Sikorsky's New High-Speed Prototype

[Antonov]

Sikorsky is showing off their new, definitely NOT Kamov-influenced, helicopter prototype:

http://news.yahoo.com/video/us-15749625/the-next-generation-of-helicopters-take-flight-25027505

[Mark M.]

I thought the pusher idea had been discarded way back in the 80s, even?

Just more to go wrong, more to fail, and the fact that you can only push a helicopter blade forward into the air so fast before you run into problems with speed of sound, etc.

IMO it's a step backwards. Better off using the turbine exhaust to boost forward speed/acceleration, like a NOTAR system, but with contra-rotating blades to negate the need for a tail rotor.

I just don't see the US using a twin-blade setup like the Kamovs, though. It's against our military mentality.

[Cobrahistorian]

I thought the pusher idea had been discarded way back in the 80s, even?

Just more to go wrong, more to fail, and the fact that you can only push a helicopter blade forward into the air so fast before you run into problems with speed of sound, etc.

IMO it's a step backwards. Better off using the turbine exhaust to boost forward speed/acceleration, like a NOTAR system, but with contra-rotating blades to negate the need for a tail rotor.

I just don't see the US using a twin-blade setup like the Kamovs, though. It's against our military mentality.

Wow.

Mark, you really need to catch up on nearly 40 years of helicopter development.

The X2 technology demonstrator is a remarkable aircraft and has already set new speed records.

Sikorsky has taken the merits of the coaxial main rotor setup that Mr. Kamov designed, refined it, and made it simpler and more efficient. Combined with a pusher prop, you are now looking at the next generation of military aircraft.

By utilizing the coaxial rotor system you don't get into the speed issues like a conventional helicopter, you're only limited by how much forward thrust you can provide. By adding a pusher prop, you're going to have a dedicated source of thrust once the add that much more speed. Supersonic speed is not needed in a helicopter. But this proven technology (that was ready for production by 1972, when the AH-56 was cancelled)is what will allow new US military rotorcraft to escort V-22s and other planned aircraft with comparable speed and range.

Jon

Edited April 27, 2011 by Cobrahistorian

[Jinxter13]

I'm wondering if this will be a replacement for the cancelled Comanche...that was really going to be one SH machine. Flying that fast, if it's a reliable and stable weaps platform it just might have a niche it can fill in the Army's inventory.

[-Neu-]

I have information relevant to this discussion!

http://www.flightglobal.com/blogs/the-dewline/2011/04/pros-cons-armed-scout-rivals.html

[Berkut]

Sikorsky has taken the merits of the coaxial main rotor setup that Mr. Kamov designed, refined it, and made it simpler and more efficient.

Jon

How? Not a sarcastic question or anything, just interested in the mechanical side of it.

And i wouldn't say X-2 is that supernew, it made its first flight, what almost three years ago? And it is pretty old program in its self. The tech or ideas is not entirely new, just more refined, which is fine.

[Tailspin Turtle]

How? Not a sarcastic question or anything, just interested in the mechanical side of it.

And i wouldn't say X-2 is that supernew, it made its first flight, what almost three years ago? And it is pretty old program in its self. The tech or ideas is not entirely new, just more refined, which is fine.

The Sikorsky rotor system is very different from Kamov's. For one thing, the Kamov rotor is not stiff-in-plane like the ABC's or the X-2's, so Kamovs cannot operate at forward flight speeds that involve retreating blade stall without excessive flapping, risking rotor-to-rotor contact. Note how far apart the Kamov rotors are versus the Sikorsky's.

Three years sounds excessive but the Sikorsky X-2, while not exactly entirely self-funded, has to compete with other Sikorsky military and civil programs like the S-76D which have a more immediate payoff.

My impression is that the big step forward is in vibration reduction whereas the ABC had a very rough ride at speed. However, my guess is that the X-2 speed capability will still be limited to short dashes due to the fuel consumption increase and also impose a payload penalty, so like the tiltrotor, it is not going to replace pure helicopters for all applications.

