The future of rotorcraft?
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The future of rotorcraft?
Large twist is good for hover, but bad for fast forward flight.
High rotor RPM is good for hover, but bad for fast forward flight.
Consider blades that are made of Extension-Twist Coupled Laminates.
In addition, consider an intermeshing helicopter with a pusher prop. The pusher prop provides all the forward thrust. As the craft's horizontal velocity is increased, the rotational speed of the rotors will be decreased. This reduction of rotor RPM results in less centrifugal force and this, in turn, results in less blade twist, due to the Extension-Twist Coupled Laminates.
At the maximum forward speed, the rotor blades will have no twist. The rotors are only required to provide lift, so now these rotors will be operating with minimal engine driven torque, and the rotorcraft will be flying, at high speed
, in a semi-helicopter / semi-gyrocopter mode.
_____________________
For those who like to read themselves to sleep, here are 449 more pages on the subject.
High rotor RPM is good for hover, but bad for fast forward flight.
Consider blades that are made of Extension-Twist Coupled Laminates.
In addition, consider an intermeshing helicopter with a pusher prop. The pusher prop provides all the forward thrust. As the craft's horizontal velocity is increased, the rotational speed of the rotors will be decreased. This reduction of rotor RPM results in less centrifugal force and this, in turn, results in less blade twist, due to the Extension-Twist Coupled Laminates.
At the maximum forward speed, the rotor blades will have no twist. The rotors are only required to provide lift, so now these rotors will be operating with minimal engine driven torque, and the rotorcraft will be flying, at high speed
, in a semi-helicopter / semi-gyrocopter mode. _____________________
For those who like to read themselves to sleep, here are 449 more pages on the subject.
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Or we could make it real easy and nail the wings down so they dont move and call it ................ Oh I dont know,,,,, maybe and airplane. a whole lot less complecated. 
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Dave:
Do you intend that the main rotor would provide any of the forward thrust, or would it all come from the prop? Reversing prop for hovering with tailwinds, or slowing down when transitioning to the hover?
Does it also have a tail rotor?
I'll look at the other pages too.
Do you intend that the main rotor would provide any of the forward thrust, or would it all come from the prop? Reversing prop for hovering with tailwinds, or slowing down when transitioning to the hover?
Does it also have a tail rotor?
I'll look at the other pages too.
look at the past
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vorticey,
Different thrust devices work better at different forward velocities. Under approximately 400 mph the propeller or ducted fan will be the most efficient. At higher velocities, your idea may well have merit.
Shawn,
I feel quite strongly that; lower rotor rpm, extremely rigid rotors, active blade twist, a separate horizontal thrust device, and the exclusion of the tail-rotor, are all mandatory features for the next (2nd) generation of rotorcraft.
It will be interesting to see what, if any, horizontal thrust is provided by the main rotor(s) of these new rotorcraft. Perhaps there is consideration for giving the rotor-blades a slight positive twist in fast forward flight, but I suspect that total autorotation is not the optimal arraignment.
With the UniCopter, the intent is that the rotors will provide some of the forward thrust. One reason is because there is not enough room to swing a sufficiently large diameter propeller. The constant speed propeller will be linked to the forward cyclic, with consideration for linking it to the aft and lateral cyclics. The tail rotor is 'verboten'.
donut king,
Yes, but I don't think that the S-72 was ever flown with its rigid rotor. Perhaps the reasons for this were; an insufficient number of blades for aerodynamic stability and/or the asymmetrical aerodynamics of a single rotor at high speeds.
Boeing's new Dragonfly is supposed to fly within the next few months.
Different thrust devices work better at different forward velocities. Under approximately 400 mph the propeller or ducted fan will be the most efficient. At higher velocities, your idea may well have merit.
Shawn,
I feel quite strongly that; lower rotor rpm, extremely rigid rotors, active blade twist, a separate horizontal thrust device, and the exclusion of the tail-rotor, are all mandatory features for the next (2nd) generation of rotorcraft.
It will be interesting to see what, if any, horizontal thrust is provided by the main rotor(s) of these new rotorcraft. Perhaps there is consideration for giving the rotor-blades a slight positive twist in fast forward flight, but I suspect that total autorotation is not the optimal arraignment.
With the UniCopter, the intent is that the rotors will provide some of the forward thrust. One reason is because there is not enough room to swing a sufficiently large diameter propeller. The constant speed propeller will be linked to the forward cyclic, with consideration for linking it to the aft and lateral cyclics. The tail rotor is 'verboten'
. donut king,
Yes, but I don't think that the S-72 was ever flown with its rigid rotor. Perhaps the reasons for this were; an insufficient number of blades for aerodynamic stability and/or the asymmetrical aerodynamics of a single rotor at high speeds.
