Sikorsky X2 coaxial heli developments.
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All due respect to NL and a big WORD! to what he wrote.. (this to the passages about test pilots, NL's considerable life achievement as one and so forth..)
I would still contend that:
Substantially perpendicular to the longitudinal axis of the rotor craft..? Now remind me.. What is the position and direction of this “pusher prop”?
Talking of 7% aux. power on the Lynx..
At 225/250 knots, what percentage of the forward thrust do the two main rotors achieve on an X2 in flight..? is it more like 7% than 93% ???
I’m just asking.. cause I do not know.. this is a fact..
I would still contend that:
HELICOPTER: A rotorcraft with A power driven rotor system whose axis (axes) is (are) fixed and substantially perpendicular to the longitudinal axis of the rotorcraft.
Talking of 7% aux. power on the Lynx..
At 225/250 knots, what percentage of the forward thrust do the two main rotors achieve on an X2 in flight..? is it more like 7% than 93% ???
I’m just asking.. cause I do not know.. this is a fact..
Not sour grapes Nick and Cfosky but fact.
The FAI will not judge the X2 as a pure helicopter and so it cannot claim the world helicopter speed record.
There are FAI records for compound helicopters...in fact the Rotodyne was one of the first back in 1959,and if we are talking auxiliary thrust then the Bell 533 compound speed record in 1969 would stand too.
Yes the X2 is a fine achievement but don't let's cheat !
The FAI will not judge the X2 as a pure helicopter and so it cannot claim the world helicopter speed record.
There are FAI records for compound helicopters...in fact the Rotodyne was one of the first back in 1959,and if we are talking auxiliary thrust then the Bell 533 compound speed record in 1969 would stand too.
Yes the X2 is a fine achievement but don't let's cheat !
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Helicopter
Cambridge advanced learners dictionary
a type of aircraft without wings, that has one or two sets of large blades which go round very fast on top. It can land and take off vertically and can stay in one place in the air.
Oxford advanced learners dictionary
an aircraft without wings that has large blades on top that go round. It can fly straight up from the ground and can also stay in one position in the air
Dictionary.com
any of a class of heavier-than-air craft that are lifted and sustained in the air horizontally by rotating wings or blades turning on vertical axes through power supplied by an engine.
thefreedictionary.com
... Helicopter was borrowed from the French word hélicoptère, a word constructed from Greek heliko- and pteron, "wing." Heliko-, the combining form of helix, "spiral," has given us helico-, which can be joined with other words and word forms to create new words. The consonant cluster pt in pteron begins many Greek words but relatively few English words. English speakers unfamiliar with Greek are thus not likely to recognize the word's elements as helico-pter; many analyze the word into the elements heli-copter, as is shown by the clipped form copter.
Why not just acknowledge the recent X2 flight as a brilliant piece of engineering, and a brilliant piece of flying, in the tradition of a long line of brilliant pioneering endeavours...
Cambridge advanced learners dictionary
a type of aircraft without wings, that has one or two sets of large blades which go round very fast on top. It can land and take off vertically and can stay in one place in the air.
Oxford advanced learners dictionary
an aircraft without wings that has large blades on top that go round. It can fly straight up from the ground and can also stay in one position in the air
Dictionary.com
any of a class of heavier-than-air craft that are lifted and sustained in the air horizontally by rotating wings or blades turning on vertical axes through power supplied by an engine.
thefreedictionary.com
... Helicopter was borrowed from the French word hélicoptère, a word constructed from Greek heliko- and pteron, "wing." Heliko-, the combining form of helix, "spiral," has given us helico-, which can be joined with other words and word forms to create new words. The consonant cluster pt in pteron begins many Greek words but relatively few English words. English speakers unfamiliar with Greek are thus not likely to recognize the word's elements as helico-pter; many analyze the word into the elements heli-copter, as is shown by the clipped form copter.
Why not just acknowledge the recent X2 flight as a brilliant piece of engineering, and a brilliant piece of flying, in the tradition of a long line of brilliant pioneering endeavours...
X2 Flight
The Talmudic discussion about whether or not the recent flight can claim a record is interesting, but as I listened to Kevin debrief the flight, I was struck by a comment he made in reference to some SAS gain changes that had been made.
Almost as an aside, he said something like: " you know you guys have the in-cockpit cameras on me, and as you probably noticed, my hand was on the cyclic only every 5-8 seconds or so".
That said quite a lot, to me anyway.
Thanks,
John Dixson
Almost as an aside, he said something like: " you know you guys have the in-cockpit cameras on me, and as you probably noticed, my hand was on the cyclic only every 5-8 seconds or so".
That said quite a lot, to me anyway.
Thanks,
John Dixson
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Would the X2 have a lot of Titanium in it for weight saving reasons?
Footnote for those who lack a classical education:
Talmudic
–adjective 1. of or pertaining to the Talmud.
2. characterized by or making extremely fine distinctions; overly detailed or subtle; hairsplitting.
