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Carter Copter Breaks Mu-1 Barrier
tyler_larson writes "Just over a week ago, Jay Carter's CarterCopter
managed to break a significant rotorcraft barrier, traveling at a mu ratio of 1. This 1-to-1 ratio (sometimes called the mu-1 barrier) represents a condition where the forward speed of the craft is the same as the speed of the tip of the rotor. This means that at a certain point, the tip of the retreating blade is "standing still" relative to the wind and producing no lift, while the rest of the blade is actually moving backwards through the air. Such a condition is normally impossible for a rotorcraft, and so the forward speed of a helicopter is limited by the the speed of the rotors. This accomplishment by the CarterCopter, which some insisted couldn't be done, proves that this new craft is not subject to that limitation."
The whole thing is moving forward while parts of it are moving backward or standing still at the same time?
:D
Sounds suspiciously like a certain operating system
Q: How fast can a helicoptor travel?
A: Mu
Obviously the Carter Copter has much more cow bell than previous attempts.
Hmmm, it looks lie it blurs the line between a helicopter and an airplane. That thing has pretty darn large wings. I guess the big deal is really having the rotors not "get in the way" traveling at that speed, since the wings really are providing most if not all the lift? What happened to those experimental copters that you could actually just shut down the rotors and have them be fixed during forward flight?
I was actually surprised to hear about the mu limitation concept. Swimmers for examle might actually swim faster than their handspeed through the water - an efficient swimmer miht actually take his and out of the water at a point AHEAD of where the same hand entered the water.
For the purposes of this, do they measure air speed or ground speed? If it's really one of those things considered to be "impossible", could it just have been a heavy head wind?
No comment.
I fly radio controlled helicopters all the time and worked for Bell for quite some time. Although this is a great accomplishment, it doesn't really break the mu-1 barrier because it is a hybrid between a helicopter and an fixed wing airplane. This is like saying "fixed wing aircraft don't need a runway" when the harrier came out. Regardless, mu-1 will always be here for the purists.
Hmm... are you referring to the V22 Osprey?
The owls are not what they seem
I do not really understand the hype. This copter
- has quite long wings, that provide lift force as in conventional airplanes, compensating for the lack of lift on the rotors when going "fast"
- has an extra vertically mounted rotor like in conventional airplanes, providing extra propultion
- barely breaks the mu barrier (1.02, and also for a very short time) with the rotor turning very slow (-> slow air speed)
So... I do not see where the break-throug is... Could somebody explain?
They cheated! It has wings.
One other way of dealing with the asymetric lift in high speed rotorcraft is to use 2 contra rotating rotors, for example the russian Kamov helicopters.
The site is dashslotted so I can't see any diagrams, but I'm having trouble picturing this. "the tip of the retreating blade is 'standing still'" made sense, but how on earth would the rest of the blade be "actually moving backward through the air"? The retreating tip stands still, but then the rest of the blade can only be moving more forward than that.
What am I missing?
xkcd.com - a webcomic of mathematics, love, and language.
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the carter copter cannot hover and it is relying on a prop on the back to provide the thrust needed for forward flight. what they have achieved is limiting the flutter associated with the approach of mu = .75. So yes, the parent is right, this is no better than a harrier with a rotor instead of motorized engine exhausts.
This means that at a certain point, the tip of the retreating blade is "standing still" relative to the wind and producing no lift, while the rest of the blade is actually moving backwards through the air. Such a condition is normally impossible...
Actually such a condition is completely impossible. If the tip of the blade is stationary and the rest of the blade is moving backwards, then the axle/chopper is moving backwards. Clearly the chopper and blades are screaming forwards except for the tip of the blade on one side which is stationary.
Karma police, I've given all I can, it's not enough, I've given all I can, but we're still on the payroll.
If a rotor on a moving craft moves quickly enough that the tip-speed is equal to the speed of the craft, then the tip of the rotor will stand still, relative to the surrounding air on its way backwards.
But all other parts of the rotor move *slower* than the tip, so no part of the rotor will move backwards relative to the surrounding air. That's just bullshit.
