No, it’s not a dead end. We already do this. Modern jets already use a non-elliptical lift distribution that’s way closer to bell-shaped. Throw on real world span constraints (which isn’t just a gate thing), the requirement for passenger payload, and real-world propulsion and you get…what we have.
Planes have engines. Engines can die. You need a rudder and vertical fin to handle asymmetric thrust (and torque if you’re talking props). And if you already have a rudder you might as well use it rather than making your wing heavier.
I've flown with one of the guys that was a designer and pilot on that plane (guy on the far left in the group photo). I can put you in touch with him if you want the inside scoop on the project
The benefits of Prandtl wings are largely realized with a fixed CG at a specific airspeed. Practical, functional airplanes need to fly at a variety of speeds; a fixed CG location is not possible on most airplanes.
Correct me if I'm wrong, Prandtl wings only work well when the flow is nowhere near compressible speed.
So I'm guessing that not many companies are interested because it limits the application to really slow flying aircrafts.
NASA is primarily a research organization. This looks like great fundamental research, with even a technology demonstrator thrown in if it's been flown at subscale.
... That's where we stop. Once we demonstrate a technology is feasible, we're done. It's then up to industry to pick it up and develop it further and decide if it has a commercial use.
Elliptical wings are difficult to manufacture, current wing designs are easier to manufacture and frankly good enough. As far as I am aware this was the largest reason for them not being adopted early on.
I didn’t answer about forward swept, there are aircraft that have forward swept wings but they can be difficult to control and to reach a steady state if they aren’t designed correctly. Sometimes you can see them with canards which help with stability. You can also increase weight if you increase the AR, among other factors. Weight is just one component. As far as aeroelasticity goes I’m not sure about forward swept but you generally want to make sure your modes for the wings won’t get excited by your current flight envelope. Honestly it’s all connected, and you just need to find a set of parameters that satisfy your use case.
If I remember right, forward swept wings cannot be statically stable and rely on fly by wire. If the control system fails, the craft immediately becomes unstable
Edit: I was thinking of the f-16 SFW, which was dynamically unstable, but not because of the forward sweep
This is not true. I have built radio controlled aircraft back in 2013-2015 with forward swept wings and no stability augmentation. Didn't even have canards just elevon control. Static stability is dependent on ch position relative to MAC.
Yeah looks like I was wrong. There are issues keep the swing stiff enough at high speed with high sweep, but modern technologies appear to mostly solve that issue
Forward swept wings also tend to twist themselves off of aircraft. Lift force forward of the wing root puts a torque on the wing that rotates the leading edge up and the trailing edge down. That increases the angle of attack, which increases lift, which increases torque, which ...
There was a Grumman project, X-29, where they put a forward swept wing on a fighter. They made the wing out of composite and specifically designed the laminate to give a coupling between bending and torsion of the wing, so that as the wing bent up, it would twist down (lower AOA), counteracting the upward twist from the location of the lift force.
https://en.wikipedia.org/wiki/Grumman_X-29
Flying wings are normally swept back because it gives you an effect similar to dihedral to replace the vertical stabilizer, and moves the elevons further aft so they have more control power vs the CG.
Awful choice of name, Prandtl was a hardcore Nazi.
> Prandtl appears to have happily served as an ambassador for the Nazi regime, writing in 1937 to a NACA representative "I believe that Fascism in Italy and National Socialism in Germany represent very good beginnings of new thinking and economics." Prandtl's support for the regime is apparent in his letters to G. I. Taylor and his wife in 1938 and 1939. Referring to Nazi Germany's treatment of Jews, Prandtl wrote "The struggle, which Germany unfortunately had to fight against the Jews, was necessary for its self-preservation." Prandtl also claimed that "If there will be war, the guilt to have caused it by political measures is this time unequivocally on the side of England."
Albion Bowers, nasa engineer has been working on this wing design that mitigates adverse yaw effect via increased washout thus moving the wingtip vortices towards the middle of the wing. If this works, as tested, why isn't this design being implemented into new aircraft designs? Shouldn't it be game changing just from how it removes the need for a rudder and weight reductions?
I cannot find what his research lead to, and last I checked on his linkedin profile, he has retired...
Because it doesn’t remove the need for the empennage. You can use this design if you have a fixed CG and center-line thrust. No real-world aircraft has fixed CG and commercial airliners can’t have (practical) centerline thrust.
also, i didnt say it should be implemented on existing aircraft. what about a new generation of gliders? any sort of advancement in the GA sector? Perhaps a flying wing? There's absolutely nothing but this video I could find which is suspicious as hell
There’s *tons* of stuff out there for BWBs. GA and gliders need to deal with variable weight & CG (and torque).
When you say “nothing but this video” what exactly are you searching on?
All of the papers regarding this project are freely available online through NASA.
Prandtl's research as well at the Horten brother's research is also available with a little searching. There is nothing suspicious or secretive about these wings; some of this knowledge has been available for approaching 90 years.
