taken over the fleet.

For the second thing, Vought had a design for a jet powered version that would have been awesome -better than the P-80 or maybe even better than the F-86

Sergei Sikorsky also worked on such a thing.

Hatfield worked on & flew the Arup planes, and in the '80s built the "Little Bird" planes which proved the Arup planform worked. In one youtube, he congratulates Rutan on the "Voyager" flight and then challenges him that if he'd used an Arup planform, it would have been stronger, faster, more room, and finished the 'round the world flight with fuel to spare.

That doesn't sound like a poor glider or cruising plane.

 

[swampyankee]

There are advantages to low aspect ratio, but efficiency is not one of them. One rather good side-by-side comparison is the Mirage F1 (swept wing) and Mirage III (delta). Both used the same engine and had similar take-off weights. The former had longer range, shorter take off distance, and maintained energy better in air combat.

 

[John Frazer]

Hardly the same as an all-wing lifting body with very low aspect ratio. We'll never know what those Sikorsky discoids might have done.

 

[swampyankee]

Hardly the same as an all-wing lifting body with very low aspect ratio. We'll never know what those Sikorsky discoids might have done.

Not without enough information to do a bit of analysis. On the other hand, there is enough information to predict that they're unlikely to aerodynamically efficient. As I said, low aspect ratio has some advantages, but at any given lift coefficient, a low aspect wing will have a larger induced drag than one with a high aspect ratio.

 

[Zipper730]

It seems to be a myth at least for very low aspect ratio (below 3-1) that they produce very high drag due to wing-tip vortices.

As I understand it, they generally produce high-drag at low speed, and work well at high speed.

It seems taper-ratio also plays a role.

See the Arup S-2 and S-4 of the early-mid 1930s. Very near 1-1 aspect ratio, all-wing little round things with a bulge for the pilot and a tailfin (S-4 had a tail-plane up on the fin)
. . .
Both planes flew for several seasons on airshow circuits (see youtubes of them). Several pilot,. No accidents. A couple of versions each.
They did not exhibit high drag at "low-A" cruise.

From what I read, admittedly all of it on wikipedia (I'm not fond of quoting wikipedia, but it's a source that's easily available) their glide ratio is was 3:1 which is the same as L/D. It seems more a testament to the propeller having enough power to push such a design with such little horsepower

See NASA studies of the '90s Wainfan "Facetmobile". Low aspect ratio unitary wing-body.
Low aspect ratio planes can stay aloft at such low speeds at very high "A", because of the enormous wing-tip vortices that develop at high-A. They wrap around and keep airflow from the leading edge over the top of the wing from detaching. Called "vortex lift", it is not present at normal flight.

That usually depends on a highly swept wing, that, or specially designed flaps.

Charles Zimmerman worked for NACA and was with the team that saw the S-2 perform an impresssive showing.

Yeah, and that became the basis for the V-173. The V-173 had some advantages in theory with the propeller right at the tip, it would negate the vortices by spinning in the opposite direction of the vortex.

For some reason, they were under the misapprehension that it would suffer high drag from the wing-tips

Because the S-2/S-4 had L/D of 3:1 which is quite poor. The Spitfire was around 13:1.

Later tests with simple 2-blade normal props rotating the opposite direction (*with* the wing-tip vortices) showed almost no change in performance.

I've never heard anything about that...

See also the Boeing model 396 proposal for a Navy flapjack fighter test plane. . . it would have led to their phenomenal fighter with the 28 cylinder 4-row radial engine

R-4360...

For the second thing, Vought had a design for a jet powered version that would have been awesome -better than the P-80 or maybe even better than the F-86

Have you any performance data?

Sergei Sikorsky also worked on such a thing.

That picture is one of the attachments you posted: It's a nice looking design, though I'm curious as to how it was projected to perform.

 

[John Frazer]

A single mention with zero corroboration or sources for that L/D or glide ratio.

I'm looking around, but other than Hatfield's own story, not much to be found.