Helicopter X-2 to reach 250 mph!!!

I am sure this is all known by many, but I would like to point out that Sikorsky is developing the new X-2 that has the capability of reaching 250 mph... for newbies, this is incredibly fast for a helicopter, especially since right now the fastest is around 150 mph.

The technology is simply this: Instead of 1 rotorhead, there are two, each with two blades. They rotate in opposite directions, cancelling out the torque force (I think) that is created by the one rotor assembly, which normally holds down the aircraft's speed. I am a newbie over here at sikorsky, so I don't know much, but I just thought that this is pretty neat.

actually , a specially prepped westland lynx holds the helicopter speed record at 249mph+

source article

so i am unsure where you get the 150mph idea from -- thats the dash speed of most service helicopters with armour , weapons and troops

and a quick scan of the x-2 specs show it is not a true helicopter anyway

source article

X2 Technology aircraft will hover, land vertically, maneuver at low speeds, and transition seamlessly from hover to forward flight like a helicopter. In a high speed configuration, one or more 'pusher props' are part of an integrated auxiliary propulsion system to enable high speed with no need to physically reconfigure the aircraft in flight.

to beat the ttheoretical limit of 250mph plus , that a true helicopter is faced with - the x2 clearly employs hybrid technology

[edit on 30-5-2006 by ignorant_ape]

Hmmmm....

Maybe I was referring to production helicopters?

I dunno, All I know is that sikorsky is in the process of building an X-2 Prototype. It should be pretty sweeeeeet.

Originally posted by ignorant_ape
and a quick scan of the x-2 specs show it is not a true helicopter anyway

How is the X-2 not a "true helicopter"? Looks like it meets the requirements to me.

Originally posted by Mouth
I am sure this is all known by many, but I would like to point out that Sikorsky is developing the new X-2 that has the capability of reaching 250 mph... for newbies, this is incredibly fast for a helicopter, especially since right now the fastest is around 150 mph.

The technology is simply this: Instead of 1 rotorhead, there are two, each with two blades. They rotate in opposite directions, cancelling out the torque force (I think) that is created by the one rotor assembly, which normally holds down the aircraft's speed. I am a newbie over here at sikorsky, so I don't know much, but I just thought that this is pretty neat.

Correct on the contra-rotating rotors cancelling the torque effect.

As I understand it, the limitations to maximum speed with a helicopter has to do with the rotor blade tips hitting/or exceeding the sound barrier - Mach 1.

The forward moving rotor blade is affected by the speed of the copter.

The maximum speed of the rotor blade tips normaly run below Mach 1, but when you add the forward speed of the copter to the advancing rotor blade speed you can exceed Mach 1 at the blade tips.

One way around this, but it's self-limiting to a degree is to run a smaller diameter rotor blade which cuts down tip speed.
Self limiting because the smaller rotor diameter needs to run at a higher rpm to generate the same amount of lift a larger, slower running rotor would.
And with a larger rotor, you're back to the Mach 1 tip speed problem.

Just like an airplane wing, a specific amount of lift is required to become airborne so a smaller diameter dual rotor system can achieve the required lift area with smaller diameter rotors and allow a higher aircraft speed.


(Edited for grammar.)


[edit on 30-5-2006 by Desert Dawg]

Yes, it certainly is a true helicopter. Sikorsky has been promoting this layout since 1980 and I have an artists impression of an ASW helicopter that looks about the same size as a Sea King that is identical to the X-2 in its general arrangement.

Kamov have been using contra rotating blades for ages.

Desert - the difference this will make is that both blades will experience the transonic supersonic effects simultaneously, in effect balancing the drag created on both sides of the helicopter.


On a traditional layout, the side which has the blade sweeping forward [if the rotor is anti-clockwise it would be the right hand side] will experience the problems, leading to loss of lift and greater drag on that side, but no such problems on the backward sweep [left side for the example]- hence the lateral unbalancing of the lift/drag forces.

Originally posted by JIMC5499
How is the X-2 not a "true helicopter"? Looks like it meets the requirements to me.

I think he is referring to the "pusher-prop". I too agree that this would probably be classified as a hybrid as it employs a propulsion system in a similar way to a plane.