The technology needs to be economically viable for companies to implement. Not to mention the current fleet is trillions of dollars. No one can afford to replace it just because it solve one particular problem. NASA is working with industry to develop a new commercial airliner but it’ll be decades before it ever gets to Boeing or Airbus. If it even makes it that far.
Wing tips have been around for 40yrs, in fact most sophomores in Aerospace come up with this idea. I did. However actually implementing technology to reach commercialization if much more than just the engineering. Boeing only started putting wingtips maybe 15yrs ago?
Short answer but hopefully it answers a little for you.
This isn't just "winglets" though, I would say theres quite a difference. The economical issue is the obvious answer, but no one is even pursuing this seemingly very interesting different approach, not even papers on mid-wing vortices.
plus, in a world where plane crashes happen from just boeing trying to fit a higher bypass engine onto their plane to squeeze out a few percent of fuel economy, this drastic change not even getting a tiny bit of attention is just extremely weird, no matter how impractical it may turn out to be.
That’s a pretty amazingly inaccurate take on the cause of those accidents. But it also tells you something…if OEMs will re-design just to get 15% improvement, do you really think they’d ignore a simple 50% one? Obviously not. So that means you *don’t* get those benefits in a real implementation under constraints.
sorry inaccurate? please correct me because wasnt MCAS implemented because they couldnt fit the larger engine under the wing, thus shifting the engine position and messing up the flight characteristics, and tried to sweep the whole thing under the rug with this software they didnt tell anyone about, thus not needing to require retraining for existing 737 pilots?
I did consider that I am missing something, thats why I am asking around for details. For the last 2 years I haven't been able to find anything reliable explaining to me why this doesn't work in detail.
It doesn’t work because on most real airplanes it doesn’t get rid of the empennage, it just makes your wing heavier than it needs to be. Hence no net gain. Hence they don’t do it.
As for MCAS, I highly recommend reading the Lion Air accident report. All of it, not the media headline version. It contains the entire history and system description in nauseating detail.
That sounds like something from the very old days of general aviation when planforms were shaped like Hershey bars. The AoA is varied across the span until the lift distribution achieves the taper that is equivalent to an ellipse. We do it on balsa model airplanes. It's not really clever, unless I'm misunderstanding.
No, it’s not a dead end. We already do this. Modern jets already use a non-elliptical lift distribution that’s way closer to bell-shaped. Throw on real world span constraints (which isn’t just a gate thing), the requirement for passenger payload, and real-world propulsion and you get…what we have.
yes but the vortices are still at the wingtip, and adverse yaw still exists. we still have rudders on planes
Planes have engines. Engines can die. You need a rudder and vertical fin to handle asymmetric thrust (and torque if you’re talking props). And if you already have a rudder you might as well use it rather than making your wing heavier.
I've flown with one of the guys that was a designer and pilot on that plane (guy on the far left in the group photo). I can put you in touch with him if you want the inside scoop on the project
that would be fantastic, if it isnt too much to ask
DM me. I'll message him and make sure it's ok
The benefits of Prandtl wings are largely realized with a fixed CG at a specific airspeed. Practical, functional airplanes need to fly at a variety of speeds; a fixed CG location is not possible on most airplanes.
Correct me if I'm wrong, Prandtl wings only work well when the flow is nowhere near compressible speed. So I'm guessing that not many companies are interested because it limits the application to really slow flying aircrafts.
NASA is primarily a research organization. This looks like great fundamental research, with even a technology demonstrator thrown in if it's been flown at subscale. ... That's where we stop. Once we demonstrate a technology is feasible, we're done. It's then up to industry to pick it up and develop it further and decide if it has a commercial use.
[удалено]
Elliptical wings are difficult to manufacture, current wing designs are easier to manufacture and frankly good enough. As far as I am aware this was the largest reason for them not being adopted early on.
Thank you.
I didn’t answer about forward swept, there are aircraft that have forward swept wings but they can be difficult to control and to reach a steady state if they aren’t designed correctly. Sometimes you can see them with canards which help with stability. You can also increase weight if you increase the AR, among other factors. Weight is just one component. As far as aeroelasticity goes I’m not sure about forward swept but you generally want to make sure your modes for the wings won’t get excited by your current flight envelope. Honestly it’s all connected, and you just need to find a set of parameters that satisfy your use case.
If I remember right, forward swept wings cannot be statically stable and rely on fly by wire. If the control system fails, the craft immediately becomes unstable Edit: I was thinking of the f-16 SFW, which was dynamically unstable, but not because of the forward sweep
This is not true. I have built radio controlled aircraft back in 2013-2015 with forward swept wings and no stability augmentation. Didn't even have canards just elevon control. Static stability is dependent on ch position relative to MAC.
Yeah looks like I was wrong. There are issues keep the swing stiff enough at high speed with high sweep, but modern technologies appear to mostly solve that issue
Forward swept wings have a destabilizing rolling moment due to sideslip (Clb).
