Sikorsky X2 coaxial heli developments.
Chief Bottle Washer
Revenge of the Nerds
From Flight Global:
Sikorsky earlier this year took a series of "glamour" shots of the engineering team for its X2 advancing blade concept pusher helicopter. With the help of dark shades, techy helicopter backdrop and slick threads, the engineers did in fact look like cool dudes.
Looks can be deceiving however, and in the case of the X2, that's a good thing.
In a world where immediacy and appearance have become paramount, there are still those who go to work in a cubicle every day and perform a seemingly astonishing feat called thinking. Call the engineers nerds if you like, but you have to like what they do.
In the case of the X2, the engineers were given extra years to think. X2 was "supposed" to fly in 2006 but didn't until 2008. But Sikorsky was in no rush, convinced the future of rotorcraft is to blend the a helicopter's vertical lift with the speed of a fixed-wing aircraft.
Like a fine wine, such a vehicle could not be served before its time. Sikorsky had tried in the 1970s with its XH-59A, an advancing blade concept design that was fast but impractical before advances like active vibration control systems.
The Bell Boeing tiltrotor approach can dash at 270kt (500km/h), but Sikorsky believes configuration changes like swivelling the engines to change the lift vector are not the way to go. But while the advancing blade concept's counter-rotating coaxial main rotors overcome the retreating blade stall barrier to rotorcraft speed, the problem remains that in acceleration past 180kt to the X2's planned 250kt cruise speed, the blade tips would go supersonic and thus need to be slowed - no mean feat.
These quandaries took thinking time to solve. Air shows came and went with Sikorsky chief Jeff Pino telling an impatient press that the X2 "will fly when we're ready for it to fly".
The engineers were ready in 2008 for a maiden flight, part of a methodically thought-out four-phase flight test plan - with no hard dates attached.
Last week test pilot Kevin Bredenbeck finished phase three of the flight-test programme, hitting a speed of 181kt in cruise, beyond what's possible for most traditional helicopters. The engineers' automated algorithms successfully slowed the main rotors for the first time, making phase four and its ultimate end goal of 250kt a very realisable goal.
When will it happen? When the thinkers at Sikorsky - the engineers - are ready for it to happen. It will be worth the wait...
Looks can be deceiving however, and in the case of the X2, that's a good thing.
In a world where immediacy and appearance have become paramount, there are still those who go to work in a cubicle every day and perform a seemingly astonishing feat called thinking. Call the engineers nerds if you like, but you have to like what they do.
In the case of the X2, the engineers were given extra years to think. X2 was "supposed" to fly in 2006 but didn't until 2008. But Sikorsky was in no rush, convinced the future of rotorcraft is to blend the a helicopter's vertical lift with the speed of a fixed-wing aircraft.
Like a fine wine, such a vehicle could not be served before its time. Sikorsky had tried in the 1970s with its XH-59A, an advancing blade concept design that was fast but impractical before advances like active vibration control systems.
The Bell Boeing tiltrotor approach can dash at 270kt (500km/h), but Sikorsky believes configuration changes like swivelling the engines to change the lift vector are not the way to go. But while the advancing blade concept's counter-rotating coaxial main rotors overcome the retreating blade stall barrier to rotorcraft speed, the problem remains that in acceleration past 180kt to the X2's planned 250kt cruise speed, the blade tips would go supersonic and thus need to be slowed - no mean feat.
These quandaries took thinking time to solve. Air shows came and went with Sikorsky chief Jeff Pino telling an impatient press that the X2 "will fly when we're ready for it to fly".
The engineers were ready in 2008 for a maiden flight, part of a methodically thought-out four-phase flight test plan - with no hard dates attached.
Last week test pilot Kevin Bredenbeck finished phase three of the flight-test programme, hitting a speed of 181kt in cruise, beyond what's possible for most traditional helicopters. The engineers' automated algorithms successfully slowed the main rotors for the first time, making phase four and its ultimate end goal of 250kt a very realisable goal.
When will it happen? When the thinkers at Sikorsky - the engineers - are ready for it to happen. It will be worth the wait...
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That photo is amazing.
Senior Pilot,
I was amazed by that photograph you posted. If you know any engineers, you'd appreciate that it must have taken quite a bit of work by the photographer to round up seven Sikorsky engineers that owned suits and dress shoes.
Who knows, maybe the suits were rented?
riff_raff
I was amazed by that photograph you posted. If you know any engineers, you'd appreciate that it must have taken quite a bit of work by the photographer to round up seven Sikorsky engineers that owned suits and dress shoes.
Who knows, maybe the suits were rented?
riff_raff
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Hellerez;
Your respected posting appears to address two related but distinct subjects.
The first is the challenges that the Advancing Blade Concept faces in its attempt to become a new generation of rotorcraft.
The second is the assessment of which configuration; the Coaxial, the Intermeshing or the Interleaving is best suited to optimize the ABC, should the above challenges be overcome.
