High wing vs low wing efficiency

Capt. Geoffrey Thorpe said:
High wing can use a thinner wing section and a strut for the less weight compared to a cantilever low wing.
Mid wing will usually be more efficient aerodynamically.
Interference drag tends to be higher with high wings. Tends.
High wing retracts suck.
If you cantilever the wings, the carrythrough is sometimes easier with a low wing.
Low wings can be more floaty.
The first cantilever wing airplane was built by Junkers in 1915. It was also the first all metal airplane.
The first aircraft with a "modern" thick airfoil (with a flatish bottom and curved top) and cantilever wings was the Fokker V-4 Triplane. Interplane struts were added for the production DR1 to reduce wing flex. 1917
The cartoon airfoil with flat bottom and curved top that everyone draws when they "explain" lift was pretty much obsolete by the 1930's.
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My thought was also possible retractable landing gear design costs? Guess I will have to ponder why cantilever wings would provide an inherently easier carrythru design, don’t see that yet. I could understand a low wing having an easier time with it.
I do know that I like the fact when you drop the gear in Cardinal RG’s and Centurions and then add 10 degrees of flaps simultaneously it nearly cancels out any need for trim changes. Wonder if that is the same for Aero Commanders & MU-2’s? Ted?
 
Briar Rabbit said:
Get the popcorn ready.

My opinion is that high wing location is generally more efficient than low wing if the wing design itself is comparable for two reasons. Meaning same chord, taper, design etc. being totally identical (which they never are from airplane manufacturer to manufacturer). So for this discussion not saying that any particular high wing is more efficient than all low wings but in general a high wing location has two benefits not available to low wing designed airplanes.

First it has some benefit from the reduced dihedral required with the wings being located on top. When it is necessary to increase the dihedral (low wing aircraft) the lift vector perpendicular to the wing angled more does not provide as much lift as a wing with minimal amount of positive dihedral and the vertical vector effectively longer.

Second it is well known that roll rate performance increases as dihedral moves away from positive dihedral and the wings move toward negative dihedral. Case in point all great fighter aircraft such as the F-18 have negative dihedral. During Vietnam I was told the old A-7 built by LTV had such negative dihedral it was nearly unflyable if the black boxes failed but the increased roll rates matched up better in the early part of the war when dogfighting the Migs. The point is with less dihedral required in high wing aircraft wouldn't they tend to have better roll response and inherently more efficient to fly?

Now not saying the benefits of high wing aircraft providing more shade in the summer, generally have two doors vs one and flying visibility to the ground should be ignored. Nor that low wing aircraft are typically easier to land and also easier to fuel, also viable points and personal taste to be considered. Just that high wing location by itself tends to make a more efficient single engine design?

I can think of many large multi engine military aircraft with high wings (C5A, C130, C141, etc) but not many large commercial air carriers. Is the landing gear too costly to design for a high wing large multi engine airplane? Boeing influence too predominate? Why not many large commercial high wing airplanes anymore?
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If either configuration were always superior, it would be the only one used. As with everything else in aviation, you make tradeoffs, and high wing vs low wing is a perfect example.

For cruise efficiency, you're assuming no wing struts for the high wing—those probably add more drag than the decreased dihedral saves—so your theoretical argument would work for something like the Cessna Cardinal, but not most other Cessna singles.

You'll also have to be more specific about "efficiency". For example, a fast roll rate is a benefit for aerobatics or combat, but a negative for ordinary flying, because it means the plane will be less stable in turbulence and harder to keep on the localiser (or any other track). So the high roll damping that comes with more dihedral is a minus for stunts, but a big plus for ordinary flying.

Low wings stay in ground effect longer than high wings, which makes them more efficient for takeoff (reach flying speed sooner), but less efficient for landing (longer float).

High wings are much better for off-runway landings because of the extra clearance, but the wider wheelbase and proximity to the ground of low wings lets them handle bigger crosswinds for landing and taxiing (unless the gear is mounted on the engine nacelles of a high-wing twin, like the Dash-8.

