Sikorsky X2 coaxial heli developments.
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
IFMU
I don't know. Will this do? 
Mart you naughty boy.
Yes, Sikorsky is going 'Back to the Future' by regurgitating the 30 year old coaxial ABC. However, suggesting that they went way back to the time when some produced coaxials with unequal rotor diameters is going toooo far.
Dave
What's the sine of 45 degrees?
Mart you naughty boy.
Yes, Sikorsky is going 'Back to the Future' by regurgitating the 30 year old coaxial ABC. However, suggesting that they went way back to the time when some produced coaxials with unequal rotor diameters is going toooo far.
Dave
Join Date: Apr 2003
Location: USA
Age: 75
Posts: 3,012
Likes: 0
Received 0 Likes
on
0 Posts
some comments:
1) Dave's idea of perfect symmetry is like a mantra to him, and of absolutely no validity from any standpint but his own. No physically symmetrical system has any degree of symmetry from the standpoint of forces and moments produced, due to all the other aspects that influence the aerodynamics.
2) He is all wet with his calculations about different rotor diameters and the ensuing loss of "symmetry" since the X2 has two identical rotor diameters, and blade sets. The illusion that ppruners have spun into a physical fact is just that, an illusion. The rotors are indexed so that they do not cross at the cardinal 90 degree points, so you see them as if they were different diameters. A gold star to IFMU for explaining this to Dave!
3) There is little similarity between the ABC/X2 and any other coax or syncropter, because the ABC type rotors are extremely stiff, with hinge offsets above 15%. This allows near stall maneuvering, a fact that is lost to those "expert" web sites that compare the X2 to a typical Kamov design.
4) The KA-50 has a hinge offset of 7.5% on the lower rotor and 2.5% on the upper, making the flapping motions quite large, and forcing the rotors to be very widely separated, with a great deal of drag (about 15% more than necessary). This low offset also makes the flapping near stall much greater, so that there can be little maneuvering at high speed, and therefore no high speed. In fact at least one and probably two KA-50's were lost to self-midair.
1) Dave's idea of perfect symmetry is like a mantra to him, and of absolutely no validity from any standpint but his own. No physically symmetrical system has any degree of symmetry from the standpoint of forces and moments produced, due to all the other aspects that influence the aerodynamics.
2) He is all wet with his calculations about different rotor diameters and the ensuing loss of "symmetry" since the X2 has two identical rotor diameters, and blade sets. The illusion that ppruners have spun into a physical fact is just that, an illusion. The rotors are indexed so that they do not cross at the cardinal 90 degree points, so you see them as if they were different diameters. A gold star to IFMU for explaining this to Dave!
3) There is little similarity between the ABC/X2 and any other coax or syncropter, because the ABC type rotors are extremely stiff, with hinge offsets above 15%. This allows near stall maneuvering, a fact that is lost to those "expert" web sites that compare the X2 to a typical Kamov design.
4) The KA-50 has a hinge offset of 7.5% on the lower rotor and 2.5% on the upper, making the flapping motions quite large, and forcing the rotors to be very widely separated, with a great deal of drag (about 15% more than necessary). This low offset also makes the flapping near stall much greater, so that there can be little maneuvering at high speed, and therefore no high speed. In fact at least one and probably two KA-50's were lost to self-midair.
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
All in good fun. 
Nick you're doing it again. You've got to put that bottle down.
Your strong support of the tail-rotor configuration would have made Igor proud. I hope you didn't hurt your neck a year ago when you did the quick about-face and started to champion the coaxial configuration.
Rebuttal comments;
!) We have had this discussion before. Virtually all of nature's creatures have lateral symmetry in respect to interaction with their environment. Virtually all of mankind's vehicles have lateral symmetry in respect to interaction with their environment. Are you saying that Darwin's evolutionary survival of the fittest is wrong? When you mention aerodynamics, are you saying that birds and airplanes have no reason for lateral symmetry?
2) What thread have you been reading? Mart said, "Interesting that top rotor diam is NOW smaller than lower rotor." Are you suggesting that I should not believe it when Mart says that Sikorsky has changed the rotor diameter?
3) You said; "There is little similarity between the ABC/X2 and any other coax or syncropter," Not so fast Quick Draw. There is much similarity between the ABC/X2 and the XH-59A ABC. Just think where the helicopter industry would be today if Sikorsky had taken that 1965 study, the subsequent XH-59A craft, plus the concluding recommendations; and then continued to improve and produce the coaxial configuration.
Dave
Nick you're doing it again. You've got to put that bottle down.
Your strong support of the tail-rotor configuration would have made Igor proud. I hope you didn't hurt your neck a year ago when you did the quick about-face and started to champion the coaxial configuration.
