Counter-rotating ring-wing rotor

[Ian Corrigible]

One for Dave Jackson and Graviman. From Flight's DEW Line blog (http://www.flightglobal.com/blogs/the-dewline/2009/06/lockheed-martin-patents-counte.html):

Lockheed Martin patents counter-rotating, ring-wing rotor (huh?)
June 2

http://www.flightglobal.com/blogs/the-dewline/counter-rotating%20ring%20wing%20rotor.jpg

Rotor-heads, enjoy! This is Lockheed Martin's latest patent filing for a new aircraft, and it completely stumps me. The patent document [see below] explains the "wings are directly driven by engines located at the wing tips. The aircraft incorporates large-span, high aspect ratio blades or wings that are joined at their outermost tips to improve the structural characteristics of the wings. ... The design enables vertical takeoff and landing capabilities, thus simplifying launch and recovery operations for the aircraft.Apture™

Interestingly, the publication of this patent filing on May 21 came only two weeks after a senior Bell Helicopter executive told me thinks Lockheed wants to jump back into the helicopter market (remember the Cheyenne?).

I/C

[ShyTorque]

(remember the Cheyenne?

Or even the Fairey Rotodyne, which is one place the tip-jet idea could have come from?

[Graviman]

Ian,

The philosophy behind this is that if you make an aircraft complicated enough it will fly. I wouldn't want to be the guy that had to package the swash plates, or figure how it altered pitch without the flex in the blade tips overcoming the "improved stiffness". It looks more like UAV fairyland to me. :}

What they want is a nice simple gearbox with a coaxial pair of deep section rotor blades. Trouble is that won't patent. ;)

Anyhow, i thought Lockheed were already involved in EH101 --> US101 ...

[slowrotor]

Why two rotors?
Tip jets are torqueless, no need for counter-rotation.

Must be a UAV.

[maxtork]

Well helicopters have often been called flying egg beaters...this concept takes that name to new levels!

Graviman...I agree that swashplates and pitch control would be difficult with that layout but I was thinking of another way they might make it work. What if you could cyclically vary thrust of the engines that are driving the rotors? As the engine comes around to the advancing side you increase thrust and decrease it on the retreating side. Since you have a coaxial it should balance out with a net forward thrust eaqual on both sides. Now the rotors are just to provide lift but directional thrust and therefore control of the craft is produced elsewhere. It would probably be easier to do this with variable pitch props instead of some type of jet. It could be something if it was scaled up to a very large aircraft that did not need great speed and had very large diameter rotors which would lower the rotor rpm.

Yeah I know, I know...there I go thinking again...one of these days I'm gonna hurt myself!

Max

[handysnaks]

It looks like a pair of conveyer belts designed to prove (or disprove), some jetblast theory!

[Dave_Jackson]

There must be something to it.

They have started testing its ability to withstand projectiles. Video of flight testing. (http://www.bigassfans.com/gnaw)


Dave

[Graviman]

Max, the problem is the one that most of these concepts overlook: autorotation... :uhoh:

[maxtork]

Yes this is true...an auto would be a bit tricky with no control!

Max

[Graviman]

Max, an auto is even harder when the rotor stops turning. ;)

Actually this is a gripe of mine with many of these rpm varying personal helicoper projects - most using fixed pitch propellors. At the very least a feathering bearing with Rel AOA controlling tip tab would get into a stable auto. With low enough diskloading (or a flare from forward speed) the descent would be survivable... :uhoh:

[maxtork]

Grav,

Yeah the rotation helps a bit too! Actually I was envisioning a system like the one you described with a feathering bearing and some sort of collective pitch control on the rotor but using the variable thrust in place of cyclic control. As you said it may make for a survivable rate of decent but I don't think I would want to go out and purposely fly an aircraft that provided no controls during an auto. It may be workable for a UAV though but you would still have to worry about what the thing would land on in case of a power outage.

I agree with you on the kit type helicopters with fixed pitch rotors. I remember seeing one that had four small engines driving two fixed pitch coaxial rotors. I guess the idea was that an engine failure would only cause a 25% loss in power leaving enough to find the ground safely. I guess everyone has their own take on that risk assesment but I don't think the trade off between less complexity and safety is a good one in this case.

Max