Low wings drop out of your way in a turn, so pattern-circuit work is simpler, while high wings go in the way and keep you from seeing where you're turning. OTOH low wings block your passengers' view of the scenery, while high wings don't. That's why people often call low wings "pilots' planes" and high wings "passengers' planes."

Low wings need a primary fuel pump, while high wings can use gravity. A high wing that runs out of fuel on "Both" is really out of fuel, while a low wing that runs a tank dry probably has enough in the other tank to get you to the nearest airport.

The spring gear on high wings is low maintenance, but it also bounces like crazy compared to the gas struts on low wings.

And so on and so on. The whole reason for the perma debate is that neither has advantages without corresponding disadvantages.

For my part, I'll thank <diety> for my low wings every time I'm taking the wing covers off or putting them back on this winter, especially on windy days. :)


D
 
David Megginson said:
If either configuration were always superior, it would be the only one used. As with everything else in aviation, you make tradeoffs, and high wing vs low wing is a perfect example.

For cruise efficiency, you're assuming no wing struts for the high wing—those probably add more drag than the decreased dihedral saves—so your theoretical argument would work for something like the Cessna Cardinal, but not most other Cessna singles.

You'll also have to be more specific about "efficiency". For example, a fast roll rate is a benefit for aerobatics or combat, but a negative for ordinary flying, because it means the plane will be less stable in turbulence and harder to keep on the localiser (or any other track). So the high roll damping that comes with more dihedral is a minus for stunts, but a big plus for ordinary flying.

Low wings stay in ground effect longer than high wings, which makes them more efficient for takeoff (reach flying speed sooner), but less efficient for landing (longer float).

High wings are much better for off-runway landings because of the extra clearance, but the wider wheelbase and proximity to the ground of low wings lets them handle bigger crosswinds for landing and taxiing (unless the gear is mounted on the engine nacelles of a high-wing twin, like the Dash-8.

Low wings drop out of your way in a turn, so pattern-circuit work is simpler, while high wings go in the way and keep you from seeing where you're turning. OTOH low wings block your passengers' view of the scenery, while high wings don't. That's why people often call low wings "pilots' planes" and high wings "passengers' planes."

Low wings need a primary fuel pump, while high wings can use gravity. A high wing that runs out of fuel on "Both" is really out of fuel, while a low wing that runs a tank dry probably has enough in the other tank to get you to the nearest airport.

The spring gear on high wings is low maintenance, but it also bounces like crazy compared to the gas struts on low wings.

And so on and so on. The whole reason for the perma debate is that neither has advantages without corresponding disadvantages.

For my part, I'll thank <diety> for my low wings every time I'm taking the wing covers off or putting them back on this winter, especially on windy days. :)


D
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Don’t disagree with anything above, and tried to mention a few of them in my original post. My thought of improved efficiency with a high wing less dihedral design is that a higher percentage of the perpendicular vector contributes to lift. And certainly there are personal choices that a notable percentage of pilots prefer low wings. But what is the driving factor in the popularity of low wing commercial carrier birds.
 
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Briar Rabbit said:
Don’t disagree with anything above, and tried to mention a few of them in my original post. My thought of improved efficiency with a high wing less dihedral design is that a higher percentage of the perpendicular vector contributes to lift. And certainly there are personal choices that a notable percentage of pilots prefer low wings. But what is the driving factor in the popularity of low wing commercial carrier birds.
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From throwing my compass over the 3-views, the dihedral angle of a high-wing Cessna 172 appears to be about 2°, while the dihedral angle of a low-wing Piper PA-28 appears to be about 5°. The math is probably a lot more complicated for the aeronautical engineers, but as a WAG, that means that the effective perpendicular area of the C172 wing in level flight is about cos(2°), or 99.94%, while the effective perpendicular area of the PA-28 wing is about cos(5°), or 99.62%. In terms of efficiency, we're into new paint job or fresh wax territory here. And if you add in the extra drag from struts (like with the C172), you're likely well into a performance deficit from the high wing.
 
