Helicopter X-2 to reach 250 mph!!!

subatomic, taking aside the fact that the Chinooks 'pusher jets' are in fact the turbines that power the rotors, what is it that you are disagreeing with me about because I can't figure where you are saying anything different from me? The Mi 6 is a helicopter to which wings can be, and are, sometimes attached. They are not integral to its design. Examples where the wings are integral are the V-22 and the Rotodyne, which are not helicopters. A helicopter that is pushed along by a propeller or a jet (Sikorsky S-72) but which gains its lift from a powered rotor is still a helicopter.

Henry Henry;

.. including the lynx. The conditions the record was achieved under bares little resemblance to the real world.

The top speed of the standard service Lynx is still in excess of 200mph, one of the fastest service helicopters in the world, it is faster with two crew and eight fully armed troops on board that an AH-64 Apache and is also fully aerobatic being capable of loops and rolls (hopefully for the troops, after they have got off).

Of course the Lynx was specially prepared for the record, all record attempt aircraft are specially prepared, but the Lynx is no 150mph plodder.

wrong.

The X-2 will be able to go 250 knots...which is 288mph.

I like its design, and hope it can achieve its speed...and hopefully will catch on. Its certianly easier to make then the X-50...which has had multiple crashes and will likely be scrapped soon.

My coolest looking helo vote would have gone to a UCAR concept , but it got cancelled. But I like the dual tilted rotor look.

I haven't seen that one before murcielago, good find

It strikes me looking at these two designs that the Helo world is really struggling to come with new ideas. Even the rotor layout shown above has been flying for decades on the Kaman Huskie and K-Max type designs and as I said before, Sikorsky has been pushing its X2 idea for two and a half decades so far.

I suppose that once you have decided to build an aircraft witha big whirly thing on top you are somewhat limited in what you can do with it, design wise.



[edit on 31-5-2006 by waynos]

Originally posted by waynos
The top speed of the standard service Lynx is still in excess of 200mph.

"Top speed." In the real world, a lynx with any meaningful amount of cargo will do less than 200mph. Still, it does hold the world record for forward flight, an impressive achievement that is unlikely to be challenged for years to come. It's even more impressive when you consider that it has held the record for decades.

Originally posted by waynos
is also fully aerobatic being capable of loops and rolls (hopefully for the troops, after they have got off).

Yeah. Nice to look at, but not very useful for anything other than airshows. These days there are several helicopters with rigid rotors capable of this, including civilian machines from both Eurocopter and Bell.

Originally posted by waynos
Of course the Lynx was specially prepared for the record, all record attempt aircraft are specially prepared, but the Lynx is no 150mph plodder.

It is, and it also holds the record for most unreliable helicopter, and has an accident rate that makes it well deserving of the widow maker nickname!

Well, it did once anyway. British engineering at its finest. *cough*

I don't know how the engineers handle it, but it might become necessary to actually slow the counter-rotating blades down as the crafts speed increases past a certain point. It will be interesting to see how much actual forward thrust the pusher can provide.

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.

The advancing blade and the retreating blade are canted - or tilted - along the blade chord at differing angles, one blade compared to the other.

Since the advancing blade has more lift due to an effectively increased airspeed it has less cant therefore less lift.

The opposite is true with the retreating blade. It has more cant which generates more lift.

These differing blade angles balance out making for an equal amount of lift transversely speaking.

When Mach 1 levels are attained at the blade tip, problems begin with loss of lift on the advancing blade and I understand vibrational harmonic problems can come into play in such a scenario.

The differences in blade angle also create forward momentum.
The higher the airspeed, the less the difference is, but there's always a difference when the heli is moving through the air.
Blade angles are the same when the heli is hovering in calm conditions.

Tha is what i call A HELICOPTER!!, damn, great machine!

It is, and it also holds the record for most unreliable helicopter, and has an accident rate that makes it well deserving of the widow maker nickname!