Rebuttal comments;
!) We have had this discussion before. Virtually all of nature's creatures have lateral symmetry in respect to interaction with their environment. Virtually all of mankind's vehicles have lateral symmetry in respect to interaction with their environment. Are you saying that Darwin's evolutionary survival of the fittest is wrong? When you mention aerodynamics, are you saying that birds and airplanes have no reason for lateral symmetry?
2) What thread have you been reading? Mart said, "Interesting that top rotor diam is NOW smaller than lower rotor." Are you suggesting that I should not believe it when Mart says that Sikorsky has changed the rotor diameter?
3) You said; "There is little similarity between the ABC/X2 and any other coax or syncropter," Not so fast Quick Draw. There is much similarity between the ABC/X2 and the XH-59A ABC. Just think where the helicopter industry would be today if Sikorsky had taken that 1965 study, the subsequent XH-59A craft, plus the concluding recommendations; and then continued to improve and produce the coaxial configuration.
Dave
Last edited by Dave_Jackson; 24th Sep 2006 at 08:10.
Join Date: Nov 2004
Location: Cambridgeshire, UK
Posts: 1,334
Likes: 0
Received 0 Likes
on
0 Posts
Virtually all of nature's creatures have lateral symmetry in respect to interaction with their environment.
IFMU, thanks for pointing that out - my goof. I imagine indexing rotors to cross at +/- 22.5 deg to the 90 deg azimuth points reduces vibration from both blade slap above structure, and having downwash from two blades impinge structure simultaneously.
Mart
Last edited by Graviman; 25th Sep 2006 at 10:29.
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
Aw Mart,
First you give Nick the opportunity to beat me up and now you try to promote Round 2.
Discussing mobility within one's enviroment. ~ Do you mean that most folk swim with one arm? 
IFMU,
Didn't you say that you gave it to your spouse a number of years ago. 
Dave
First you give Nick the opportunity to beat me up
and now you try to promote Round 2.
Dave, ...... most folk are not ambidextrous...
IFMU,
But why isn't my heart in the middle of my chest?
Dave
Join Date: Nov 2004
Location: Cambridgeshire, UK
Posts: 1,334
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by DJ
Discussing mobility within one's enviroment. ~ Do you mean that most folk swim with one arm?
Nature produces the solutions it does, by optimising it's "designs" over time to suit their environment. We have the advantage of understanding ours (Navier-Stokes and compressible flow in this case - or using CFD). While perhaps the response provoked was a little strong for what was just an honest mistake on my part, you should argue the case for your concepts on weight and aerodynamics benefit. Already X2 design indicates a need to index the blades, so perhaps intermeshing will hold some advantage
Mart
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
At the risk of belaboring a point.
Mart,
Being ambilevous is a mental decision, which is made by the 'operator'. His physical body is latterly symmetrical and it can operate equally either way.
Rolling an airplane is a mental decision, which is made by the 'operator'. The physical fuselage is latterly symmetrical and it can operate equally either way.
I do. I also seek and appreciate technical critique.
On the web pages, the potential faults are noted, as well as the potential attributes.
I would suggest that lateral symmetry is very important in two respects;
1/ When Nick's unequal forces and moments are imparted to a craft, either by the pilot or by perturbations, lateral symmetry makes it much easier for the craft to return to its neutral position.
2/ Lateral symmetry allows a craft to spend less of its power and resources fighting dissymmetry.
Dave
Being ambilevous is a mental decision, which is made by the 'operator'. His physical body is latterly symmetrical and it can operate equally either way.
Rolling an airplane is a mental decision, which is made by the 'operator'. The physical fuselage is latterly symmetrical and it can operate equally either way.
you should argue the case for your concepts on weight and aerodynamics benefit.
On the web pages, the potential faults are noted, as well as the potential attributes.
Nick said;
No physically symmetrical system has any degree of symmetry from the standpoint of forces and moments produced, due to all the other aspects that influence the aerodynamics.
No physically symmetrical system has any degree of symmetry from the standpoint of forces and moments produced, due to all the other aspects that influence the aerodynamics.
1/ When Nick's unequal forces and moments are imparted to a craft, either by the pilot or by perturbations, lateral symmetry makes it much easier for the craft to return to its neutral position.
2/ Lateral symmetry allows a craft to spend less of its power and resources fighting dissymmetry.
Dave
Join Date: Apr 2003
Location: USA
Age: 75
Posts: 3,012
Likes: 0
Received 0 Likes
on
0 Posts
Mart,
About 20 pprune-years ago, I tried to get Dave off his symmetry mantra, and it did no good then, either! Good luck! No argument can work because he believes it in his heart, where logic can't unseat it.
About 20 pprune-years ago, I tried to get Dave off his symmetry mantra, and it did no good then, either! Good luck! No argument can work because he believes it in his heart, where logic can't unseat it.