Briar Rabbit said:
Anyway I am still curious why there have not been many high wing commercial air carrier airplanes? If the 737Max had been a high wing design it would not have been necessary to move the engines forward and try to correct the flight issues with the disastrous TCAS system.
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The spar carrythrough structure gets in the way in the cabin ceiling. So they have to raise the structure and create a hump in the fuselage.

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Briar Rabbit said:
Anyway I am still curious why there have not been many high wing commercial air carrier airplanes? If the 737Max had been a high wing design it would not have been necessary to move the engines forward and try to correct the flight issues with the disastrous TCAS system.
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A couple of reasons come to mind:

- A low wing allows you to run the spar carry through under the passenger compartment. In front of and behind that carry through, you have a space the width of the fuselage and height of the carry through that can be used for fuel, luggage, landing gear, etc. Wouldn't you rather work in the gear wells, load baggage, etc. at more or less shoulder height?

- Engine height. Wouldn't you rather maintain engines at 8' off the ground as opposed to 20' off the ground?
 
asicer said:
P'shaw

3VBzl.jpg
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Hah! Only nine wings? Nobody ever topped Horatio Phillips:

phillips_multiplane-2.jpg
Phillips-Multiplane-Version.jpg
 
Having learned in Cessnas and flying them for years, I favored high wings for visibility, shade, and stability. But buying a Diamond DA40 has made me a fan of low wing aircraft. The Diamond overcomes the shortage of doors and poor accessibility of many low wings, I would argue they have better accessibility than most small aircraft. But the best benefit is ease of landing with greater ground effect than high wing aircraft, you’re literally riding on a cushion of air as you land. The biggest inconvenience are heat in the summer sun and constantly having to switch fuel tanks. A high wing can draw efficiently from both tanks until empty, most low wings select only one wing tank at a time and must keep some balance, max 8 gallon difference in a DA40.
 
David Megginson said:
From throwing my compass over the 3-views, the dihedral angle of a high-wing Cessna 172 appears to be about 2°, while the dihedral angle of a low-wing Piper PA-28 appears to be about 5°.
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I looked through some old references -- C-172 and C-182 dihedral are both approx. 1.4°; all PA-28s and their progeny are 7°.
 
Briar Rabbit said:
You are correct, had it confused with the F8 which looks similar, also built by LTV and initially was successful against the MIG 17’s at the early part of the war. It has been a long time since engineering school but I do remember the A7 being used as an example of airplanes with negative dihedral (or more correctly anhedral) having improved roll rates and that the first flight demonstration of the A7 impressing onlookers with fast roll rates even though loaded with more than 7,000 lbs of ordinances on the pylons. Another example discussed at the time was the designers having to change the wing tips of the F4 because it was not adequately stable. This change is called a polyhedral wing. Interestingly swept wing designs also increase some degree of roll stability.

Anyway I am still curious why there have not been many high wing commercial air carrier airplanes? If the 737Max had been a high wing design it would not have been necessary to move the engines forward and try to correct the flight issues with the disastrous TCAS system.
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what is wrong with the max Traffic Collision Avoidance System?
 
Pilawt said:
I looked through some old references -- C-172 and C-182 dihedral are both approx. 1.4°; all PA-28s and their progeny are 7°.
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Thanks for looking that up. So around 99.26% effective surface for the PA-28. Again, probably not a significant difference compared to the extra drag from the wing struts on the 172 and 182.
 
Briar Rabbit said:
...So for this discussion not saying that any particular high wing is more efficient than all low wings but in general a high wing location has two benefits not available to low wing designed airplanes.
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Briefly, with all other things being equal there will be little difference in performance between a wing mounted above a fuselage and the same wing mounted below. The problem is that all other things cannot be made equal, and the additional constraints and inherent characteristics do not result in higher performance with a high wing. There are reasons long range airliners, gliders, 'round the world record setters, etc, tend towards mid or low wings.

So then, on to your "...two benefits not available to low wing airplanes..."