Also I think the mu-1 ratio has always dealt with the fact that most modern helicopters deal with rigid wings and the lift generated is from around 3/4th distance from the central point. I don't know if that's going to hold for the future (just like moore's law when quantum computers come... sheesh ).
Insult me if I'm wrong. And TFA is slashdotted already . Can't more people use greasemonkey cacher ?.Quidquid latine dictum sit, altum videtur
This means that at a certain point, the tip of the retreating blade is "standing still" relative to the wind and producing no lift, while the rest of the blade is actually moving backwards through the air
If at a certain condition the tip of the retreating blade is "standing still" relative to the wind, and the copter (i.e. the center of the rotor) is moving forward, then there is no way for the rest of the blade to be moving backwards.
At this situation, if you take the speed (relative to wind) of each point of this blade when it's perpendicular to the direction of the moving copter, it's zero at the tip, and equal to the copter at the center of the rotor. If the copter is moving forward through the air, no part of the blade can be moving backwards through the air. In relation to the air, the slowest moving part of the blade is that tip with zero speed. All other parts of the blade have positive speed.
The tip of the rotor stays still in the air. The rest of the rotor is swinging toward the rear of the aircraft more slowly than the tip, and therefore moving forward in the air.
However, it is _facing_ backward, as this is the retreating blade of the rotor we're talking about. The air therefore pushes against the _trailing_ edge of the rotor blade (except at the tip, which experiences an eerie calm). In a regular helicopter, the air only ever pushes against the _leading_ edge of the blade.
Thus, the blade moves backward relative to the surrounding air, though it is still travelling in the direction that is forwards for the helicopter.
Now, wash your mouth out with soap. You could have just said 'I don't understand' rather than making with the rudeness and attitude. WTF is up with American public schools??
Whence? Hence. Whither? Thither.
We are talking about Relative motion here. Imagine me running west for an hour. Ideally I have run about 10 kms in that hour - but from the perspective of someone stationary in orbit (I mean someone stationary with respect to earth's gravity centre) - you have moved around 800 kms (depending on where the observer is, calculate tangents and multiply by cosine of your lattitude to get correct answer).
Anyway, the fact here is that - the relative velocity of the tip of the wing with respect to the air around it is Zero. Zero air speed over the wing == zero lift and down comes the copter.But the speed of the wing parts nearer to axle is lesser - but since this is the retreating part of the wing - it does go forward with reference to the air speed (ie it's air speed is positive). Since we always assumed that the air speed of the retreating wing is always negative (ie it moves backwards) , this essentially puts extra stresses on the wing planes.
Ah !!Quidquid latine dictum sit, altum videtur
...all four hooves are off the ground at once!
I've got pictures to prove it!
I've heard a (traditional airplane) pilot who took a few helicopter lessons refer to it as "ten thousand components doing their best to come apart".
Knights do not say mu. Kittens say mu.
"Oh drat these computers, they're so naughty and so complex, I could pinch them." --Marvin the Martian
Hmm... are you referring to the V22 Osprey?
From the sound of it he is referring to the Sikorsky X-Wing The idea was to build a conventional helicopter that had rotors who generated lift no matter how they were oriented by using compressed air that was bled over the rotor surfaces to create lift. I am no aerodynamicist but I think this concept is called a boundary layer control system (like blown flaps). The X-Wing would thus be able to take off like a Helo but could fix the rotors in place and have them act like conventional wings for high speed flight. The X-Wing was abandoned in favor of the V-22 which is a more elegant if troubled solution. I rather liked the X-Wing though it was the closest engineers ever got to creating a real world AirWolf.
Only to idiots, are orders laws.
-- Henning von Tresckow
Q. Does a cow have a buddha nature?
A. Mu.
Aide-toi, le Ciel t'aidera - Jeanne D'Arc.
From the picture given, it looks like they've got an alternate engine just under the rotor. And considering the wings, they could just go really fast, glide, then slow the rotor speed to match the forwards velocity.