Boeing's new Dragonfly is supposed to fly within the next few months.
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Dave:
I'm sure you've thought of it, but one of the inherent problems with gyrocopters (not that you are advocating a pure gyrocopter, but there are some relevant things about them) is that they have a minimum airspeed that is dictated by the very poor efficiency of the propeller at slow airspeeds. No autogyro can fly slower than about 40 KIAS because of this, and you may have solved this probelm partly by having a powered main rotor.
But there are a whole host of other concerns that are relevant. Without a tail rotor or some other device to provide side thrust, how do you intend to meet the requirement of being able to handle winds from the rear and side?
Deeply interested in this, but there are often reasons why 'new' concepts have not been tried by the big boys.
I'm sure you've thought of it, but one of the inherent problems with gyrocopters (not that you are advocating a pure gyrocopter, but there are some relevant things about them) is that they have a minimum airspeed that is dictated by the very poor efficiency of the propeller at slow airspeeds. No autogyro can fly slower than about 40 KIAS because of this, and you may have solved this probelm partly by having a powered main rotor.
But there are a whole host of other concerns that are relevant. Without a tail rotor or some other device to provide side thrust, how do you intend to meet the requirement of being able to handle winds from the rear and side?
Deeply interested in this, but there are often reasons why 'new' concepts have not been tried by the big boys.
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Hi Shawn:
You're correct. The use of the word 'gyrocopter', while discussing the attributes required for future rotorcraft, is an oversimplification of a complex situation.
The world's two most advanced helicopters at the end of WWII did not use tail rotors and I suspect that the tail rotor will be a serious impediment to very fast forward flight in the future.
Boeing has stated " The Chinook was developed in the late 1950s, less than a decade after the B-52 bomber entered service. Since then, two follow-on bombers have been fielded, but no new heavy-lift helicopter. There are many reasons for why rotorcraft technology has not significantly advanced in the past 60 years, but I do believe that it is now on the threshold of a new generation. To put it flippantly, today's rotor-blade, which has the dynamics of a wet noodle, and the little fan at the back will never stand up to the rigors of future fast forward flight.
Just a not-so-humble opinion.
You're correct. The use of the word 'gyrocopter', while discussing the attributes required for future rotorcraft, is an oversimplification of a complex situation.
The world's two most advanced helicopters at the end of WWII did not use tail rotors and I suspect that the tail rotor will be a serious impediment to very fast forward flight in the future.
Boeing has stated " The Chinook was developed in the late 1950s, less than a decade after the B-52 bomber entered service. Since then, two follow-on bombers have been fielded, but no new heavy-lift helicopter. There are many reasons for why rotorcraft technology has not significantly advanced in the past 60 years, but I do believe that it is now on the threshold of a new generation. To put it flippantly, today's rotor-blade, which has the dynamics of a wet noodle, and the little fan at the back will never stand up to the rigors of future fast forward flight.
Just a not-so-humble opinion.
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I of course disagree with Dave Jackson, I think that the conventional helicopter layout has many advantages (mainly efficiency and yaw control) that will make it the configuration of choice for at least the next 30 years.
Dave, you wrote: "The world's two most advanced helicopters at the end of WWII did not use tail rotors and I suspect that the tail rotor will be a serious impediment to very fast forward flight in the future."
Dave, which helicopters are you refering to? I thought that the Sikorsky machines were the most advanced... Remember the german machines had serious metal fatigue problems that limited the life of many components to something on the order of 20 hours.
Also, I disagree that a tail rotor is an impediment to speed, it is a nice vertical stabilizer at speed.
What the helicopter really needs is a low cost powerplant...
Hans Conser
Dave, you wrote: "The world's two most advanced helicopters at the end of WWII did not use tail rotors and I suspect that the tail rotor will be a serious impediment to very fast forward flight in the future."
Dave, which helicopters are you refering to? I thought that the Sikorsky machines were the most advanced... Remember the german machines had serious metal fatigue problems that limited the life of many components to something on the order of 20 hours.
Also, I disagree that a tail rotor is an impediment to speed, it is a nice vertical stabilizer at speed.
What the helicopter really needs is a low cost powerplant...
Hans Conser
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The real future of rotorcraft.