I elected to address your second 'benefit' first, because some of the fundamentals I'm going to address here will affect your first 'benefit'.
Briar Rabbit said:
Second it is well known that roll rate performance increases as dihedral moves away from positive dihedral and the wings move toward negative dihedral. Case in point all great fighter aircraft such as the F-18 have negative dihedral. During Vietnam I was told the old A-7 built by LTV had such negative dihedral it was nearly unflyable if the black boxes failed but the increased roll rates matched up better in the early part of the war when dogfighting the Migs. The point is with less dihedral required in high wing aircraft wouldn't they tend to have better roll response and inherently more efficient to fly?
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I contend that a roll rate increase with anhedral (negative dihedral) is not "well known," nor does it have a significant effect on roll rate when compared to things like aspect ratio and roll control power. Dihedral is added to airplanes to increase the tendency to roll away from sideslip (sideslip in the aerodynamic sense, irrespective of slip or skid). Wind in your left ear (due to, say, right pedal), airplane rolls right. That is referred to as "positive dihedral effect," or sometimes "lateral stability," but that term tends to cause confusion. Note that wing sweep, typically required to reduce drag at transonic/supersonic speeds, also has the same effect as dihedral; as do high-mounted wings, both increasing dihedral effect. Positive dihedral effect is a good thing for handling qualities, so designers will strive for an airplane that exhibits positive dihedral effect, but it is also possible to have too much of a good thing. High-mounted swept-wing airplanes like the A-7, F-8, AV-8 incorporate anhedral to reduce the strong rolling moment with sideslip (among other reasons like outrigger placement).

As for anecdotal performance gains, your description about the A-7 is pretty far off the norm, in my experience. It wasn't the best handling aircraft but most of those handling quirks weren't a result of the anhedral, the anhedral *improved* handling. Clearly I say this based on analysis, having never flown an A-7 *without* anhedral, but the aerodynamics are pretty straightforward. I have enough time in A-7's *with* anhedral and a couple of other airplanes you referenced to say that while they were/are reasonably maneuverable, the highest roll rates of any comparable airplanes I've flown have been on low-wing airplanes with little to no conventional dihedral (T-38, A-4). That roll rate in and of itself doesn't lead to that much of a tactical advantage compared to other drivers like excess power, wing loading, and L/D.

Briar Rabbit said:
First it has some benefit from the reduced dihedral required with the wings being located on top. When it is necessary to increase the dihedral (low wing aircraft) the lift vector perpendicular to the wing angled more does not provide as much lift as a wing with minimal amount of positive dihedral and the vertical vector effectively longer.
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As a result it will have a slightly lower L/D. If it's possible (hint: it is) to increase dihedral effect without physical dihedral, the low-wing doesn't necessarily need it, if L/D is that precious. What about the high wing with anhedral? That will suffer the same 'loss of lift' due to tilting the lift vector, also negating the advantage of the high wing. When things like intersection drag, structure, landing gear, etc, are all added in the perceived benefit of the high wing due to less dihedral alone gets lost in the noise.

Nauga,
who put the spoiler at the end
 
nauga said:
Briefly, with all other things being equal there will be little difference in performance between a wing mounted above a fuselage and the same wing mounted below. The problem is that all other things cannot be made equal, and the additional constraints and inherent characteristics do not result in higher performance with a high wing. There are reasons long range airliners, gliders, 'round the world record setters, etc, tend towards mid or low wings.

So then, on to your "...two benefits not available to low wing airplanes..."

I elected to address your second 'benefit' first, because some of the fundamentals I'm going to address here will affect your first 'benefit'. I contend that a roll rate increase with anhedral (negative dihedral) is not "well known," nor does it have a significant effect on roll rate when compared to things like aspect ratio and roll control power. Dihedral is added to airplanes to increase the tendency to roll away from sideslip (sideslip in the aerodynamic sense, irrespective of slip or skid). Wind in your left ear (due to, say, right pedal), airplane rolls right. That is referred to as "positive dihedral effect," or sometimes "lateral stability," but that term tends to cause confusion. Note that wing sweep, typically required to reduce drag at transonic/supersonic speeds, also has the same effect as dihedral; as do high-mounted wings, both increasing dihedral effect. Positive dihedral effect is a good thing for handling qualities, so designers will strive for an airplane that exhibits positive dihedral effect, but it is also possible to have too much of a good thing. High-mounted swept-wing airplanes like the A-7, F-8, AV-8 incorporate anhedral to reduce the strong rolling moment with sideslip (among other reasons like outrigger placement).