Quidquid latine dictum sit, altum videtur
you've got a fixed wing and a rotating wing.
when the slow portion of the rotating wing stalls, the forces on that wing go all out of whack and the thing vibrates like hell (that's the technical term anyway). If you make the transition smooth, and have an alternate source of lift, the fixed wing, you can keep flying.
it's neat, but it's ASFAICS it's got little practical value.
another way to make a helicopter fast is to make a smooth transition between sub-supersonic for the fast end of the wing. SOA is still pretty effing noisy though.
Fast and smooth comes from counter rotating wings. In all cases, rotating wings are much less efficient than fixed because of the much wider airspeed envelope the operate in.
I've traveled twice in an ex-Soviet military helicopter. The second time, only because the alternative if I wanted to get back was even worse.
I understand these are pretty reliable as helicopters go. And twice was enough to last me the rest of my life. So my reaction to this achievement is, perhaps unadventurously, Dangerous, ludicrously expensive and environmentally unfriendly form of travel made even more excitingly dangerous,ludicrously expensive and environmentally unfriendly. Wow.
Panurge has posted for the last time. Thanks for the positive moderations.
Since the tip that's moving a zero speed, the other parts of blade (towards the rotor) will move 'backwards' relative to the air, causing a negative lift. However, I don't see the use of all this. Why not increase the rotor speed?
Owned by Fanwing for quite some time now.
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if they just make the wings on the side a LITTLE bigger.
"He's a real midnight golfer"
Now give the craft a forward velocity of 100 kph.
Sure, now the blade on the return side is stagnant (unmoving) relative to the airflow, but only at exactly 1 point. At all other angles, its not.
Now, to get rid of even that one point, increase the tip rotational speed to 200 kph
The blade is now providing lift even at that point because it is still moving at 100 kph relative to the local airflow.
With the kamov helicopters, for example, the http://www.ctrl-c.liu.se/misc/ram/ka-50.htmlHokum .
;)
However, like the space race, we try to ignore what the russians managed to do first, eh?
http://www.frenchgeek.com/
Unfortunately, this doesnt help me with my helicopter flying ability in battlefield 2: I still keep doing the same thing:
"Hey, you guys in my copter, I'm pretty sure this thing can break the mu-1 barrier! See, check it...."
For some reason, I get a ton of "You have Teamkilled some guys" messages, then a little later, I'm back at the server browser. I think Battlefield 2 is dumping me whenever I get close to the mu-1 barrier.
Next time, I think I'll try the apache...
Vincent J. Murphy
Spandex Justice
still american black ops have had one that fast and it runs silent. Didn't anyone one see conspiracy?
--- Strange but true facts. I can't cook
They are using a slow rotor speed to allow them to get high speeds. 100kts rotor + 500kts airspeed gets near to mach 1.
Normally the lower limit is MU as the returning blade starts to go slower than the aircraft and loses lift.
The upper limit is the advancing blade reaching mach 1 which produces too much drag.
If they increase the rotor speed thay cannot get the higher speeds and normaly mach 0.5 is the upper limit.
By exceeding mu they allow themselves to exceed mach 0.5.
So many airspeed questions...
but is it an european or an african helicopter ?
was said to be impossible too, but it happened...somehow.
http://www.walkingtaco.com
Does it come in black?
WARNING: Smartphones have side effects--most of them undocumented.
It's the KLF (also knows as the JAMMS), furthermore known as the Justified Ancients of Mu Mu that go "Mu" :)
Troc.
Troc's dubious podcast and blog: http://www.trocnet.net
2) Increasing the blade speed is only possible until its air speed = mach 1 and then things shake apart. Lots of helicopters can go over 100MPH, it's getting to 350MPH (mach 0.5) that's a problem. You have forward motion of 350mph and with a "stationary" blade tip on one side you get 700MPH blade tip on the other side. Then you're done.
Even fixed wing aircraft with a propeller keep their tip speed at or below about 0.9 mach. Above that speed really bad things start to happen.
Also, iirc, around the time of the first OPEC crisis, McDonald-Douglas was working on a supersonic turboprop with 6 curved blades per engine.
They mesure airspead. Groundspead is totally irrelivant.
:-/. It's quite an amazing machine.