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Dave's wish for new ways to do things, and new capability for VTOL, is wonderful, and the work of the cartercopter crew must continue. The reasons why the ideas he proposes have not been successful in the past are quite explicable:
1) physics - the concept of an efficient hovering machine that also goes 250+ mph usually grounds out on the rocks of lost payload. Don't lose sight of payload efficiency in the hover, that's what we do, any compromise to this forgets why we were invited to the party. From tilt rotors to jump jets, to stop rotors and reverse flow rotors, the loss in hover efficiency has never been countered by speed. In other words, the product of speed time payload is what we seek, with a safe, fully controlled hover at each end. Anyone can make a VTOL go 500 knots, but it takes a very wise engineer to make it carry something useful, and do it in normal environments (wind and such). Real figures as to hover, cruise performance, and cost are quite scarce, so far.
2) money - The DARPA/NASA/Sikorsky X wing reached no fundamental engineering limits in its tests years ago, nor did the HLH. They ran aground when they ran out of money, and showed returns marginal enough to cause the moneybags to close the pocketbook. (Remember what caused the cancellation of the original Star Terk? ratings - money - the one monster Kirk could not defeat.)
3) mania - It takes a wise designer to keep preconceptions from screwing up his design. A campaign to rid a design of a feature (tail rotor, wiggly blade) must be undertaken because something better is found, not because these things are inherently ugly. Some of us seek metaphysical harmony, not engineering sense, and this can cloud judgement. Seeking tailrotorless symmetrical rotorcraft for their own sake is not the game. Making practical, monitarily justified machines that work in the real world is the game. The cathedral of Notre Dame has the marks of centuries of structural patches on its buttresses, evidence of the hodgepoge of fixes and claptrap that from day one been used to keep it standing. Those designers were not embarassed to try some screwball fix, they did what it took to keep the enormous space within dry and warm for its occupants. Remember the old adage - if its stupid but it works, it is not stupid.
1) physics - the concept of an efficient hovering machine that also goes 250+ mph usually grounds out on the rocks of lost payload. Don't lose sight of payload efficiency in the hover, that's what we do, any compromise to this forgets why we were invited to the party. From tilt rotors to jump jets, to stop rotors and reverse flow rotors, the loss in hover efficiency has never been countered by speed. In other words, the product of speed time payload is what we seek, with a safe, fully controlled hover at each end. Anyone can make a VTOL go 500 knots, but it takes a very wise engineer to make it carry something useful, and do it in normal environments (wind and such). Real figures as to hover, cruise performance, and cost are quite scarce, so far.
2) money - The DARPA/NASA/Sikorsky X wing reached no fundamental engineering limits in its tests years ago, nor did the HLH. They ran aground when they ran out of money, and showed returns marginal enough to cause the moneybags to close the pocketbook. (Remember what caused the cancellation of the original Star Terk? ratings - money - the one monster Kirk could not defeat.)
3) mania - It takes a wise designer to keep preconceptions from screwing up his design. A campaign to rid a design of a feature (tail rotor, wiggly blade) must be undertaken because something better is found, not because these things are inherently ugly. Some of us seek metaphysical harmony, not engineering sense, and this can cloud judgement. Seeking tailrotorless symmetrical rotorcraft for their own sake is not the game. Making practical, monitarily justified machines that work in the real world is the game. The cathedral of Notre Dame has the marks of centuries of structural patches on its buttresses, evidence of the hodgepoge of fixes and claptrap that from day one been used to keep it standing. Those designers were not embarassed to try some screwball fix, they did what it took to keep the enormous space within dry and warm for its occupants. Remember the old adage - if its stupid but it works, it is not stupid.
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Hans,
What do you mean "I of course disagree with Dave Jackson, ..."
The following are a few specific responses to you concerns.
Efficiency:
All rotorcraft aerodynamists will say that current helicopters are extremely inefficient, in both hover and forward flight. A couple of reasons are;
Yaw Control:
Yaw control can be achieved by;
The two helicopters are the Flettner FL282 and the Focke Achgelis Fa223 . Both were in production during WWII. At the end of the war, Germany was restricted from continue with the development of their aircraft.
Many, many moons ago Mr. Glidden Doman chaired a dinner meeting of the American Helicopter Society. Both Anton Flettner and Igor Sikorsky were present. After the dinner, an 8mm film of the Flettner FL282 was presented, which showed the technical details of this craft. Mr. Doman told me directly that Igor was very obviously taken aback at the technological sophistication of FL282.