As for anecdotal performance gains, your description about the A-7 is pretty far off the norm, in my experience. It wasn't the best handling aircraft but most of those handling quirks weren't a result of the anhedral, the anhedral *improved* handling. Clearly I say this based on analysis, having never flown an A-7 *without* anhedral, but the aerodynamics are pretty straightforward. I have enough time in A-7's *with* anhedral and a couple of other airplanes you referenced to say that while they were/are reasonably maneuverable, the highest roll rates of any comparable airplanes I've flown have been on low-wing airplanes with little to no conventional dihedral (T-38, A-4). That roll rate in and of itself doesn't lead to that much of a tactical advantage compared to other drivers like excess power, wing loading, and L/D.

As a result it will have a slightly lower L/D. If it's possible (hint: it is) to increase dihedral effect without physical dihedral, the low-wing doesn't necessarily need it, if L/D is that precious. What about the high wing with anhedral? That will suffer the same 'loss of lift' due to tilting the lift vector, also negating the advantage of the high wing. When things like intersection drag, structure, landing gear, etc, are all added in the perceived benefit of the high wing due to less dihedral alone gets lost in the noise.

Nauga,
who put the spoiler at the end
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I think we agree on more of this than you might think. When I stated “being totally identical (which they never are from airplane manufacturer to manufacturer)” I should have included more than just the wing design itself such as aspect ratio, excess power, etc. And we should also acknowledge that stability in general aviation airplanes needs to be considered and may be adversely affected by attempts to increase roll rate performance. I still believe that all other factors being the same an airplane with anhedral will have faster roll rates than an airplane with positive dihedral. The case that comes to mind is the 67/68 Centurions that have 3 degrees dihedral versus later models with 1 1/2 degrees. The 67 model was equipped with a 3 degree wing design to improve stability at slow flight. This was changed in 69 and an aileron/rudder interconnect was incorporated and as you have pointed out countered side slip. But the 69 and newer Centurions do have a bit higher roll rate.
I have never had the opportunity to fly an airplane with anhedral but do recall class discussions about how impressive the test flights of the A7 were regarding the airplanes roll performance with full loaded pylons and did look up the airplane on Wikipedia which references that sentiment. Other handling characteristics may have been lousy for all I know?
The C5A is an example of a high wing with anhedral because it hauls so much weight below the wings and not because it required more roll rate performance I suppose.

“There are reasons long range airliners, gliders, 'round the world record setters, etc, tend towards mid or low wings.”
So if a high wing airplane has less need for dihedral in general, and lower positive dihedral has a more favorable lift/drag ratio than an airplane needing more positive dihedral due to tilting the lift vector the point of the discussion is what are the reasons most commercial airliners are mid or low wings? I would think an improvement on L/D at any level would be desirable in a large airliner. What are the additional constraints and have suggested landing gear as one of them? What else?
 
Briar Rabbit said:
I still believe that all other factors being the same an airplane with anhedral will have faster roll rates than an airplane with positive dihedral.
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Without getting into whether that's true, what's your intended benefit for faster roll rate? Aerobatics? Mock combat?

For normal (non-stunt) flying, I'd prefer a more-stable platform with decent roll damping.
 
Briar Rabbit said:
I still believe that all other factors being the same an airplane with anhedral will have faster roll rates than an airplane with positive dihedral. The case that comes to mind is the 67/68 Centurions that have 3 degrees dihedral versus later models with 1 1/2 degrees. The 67 model was equipped with a 3 degree wing design to improve stability at slow flight. This was changed in 69 and an aileron/rudder interconnect was incorporated and as you have pointed out countered side slip. But the 69 and newer Centurions do have a bit higher roll rate.
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In a coordinated roll there is no significant difference in rolling moment or roll damping produced by identical wings with dihedral or anhedral, as 10 minutes with a free-body diagram would indicate. Adverse yaw will decrease roll performance in a wing exhibiting positive dihedral *effect* regardless of the geometric dihedral, and proverse yaw will increase the roll performance of that same wing. An aileron-rudder interconnect can increase roll performance if it or the pilot overcompensates for adverse yaw resulting in proverse yaw. The roll performance of the A-7 with pylons and stores is far more a factor of the control power available and the (relatively) low aspect ratio. The A-7, loaded or otherwise, exhibits positive dihedral effect, and does not have the roll performance of either the A-4 or T-38, both low-wing with positive dihedral effect. In neither the Centurion nor the A-7 example was (or should be) the roll performance attributed to decreased dihedral or anhedral.