Yup. Groundspeed is only relevant to the persons inside the aircraft who are in a hurry to get from point A to point B in some amount of time. To the aircraft itself, any aircraft, the only speed it knows about is airspeed. By definition, mu is a ratio based purely on airspeed.
BTW, I've seen the CarterCopter up close and personal once... even got to touch it, but they wouldn't let me sit inside for a photo
The CarterCopter never claimed to be a helicopter... only a rotorcraft. (Gyroplanes and helicopters are both types of "rotorcraft"... FAA's definition) The CarterCopter folks only wanted to be the first "rotorcraft" to break 1.0 mu. Still, it's pretty neat what they've accomplished with their applied engineering and they've acually built and flown their machine unlike many other hyped up experimental flying machine concepts such as Moller's Skycar.
Tilt-rotor aircraft aren't gliders. Anyways, the X-Wing's been mentioned, but there have been other canard rotor wing (CRW) designs. The concept's been around since the 70s, though more recently has Boeing started to re-investigate it. One of the main problems with it is that efficient rotors and efficient fixed-wings have some contradictory requirements, like blade/wing size and blade twist. The blade/wing doesn't make a good rotor nor a very good wing. But they're working on it.
I was having a tough time of this too until you pointed out IT IS THE BLADE not the Whole Propeller!
If you look at the whole Propeller if the outside tip is rotationg around the object at X speed and object is moving at X speed relitive to the ground. then one side of Propeller is moving at 0 to the ground and the oppistie side is moving at 2X to ground.
Now when you view a single blade in the above. When the tip is moving at 0 to the ground, then center of the blade is still moving at X. So the leading edge of the blade, pointing to rear of craft (oppisite in direction of X) is no longer cutting though the air, bu actually the rear edge of the blade near the center hub is Cutting though the air in at X.
This view then leads to the view - if a helicoper was a fixed wing craft... the faster you go the short the wing becomes oneside of the craft and the longer it becomes on the other, until there is not enough control surface area to keep the plan in level flight.
It used to be considered impossible to sail a boat upwind, too. The world of fluid dynamics is full of weird cheats, so the word "impossible" really shouldn't be used in describing yet-unacheived feats in the field.
There's no failure quite as dissatisfying as a complete and total solution to the wrong problem.
Well you referenced him, didn't you? In any case I don't find world records of any real significance, though the Lynx's BERP blade tip design was pretty remarkable.
I suspect the wings on that "helicopter" provided the lift during "mu-1" flight instead of the rotors.
Boeing is/was working on a UAV with a rotor blade for VTOL that locked into position for plane flight. However, I haven't heard anything of it since I read about it crashing on the Boeing news site.
"It's not that helicopters actually fly. It's just that they're so ugly, the earth naturally repels them."
-- Any jet jockey
Instead of defeating the Mu-barrier (retreating blade stall), it would impress me more if they could overcome compression effects when the forward-moving blade gets close to the speed of sound.
Page is down for me, but for those curious there are more funny things you won't believe they can fly (German text, but some pics). I saw one of these 2 weeks ago, looks _very_ strange how they fly. The top rotor is not driven by an engine, only the rotor on the rear. The top rotor is then rotated by the wind, giving lift to the aircraft.
Does the Boeing V-22 Osprey fit the bill? It uses helicopter-like rotors for VTOL, but then these switch to be forward-facing to provide it with conventional airplane capabilities. Although its hover capabilities are pretty good, it won`t replace the harrier-style entirely. The harrier-VTOL concept makes the VTOL part very inefficient, because the use of that vehicle requires it to be high-speed in other circumstances (harrier is twice as fast as the Osprey). It`s all engineering trade-offs.
Don't see what the big deal is. As I recall, Airwolf could do that all the way back in 1985.
This beast looks like a prop plane with top-mounted prop. Has anyone got a jet version designed? If Carter's Mu-1 tech leaves Mu as far behind as supersonic tech did Mach-1, what will vertical jet craft look like?
--
make install -not war
They get extra lift from the stubby little wings on its side. If they subtract those wings from the lift equation are they really going faster than MU. They could just get up to speeed, shut down the rotor and glide.