Well, I have never heard the Lynx referred to as the 'wido maker' and must now wonder if your post is driven by a personal dislike of it? The Lynx has been extremely successful and I don't think any of its operators bought it at gunpoint?

re-the aerobatic capability, I never claimed it was unique, but it was the first, the Lynx is now a quite old design, around 35 years in fact, so its to be expected that it is no longer cutting edge.

edit; of course I had to consider that you have a point and may be correct so I have just searched online using the phrases "Westland Lynx widowmaker","Westland Lynx reputation" and "Westland Lynx reliability"

I found not one single result (other than this very thread) that backed up your claim and in fact hundreds that say the opposite. I'd be grateful therefore if you could point me in the direction of of some sources which I have obviously missed.

[edit on 31-5-2006 by waynos]

Actually, last time I looked at Guiness, the Mi-24 was the fastest _service_ (unmodified) helicopter in use with a top speed around 200 knots. Of course you don't dare maneuver it there because the margins on boom slap are so tight you don't dare.

More importantly, I recall a more or less vanilla S-76 did a 500km course at an average 187 knots in cruise which is the same as saying an F-22 can sustain Mach 1.5 longer than a MiG-24 can sprint out to 2.65 or so.

Indeed, many civillian helos beat their military counterparts by virtue of much more capable rotor systems and MUCH MUCH cleaner (and lighter) system design. In the early 1980's the USAr used both MD-500 and H-76 (militarized Spirit) to flat out embarass both the Apache and Snake during 'air to air training' exercises.

That said, the X-2 looks like nothing more or less than the XH-59 ABC with a fantail as opposed to a pair of turbojets and so, IMO, if you don't disqualify the X-2 as a compound, the 289 knot capability of it's grandpappy still makes Sikorsky the owner of the fastest chopper in the world.

Followed by Lunchmeat with their 260 knot XH-51 Little Chief.

Followed by Lunchmeat again with the 220 knot AH-56 (again, as a production ready _service_ helo).

The big problem with RBS or Retreating Blade Stall is that, even if you don't try to use collective pitch changes to retain lift on the retreating side, the loss of lift causes the aft moving blade to droop and any subsequent loading change makes it start to buzz which eventually makes the blade itself give up, separates the blade from the hub or cuts the boom. Rigid Rotor systems change this by virtue of effectively tying the _disk_ plane to the advancing blade position with a stiff hubmount for all blades.

This means that the retreating rotor can neither droop on it's own nor rub at the mast and keeps everybody toes the same blade line regardless of inertial/lift forces.

It is also why the Hokum is a joke rather than some kind of super-chopper because it's rotor system is not rigid and so if you try and load the aircraft in a particularly turn direction at speed, you will either mesh the disks or again start separating blades.

THE BIG QUESTION then becomes "Does it matter?". Because if you have a competent ASE suite you can fly at 1G and 3-5,000ft, almost entirely outside the trashfire envelope while defeating MANPADS and AHM with relative (MAWS time to see it coming) ease. Even as you can SEE to ranges heretofore undreamt of by beanie prop jocks (40-60km, easy). With these kinds of capabilities, the armed military helicopter becomes less a direct combat (a yankin' and a bankin') fires delivery platform than one which is designed to function as an econobus for sensor systems and standoff muntions. Most of which can be dropfired.

This in turn potentially reopens up the idea of a 'cabin cruiser' system which can trade what is actually rather pathetic agility anyway (+3/-1.5G for the Apache) for very long sensor coverage and very fast (for a choppper) refresh of wide scouting=organic ISR sanitization areas. If all your sensors are side/downlooking, there is no reason to close with a target and so the frontal target area minimization and all round view justification of a conventional gunship is also gone.

If you are carrying no weapons wings or fixed gear or cannon or optical systems (because a big cabin means internal stowage on a wider gear track with shorter = more upright wheelbase), the other justification for the tandem seated gunship configuration: reduced frontal drag (Snake vs. Hog) is also removed.