Interesting though, I had never heard of the theoretical speed limit of a helicopter before but it definately makes sense.

ok - i gotta be a pedantic S.O.B and point out that the definition of helicopter i am using is

A powered rotor provides both lift and propulsion.

as the x-2 clearly states that its increased top speed is provided by a

pusher-prop

then it is not a true helicopter - the x-2 will beat the 250mph barrier because its main rotrs will be providing lift and only a fraction of thrust

this will prevent the issues of blate tips going supersonic -- as they main rotors will not be able to sustain the forward flight speed

this is the basis for my contention that it is not a true helicopter -- but a hybrid as i claimed

Hey it hovers with the main rotors, in my book thats a helicopter, regardless of how it gets to 250mph, it still gets some thrust from main rotors, but this is obvious, how else would it hover ? Thats alot of damn thrust to keep something that heavy floating in air.

as someone mentioned the Kamov i thought i would post a picture of the Ka-50 `Black Shark` or Hokum in nato speak.


twin rotors are not new for the russians - they`ve been doing it for years

Originally posted by ignorant_ape

A powered rotor provides both lift and propulsion.

as the x-2 clearly states that its increased top speed is provided by a

pusher-prop

then it is not a true helicopter - the x-2 will beat the 250mph barrier because its main rotrs will be providing lift and only a fraction of thrust

this will prevent the issues of blate tips going supersonic -- as they main rotors will not be able to sustain the forward flight speed

this is the basis for my contention that it is not a true helicopter -- but a hybrid as i claimed

As long as the main rotor is powered it's a helicopter.

I'd be curious about how they are going to handle the blade loads. As the speed on a helicopter increases you wind up with an effect that tends to roll the aircraft along it's long axis. What happens here is as the rotor blade advances in the same direction as the aircraft is travelling it generates lift from both the velocity of the blade's rotation, as well as the speed of the aircraft, the blade advance cycle. When the blade crosses the long axis of the aircraft it starts the blade retreat cycle. The blade during the retreat cycle doesn't generate as much lift because the aircraft's velocity is subtracted from the blade's velocity, which decreases the blade's lift. At normal speeds this isn't much of an issue, but at higher speeds it could be a problem. The tandem rotor might be a solution for this if they can keep the blade paths of each rotor seperate.

I concur with JimC.

An aircraft that flies by means of a powered rotor alone is a helicopter, with an unpowered rotor it is an autogiro, a combination of rotor(s) and wings makes for a convertiplane or hybrid.

even the definition posted fits;

A powered rotor provides both lift and propulsion.

it doesn't say ALL propulsion, or even most of it.

Geez, I didn't know so many people even knew about the X-2. I can find out as much info as I can, since I work in the publications department here at Sikorsky. If anyone has any questions (that do not involve classified information) I'd be happy to find out.

Originally posted by ignorant_ape
actually , a specially prepped westland lynx holds the helicopter speed record at 249mph+

so i am unsure where you get the 150mph idea from -- thats the dash speed of most service helicopters with armour , weapons and troops

... including the lynx. The conditions the record was achieved under bares little resemblance to the real world. The machine was heavily modified and stripped of everything but the bare essentials.

Sure thing Mouth.
If you can get us some pics of it in construction or maybe something else connected to the project that would be great.


And yes Russians have been doing it for a long time (twin rotors that is).
But the X2 has a pusher prop to provide the forward thrust at high speeds wich leads to the main rotors being run at lower rpms(they only have to provide lift) and so they can avoid the Mach1 problem on the blades and push the speed limit to 250+ mph.

PS: nice avatar Mouth

[edit on 30-5-2006 by vorazechul]

I have to disagree with you waynos because...

a Chinook has two small pusher jets at the back but it is a helicopter. If it has a powered rotary wing for lift it is a helicopter if it also has wings it may still be a helicopter (Mil Mi6) or a convertiplane (Girodyne) or a tilt rotor (Bell BA609) if the rotor blades are not powered it is an auto-giro.

Originally posted by Subatomic
I have to disagree with you waynos because...

a Chinook has two small pusher jets at the back but it is a helicopter.

It does not. Those are the main engines.

oops i stand corrected

I think one of the coolest designs was the x wing chopper. Never seem to get off the ground though. Was a while ago, but the main rotors acctually stopped in mid air and acted as a lifting surface while jet engines provided thrust. I think i still have some pics from the HAI convention in cali, see if i can find and scan.