Kittens say mu.
Especially Greek kittens.
"I'm not impatient. I just hate waiting." - My Dad
I'm one of the engineers for Carter Aviation Technologies. I'm also the webmaster. I've been reading through a bunch of the comments above, and thought that I'd just comment on a few of them. I know I'm not keeping all of the threads together, and that this post is rather long, but I have a lot of work to do today, and don't have time to keep track of a lot of threads. This will be my only post. If you want to specifically ask me anything, my e-mail address is jrlewis_at_wf.net.
The significance of mu-1 is that it allows you to slow down the rotor blade to reduce rotational drag, and keep the advancing blade from going so fast as to get into compressibility effects (close to the speed of sound). This lets you fly a whole lot faster on less power. The reason we don't just stop the blades is explained in our FAQ. But basically, keeping the rotor spinning gives you centrifugal force to help support the blade. If you stop the rotor, it becomes a wing, and then needs all of the same structural requirements of a wing, which adds a lot of weight. For high speed subsonic flight, the added weight more than offsets the drag savings.
The CarterCopter was only a technology demonstrator, meant to prove the high speed portion of the flight. For that regime, we plan for the rotor to be in autorotation, so we designed our prototype as a gyroplane. We figured, why add all the extra components to our demonstrator when hovering flight with a rotor is already a well understood concept? Future production versions probably will have true helicopter capabilities, but the rotor will still be in autorotation at high speed. That's not to say that a gyroplane isn't practical. Most uses of helicopters are for their vertical takeoff and landing ability, not their hovering. Only specialized missions, like search and rescue, require hover. As was demonstrated back in the 30's and 40's, autogyros are capable of "jump" takeoffs by prerotating the rotor prior to takeoff, and can easily perform zero roll landings.
When we say that the retreating blade has reverse flow, we are looking at it from the frame of reference of the rotor blade. With no forward speed, air flows over the rotor blade from leading edge to trailing edge. As you start moving forward, inboard portions of the retreating blade see airflow from trailing edge to leading edge. At mu-1, all airflow inboard of the tip is from trailing edge to leading edge, which makes the blade unstable. So we've devised and demonstrated a way to keep the blade stable with total "reverse" flow on the retreating blade.
I saw someone mention world speed records of helicopters. The thing to remember is that speed records aren't always set by efficient machines, which is what we're trying to accomplish. The official record was the British Westland Lynx, at 249 mph. The unofficial highest speed I've heard of is a heavily modified Bell Huey. It was so inefficient that it could only fly at high speed for about 15 minutes before running out of fuel. It's top speed was somewhere around 315 mph. But, what we've accomplished is efficient high speed flight. We think that future versions (jet powered) will be able to fly at 300-400 mph.
Finally, regarding the website, I apologize for the site going down this morning. We were not expecting to be on /. and get a lot of traffic. A couple months ago, we were on 60 Minutes, and the producers told us to expect millions of hits. I did a lot of work, temporarily moving the site to a different server, and we got jack sh_t for traffic. Now, all of a sudden, we get on /. and I get caught with my pants down. But what're ya gonna do?
Kittens give Morbo gas.
A helicopter is a collection of spare parts flying in close formation, centered on an oil leak.
(I used to "fix" helicopters)
I used to have a cool sig, back when I cared
You say:
'In a regular helicopter, the air only ever pushes against the _leading_ edge of the blade.'
That's not correct.
You describe what is going on at mu-1 accurately. But actually, there's another way to use mu. mu is the percentage of the retreating blade which is moving backwards in the air (relative to its direction of rotation).
For example, if a helicopter is stationary (mu-0), then all the retreating blade is moving forward in the air.
At mu-1 the entire blade is going backwards (except for an infinitely small area at the tip).
At mu-0.1, then the inner 10% of the blade is moving forward (along the direction of rotation) slowly enough that the direction of travel overcomes this and it is slipping backwards through the air.
So at any speed over mu-0, a portion of the retreating blade is going backwards. And since regular helicopters can exceed mu-0, your statement that in a regular helicopter air only ever pushes against the leading edge of the blade is incorrect.