And so 'suddenly', with no requirement for agility or for external weapons loads or for visibility OVER a target the rotor system complexity of a coax is also removed and you can go with a simple, single, hingeless/rigid main rotor system that offloads to wings or a lifting body shape in principle cruise flight while maintaining an internal volume sufficient to be a useful liason/utility platform on the civil market.

This in turn being the principle problem I have with the X-2-

www.defenseindustrydaily.com...

As proposed. Particularly since, if I am operating a standoff sensor collection suite (including monitoring of previously emplaced UGS on a detex-flyby basis) while acting as a drone controller for MOUT overhead apertures, I can sit the cabin like any ASW operator and 'feel no pain' of up-front exposure.

Which means the frontend can be shorter and single-pilot optimized (SHADOW) to further assist in configuration, weight and streamlining issues.

We are now at the point where row-boat/shoot-ducks division of labor no longer makes for a viable workload reduction effort in a direct attack platform of as limited a performance margin as the conventional Helo. Anaconda showed this when we had 4 AH-64 shot up within the first 30 minutes and supporting air basically ceased to exist. Falujah repeated the lesson when we had something like 24 more Indians torn to pieces and one downed by a bloody farmer and his stinkin' Carcano boltaction. We should not NEED a third.

The question then becomes whether we are willing to kick the Army in the nuts to show them that SPO _works_ (fully automated terrain avoidance and approach to hover plus 360` night/synthetic vision systems) in a way that lets us retain a useful civil market advantage (low drag and high performance in a 6-8 passenger cabin with 250nm range or 500nm with 4 passengers and aux tanks) once they finally get a Kiowa/Comanche/Longranger RAH-rah replacement for their precious armed scout role.


KPl.

ch,
I had the impression that this X-2 is intended almost solely for the civilian market.

And altough I'm not very familiar with the problem associated with loss of lift on the retrieving blade of the rotor.....wouldn't a twin rotor solve most of it??

And even other wise I can see only advantiges in the twin rotor design:

Since you have two rotors the blades don't have to be as long as those of a single rotor to create the needed lift and so they would occupy less space in an urban area.
What's more important, a rotor with a smaller diameter would result in a slower speed on the tips of the blades and thus a design with increased forward speed is made without sacrificing the lift at lower speeds and hover

Completes first flight

www.flightglobal.com...
speedster-completes-first-flight.html

A picture of the first flight from Sikorsky and a few concepts.

Thought they were worth sharing.

I saw photos of the first flight of the Sikorsky X2, very nice.

Now, I'm somewhat knowledgeable in single rotor & tail rotor arrangement, with the cyclic & collective stick.

Can someone explain to me (and other, I suppose) how the X2 will be control?

Is the main rotor (counter-rotating) have fix blade? (or pitch can vary, can the whole rotor be tilted?).

I read somewhere that one of the main rotor could induce (how) less counter moment and control the Yaw motion that way.

I guess, the push propeller must have variable pitch blade (for roll & pitch?).

Do you think, that this could challenge the V-22 (same speed range, less complex).

Thanks in advance.

I read this somewhere:

On the military side Sikorsky envisions an X2-sized armed helicopter that could fly escort for the Bell Boeing V22 Osprey ...

www.flyafrica.info...

Could you imagine this if it ever happens, Sikorsky competitor of Bell Helicopter having to ensure safety for the V-22 because it cannot do it by itself?

If Sikorsky pull this concept thru and apply it to it's line of helicopter, several customers will go for the added speed (EMS operation. taxi to Oil Rig, etc.) other manufacturers will not be able to cope (except perhaps Bell with the tilt rotor BA609 (same speed range).

Sikorsky make another milestone on the road to 250 knots with the X2.

225 knots achieved in a test flight, although its not yet an official record.

www.flightglobal.com...