Talmud
–noun
the collection of Jewish law and tradition consisting of the Mishnah and the Gemara and being either the edition produced in Palestine a.d. c400 or the larger, more important one produced in Babylonia a.d. c500.
Footnote for those who lack a classical education:
Talmudic
–adjective 1. of or pertaining to the Talmud.
2. characterized by or making extremely fine distinctions; overly detailed or subtle; hairsplitting.
Talmud
–noun
the collection of Jewish law and tradition consisting of the Mishnah and the Gemara and being either the edition produced in Palestine a.d. c400 or the larger, more important one produced in Babylonia a.d. c500.
Last edited by Shell Management; 28th Jul 2010 at 12:55.
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Just the facts.
" you know you guys have the in-cockpit cameras on me, and as you probably noticed, my hand was on the cyclic only every 5-8 seconds or so".
It may also be of interest to know that this video resulted in Sikorsky removing their claim to being the first to land a helicopter on the deck of a ship.
Originally Posted by The Sultan
Still 8 knots short of what James May has done on a road with a streetworthy car, and 150 knots short of what a tiltrotor can do.
Originally Posted by NickLappos
If all else failed, he could load the X2 into an Osprey and get to at least 275 knots!
All record talk and griping aside, anybody who cannot appreciate or understand the achievement should get off the internet and do something useful! Beyond the 250 kts, assuming they achieve it, is the promise that this 250 kts is not just a flash in the pan. It is a useable technology to really make a rotorcraft faster and retain the good things that make it a helicopter. Low disc loading, and helicopter-like complexity rather than what we ended up with on the Osprey some would see as a plus. There is no marketing or spinning that can achieve 225 kts. That is all engineering.
There is no 't' in Schweizer!
Originally Posted by dangermouse
(if I fitted a J79 to a Bell47 it would probably go faster than 250 kts but you wouldnt call it a helicopter)
I think this is pretty cool. Way faster than anything I fly. Half the speed of the long tubes I sometimes pay to fly in where I get to sit in the back and drink overpriced beer.
-- IFMU
CT post article
Sikorsky's X2 speeds to 259mph - Connecticut Post
I like the last bit in the article:
I like the last bit in the article:
Company officials said that the X2's shot at the 250-knot goal will be made in a few months. This raises the question: How fast will it go?
"I'd say that at about 300 knots, you'd start running into other issues," Cizewski said.
"I'd say that at about 300 knots, you'd start running into other issues," Cizewski said.
What will determine the Maximum Speed?
One has to ask, what will the limiting factor be? One of the limiting factors in the X-59 was the close proximity of the advancing and retreating blade tips as the speed increased. It appears as if the blades, at the 3 o clock position, are getting very close.
I wonder if the right bank with respect to the photo frame gives the illusion of closeness.
-- IFMU
-- IFMU
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This is just an optical illusion - blades would have to be parallel in the image. There is instrumentation on board X2 to monitor blade tip proximity.
Dave, Flettner definately deserves recognition as a very capable helicopter pioneer. His designs were clever to the point of being ahead of their time.
Dangermouse, none of this detracts from the achievement of the G-LYNX team. It is still the fastest single main rotor helicopter.
Personally i feel that all Rotorheads should be unanimous is wishing the X2 team, and Keven Bredenbeck, the very best of luck & talent in getting this remarkable machine to show its true potential. Another significant step in the history of pioneering aircraft development.
Dave, Flettner definately deserves recognition as a very capable helicopter pioneer. His designs were clever to the point of being ahead of their time.
Dangermouse, none of this detracts from the achievement of the G-LYNX team. It is still the fastest single main rotor helicopter.
Personally i feel that all Rotorheads should be unanimous is wishing the X2 team, and Keven Bredenbeck, the very best of luck & talent in getting this remarkable machine to show its true potential. Another significant step in the history of pioneering aircraft development.
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Graviman
If the technical side of the Advancing Blade Concept is still of interest, you may find the document 'Influence of Lift Offset on Rotorcraft Performance' informative.
The author, Wayne Johnson, wrote the 1088 page book 'Helicopter Theory'.
Dave
If the technical side of the Advancing Blade Concept is still of interest, you may find the document 'Influence of Lift Offset on Rotorcraft Performance' informative.
The author, Wayne Johnson, wrote the 1088 page book 'Helicopter Theory'.
Dave
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Lift offset
Dave
What is the precise definition of lift offset ?
The article you refer to uses the "optimal range" for coaxial at 0.25 which seems low to me. This may rather structurally limited and not aerodynamically optimal.
For instance at 120 knots a theetering rotor produces variations of 35% minimum - 65% maximum on the blades (50%-50% would be equal load in my definitions). How much lift offset is this ?
d3
What is the precise definition of lift offset ?
The article you refer to uses the "optimal range" for coaxial at 0.25 which seems low to me. This may rather structurally limited and not aerodynamically optimal.
For instance at 120 knots a theetering rotor produces variations of 35% minimum - 65% maximum on the blades (50%-50% would be equal load in my definitions). How much lift offset is this ?
d3
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Hi d3,
IMHO, the precise definition of 'lift offset' is; the distance between the center of a rotor's mast and the center of the rotor's thrust vector.