So it looks like perhaps you should refrain from teaching both geography and aerospace engineering.
http://lkml.org/lkml/2005/8/20/95
Their site is currently running at 1-FU ...
... didn't need to see a glorified helicopter anyways.
It's the point where you're only able to get in as fast as the screams leaving their NOC.
Oh well
-c
They did crash the thing at some point, it impacted the ground at about 70 MPH, the gear absorbed most of the impact, and the only part of the thing that survived was the cockpit, which was relatively unharmed.
I wonder if two counter rotating blades mounted on small winglets on either side of the fuselage would allow a mu of greater than 1 without unbalancing the lift?
If you are not allowed to question your government then the government has answered your question.
I'm a MechE who did an internship at Sikorsky 3 years ago. They had an "Intro to rotorcraft" pamphlet which was rather enlightening.
What gets me the most is that fundamentally, it's an unstable flying machine. But each corrective measure yeilds a slightly lesser instability, which requires further adjustments.
Yes, each blade changes pitch during rotation. Advancing blade flattens out, while the retreating blade increases pitch. This keeps the copter level.
To generate more or less lift for altitude adjustment, there is a "collective" pitch increase or decrease in addition to the cyclic pitch adjustment.
But what I didn't understand overall was that the rotor blades do not rotate in a flat plane. They rotate in a wide "cone" whose central axis indicates the overall main rotor force vector. By changing the shape of the cone, you change the direction of the force. This is done by "flapping" each rotor blade, like a bird wing, with respect to the central hub. So, for a helicopter moving forward, a given rotor blade will swing up on the back half of it's rotation, and drop back down for the forward half of the cone. The inclined angle allows the blade's aerodynamic lift to provide a forward component of thrust. This "cone" is adjusted for whichever direction the pilot whishes to move.
The tail rotor, as most people know, provides the counter rotating force from the main rotor. But it also provides a sideways thrust, so without correction, the entire helicopter would drift sideways. So to correct for this, the main rotor blades always flap slightly on one side to counteract this effect and keep the helicopter stationary.
Rotor blades not only change pitch and flap, but they also lead and lag freely. The angle between blades as viewed from above is not always equal. The main reason is that not only do you have stall speed problems on the retreating blade, but you've got shock wave problems on the advancing blade.
It's all a tricky balancing act.
"No fair, you changed the outcome by measuring it!" - Professor Hubert J. Farnsworth
The British flag in an apparent outline of Great Britain goes to this link:
http://www.gyrotec.de/Navi/Navigation-eng.htm
The other response calls it a gyrocopter, the English page calls it a gyroplane, and the name I usually heard is autogyro.
Unfortunately, there's no American version of the website. {emoticon}
Tag lost or not installed.
Airwolf could do Mach1, and shoot down migs! Where is Stingfellow Hawke anyway?
The difference is, the Hokum has two counter rotating main roters, so while one is stalling on the left, the other is generating lift, and the same on the right.
. gif
This also prevents the Hokum from falling out of the sky when the blade tips become super sonic which also causes the blade to lose lift.
This is why the Hokum has such a high top speed, not because of brute force, but because of good design.
http://www.inetres.com/gp/military/ar/rotor/Ka-50
In the movie The 6th Day, there was something that looked like a tailless helicopter with twin blade rotors that were unusually wide and could lock into swept wing position when transitioning from helicopter mode to fast, jet assisted flight. There's a lame picture in the link that doesn't really do it justice. If anyone can find a better link...
Signatures are a waste of bandwi (buffering...)
I have been following the Carter Copter for almost twelve years now and finally they have achieved what they stated (back in 93?) was one of their primary goals.
Congrats to the Carter Copters team! NASA should be proud or at least pleased that this is yet more support to the feasibility of SATS.
The truth suffers more from convictions than from lies.
I gather that's greater than mu=1. Plus, the sonic boom makes for a nice shower of rotor fragments over your enemy.
