The next big advance in flight?

[unixronin]

radarrider pointed out this article about a guy who may just have come up with a quieter, safer, more efficient replacement for the majority of helicopter applications.  This could be The Next Big Thing in aviation.

Comments

[ehintz.livejournal.com]

I'm partial to the Carter Copter (http://www.cartercopters.com/) myself... Besides VTOL capability, it can hit turboprop speeds in flight at altitude. Pretty elegant design. The single engine prototype can't hover, but the dual engine model will (by using one of the engines to counter the rotor torque).

[unixronin.livejournal.com]

Compound rotorcraft have been tried before, and so far no-one's managed to make it work well. I wish Carter luck, but I'm not holding my breath. I'm curious what they plan on doing with that rotor in high-speed flight; it's an aerodynamic problem that's never been satisfactorily solved yet. (In fact, the technical difficulty of solving it is what led Bell-Textron to experiment with tilt-rotor technology in the first place.)

[ehintz.livejournal.com]

They slow it down drastically. Something like 25rpm... at cruise the rotor is excess baggage, virtually all the lift is provided by the body of the aircraft. This solves the problem of dissymetry of lift between the advancing and retreating blades, as well as the problems with rotor tips nearing supersonic speeds. Their FAQ (http://www.cartercopters.com/faq-general.htm) has a decent overview of the engineering behind the concept...

[unixronin.livejournal.com]

OK, so they get out of advancing-blade compressibility, and the rotation's fast enough to minimize aerodynamic divergence on the rotor, but if you read carefully, they're trying to minimize the admission but they still have unsolved rotor stability problems due to retreating-blade aerodynamics at high µ.

[ehintz.livejournal.com]

I guess it's subject to interpretation... perhaps they are waffling, perhaps not-I'll certainly grant that they could be. Too bad they had the gear accident, they were going to do the attempt sometime around late Dec of '03 IIRC. I guess once they make the attempt we'll know...

[ilcylic.livejournal.com]

Neat!

I'm not quite clear though, does the one wing/engine/fan combo provide both vertical lift and forward propulsion?

-Ogre

[ilcylic.livejournal.com]

Needless to say, I hear that 100hp / 1.5 ton figure and think "Sounds like motorcycle power to weight ratios"... that'd make a bad ass way to get to work.

-Ogre

[unixronin.livejournal.com]

As I understand it, yes, the fan appears to provide thrust as well as lift. In some ways, it's a logical extension of the augmented-lift designs of some short-field tactical transports (technically including the C-130). It's unclear to me thus far how one obtains high lift at low speeds (or vice versa) with the fan/wing, though I could speculate on solutions such as varying the pitch of the entire fan/wing assembly.

[ilcylic.livejournal.com]

Well, though it would cause acceleration, it seems like you could get high lift at low speeds by speeding up the fan, thereby throwing more air over the top of the airfoil. Rolling the airfoil along the fan axis would also help give you thrust "up".

I wonder though, it sounds like this fan could cause a hell of a lot of gyroscopic effect. A big long object spinning really fast... then trying to turn. Could have exciting effects.

-Ogre

[unixronin.livejournal.com]

Oh, sure, there'd be gyroscopic effect. But remember, it's a long, not very wide, not all that heavy object. It's going to produce a lot less gyroscopic effect than a conventional helicopter rotor, I'd think.

Also hearken back to your motorcycle comment, and consider that this is rotating in exactly the same plane relative to the airframe as a motorcycle's front wheel (although in the opposite direction). If I have the picture of the resultant forces correct in my head, the effect of the gyroscopic precession forces is going to be to bank the aircraft into any turn, which would reduce the control surface deflection (and control force) necessary to achieve a given angle of bank in a turn. (But I'll freely admit I haven't actually worked it out properly and could easily have it backwards, in which case it'll generate a self-leveling moment that'll try to keep the aircraft flying straight and level.)

[ilcylic.livejournal.com]

Not that wide? (First, let me clarify. For the purposes of this conversation, "long" means "axial length of the cylinder", and "wide" means "diameter of the cylinder".)

It looks like it is remarkably wide. That is, unless it scales strangely when they get up to the full size ones, the diameter of the fan unit cylinder will be at least twice the diameter of any motorcycle wheel I've ever ridden.

Also, on a motorcycle, you turn the wheel, precession pushes you over, and you turn. This, you're going to dip a wing, initiating precession in another axis, and, I believe, trying to curve you the wrong way around.

Thoguh, I may also be wrong. I'll just have to build a long rotating tubular gyroscope, and see what it does when I twist it. :)

-Ogre

[unixronin.livejournal.com]

Oh, sure, it's wide compared to a motorcycle wheel. But not compared to a helicopter's main rotor. :)

If you think about the motorcycle, though, you start out by countersteering opposite to the direction you want to turn. Once you're in the turn it's forward pressure on the inside grip that keeps you in the turn -- if you ease off the pressure, letting the wheel turn back in, the bike comes back up and you straighten out.

In the motorcycle case, though, there's traction forces at work too, in addition to the opposite direction of rotation. The two situations aren't precisely analogous -- that's why I can't quite get straight my head what the final effect of the resultant forces will be. And I don't have anything immediately at hand right now that I can use to test it.

Or maybe I do.... hmmm. I have a big-ass fan sitting on top of my monitor, blowing air through it to keep it cool enough to work properly. If I lift it free and turn it up to high, then twist it rapidly, it confirms my initial mental image that the resultant forces as you enter a turn will tend to bank the aircraft more into the turn. Since you'll probably be banking into the turn anyway, I believe there may also be a net resultant opposing the turn.

[ilcylic.livejournal.com]

Not wide compared to a helicopter blade. True. Hrmmm.

But the mass of the unit might be heavier overall. And mass is part of what counts in a gyroscope.

You're right about the countersteering and the traction. So, again, I have no good idea what the effect will be.

I'd better just build something and test it before I go crazy.

-Ogre

[ilcylic.livejournal.com]

I kinda wonder that noone thought of this before. I mean, if I had known that people were looking for a solution to this problem, embedding a squirrel cage fan inside of an airfoil probably would have occured to me.

Oh well, anyway.

I wanna build one.

I think I was born 100 years too late. I would love to have been able to build my own car, motorcycle, airplane, whatever. Nowadays you have to jump through so many goddamned government hoops it's almost not worth the effort.

-Ogre

[unixronin.livejournal.com]

Yeah, I know what you mean. I've had all kinds of ideas that I've later discovered have Already Been Done.

[greyman.livejournal.com]

I have a big problem with this idea... squirrel cage blowers use centripetal acceleration to fling the fluid out in the radial direction. Of course, we usually surround them with a housing so the flow gets directed, but the inlet is on the *center*, and the outlet is on the *edge*.

The airflow on this thing, at 0 airspeed, would be radially outward in the unshrouded direction. You'd need an inlet on the wingtip. The air would flow in the wingtip, along the wing, and out... not only back along the wing (and not much of that) but also UP and FORWARD.

Now, I see from the picture that the blades aren't very wide, so the radial acceleration is minimized That means they don't move much air, though.

Color me confused.

[unixronin.livejournal.com]

The pictures sure make it look like the fan is at least partially shrouded; we haven't the bandwidth to play the videos. (Well, actually, maybe I could download them overnight.) The fact that they have flying models would seem to imply that on at least some level, it works. Beyond that, I only know what's on the site.