[jabow]

The test pilot's last statement caught my attention: "I hope we don't wait for 10 yrs or wait for a big contract to develope this techniology".

That was EXACTLY my thinking back in 1977 when I wrote the first Flight Manual for Bell's XV-15 Tilt-rotor!! I thought we'd have commerical tilt-rotors everywhere. Well, I'm still waiting!!

Development cost is such that companies just don't do anything on their own. Period!!

Bo

[Berkut]

The Sikorsky rotor system is very different from Kamov's. For one thing, the Kamov rotor is not stiff-in-plane like the ABC's or the X-2's, so Kamovs cannot operate at forward flight speeds that involve retreating blade stall without excessive flapping, risking rotor-to-rotor contact. Note how far apart the Kamov rotors are versus the Sikorsky's.

Three years sounds excessive but the Sikorsky X-2, while not exactly entirely self-funded, has to compete with other Sikorsky military and civil programs like the S-76D which have a more immediate payoff.

My impression is that the big step forward is in vibration reduction whereas the ABC had a very rough ride at speed. However, my guess is that the X-2 speed capability will still be limited to short dashes due to the fuel consumption increase and also impose a payload penalty, so like the tiltrotor, it is not going to replace pure helicopters for all applications.

Aha, thank you for the explanation. I did notice the difference in height of the rotors, so i suspected it had something to do with contact between the blades.

I understand you have worked with several NASA helo programs? Are you on the Secret Project forum?

[Tailspin Turtle]

Aha, thank you for the explanation. I did notice the difference in height of the rotors, so i suspected it had something to do with contact between the blades.

I understand you have worked with several NASA helo programs? Are you on the Secret Project forum?

Not so much on NASA programs. I worked for Bell Helicopter and was assigned to the XV-15 program for awhile. Some of my friends/acquaintances were involved with the ABC program so I have some familiarity with it. I was also responsible for the Bell proposal for the RSRA program (NASA wanted Sikorsky but needed another bidder to keep them honest - my assignment was to submit something we wouldn't be ashamed of but at minimum cost to Bell and with no chance of success). I visit the Secret Project forum from time to time and occasionally have something to contribute.

[mingwin]

i read in AFM (airforce magasine) that Sikorsky is to complete the preliminary design of it's S-97 X2 this year (2011) with first flight in four years.

[dmk0210]

By utilizing the coaxial rotor system you don't get into the speed issues like a conventional helicopter, you're only limited by how much forward thrust you can provide. By adding a pusher prop, you're going to have a dedicated source of thrust once the add that much more speed. Supersonic speed is not needed in a helicopter. But this proven technology (that was ready for production by 1972, when the AH-56 was cancelled)is what will allow new US military rotorcraft to escort V-22s and other planned aircraft with comparable speed and range.

That is a very impressive machine. And correct me if I'm wrong, but it's a technology demonstration craft, basically an X-plane, right?

I'm curious though, why wouldn't the exhaust from the gas turbine be useful for forward propulsion instead of a propeller? Sort of like a turbo-prop.

Edited April 28, 2011 by dmk0210

[Scooter Man]

I have absolutely NO technical knowledge of this technology - nevertheless I just think that new heli looks "KOOL!"

[Mark M.]

Wow.

Mark, you really need to catch up on nearly 40 years of helicopter development.

No denying that!

But the problem isn't that technology has improved... The problem is that a helicopter moving forward through the air also has a rotor blade advancing forward on one side. The faster the forward motion, the closer that advancing blade's tip reaches to the sound barrier, and this isn't something that's good for helicopter blades (OR for conventional prop blades either).

So regardless of technology advancing and newer designs, you are still limited to how fast you can go because it is a helicopter, no?

I'm also still skeptical because the demonstrator is about the size and weight of a F1 race car. You make it double wide, have armor plating, give it wing stubs, a gun, rocket pods, anything... all of a sudden you need a beefier engine, it has much more drag, more mass, the acceleration drops down the toilet, etc... etc...