The site even says it's a hybrid fixed-wing/rotary-wing: no one said a hybrid couldn't break the mu-1 barrier. And the statement that "When the tip is stationary, other parts are moving backwards" is false, too. The tip is the extremum.
In a standard modern helicopter, is any of the rotor's airfoil (ie near the center) in negative airflow? Or is it spun so fast that none of it is? Or is that the point where the airfoil ends next to the hub?
It would seem to me that the ideal design for a helicopter is to make the rotor be a long non-lift pole with the airfoils only at the ends, so there is no airfoil in low or negative wind. Obviously that is not how they are built, instead the airfoil goes almost to the hub and has pretty much the same cross section over the entire length. Any explanation for this?
Probably because this article had nothing to do with speed other than the ability to break a theoretical barrier which could lead eventually to breaking a speed record.
If you are not allowed to question your government then the government has answered your question.
You forgot to mention that it crashed on a subsequent flight and sustained considerable damage.
While a Harrier isn't particularly "stealthy" to begin with, add rotor blades to the top of it, and any chance it would have in a hostile electronic environment is completely gone.
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I would think a design similar to the ka-50 would be able to operate at MU-1 without unbalancing the lift. However, they haven't done it, which is the point of the article, I think.
Also, I could not find any reference to the blades of the KA-50 operating at supersonic speeds.
If you are not allowed to question your government then the government has answered your question.
Tom Swift invented something like this a long time ago. I believe it was called the jetcopter or something like that. At speed, lift was provided by wings. But, instead of leaving the rotors stupidly windmilling above the jet (which was supersonic, BTW), they were folded up and put away.
The Moller Aircar (www.moller.com) has the same capabilities as the Carter Copter (except for the minor detail that it has been vaporware for the past thirty years or so). It gets vertical lift from ducted fans. Ducted fans require more energy, but you don't need to hover for very long under normal circumstances.
21 M ???
aarghhh
I'm on a modem... (the orginal fit on one 360 K floppy!!)
great job anyway, I'll see if I can download it somehow
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I never understood why they don't make a hybrid plane/helicopter with wings, a jet engine, and rotor blades. I'm not sure how easy it would be, but the design would be much better than something like a harrier, which is probably one of the worst designs as far as veritcal liftoff goes.
While this sounds like a nice idea a first its suffers from the fact that it is quite impractical. For example, at the high speeds at which jets typically operate the rotor blades would significantly increase the drag over the stream lined jet body, if not making the handling characteristics altogether unstable. Also the wings will interfere with the rotor downwash, reducing lift and making the flight more unstable. Of course there is also the issue of increase weight of the dual system further increaseing the power and fuel requirements of the craft. This is why VTOL planes stick with a single propulsion system, such as a jet with thrust vectoring or mini-rotors that can be rotated and function as propellers.
I'm surprised that nobody else has noticed that this craft isn't a helicopter -- it's a gyrocopter, and there's a huge difference!
Yes, the Mu still applies, but gyrocopters pre-date helicopters by several decades and are far simpler in design.
Except when pre-rotating, an autogyro's rotors are un-powered and are not connected to the engine.
A gyrocopter's rotors simply windmill in the airflow generated by the craft's forward motion or passage through the air.
In theory, gyrocopters are safer than helicopters (since they're already autorotating/gliding) at all times, thus reducing the risks associated with engine failure) but the reality is that there are far more autogyro crashes per craft-flying than there are helicopter crashes.
Just around these parts alone there have been two serious autogyro crashes in the past 12 months.
The autogyro concept has been revised and reinvented numerous times since the mid 1930s, but none of these new incarnations have ever been a commercial success of any scale.
Anyone know what the 55lbs of depleted uranium in each blade tip called out on the drawing at http://www.cartercopters.com/first_proto.html is for? I can imagine that they needed the centrifugal force to keep the blades rigid regardless of wind flow over them, but why go all the way to depleted uranium? Seems it would limit the producibility a bit.