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
Mart,
About 20 pprune-years ago, I tried to get Nick off his tail-rotor mantra, and it did no good then, either! Technical logic didn't work. It took a move by Sikorsky to convince him.
Nick,
Please tell why lateral symmetry is not an advantage, or why it is a disadvantage
Dave
About 20 pprune-years ago, I tried to get Nick off his tail-rotor mantra, and it did no good then, either! Technical logic didn't work. It took a move by Sikorsky to convince him.
Nick,
Please tell why lateral symmetry is not an advantage, or why it is a disadvantage
Dave
Join Date: Apr 2003
Location: USA
Age: 75
Posts: 3,012
Likes: 0
Received 0 Likes
on
0 Posts
Dave,
I am constantly amazed at those who show faces on Mars, apricot-pit cures for cancer or lateral symmetrical reasons to screw up a helicopter's general arrangement, and then say to others "Prove me wrong!"
Give it a rest, Dave, or at least give it some data. People who have been studying, designing and building helicopters for 70 years have relied on data to make decisions, not quasi-religious theories....
I am constantly amazed at those who show faces on Mars, apricot-pit cures for cancer or lateral symmetrical reasons to screw up a helicopter's general arrangement, and then say to others "Prove me wrong!"
Give it a rest, Dave, or at least give it some data. People who have been studying, designing and building helicopters for 70 years have relied on data to make decisions, not quasi-religious theories....
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
Nick,
Your post mentions; 'faces on Mars", "apricot-pit cures for cancer", and "quasi-religious theories".
I have more than 1,000 web page, all technical and all related to rotorcraft. Yes, many, many have errors and many are theoretical concepts.
You don't have to "Prove me wrong", but if you wish to attack, please load your gun with technical ammunition.
Dave
Your post mentions; 'faces on Mars", "apricot-pit cures for cancer", and "quasi-religious theories".
I have more than 1,000 web page, all technical and all related to rotorcraft. Yes, many, many have errors and many are theoretical concepts.
You don't have to "Prove me wrong", but if you wish to attack, please load your gun with technical ammunition.
Dave
Last edited by Dave_Jackson; 25th Sep 2006 at 23:52.
Conversely, any coax needs some indexing, assuming they use gears with teeth. Now, if the X2 technology uses a transmission like the one in my 1971 Harley golf cart, then indexing would be yesterday's news.
-- IFMU
Pretend that the're attached to Nicol Kidman.
Join Date: Nov 2004
Location: Cambridgeshire, UK
Posts: 1,334
Likes: 0
Received 0 Likes
on
0 Posts
Returning to the subject of the X2..
Fight's On!
Seriously, I have a great respect for Nick's authority on Helos. I genuinely consider myself priviledged that a pilot of his standing not only considers my postings, but will willingly share his design and piloting experience with us heli industry wannabes.
Hip Hip...Hoorah!
On with the thread: I can see how 15% effective hinge offset would allow near stall maneuvering without producing unwanted blade oscillations. The 4 blade rotors of the X2 should also reduce vibrations over S69 3 blade rotors. I guess a lot was learnt on Comanche which will benefit X2.
How much of the Comanche FBW has been reincarnated for X2? I imagine the Schweizer 333 test flights were more systems integration development than a major hardware redesign.
Mart
Last edited by Graviman; 28th Sep 2006 at 17:26. Reason: Realised that 4 blade balances hub lead-lag forces (but not shaft torque).
Join Date: Nov 2004
Location: Cambridgeshire, UK
Posts: 1,334
Likes: 0
Received 0 Likes
on
0 Posts
Done some more homework...
Some other web refs:
http://www.aiaa.org/pdf/inside/05_TC...st%20flight%22
http://www.commsdesign.com/press_rel...lineId=X391647
The last site gives some info on FBW system:
Engine: LHTEC
Data Concentrator Units: Hamilton Sundstrand:
Central Processing Units: Honeywell.
Rotor Blades: Eagle Aviation
Cockpit Display: Chelton Flight Systems.
Perhaps early considerations:
http://avia.russian.ee/helicopters_eng/sik_s-2-r.html
Mart
http://www.aiaa.org/pdf/inside/05_TC...st%20flight%22
http://www.commsdesign.com/press_rel...lineId=X391647
The last site gives some info on FBW system:
Engine: LHTEC
Data Concentrator Units: Hamilton Sundstrand:
Central Processing Units: Honeywell.
Rotor Blades: Eagle Aviation
Cockpit Display: Chelton Flight Systems.
Perhaps early considerations:
http://avia.russian.ee/helicopters_eng/sik_s-2-r.html
Mart
Last edited by Graviman; 5th Oct 2006 at 08:32.
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