Flettner FL282 Transmission & Rotors shows a rediscovered and refurbished transmission & rotorhubs. For a 60 year old helicopter, it is quite something.
You mentioned "Remember the german machines had serious metal fatigue problems that limited the life of many components to something on the order of 20 hours.". The only reference to 20 hours that I can recall is from Prewitt's evaluation of the Fl282 after the war. The Maintenance section of the report says "It was interesting to note that during the twenty hours of flying this machine, no difficulties occurred in regard to maintaining the helicopter in flying condition."
_____________________
Nick,
Your points are all valid, but I think that advancements require both the dream of concept and the reality of detail.
At the risk of overselling one specific craft, Flettner and Hohenemser made a beautiful team. Flettner was the dreamer who kept on coming up with wild and wonderful ideas, whereas Hohenemser was the engineer who kept bringing Flettner back down to earth.
There must be a new future for rotorcraft, and I suspect that it will arise, in part, from the likes of Stepniewski's " Low Tip Speed Design Philosophy" and Sikorsky's "Reverse Velocity Rotorcraft Concept"
What do you mean "I of course disagree with Dave Jackson, ..."
The following are a few specific responses to you concerns.
Efficiency:
All rotorcraft aerodynamists will say that current helicopters are extremely inefficient, in both hover and forward flight. A couple of reasons are;
- The tail rotor consumes between 8 to 15% of the power, depending on whether a Western or Eastern (Kamov) spin is put on the information.
- In fast forward flight, the root of the retreating blade and the tip of the advancing blade are imparting a downward (negative) thrust on the craft.
Yaw Control:
Yaw control can be achieved by;
- Opposed cyclic, on twin rotor craft
- Differential collective, on twin rotor craft
- Lateral differential cyclic, on the propeller(s) of horizontal thrusters
- Rudder or deflectors, if located in the airflow.
The two helicopters are the Flettner FL282 and the Focke Achgelis Fa223 . Both were in production during WWII. At the end of the war, Germany was restricted from continue with the development of their aircraft.
Many, many moons ago Mr. Glidden Doman chaired a dinner meeting of the American Helicopter Society. Both Anton Flettner and Igor Sikorsky were present. After the dinner, an 8mm film of the Flettner FL282 was presented, which showed the technical details of this craft. Mr. Doman told me directly that Igor was very obviously taken aback at the technological sophistication of FL282.
Flettner FL282 Transmission & Rotors shows a rediscovered and refurbished transmission & rotorhubs. For a 60 year old helicopter, it is quite something.
You mentioned "Remember the german machines had serious metal fatigue problems that limited the life of many components to something on the order of 20 hours.". The only reference to 20 hours that I can recall is from Prewitt's evaluation of the Fl282 after the war. The Maintenance section of the report says "It was interesting to note that during the twenty hours of flying this machine, no difficulties occurred in regard to maintaining the helicopter in flying condition."
_____________________
Nick,
Your points are all valid, but I think that advancements require both the dream of concept and the reality of detail.
At the risk of overselling one specific craft, Flettner and Hohenemser made a beautiful team. Flettner was the dreamer who kept on coming up with wild and wonderful ideas, whereas Hohenemser was the engineer who kept bringing Flettner back down to earth.
There must be a new future for rotorcraft, and I suspect that it will arise, in part, from the likes of Stepniewski's " Low Tip Speed Design Philosophy" and Sikorsky's "Reverse Velocity Rotorcraft Concept"
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Dave,
Igor always commented on how the failure of many early helicopters was due to the designer seeking the perfection of balanced anti-torque through multiple rotor heads, either co-axial or otherwise. He said, "I believe in one God and one main rotor" only half in gest.
The wasted power hidden in carrying the friction, drag and weight of two transmission load paths, two full sets of rotor controls and/or the propulsive thruster is seldom given, but it is appreciable. The ABC cost 5% of the empty weight for the extra mechanism, and about 5% more drag. kamov has published similar numbers for their co-axials, with drag as probably 10% higher (due to the greater separation of their disks making a higher head mechanism.
In other words, all helos we envision "waste" at least 5% of their power, pick your poison.
I have said before, in the other dozen or so threads you have started on this same subject, that the persuit of symmetry as some mystical goal of perfection is not engineering.
Igor always commented on how the failure of many early helicopters was due to the designer seeking the perfection of balanced anti-torque through multiple rotor heads, either co-axial or otherwise. He said, "I believe in one God and one main rotor" only half in gest.