It wasn't *really* off topic. That was on the bottom of their page.
rewriting history since 2109
This thread sounds like it has people who know what they're talking about, so here goes:
Given that mu is the ratio of "the forward speed of the craft to the speed of the tip of the rotor", I'm not sure how this is possible. When I see that statement, I take that to mean the maximum forward airspeed of the rotor tip is the same as the airspeed of the rotorcraft. If this is the case, isn't the blade standing still!? Think about this: when a blade-tip is perfectly perpendicular to the helicopter (longitudinal axis)and on the advancing side, if its airspeed is the same as the helicopter's, it shouldn't be moving relative to the helicopter...
So can someone unravel my confusion?
RTFA.
They got to MU whilst travelling at 170kts and manually reducing the rotor speed to 107 rpm (a meaningless coincidence that those numbers look similar) - not mach 0.5. They achieved mach 0.5 at a much higher rotor speed.
-- Brendan Hills
Three points to note:-
1) Helicopter blades have hinges near the hub allowing the blades to move up and down independently (flapping).
2) The blades are not flat during flight, they form a cone. The angle of the cone is dependent on the weight of the Helicopter. As pitch is added to the blades via the collective lift increases causing the blades to flap up and form a cone. The blades will continue to flap up until the lift is greater than the weight of the Helicopter when the flapping will stop and the Helicopter will lift off the ground.
3) Although the blades form a cone, they are known as the disc. It is the disc that flies, the fuselage is just hanging off it.
Consider a Helicopter hovering in still air, the blades form a cone with its axis perpendicular to the ground.
No consider a breeze of x knots starts to blowing towards the front of the Helicopter. The advancing blade will create more lift and the retreating blade will create less lift. When the blades are in line with the fuselage the lift will be unchanged.
Following one blade from the point where it is in line with the fuselage and at its rearmost position, as it moves round lift is increasing. This will cause it to flap up. The act of flapping up will change the airflow over the blade as it now has a vertical component. This vertical component will reduce the angle of attack of the blade thereby reducing lift. So equilibrium is achieved by the flapping rate counteracting the increase in airflow over the blade.
Once the blade is again in line with the fuselage, but now in its foremost position, there is no increase in airflow, so the blade no longer flaps up.
The blade now becomes the retreating blade and the airflow across it decreases. This will cause the blade to flap down, again changing the airflow by introducing a vertical component. This time, however, the change in airflow is opposite to that on the advancing blade. This causes an increase in the angle of attack and increases lift. And again an equilibrium is reached, but his time the flapping counteracts the decrease in lift due to decreased airflow.
So we can see that the lift has remained constant without any input from the pilot or magic pitch changing mechanism that somehow "knows" whether the helicopter is flying forwards, backwards or sideways, and therefore which is the retreating or advancing blade.
Unfortunately, that is not the end of it. What has happened is that the blade has flapped up while advancing, and flapped down while retreating. The result of this is that the blade is higher at the front than it is at the back, or that the cone has been "tilted" backwards (known as flapback, unsurprisingly). This tilting of the cone will cause the disc to fly backwards, i.e. in the direction of the breeze.
As the Helicopter is just suspended under the disc, inertia will create a delay before the fuselage follows the disc, and when it does so the hub will move first causing the shaft driving the rotors to tilt backwards. The effect of this is to increase the tilt of the disc and speed up the rearwards flight until the whole helicopter is moving backwards.
Once it is moving backwards the fuselage will try to return to its original position under the disc. this will tilt the drive shaft forwards again and slow the rearwards flight down. But the fuselage now has momentum and will continue rearwards, thereby tilting the disc further forwards until the momentum is overcome.
When the fuselage starts to move back to its original position again...
If unchecked by the pilot this oscillation will increase until it is irrecoverable. Hence, whilst they are statically stable, helicopters are dynamically unstable. But they are just so much fun.
Trust me, I'm a helicopter flying instructor.
Yeah, there have been a number of gyro crashes, specifically on one make of gyro. A research unit at Glasgow University discovered that this was due to a design fault that caused the aircraft to become unstable in some situations, leading to the dreaded Pilot Induced Oscillation (PIO).
A retro-fit is now available: the engine angle is adjusted so that the line of force passes through the aircraft's centre of gravity, and an enlarged tailplane is fitted.