Those "short bursts" are gone because you can't accelerate very far when you're 10x heavier.

IMO it's old technology. The DESIGN, I mean. Whether or not the actual parts are new, it's like building a modern-day zepplin. Might be new, but it's old and disproven.

What I'd like to see are more XV-15 style gunships. Like an OV-10 Bronco, but with tilt rotor tech. No cargo bay, add armor, all of a sudden you got something that can keep up with V-22s.

Like the AH-1 to escort the UH-1. Only, based on tilt rotor tech.

Edited April 28, 2011 by Mark M.

[Hawkeye's Hobbies]

Forward speed in a helicopter is limited no matter how big of a fan or jet you use to push it forward through the air. Anytime you have a spinning prop or rotor, tip speed becomes an issue and has serious aerodynamic issues to deal with. Back when they were trying to make a supersonic turboprop fighter using the F-84 as a base platform the prop tips turned above Mach and the vibrations were deafening as well as structurally tasking. They rediscovered this when they tried to do the same thing with airliners using an DC-9-80 series with pusher fans.

High forward speed with a rotor that is providing lift facing the ability to sustain lift the faster the airframe is moving. Hence the reason of the concept of a disc with retractable rotor vanes. Once the aircraft reaches as certain forward speed the rotors are retracted and the disc acts as the wing which provides the lift. Slow down and the rotors are extended to give the necessary lift and V/STOL landing attributes of a pure helicopter.

[Mark M.]

I do recall those disc rotor designs.. quite interesting (but how would a disc work with regards to lift and other quirks? No doubt not the best airfoil shape), as well as the rotor blades that stopped and became fixed wings.

I believe the latter only existed really as concept sketches, too many problems to work out.

[wh1skea]

I do recall those disc rotor designs.. quite interesting (but how would a disc work with regards to lift and other quirks? No doubt not the best airfoil shape), as well as the rotor blades that stopped and became fixed wings.

I believe the latter only existed really as concept sketches, too many problems to work out.

You might be surprised how well a disc can be used as an airfoil....

[Mark M.]

I do remember that, but as far as using it for faster more manuverable helicopters? Might produce the lift, but would it be good for any manuvering?

That much I don't recall from the flying pancake. I thought it was mostly level flight testing.

'Course the answer may be "Well they slow down to manuver, using the rotors instead of the disc"... If that's the case then never mind.

[Mark M.]

Oh, regarding commercial tilt rotors:

http://media.defenseindustrydaily.com/images/AIR_BA609_lg.jpg

BA609, baby! I hope this takes off and becomes mainstream, really.

[11bee]

Wow.

Mark, you really need to catch up on nearly 40 years of helicopter development.

The X2 technology demonstrator is a remarkable aircraft and has already set new speed records.

Sikorsky has taken the merits of the coaxial main rotor setup that Mr. Kamov designed, refined it, and made it simpler and more efficient. Combined with a pusher prop, you are now looking at the next generation of military aircraft.

By utilizing the coaxial rotor system you don't get into the speed issues like a conventional helicopter, you're only limited by how much forward thrust you can provide. By adding a pusher prop, you're going to have a dedicated source of thrust once the add that much more speed. Supersonic speed is not needed in a helicopter. But this proven technology (that was ready for production by 1972, when the AH-56 was cancelled)is what will allow new US military rotorcraft to escort V-22s and other planned aircraft with comparable speed and range.

Jon

Very interesting. The catch will be trying to sell the idea to a very cash-strapped DoD and move it from a one-off demonstrator to something that has tactical value. Regardless, it good to see stuff like this happening. Current US military helicopter designs are not exactly cutting-edge these days.

[Tailspin Turtle]

That is a very impressive machine. And correct me if I'm wrong, but it's a technology demonstration craft, basically an X-plane, right?

I'm curious though, why wouldn't the exhaust from the gas turbine be useful for forward propulsion instead of a propeller? Sort of like a turbo-prop.

