The spread between the Coaxial-ABC and the Interleaving-ABC will be even greater.

Dave

Dave,
What is the drag penalty for those two masts sticking up, with not only double the profile drag, but also interference between them? That's one thing that seems unequal.
As far as the 15% benefit with respect to disk area, how much of that is undone by the fact that the lift vectors of the synchrocopter waste some of their effort against each other, since they are inclined outwards? You could probably do a ROM estimate of the lost lift of each rotor by multiplying it by the cosine of the shaft angle.
I have read that the original ABC had big vibration problems. It had two 3-bladed rotors. How is anything with 2-blade rotors going to be better? I would bet you would have a hard time getting to respectable single rotor helicopter speeds before you lost your fillings, or busted something.
-- IFMU

IFMU,
The rotors on both craft are identical. Four blades each, etc., etc. The induced, profile and parasitic drags should be equal.


The upper blades, which are facing outward, are the retreating blades. They produce little thrust compared to the advancing blades during cruise.

I believe that this offers an advantage over the Coaxial. A problem with the Coaxial is that on one side of the craft the low thrust retreating blades are located underneath the high thrust of the advancing blades. In addition, the Coaxial's lower retreating blades span the full length of the upper blades. This is source of strong rotor-to-rotor vibration.

I think that it has something to do with symmetry. ;)


Yes. It's top speed was limited by excessive vibration. These pages are on the subject of rotor induced vibration on ABC, 3 and 4 blade rotors.
OTHER: Aerodynamics - Vibration - Rotor Induced - Analysis of Coaxial
DESIGN: UniCopter ~ Rotor - Disk - Lateral Dissymmetry of Lift and Drag? - (3-blades)
DESIGN: UniCopter ~ Rotor - Disk - Lateral Dissymmetry of Lift (Drag?) - 4-blade Rotors

Dave

IFMU, in theory the intermesher will not lose efficiency since the downwashes force each other back to vertical. The rotors may actually improve the way the wake contraction is handled, although a ring rotor would offer greater benefits for coaxial only.

The main arguement for interleaving to my mind is maximising rotor area for a given weight. If you see aircraft width as a constraint, this points towards tandem layout. However, rear rotor will suffer from losses due to inflow.

I'm jus gonna sit right here on my fence...:}

Mart

Sikorsky X2
 

Sikorsky X2 Might be flying soon

www.sikorsky.com

Great news! Any snipets of info come your way, Levo?

Mart

Subtlety Vs Brute Force
 

Neat set of ideas if they can just get 'em together for critical mass? Wonder if the synergy really works to 250 kts? If it does then X2 is to Osprey as nailgun is to sledge hammer?

The Sikorsky website is not available for me.
Is it down?
If not, could anybody please post the news here, that we have conserved it?

Thanks

hotzenplotz,

When I looked all I saw was a picture on the homepage. Not a real picture, just a CAD rendering. Unless I missed something.

-- IFMU

When I click the link than this happens:

http://img525.imageshack.us/img525/6...benanntje6.jpg

:confused:

Hotzenplotz, link/site seems to be down at the moment. I followed it and couldn't see any new info. Levo may just have been fishing for an update.

Mart

Thank you for the info.
Now I know thats not a problem of my provider.

Hotzenplotz,

Homeland Security has control over the Internet. They check every attempt to access a defense supplier's site.

You have been denied access because your 'Location' is questionable. :)

:} :ok:

http://img144.imageshack.us/img144/1...omelandip1.jpg

sites working
 

Hi try typing it in then enter just tryed it and its ok sikorsky site seams to work for me its a twin rotor with a propeller on the rear instead of a tail rotor tis is what it says inthe mag

Although the project was temporarily shelved in 2006 due to industrial action ,Sikorsky says it plans to resume development of its x2 next genaration helicopter later this year. The x2 has a coaxial design (2 rotors on the sane axis) and a pusher prop to provide additional forward propulsion. Its expected to reach speeds of 250 kts soon to fly as soon as project starts again.

Yes, the site is up again.

But I can’t find any real news about the X-2 program.

Too bad, I expected to find the date for the first flight or something… :(

Sit tight, Guys, the X2 is coming. Sikorsky folks are getting ready to shake it down, but these things take time.
I flew the original ABC upon which the X2 is based, and can assure you, the X2 will be worth the wait!

Seriously looking forward to this one, Nick!

Let the Sikorsky/Schweizer design team know we are all enthusiastic, but pragmatic with it. I'd much rather wait to see a well sorted prototype, than end up discussing what went wrong with the program. :ok:

Mart

I flew the original ABC
 

More detail Nick. How do they test systems for a co-axial with pusher on a bird that isn't?

22clipper,
I am not sure what your question is.