The wasted power hidden in carrying the friction, drag and weight of two transmission load paths, two full sets of rotor controls and/or the propulsive thruster is seldom given, but it is appreciable. The ABC cost 5% of the empty weight for the extra mechanism, and about 5% more drag. kamov has published similar numbers for their co-axials, with drag as probably 10% higher (due to the greater separation of their disks making a higher head mechanism.
In other words, all helos we envision "waste" at least 5% of their power, pick your poison.
I have said before, in the other dozen or so threads you have started on this same subject, that the persuit of symmetry as some mystical goal of perfection is not engineering.
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Nick,
Your points are well taken, but may be subject to a little fine-tuning.
Power Loss:
Dual rotor helicopters and 'single' rotor helicopters have two rotors each. In fact, the Chinook CH-47 has a similar load path to that of helicopters with tail rotors. The primary difference is a 50-50 power split between the rotors versus a 90-10 power split. In both cases, the total power train losses will be around 4-6%
Drag:
Aerodynamists say that drag increases as the rotor-hub is brought closer to the fuselage, due to the interaction between the two. It is also said that if the hub is brought very close to the fuselage, and the two are faired together, the drag will actually decrease.
As rotor rigidity has increased, the rotor-hubs have been brought closer to the fuselage. One of the theoretical advantages of the Absolutely Rigid Rotor is the ability to locate the rotor tight to the fuselage, and then fair them together.
Engineering
We have a difference, in that you are promoting existing products whereas I am promoting the research and development of new ones. Please don't underestimate the importance of overall conceptualization.
Conceptualization is normally done by those who know a little about many subjects. Detail engineering is done by those who know a lot about few subjects. In my company, I hired engineers to do the detail work.
Your points are well taken, but may be subject to a little fine-tuning.
Power Loss:
Dual rotor helicopters and 'single' rotor helicopters have two rotors each. In fact, the Chinook CH-47 has a similar load path to that of helicopters with tail rotors. The primary difference is a 50-50 power split between the rotors versus a 90-10 power split. In both cases, the total power train losses will be around 4-6%
Drag:
Aerodynamists say that drag increases as the rotor-hub is brought closer to the fuselage, due to the interaction between the two. It is also said that if the hub is brought very close to the fuselage, and the two are faired together, the drag will actually decrease.
As rotor rigidity has increased, the rotor-hubs have been brought closer to the fuselage. One of the theoretical advantages of the Absolutely Rigid Rotor is the ability to locate the rotor tight to the fuselage, and then fair them together.
Engineering
We have a difference, in that you are promoting existing products whereas I am promoting the research and development of new ones. Please don't underestimate the importance of overall conceptualization.
Conceptualization is normally done by those who know a little about many subjects. Detail engineering is done by those who know a lot about few subjects. In my company, I hired engineers to do the detail work.
Last edited by Dave_Jackson; 28th Apr 2003 at 05:55.
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So Dave, when you agree that the losses for various types of configurations is about 5%, you agree that the previous reference you made to an inefficient tail rotor is incorrect, right? All configurations lose about 5%, you now say. fair enough.
Regarding drag, the extra presented area of the two heads in your pet configuration will ALWAYS have more drag than a similar single rotor helicopter with one head. When you mix your magic (one config with two super-low heads, one without) you get screwy results. A synchropter will ALWAYS have more drag than a single rotor.
Regarding "promotion" of concepts, you are again confused. One "promotes" using PR, wild unsupported ideas about symmetry and balloons for the kids. One is not necessarily promoting when one sticks to the facts. As Lenin said, "Facts are stubborn things!"
Regarding drag, the extra presented area of the two heads in your pet configuration will ALWAYS have more drag than a similar single rotor helicopter with one head. When you mix your magic (one config with two super-low heads, one without) you get screwy results. A synchropter will ALWAYS have more drag than a single rotor.
Regarding "promotion" of concepts, you are again confused. One "promotes" using PR, wild unsupported ideas about symmetry and balloons for the kids. One is not necessarily promoting when one sticks to the facts. As Lenin said, "Facts are stubborn things!"
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Nick and Dave,
I have been following your exchanges concerning helicopters for a long time and I appreciate the knowledge gained.