I, and no doubt others, would be pleased to discuses and provoke thought regarding the above, should Senior Pilot not object.
Dave
Your respected posting appears to address two related but distinct subjects.
The first is the challenges that the Advancing Blade Concept faces in its attempt to become a new generation of rotorcraft.
The second is the assessment of which configuration; the Coaxial, the Intermeshing or the Interleaving is best suited to optimize the ABC, should the above challenges be overcome.
I, and no doubt others, would be pleased to discuses and provoke thought regarding the above, should Senior Pilot not object.
Dave
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Originally Posted by IFMU
Meanwhile, a flurry of news on X2 announced on the anniversary of Igor Sikorsky's birthday
I/C
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Dave,
Besides rotor configurations, another comparison worth some discussion might be how does X2 stack up vs. Boeing's A160 OSR. The OSR is specifically designed for variable rotor speed, so one would imagine that it should be capable of high forward speeds. Right?
riff_raff
Besides rotor configurations, another comparison worth some discussion might be how does X2 stack up vs. Boeing's A160 OSR. The OSR is specifically designed for variable rotor speed, so one would imagine that it should be capable of high forward speeds. Right?
riff_raff
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riff_raff,
True they both have highly rigid rotors but their applications are very different. Here is an earlier discussion about the craft; A160 Hummingbird rigid rotor design
The A160 has no need to consider the reverse velocity airflow on the retreating side of its rotor. However, for the ABC, the ability to deal with this reverse velocity is at the heart of whether the concept can be viable.
Earlier in this thread Hellerez mentioned the Russian ABC proposal with its coaxial propellers and its targeted speed of 400 kts. Their knowledge of coaxial propellers exceeds that of all others. It will therefore be very, very interesting to see what they propose to overcome this 'reverse velocity' barrier, particularly at their higher speed.
Dave
True they both have highly rigid rotors but their applications are very different. Here is an earlier discussion about the craft; A160 Hummingbird rigid rotor design
The A160 has no need to consider the reverse velocity airflow on the retreating side of its rotor. However, for the ABC, the ability to deal with this reverse velocity is at the heart of whether the concept can be viable.
Earlier in this thread Hellerez mentioned the Russian ABC proposal with its coaxial propellers and its targeted speed of 400 kts. Their knowledge of coaxial propellers exceeds that of all others. It will therefore be very, very interesting to see what they propose to overcome this 'reverse velocity' barrier, particularly at their higher speed.
Dave
Their knowledge of coaxial propellers exceeds that of all others.
-- IFMU
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Originally Posted by Dave Jackson
The second is the assessment of which configuration; the Coaxial, the Intermeshing or the Interleaving is best suited to optimize the ABC, should the above challenges be overcome.
I, and no doubt others, would be pleased to discuses and provoke thought regarding the above, should Senior Pilot not object.
I, and no doubt others, would be pleased to discuses and provoke thought regarding the above, should Senior Pilot not object.
. We could have this discussion on another thread if you wish. X2 configuration would have been chosen using the least risk approach - always a good idea when doing something this new. Optimisation of similar future concepts is another discussion.
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One approach to aero development that seems to be gaining wider acceptance these days is sub-scale model flight test. This is being done with Boeing's BWB (X-48) and with Saab's stealth fighter concept .
Maybe a sub-scale test of the various ABC rotor configurations Dave mentions would be a worthwhile endeavor for someone. It wouldn't be a garage/hobbyist level project. But I'm sure something like a 1/16th scale powered model with interchangeable drivetrain, rotors and some basic data acquisition/instrumentation would be well within the budget of most any university's aero engineering dept. It could even be validated with some CFD work by a few grad students. Seems like a better academic research project than most of the ones I've seen.
riff_raff
Maybe a sub-scale test of the various ABC rotor configurations Dave mentions would be a worthwhile endeavor for someone. It wouldn't be a garage/hobbyist level project. But I'm sure something like a 1/16th scale powered model with interchangeable drivetrain, rotors and some basic data acquisition/instrumentation would be well within the budget of most any university's aero engineering dept. It could even be validated with some CFD work by a few grad students. Seems like a better academic research project than most of the ones I've seen.
riff_raff
Chief Bottle Washer
Originally Posted by CEFOSKEY
Whats the deal with "hellerez" apparently posting and then immediately deleting the posts in this thread? I have yet to actually catch one, only mentions of them in the subsequent responses.
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Originally Posted by Senior Pilot
His post is here: No 739. Not at all sure why you don't seem to be able to read it
His post is here: No 739. Not at all sure why you don't seem to be able to read it
In fact, at the time of his missing post 'hellerez' was not even listed as a member of PPRuNe.
Dave
Probably because there is no 'hellerez' registered with PPRuNe. The Rotorhead that we are discussing is 'helierez', and his post was there throughout the period being discussed.