Assuming I understand your your 120 knots example properly, if the teetering rotor was replaced by an 'Absolutely' Rigid Rotor the offset will be; (35% + 15%) = (65% - 15%). I.e it will be 15%
Entering the phrase 'lift offset' into your Internet's [Find box]. after bringing up the following 2 web pages, will get Sikorsky information on the phrase.
0891
1465
Perhaps the lift of the small wing is reducing the offset in Johnson's example craft.
__________________________
It is interesting to see that Johnson is looking favorably at the Side-by-Side-ABC. Stepniewski's last publication before his death recommended the Intermeshing-ABC. Two highly respected rotorcraft aerodynamics have now shown support for the Bilateral-ABC configurations
Sikorsky has apparently hung its hat on the coaxial configuration. If some other company, or perhaps some other country, decides to embrace the Bilateral-ABCs, things could get really interesting.
Dave
IMHO, the precise definition of 'lift offset' is; the distance between the center of a rotor's mast and the center of the rotor's thrust vector.
Assuming I understand your your 120 knots example properly, if the teetering rotor was replaced by an 'Absolutely' Rigid Rotor the offset will be; (35% + 15%) = (65% - 15%). I.e it will be 15%
Entering the phrase 'lift offset' into your Internet's [Find box]. after bringing up the following 2 web pages, will get Sikorsky information on the phrase.
0891
1465
Perhaps the lift of the small wing is reducing the offset in Johnson's example craft.
__________________________
It is interesting to see that Johnson is looking favorably at the Side-by-Side-ABC. Stepniewski's last publication before his death recommended the Intermeshing-ABC. Two highly respected rotorcraft aerodynamics have now shown support for the Bilateral-ABC configurations
Sikorsky has apparently hung its hat on the coaxial configuration. If some other company, or perhaps some other country, decides to embrace the Bilateral-ABCs, things could get really interesting.
Dave
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Dave,
Paper looks interesting, particularly the use of free wake geometry in Camrad II. Interesting that tandems require similar power to coaxials - that may be one to watch.
The side-by-side configs will always apparently fair better because they increase the span of the lifting system. To compare apples with apples i think a constraint of the config should be to define the span then size the rotor accordingly - this defines the landing areas the machine can access. I suspect that coaxial starts to look better with this constraint.
At some point (after proj deadline in Sep) i would like to do a more basic comparison. I've now got a reasonable model for reverse flow, and am just starting to think about inflow effects (critical for counterrotating machines). Don't hold your breath just yet though!
Paper looks interesting, particularly the use of free wake geometry in Camrad II. Interesting that tandems require similar power to coaxials - that may be one to watch.
The side-by-side configs will always apparently fair better because they increase the span of the lifting system. To compare apples with apples i think a constraint of the config should be to define the span then size the rotor accordingly - this defines the landing areas the machine can access. I suspect that coaxial starts to look better with this constraint.
At some point (after proj deadline in Sep) i would like to do a more basic comparison. I've now got a reasonable model for reverse flow, and am just starting to think about inflow effects (critical for counterrotating machines). Don't hold your breath just yet though!
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I recall you saying it would provide for some great performance/speed increases. Any guess~timate how much AS it would have added to the last flight using the same power/Q pulled if installed?
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Have any details of rotorhub system ever been released for XH-59/S-69? I recall mention of internal pitch links for top rotor and conventional swash plate for lower rotor.
I imagine that in cruise the air between the rotors is sourced from rotors in starboard azimuth (upper lift and lower reverse flow) and sunk from rotors in port azimuth (upper reverse flow and lower lift). This would set up a crossflow which would tend to pull any hub fairing to port slightly (tapered roots will help reduce this). Also the fountain effect in hover could be lots of fun'n'games.
Early days of a new type - teething troubles are to be expected.
I imagine that in cruise the air between the rotors is sourced from rotors in starboard azimuth (upper lift and lower reverse flow) and sunk from rotors in port azimuth (upper reverse flow and lower lift). This would set up a crossflow which would tend to pull any hub fairing to port slightly (tapered roots will help reduce this). Also the fountain effect in hover could be lots of fun'n'games.
Early days of a new type - teething troubles are to be expected.
Last edited by Graviman; 5th Aug 2010 at 11:36. Reason: Readability.
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Graviman
This voluminous report should provide a wealth of data on the XH-59A for the program that you are developing.
Performance and Loads Data from a Wind Tunnel Test of a Full-Scale, Coaxial, Hingeless Rotor Helicopter.
Also, a US patent on the faring between the X2's rotors is available on the net.
Dave
This voluminous report should provide a wealth of data on the XH-59A for the program that you are developing.
Performance and Loads Data from a Wind Tunnel Test of a Full-Scale, Coaxial, Hingeless Rotor Helicopter.
Also, a US patent on the faring between the X2's rotors is available on the net.
Dave