Sikorsky X2 coaxial heli developments.
Joined: Apr 2003
Posts: 1,635
Likes: 1
From: Vancouver, BC, Canada
Originally Posted by Jack Carson;
".. some subsets of rotorcraft technology may approach physical limits due to power requirements or material limitations. ... Co-axial rotor systems may have just such a boundary."
".. some subsets of rotorcraft technology may approach physical limits due to power requirements or material limitations. ... Co-axial rotor systems may have just such a boundary."
A link to this subject of; Empty Weight and Payload;
The spread between the Coaxial-ABC and the Interleaving-ABC will be even greater.
Dave
Joined: Mar 2005
Posts: 1,289
Likes: 289
From: Poplar Grove, IL, USA
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
Joined: Apr 2003
Posts: 1,635
Likes: 1
From: Vancouver, BC, Canada
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
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?
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.
I have read that the original ABC had big vibration problems. It had two 3-bladed 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
Joined: Nov 2004
Posts: 1,334
Likes: 0
From: Cambridgeshire, UK
Originally Posted by IFMU
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.
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
Joined: Jun 2006
Posts: 95
Likes: 0
From: uk
Joined: Feb 2006
Posts: 292
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From: Sydney
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?
Joined: Apr 2003
Posts: 1,635
Likes: 1
From: Vancouver, BC, Canada
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.
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.
Joined: Jun 2006
Posts: 95
Likes: 0
From: uk
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.
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.
Joined: Apr 2003
Posts: 3,012
Likes: 1
From: USA
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!
I flew the original ABC upon which the X2 is based, and can assure you, the X2 will be worth the wait!
Joined: Nov 2004
Posts: 1,334
Likes: 0
From: Cambridgeshire, UK
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.
Mart
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.
Mart