Nick, I also am interested in alternative helicopter designs. My motivation is ease of control. I have a friend with a R-22 and he has let me take the controls many times. I also have flown many fixed wing aircraft. Except for getting your descent and landing timing correct, the fixed wing aircraft are no more difficult to control than a car. The R-22 is unstable and difficult to control and it definately has my attention when I am trying to fly it. If anyone ever made a fixed wing aircraft with the stability of a R-22 they would never sell a single one. I know all helicopter pilots find the control of a helicopter as natural as driving a car, but that is a skill aquirred through many hours of carefull study. I feel if you could eliminate all the torque compensation issues that would be a step forward in the creation af an easy to fly helicopter. Therfore I am not very concerned about small differences in efficiency (5%) since a helicopter is already a very inefficient flying machine. Also concerning drag, if speed is limited by issues such as retreating blade stall or supersonic tips does it really matter if the second rotor has more drag than a smaller tail rotor?
So, Nick I would be interested in any insight you can provide into the potential for a tailrotorless design being easier to fly. Was the ABC easy to fly? Is a K-Max easy to fly? Also, can you comment on the pros and cons of servo flap control as on a K-Max or H-43? That is another area I am quite interested in as it seems to be an easy way to eliminate some critical highly loaded hardware in the rotor head.
If any of you reading this follow the Discovery Wings channel as I do you may have seen the recent Choppers episodes where they interview Charles Kaman. These episodes show early footage of synchropters flying around doing amazing things for their time. This was while the tailrotor design was in its infancy. The narrator specifically states that the intermeshing rotor helicopters performed extremely well. But then the intermeshing rotor helicopters just dissappear. There is no mention in the program as to why seemingly overnight the were replaced with helicopters that at that time had inferior capabilities. One guess I have is the reason was political since the best intermeshing designs were German. I would be interested in any comments anyone has as to why, other than Kaman's apparantly successfull designs intermeshing helicopters have disappeared.
I know I may sound biased in Dave's favor but I am really just looking for a helicopter design that approaches the design goals of the new Cirrus aircraft which are safe, easy to fly and accessible.
Thanks,
Rene
I have been following your exchanges concerning helicopters for a long time and I appreciate the knowledge gained.
Nick, I also am interested in alternative helicopter designs. My motivation is ease of control. I have a friend with a R-22 and he has let me take the controls many times. I also have flown many fixed wing aircraft. Except for getting your descent and landing timing correct, the fixed wing aircraft are no more difficult to control than a car. The R-22 is unstable and difficult to control and it definately has my attention when I am trying to fly it. If anyone ever made a fixed wing aircraft with the stability of a R-22 they would never sell a single one. I know all helicopter pilots find the control of a helicopter as natural as driving a car, but that is a skill aquirred through many hours of carefull study. I feel if you could eliminate all the torque compensation issues that would be a step forward in the creation af an easy to fly helicopter. Therfore I am not very concerned about small differences in efficiency (5%) since a helicopter is already a very inefficient flying machine. Also concerning drag, if speed is limited by issues such as retreating blade stall or supersonic tips does it really matter if the second rotor has more drag than a smaller tail rotor?
So, Nick I would be interested in any insight you can provide into the potential for a tailrotorless design being easier to fly. Was the ABC easy to fly? Is a K-Max easy to fly? Also, can you comment on the pros and cons of servo flap control as on a K-Max or H-43? That is another area I am quite interested in as it seems to be an easy way to eliminate some critical highly loaded hardware in the rotor head.
If any of you reading this follow the Discovery Wings channel as I do you may have seen the recent Choppers episodes where they interview Charles Kaman. These episodes show early footage of synchropters flying around doing amazing things for their time. This was while the tailrotor design was in its infancy. The narrator specifically states that the intermeshing rotor helicopters performed extremely well. But then the intermeshing rotor helicopters just dissappear. There is no mention in the program as to why seemingly overnight the were replaced with helicopters that at that time had inferior capabilities. One guess I have is the reason was political since the best intermeshing designs were German. I would be interested in any comments anyone has as to why, other than Kaman's apparantly successfull designs intermeshing helicopters have disappeared.
I know I may sound biased in Dave's favor but I am really just looking for a helicopter design that approaches the design goals of the new Cirrus aircraft which are safe, easy to fly and accessible.
Thanks,
Rene
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Rene,
The decision for the market to drop one design over another never occurs in one swoop, it takes bunch of individual decisions by a bunch of different buyers to end up dropping one design over another. Also the factors that make or break one idea over another are seldom easy to convey in a Discovery Channel show, even if the producers want to go there (which they don't, because lost causes sell deodorant). I tried once in a show to discuss the effects of disk loading and efficiency, it was all cut.