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I had the same experience, Chris. At first I couldn't see it then when i checked back after reading Dave's post there it was. I figured Hellierez had deleted after posting.
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CEFO
Yes it is faster than I have been in a rotorcraft.
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.
The Sultan
Yes it is faster than I have been in a rotorcraft.
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.
The Sultan
Well done Sikorsky....for continuing the spin. The X2 will have to reach 274 kt to beat the Bell Model 533 and even then neither are true helicopters so arguably it has to also beat the V-22 tilt rotor at 302kt.
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no record for the X2
As discussed many times here
the X2 aint a helicopter, it's a compounded rotorcraft so the Lynx record still stands
(if I fitted a J79 to a Bell47 it would probably go faster than 250 kts but you wouldnt call it a helicopter)
DM
the X2 aint a helicopter, it's a compounded rotorcraft so the Lynx record still stands
(if I fitted a J79 to a Bell47 it would probably go faster than 250 kts but you wouldnt call it a helicopter)
DM
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Congratulations Sikorsky/Schweitzer X2 design team & flight test team: for designing, building & developing the worlds fastest practical VTOL machine! 
Congratulations to Kevin Bredenbeck: for having the gumption to fly it!
Practical because disk loading is no higher than an S76, so this remarkable machine can safely access the same sites that any conventional helicopter can get into. The concept may have its detractors, who will point out that the machine has not achieved any specific target first. However, the overall capability of this machine from hover to dash speed will revolutionise the helicopter concept. In the near future folks will argue the merits of other configurations against the conventional coaxial configuration...
Congratulations to Kevin Bredenbeck: for having the gumption to fly it!
Practical because disk loading is no higher than an S76, so this remarkable machine can safely access the same sites that any conventional helicopter can get into. The concept may have its detractors, who will point out that the machine has not achieved any specific target first. However, the overall capability of this machine from hover to dash speed will revolutionise the helicopter concept. In the near future folks will argue the merits of other configurations against the conventional coaxial configuration...
Last edited by Graviman; 28th Jul 2010 at 11:40. Reason: Nick is right - tp should get the respect deserved directly.
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Sounds like some sour grapes from some ppruners regarding what is a helicopter. First thing I did this am was run to the FAI site to find the same words posted below. While common usage differentiates between helos, compounds (aux thrust) and winged compounds, the FAI does not.
Regarding aux thrust, I also recall that the Lynx (whose picture, signed by Trevor Egginton hangs 5 feet from me on my office wall as I write this) had a shaped exhaust to extract all the thermodynamic power the engines had that the transmission couldn't handle. It had 7% aux thrust, as I recall, a big push, indeed.
Having flown the old ABC to these speeds, I guess I too could claim a "record" but wouldn't until the FAI was around, and the aircraft was sealed by their representative. Having helped set a bunch of records back in the day, the official system is fair and the ONLY way a record is set. I also know that the WPB X2 bunch will have them drop by shortly, and blow away the existing helo records.
Having known the previous record holders, all great pilots and great gentlemen, I know they will not grouse like those ppruners below. The daring that is shown when an S67 Blackhawk, or a Russian A10, or a vastly modified Lynx is flown to impossible speeds is also coupled with a sense of dignity and respect. When the X2 sets that record, those pilots, wherever they are, will salute and smile, because they know that we are all fighting something far greater than each other, we are fighting the forces of nature, a much more challenging adversary.
Congratulations, Kevin.
PS, I told Kevin once that he could come to Xworx and do his flying, and be assured of great speed, regardless. If all else failed, he could load the X2 into an Osprey and get to at least 275 knots!
Regarding aux thrust, I also recall that the Lynx (whose picture, signed by Trevor Egginton hangs 5 feet from me on my office wall as I write this) had a shaped exhaust to extract all the thermodynamic power the engines had that the transmission couldn't handle. It had 7% aux thrust, as I recall, a big push, indeed.
Having flown the old ABC to these speeds, I guess I too could claim a "record" but wouldn't until the FAI was around, and the aircraft was sealed by their representative. Having helped set a bunch of records back in the day, the official system is fair and the ONLY way a record is set. I also know that the WPB X2 bunch will have them drop by shortly, and blow away the existing helo records.
Having known the previous record holders, all great pilots and great gentlemen, I know they will not grouse like those ppruners below. The daring that is shown when an S67 Blackhawk, or a Russian A10, or a vastly modified Lynx is flown to impossible speeds is also coupled with a sense of dignity and respect. When the X2 sets that record, those pilots, wherever they are, will salute and smile, because they know that we are all fighting something far greater than each other, we are fighting the forces of nature, a much more challenging adversary.
Congratulations, Kevin.
PS, I told Kevin once that he could come to Xworx and do his flying, and be assured of great speed, regardless. If all else failed, he could load the X2 into an Osprey and get to at least 275 knots!