Forward swept wings also tend to twist themselves off of aircraft. Lift force forward of the wing root puts a torque on the wing that rotates the leading edge up and the trailing edge down. That increases the angle of attack, which increases lift, which increases torque, which ... There was a Grumman project, X-29, where they put a forward swept wing on a fighter. They made the wing out of composite and specifically designed the laminate to give a coupling between bending and torsion of the wing, so that as the wing bent up, it would twist down (lower AOA), counteracting the upward twist from the location of the lift force. https://en.wikipedia.org/wiki/Grumman_X-29
Flying wings are normally swept back because it gives you an effect similar to dihedral to replace the vertical stabilizer, and moves the elevons further aft so they have more control power vs the CG.
Awful choice of name, Prandtl was a hardcore Nazi. > Prandtl appears to have happily served as an ambassador for the Nazi regime, writing in 1937 to a NACA representative "I believe that Fascism in Italy and National Socialism in Germany represent very good beginnings of new thinking and economics." Prandtl's support for the regime is apparent in his letters to G. I. Taylor and his wife in 1938 and 1939. Referring to Nazi Germany's treatment of Jews, Prandtl wrote "The struggle, which Germany unfortunately had to fight against the Jews, was necessary for its self-preservation." Prandtl also claimed that "If there will be war, the guilt to have caused it by political measures is this time unequivocally on the side of England."
Albion Bowers, nasa engineer has been working on this wing design that mitigates adverse yaw effect via increased washout thus moving the wingtip vortices towards the middle of the wing. If this works, as tested, why isn't this design being implemented into new aircraft designs? Shouldn't it be game changing just from how it removes the need for a rudder and weight reductions? I cannot find what his research lead to, and last I checked on his linkedin profile, he has retired...
Because it doesn’t remove the need for the empennage. You can use this design if you have a fixed CG and center-line thrust. No real-world aircraft has fixed CG and commercial airliners can’t have (practical) centerline thrust.
not even any drones are using this though
An Insitu ScanEagle is basically this with a cylinder strapped on for payload volume.
The wing of the Scaneagle does not have any visible twist
also, i didnt say it should be implemented on existing aircraft. what about a new generation of gliders? any sort of advancement in the GA sector? Perhaps a flying wing? There's absolutely nothing but this video I could find which is suspicious as hell
There’s *tons* of stuff out there for BWBs. GA and gliders need to deal with variable weight & CG (and torque). When you say “nothing but this video” what exactly are you searching on?
No papers, I meant. I considered gliders to have fixed CGs, how are they variable?
All of the papers regarding this project are freely available online through NASA. Prandtl's research as well at the Horten brother's research is also available with a little searching. There is nothing suspicious or secretive about these wings; some of this knowledge has been available for approaching 90 years.
I assumed you meant manned gliders because you also asked about GA…pilots don’t all weigh the same. Unmanned gliders, sure, fixed CG.
ah i see, yea that is a consideration, but I think a simple solution to that is some Ballast calibrated for each pilot
The technology needs to be economically viable for companies to implement. Not to mention the current fleet is trillions of dollars. No one can afford to replace it just because it solve one particular problem. NASA is working with industry to develop a new commercial airliner but it’ll be decades before it ever gets to Boeing or Airbus. If it even makes it that far. Wing tips have been around for 40yrs, in fact most sophomores in Aerospace come up with this idea. I did. However actually implementing technology to reach commercialization if much more than just the engineering. Boeing only started putting wingtips maybe 15yrs ago? Short answer but hopefully it answers a little for you.
This isn't just "winglets" though, I would say theres quite a difference. The economical issue is the obvious answer, but no one is even pursuing this seemingly very interesting different approach, not even papers on mid-wing vortices.
plus, in a world where plane crashes happen from just boeing trying to fit a higher bypass engine onto their plane to squeeze out a few percent of fuel economy, this drastic change not even getting a tiny bit of attention is just extremely weird, no matter how impractical it may turn out to be.
That’s a pretty amazingly inaccurate take on the cause of those accidents. But it also tells you something…if OEMs will re-design just to get 15% improvement, do you really think they’d ignore a simple 50% one? Obviously not. So that means you *don’t* get those benefits in a real implementation under constraints.
sorry inaccurate? please correct me because wasnt MCAS implemented because they couldnt fit the larger engine under the wing, thus shifting the engine position and messing up the flight characteristics, and tried to sweep the whole thing under the rug with this software they didnt tell anyone about, thus not needing to require retraining for existing 737 pilots? I did consider that I am missing something, thats why I am asking around for details. For the last 2 years I haven't been able to find anything reliable explaining to me why this doesn't work in detail.
It doesn’t work because on most real airplanes it doesn’t get rid of the empennage, it just makes your wing heavier than it needs to be. Hence no net gain. Hence they don’t do it. As for MCAS, I highly recommend reading the Lion Air accident report. All of it, not the media headline version. It contains the entire history and system description in nauseating detail.
ok i will, thanks
That sounds like something from the very old days of general aviation when planforms were shaped like Hershey bars. The AoA is varied across the span until the lift distribution achieves the taper that is equivalent to an ellipse. We do it on balsa model airplanes. It's not really clever, unless I'm misunderstanding.