Briar Rabbit said:
I would think an improvement on L/D at any level would be desirable in a large airliner.
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Did you read the part about sweep and high mounting also causing dihedral effect, part of the reason so many high-wing transports have anhedral? The sign of the angle doesn't matter, anhedral or dihedral will decrease L/D compared to a perfectly flat wing. Now consider a high-wing airplane that needs anhedral...have you ever seen the wings on an airliner flex? That leads to positive geometric dihedral. On the high-wing airplane you can either put in *more* anhedral so that when it flexes it results in the proper amount (decreasing L/D at the design condition, and even more decrease at off-design conditions), or you can make the wing stiffer. Which means heavier. Potentially a *lot* heavier.

Nauga,
who has banged his head on the canopy
 
I think it's time for the OP, @Briar Rabbit , to come clean on why this matters to them. I don't think it was a straight-forward enquiry, because the OP kept postulating new advantages for high wings and dismissing them for low wings, so they seem to have a stake in the outcome. So what was it? Hangar bet? Research project? Just wanted to stir things up a bit? ;)
 
David Megginson said:
I think it's time for the OP, @Briar Rabbit , to come clean on why this matters to them. I don't think it was a straight-forward enquiry, because the OP kept postulating new advantages for high wings and dismissing them for low wings, so they seem to have a stake in the outcome. So what was it? Hangar bet? Research project? Just wanted to stir things up a bit? ;)
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I've been curious about this too. For commercial jets, I'm sure low wings are more "efficient", defined as total cost of acquisition and ownership, otherwise a different configuration would be used. What I don't know is whether low-wing planes of those sizes and speed are so much cheaper to build that the initial cost overrides fuel savings during their operating life. Maybe, as mentioned earlier, maintenance is less expensive. Maybe they are more fuel efficient, or some combination of "all of the above".
 
Cap'n Jack said:
I've been curious about this too. For commercial jets, I'm sure low wings are more "efficient", defined as total cost of acquisition and ownership, otherwise a different configuration would be used. What I don't know is whether low-wing planes of those sizes and speed are so much cheaper to build that the initial cost overrides fuel savings during their operating life. Maybe, as mentioned earlier, maintenance is less expensive. Maybe they are more fuel efficient, or some combination of "all of the above".
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Cheap was certainly the reason for Fred Weick's original PA-28 design. He'd boasted to William Piper in the 1950s that he could design an entry-level, all-metal airplane that was cheaper to build than Piper's existing rag-and-tube planes. When Piper called him on it, he came up with a whole collection of cost savings, including the Hershey Bar wing (so that all ribs could be the same size), no two-way bends in the sheet metal (to reduce the effort and skill demands on the shop floor), and the carry-though wing spar. Before that, Piper Aircraft had been a high-wing company.
 
David Megginson said:
I think it's time for the OP, @Briar Rabbit , to come clean on why this matters to them. I don't think it was a straight-forward enquiry, because the OP kept postulating new advantages for high wings and dismissing them for low wings, so they seem to have a stake in the outcome. So what was it? Hangar bet? Research project? Just wanted to stir things up a bit? ;)
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No hangar bet, definitely not a research project, no intent in stirring the pot, just enjoying increasing my knowledge.
 