The X-2 is a technology demonstrator in that it is really too small to have much mission capability. Otherwise, there don't seem to be too many compromises.

One of the short comings of most "high-speed" helicopter demonstrators is the use of separate engines for lift and thrust. The ABC had turboshaft engines to turn the rotors and jet engines to go "fast". The X-2 rotor lift and cruise thrust both come from one engine driving the appropriate gearboxes for the rotor or the aft propeller. Another reason for not using jet engines on compound helicopters is that they are inefficient compared to turboprop propeller thrust at the speeds and altitudes that the compounds can achieve.

[jabow]

Oh, regarding commercial tilt rotors:

http://media.defenseindustrydaily.com/images/AIR_BA609_lg.jpg

BA609, baby! I hope this takes off and becomes mainstream, really.

IMHO, the 609 is the wrong a/c for the 1st Commerical T/R. It competes with Biz-jets/turbo-props IF they can keep cost down, and that's the challenge.

Developed back when the company was run by fixed wing guy. He wanted an airplane that can hover, NOT a helicopter that flies like an airplane. BIG difference.

IMHO, it should have been a bigger non-pressurized cabin with big or sliding door for e-z cargo/litter access. Rear ramp would be okay, too. Then the Coast Guard would be flying it for long range SAR missions.

My 2 cents.

Bo

[jabow]

The X-2 is a technology demonstrator in that it is really too small to have much mission capability. Otherwise, there don't seem to be too many compromises.

One of the short comings of most "high-speed" helicopter demonstrators is the use of separate engines for lift and thrust. The ABC had turboshaft engines to turn the rotors and jet engines to go "fast". The X-2 rotor lift and cruise thrust both come from one engine driving the appropriate gearboxes for the rotor or the aft propeller. Another reason for not using jet engines on compound helicopters is that they are inefficient compared to turboprop propeller thrust at the speeds and altitudes that the compounds can achieve.

Unless you can muffle jet thrust, it's very difficult to hover!! Ya can feather a prop.

Bo

[Mark M.]

Jabow: I would think coast guard use is limited. It would make for a very small order and that's it. The real money will come from the commercial side. That's exactly where you want to compete (or rather, where you want to compete and win).

I don't know much about the "fixed wing guy" but what you're describing is 6 of 1, half a dozen of the other to me. Helos only go up and down well, they don't fly forward well. Planes fly forward well, they don't go up and down well. Regardless of the design intent (fixed wing that lands like a chopper vs chopper that flies like a fixed wing) the end design, IMO, is going to look the same.

I still say we need attack XV-15s! Give them smaller blades, smaller wings, smaller surface area, underwing pylons, and stick a gun on there just for killing tanks. It might put the Apache to shame!

That... or... wait for the F-35B to be finished.

[jabow]

Jabow: I would think coast guard use is limited. It would make for a very small order and that's it. The real money will come from the commercial side. That's exactly where you want to compete (or rather, where you want to compete and win).

I don't know much about the "fixed wing guy" but what you're describing is 6 of 1, half a dozen of the other to me. Helos only go up and down well, they don't fly forward well. Planes fly forward well, they don't go up and down well. Regardless of the design intent (fixed wing that lands like a chopper vs chopper that flies like a fixed wing) the end design, IMO, is going to look the same.

I still say we need attack XV-15s! Give them smaller blades, smaller wings, smaller surface area, underwing pylons, and stick a gun on there just for killing tanks. It might put the Apache to shame!

That... or... wait for the F-35B to be finished.

The pressurized cabin is the real issue. Can't make big doors and don't need to fly at 25K Ft. A 'truck' tiltrotor has many more uses than a 'sports car' tiltrotor.

With the tilt funtion, it's very, very difficult to hold cost down as to compete with fixed wing a/c. Can't compete with payload either. Wrong design.

And, there were several hundred sold at the project cost of the 609. Meeting that projected cost ......... now that's the problem.

Oh, re the F-35, put me down for a 'doubting Thomas' on that one, too.

Bo

Edited April 28, 2011 by jabow