The idea that politics and some dirty work help to bury a carboretor that runs on water, or a Tucker car that gets 100 mpg or a synchropter that is better than a helicopter is pure bunk, the paranoid fumings of those with too much time and too little understanding. Believe it or not, syncropters have too many parts, too much drag and too little to offer the modern helicopter market. Dave doesn't believe it, but even Charlie Kaman does. He designed the very nice H-2 long after as a single rotor because it was the best for his customer, and he sold hundreds of them.
Flight stability and ease of handling is easy to get, these days, and it does not require us to perform the dubious trick of horsing around with the physical layout of the aircraft, like removing tail rotors or making two rotorheads.
Simple, capable flight stabilization systems using microprocessors and simple sensors are so mature that many RC helicopters use them, and the whole system costs a few hundred dollars. With a push from you folks, these systems will be adapted to the machines, and a cheap hands-off helicopter will be available, for a lot less than messing around with how the rotors are bolted on and where the anti-torque comes from.
Dave's arguments for symmetry are so seductive, you can start to believe that some wonderful balance of nature will make a hands-off flying machine.
Not true! The coaxials have the same need for autopilots and stability systems as the regular helos, mostly because rotors themselves are so darn unstable to begin with. Remember all those discussions about NOTAR being so stable that it was hands off? Notars need autopilots (in some of the models) because they are less stable than regular helos.
The world is not against development and change (quite the opposite), all configurations get a fair shake in the marketplace. I am certainly against the overblown promises of yet another scheme to make the all-singing-all dancing helicopter. I do believe that some of Dave's ideas are questionable, and are based not on engineering data, but on metaphysical arguments about purity and symmetry.
The decision for the market to drop one design over another never occurs in one swoop, it takes bunch of individual decisions by a bunch of different buyers to end up dropping one design over another. Also the factors that make or break one idea over another are seldom easy to convey in a Discovery Channel show, even if the producers want to go there (which they don't, because lost causes sell deodorant). I tried once in a show to discuss the effects of disk loading and efficiency, it was all cut.
The idea that politics and some dirty work help to bury a carboretor that runs on water, or a Tucker car that gets 100 mpg or a synchropter that is better than a helicopter is pure bunk, the paranoid fumings of those with too much time and too little understanding. Believe it or not, syncropters have too many parts, too much drag and too little to offer the modern helicopter market. Dave doesn't believe it, but even Charlie Kaman does. He designed the very nice H-2 long after as a single rotor because it was the best for his customer, and he sold hundreds of them.
Flight stability and ease of handling is easy to get, these days, and it does not require us to perform the dubious trick of horsing around with the physical layout of the aircraft, like removing tail rotors or making two rotorheads.
Simple, capable flight stabilization systems using microprocessors and simple sensors are so mature that many RC helicopters use them, and the whole system costs a few hundred dollars. With a push from you folks, these systems will be adapted to the machines, and a cheap hands-off helicopter will be available, for a lot less than messing around with how the rotors are bolted on and where the anti-torque comes from.
Dave's arguments for symmetry are so seductive, you can start to believe that some wonderful balance of nature will make a hands-off flying machine.
Not true! The coaxials have the same need for autopilots and stability systems as the regular helos, mostly because rotors themselves are so darn unstable to begin with. Remember all those discussions about NOTAR being so stable that it was hands off? Notars need autopilots (in some of the models) because they are less stable than regular helos.
The world is not against development and change (quite the opposite), all configurations get a fair shake in the marketplace. I am certainly against the overblown promises of yet another scheme to make the all-singing-all dancing helicopter. I do believe that some of Dave's ideas are questionable, and are based not on engineering data, but on metaphysical arguments about purity and symmetry.
Last edited by NickLappos; 29th Apr 2003 at 01:17.
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Once again, Nick is right on the money.
Nearly every light helicopter could stand a stabilization system, and the first person to crack the cost problem for this would be real hero - if the pilots can be taught to accept it.
Far easier to design the stabilization system than to re-design the whole helicopter.
R&D, yes please, but something that has some possibility of working.
Nearly every light helicopter could stand a stabilization system, and the first person to crack the cost problem for this would be real hero - if the pilots can be taught to accept it.
Far easier to design the stabilization system than to re-design the whole helicopter.
R&D, yes please, but something that has some possibility of working.
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Oh, Oh. Up against the top guns.
Nick,
"So Dave, when you agree that the losses for various types of configurations is about 5%, you agree that the previous reference you made to an inefficient tail rotor is incorrect, right? All configurations lose about 5%, you now say. fair enough."
Not exactly. We are talking of two different sources of loss.