Briar Rabbit said:
No hangar bet, definitely not a research project, no intent in stirring the pot, just enjoying increasing my knowledge.
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Then I'll suggest that this Wikipedia page will tell you everything you need to know about most of the aviation perma-debates, including high-wing vs low-wing, Garmin vs Avidyne, multigrade oil vs mineral oil, Hershey Bar vs Warrior wing, ForeFlight vs Garmin Pilot, etc etc etc :)

https://en.wikipedia.org/wiki/Narcissism_of_small_differences
 
nauga said:
In a coordinated roll there is no significant difference in rolling moment or roll damping produced by identical wings with dihedral or anhedral, as 10 minutes with a free-body diagram would indicate. Adverse yaw will decrease roll performance in a wing exhibiting positive dihedral *effect* regardless of the geometric dihedral, and proverse yaw will increase the roll performance of that same wing. An aileron-rudder interconnect can increase roll performance if it or the pilot overcompensates for adverse yaw resulting in proverse yaw. The roll performance of the A-7 with pylons and stores is far more a factor of the control power available and the (relatively) low aspect ratio. The A-7, loaded or otherwise, exhibits positive dihedral effect, and does not have the roll performance of either the A-4 or T-38, both low-wing with positive dihedral effect. In neither the Centurion nor the A-7 example was (or should be) the roll performance attributed to decreased dihedral or anhedral.

Did you read the part about sweep and high mounting also causing dihedral effect, part of the reason so many high-wing transports have anhedral? The sign of the angle doesn't matter, anhedral or dihedral will decrease L/D compared to a perfectly flat wing. Now consider a high-wing airplane that needs anhedral...have you ever seen the wings on an airliner flex? That leads to positive geometric dihedral. On the high-wing airplane you can either put in *more* anhedral so that when it flexes it results in the proper amount (decreasing L/D at the design condition, and even more decrease at off-design conditions), or you can make the wing stiffer. Which means heavier. Potentially a *lot* heavier.

Nauga,
who has banged his head on the canopy
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Let me start with the second section first - totally agree. I don’t remember why swept wings create the effect of dihedral but I do recall that is the case (it has been 50 years since engineering lectures). And certainly agree high wings also have that affect which I thought I made clear in the first post. And definitely aware of the wings flexing on large airplanes, as I recall the vertical wing tip movement on a B52 during a normal GAG cycle is 16 to 22 feet.

Regarding the first part of your reply I agree rolling moment will be the same regardless of anhedral /dihedral. And I understand and agree with the yaw affect. No doubt you are correct with the comparison of the A7, A4 & T34. But I am struggling with understanding why anhedral will not produce a faster roll than dihedral. Here is what is going through my mind. Consider a hypothetical airplane with 10 degrees of anhedral and start the bird into a 10 degree roll to the left. At this point the lift factor on the left wing is tilted 20 degrees to the left of vertical while the lift factor on the right wing is exactly vertical resulting in more lift on the right wing and therefore would this not increase the roll speed? Conversely let’s do the same thing with a hypothetical airplane having 10 degrees of dihedral. Now in our progressive 10 degree left roll the lift factor on the dihedral left wing is vertical and the lift factor on the right wing is tilted 20 degrees with a result of more lift on the left wing slowing up the roll and instead adding stability to roll it back to level? Where am I going wrong?

Just seems to me that the wing placement on an airliner would make a higher placement more efficient with less dihedral needed?

Good discussion, thanks for your input!
 
Briar Rabbit said:
Ok. Did not intend to start a “feud” and disappointed if it was perceived that way.
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That's not what I meant by my post. I'm just poking fun at all of us, including me. When one's caught up in something, the debates start being about more- and more-trivial things — that's true of every field (think camelCase vs underscores and spaces vs tabs in computer programming). We all get excited about tiny things that have little practical impact on our flying, but let us divide up into camps. I'm always reminded (by my own posts as much as anyone else's) of the Judean People's Front vs the People's Front of Judea in Monty Python and the Holy Grail.