Virtually all helicopters have two rotors. The mechanical losses, due to friction, in delivering power from the engine to the rotors will be ROUGHLY the same for all rotor configurations, and this value will be around 5%.
The other loss is that of lift. A helicopter with a tail rotor must apply approximately 10% of its remaining power at the little rotor, just to counteract the torque of the single main rotor. The dual rotor helicopter applies all its remaining power to lift, which is generated by the two counterrotating main rotors.
"A synchropter will ALWAYS have more drag than a single rotor"
I agreed that the drag will be slightly higher, BUT, the intermeshing configuration should be faster.
This is because; its rotors are smaller, there is no tail rotor drag, and most importantly, the 10% saving in power [mentioned above] can be applied to forward thrust.
One should not think in terms of the slow Kaman Huskie. The intermeshing Flettner FL282 was faster than its contemporary, the Sikorsky R-4B.
"I do believe that some of Dave's ideas are questionable."
You're being very polite to use the word "some".
I couldn't agree more with your comment. But; ideas create other ideas, and with enough synergy the occasional good one comes forth.
Shawn,
"Nearly every light helicopter could stand a stabilization system."
True, but Gareth Padfield mentions in his book "Helicopter Flight Dynamics: The Theory and Application of Flying Qualities and Simulation Modeling " that the helicopter should first have the ability to dynamically enact the desired actions in the most effective means possible. He also comments on the importance of this when components fail.
Stability Augmentation Systems cannot be used as a Band-Aid to cover over aerodynamic or dynamic inadequacies.
Nick,
"So Dave, when you agree that the losses for various types of configurations is about 5%, you agree that the previous reference you made to an inefficient tail rotor is incorrect, right? All configurations lose about 5%, you now say. fair enough."
Not exactly. We are talking of two different sources of loss.
Virtually all helicopters have two rotors. The mechanical losses, due to friction, in delivering power from the engine to the rotors will be ROUGHLY the same for all rotor configurations, and this value will be around 5%.
The other loss is that of lift. A helicopter with a tail rotor must apply approximately 10% of its remaining power at the little rotor, just to counteract the torque of the single main rotor. The dual rotor helicopter applies all its remaining power to lift, which is generated by the two counterrotating main rotors.
"A synchropter will ALWAYS have more drag than a single rotor"
I agreed that the drag will be slightly higher, BUT, the intermeshing configuration should be faster.
This is because; its rotors are smaller, there is no tail rotor drag, and most importantly, the 10% saving in power [mentioned above] can be applied to forward thrust. One should not think in terms of the slow Kaman Huskie. The intermeshing Flettner FL282 was faster than its contemporary, the Sikorsky R-4B.
"I do believe that some of Dave's ideas are questionable."
You're being very polite to use the word "some".
I couldn't agree more with your comment. But; ideas create other ideas, and with enough synergy the occasional good one comes forth.Shawn,
"Nearly every light helicopter could stand a stabilization system."
True, but Gareth Padfield mentions in his book "Helicopter Flight Dynamics: The Theory and Application of Flying Qualities and Simulation Modeling " that the helicopter should first have the ability to dynamically enact the desired actions in the most effective means possible. He also comments on the importance of this when components fail.
Stability Augmentation Systems cannot be used as a Band-Aid to cover over aerodynamic or dynamic inadequacies.
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There we go again! You bash about the amount of loss to squeeze some hope from your arguments, Dave. The losses in this case are what they are, about the same for all configurations, no matter how you try to squeeze them.
I like your use of Gareth Padfield's book as a reference, since he and I worked together on several panels and papers. Gareth is one of the foremost authorities on how to use digital controls to improve the handling qualities of aircraft, in spite of the ideosynchrocies of their rotors. He would laugh at an argument that proposes developing a whole new rotor configuration purely to derive some improvement in handling.
I would also derive some eenjoyment at a guy who has, as his best arrow to shoot, a comparison between the Flettner and the R-4! Dave, you are as stubborn as Lu, and as likely to admit you are cornered!
I like your use of Gareth Padfield's book as a reference, since he and I worked together on several panels and papers. Gareth is one of the foremost authorities on how to use digital controls to improve the handling qualities of aircraft, in spite of the ideosynchrocies of their rotors. He would laugh at an argument that proposes developing a whole new rotor configuration purely to derive some improvement in handling.
I would also derive some eenjoyment at a guy who has, as his best arrow to shoot, a comparison between the Flettner and the R-4! Dave, you are as stubborn as Lu, and as likely to admit you are cornered!