FWIW, here's where I stand on some of the small differences we go over and over and over again in aviation forums:
  • Prefer low wing to high wing
  • Prefer fixed gear to retractable
  • Prefer LOP to ROP
  • Prefer Android to iOS
  • Prefer Garmin to Avidyne
  • Prefer maintenance minimalism (per Mike Busch) to maximalism
  • Prefer full flaps on landing (even in a crosswind)
  • Think IFR is a good way to fly cross country
  • Leave my Tanis heater plugged in 24/7 in the winter (instead of putting it on a remote switch)
  • Prefer the overhead entry to 45° (but I'm Canadian, so that's expected)
I wonder if those are enough to identify me uniquely among PoA members. That's 10 bits of information (or 2^10 == 1,024 possibilities), but I doubt the distribution is even across members.
 
David Megginson said:
That's not what I meant by my post. I'm just poking fun at all of us, including me. When one's caught up in something, the debates start being about more- and more-trivial things — that's true of every field (think camelCase vs underscores and spaces vs tabs in computer programming). We all get excited about tiny things that have little practical impact on our flying, but let us divide up into camps. I'm always reminded (by my own posts as much as anyone else's) of the Judean People's Front vs the People's Front of Judea in Monty Python and the Holy Grail.

FWIW, here's where I stand on some of the small differences we go over and over and over again in aviation forums:
  • Prefer low wing to high wing
  • Prefer fixed gear to retractable
  • Prefer LOP to ROP
  • Prefer Android to iOS
  • Prefer Garmin to Avidyne
  • Prefer maintenance minimalism (per Mike Busch) to maximalism
  • Prefer full flaps on landing (even in a crosswind)
  • Think IFR is a good way to fly cross country
  • Leave my Tanis heater plugged in 24/7 in the winter (instead of putting it on a remote switch)
  • Prefer the overhead entry to 45° (but I'm Canadian, so that's expected)
I wonder if those are enough to identify me uniquely among PoA members. That's 10 bits of information (or 2^10 == 1,024 possibilities), but I doubt the distribution is even across members.
Click to expand...


I just put all my relevant preferences in my signature line so people know up front.
 
David Megginson said:

FWIW, here's where I stand on some of the small differences we go over and over and over again in aviation forums:
  • Prefer low wing to high wing
  • Prefer fixed gear to retractable
  • Prefer LOP to ROP
  • Prefer Android to iOS
  • Prefer Garmin to Avidyne
  • Prefer maintenance minimalism (per Mike Busch) to maximalism
  • Prefer full flaps on landing (even in a crosswind)
  • Think IFR is a good way to fly cross country
  • Leave my Tanis heater plugged in 24/7 in the winter (instead of putting it on a remote switch)
  • Prefer the overhead entry to 45° (but I'm Canadian, so that's expected)
Click to expand...

I see you are pretty smart but there are a few areas where you need some correction! :p:D
 
Briar Rabbit said:
The C5A is an example of a high wing with anhedral because it hauls so much weight below the wings and not because it required more roll rate performance I suppose.
Click to expand...

Look at the B-47, B-52, An-124, M400, C5, C141, and other aircraft with high mounted swept wings. They use anhedral to damp dutch roll and other negative consequences of yaw/roll coupling which would be magnified without the anhedral.
 
Yall talk about high wings = birds.

How many ****ing planes have wings that flap like a bird?
 
kyleb said:
They use anhedral to damp dutch roll and other negative consequences of yaw/roll coupling which would be magnified without the anhedral.
Click to expand...
That yaw/roll coupling is the dihedral effect mentioned in posts 58 and 63.

Nauga,
and Cl,beta
 
I believe there are too many variables in this equation to accurately determine which configuration is more efficient. If it were calculable, the difference would be microscopic.

For most people, in their mind, the best car brand is the one they’re driving. In this argument the same thing applies, for most people, with high wing versus low wing. What that person flies is the best. People tend to find a way to justify in their mind most everything.
 
EdFred said:
Yall talk about high wings = birds.

How many ****ing planes have wings that flap like a bird?
Click to expand...
Actually, most soaring birds do not flap their wings except for takeoff, so the point is valid. To add to it, our brethren, the world’s fastest flying creatures are true high wings (although they flap to get that fast). The Mexican free tailed bat achieves 100mph in level flight. That is as fast as my Cessna.

The Raptor’s wings flap up and down because the airplane is so unstable. Maybe that is actually a new design feature.
 
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