Sikorsky X2 superwhirlybird enters ground spin-up phase Those like us on the Vulture flying-car desk, who chafe at the limitations of present-day hovering aircraft, like to keep an eye on Sikorsky's X2 prototype. The helicopter firm announced today that the X2 made its first ground runs with blades fitted last week, and everything went swimmingly. "We continue to move our …
... at something to know it's wrong.
Even if it was whisper quiet and could do 400 Knotts whilst sipping gently at a non-organic fuel, people still wouldn't use it simply because it just doesn't look right.
What would be so wrong with a good old fashioned jet turbine, mounted just below the rotor disc, with harrier-style nozzles to aid VTOL ?
Mine is the one with the oil stains.
Sure, nothing new. Well, except that it uses a pusher prop driven from the main transmission combined with coaxial, making it very different from the AH-56: and avoiding the need for extra push engines as on the S-69/XH-59A. (The YH-59 high-speed test bird, which got up to X2-like speed, had to carry no fewer than four turbojets as well as its rotor drive). Sikorsky wanted to build an XH-59B on X2 lines at the time, but it didn't happen.
This isn't even to mention that X2 has variable speed rotors, too, which is potentially rather significant all on its own - as I did my best to point out. And a few other things that I didn't find room for in the article - low-drag hub etc.
Just out of interest, what would be news? Hyperdrive?
Anyway, if you can't see why revolutionary is a better word to use here than evolutionary ...
I see it was a mistake to start looking at comments again.
I'm sorry, I don't care how good the X2 is, it's just not as goddamn cool as the Osprey.
I want my AnimeCopter NOW!
@Sam: "Wasn't there a design where two lots of rotors intermeshed?" - What, you mean for this specific project? Intermeshing rotor configurations have been round for a while.
What pissed me off a big about the Comanche vs Hokum was the specs they used. Despite having a bigger engine and contra-rotating blades, the game had all the advantages on the Comanche: accelleration, top speed, maximum lift. And where they had the Hokum better off (carry weight) was nerfed by having only the smaller weapons available, so you couldn't hook on HARMs or similarly useful (and heavy) arms and so even up the balance.
"Wasn't there a design where two lots of rotors intermeshed?"
Do you mean tandem rotors, one on each end and a body slung between? These are more common than you realise. They have feature in designs dating from the late 40s.
They're used in heavy lifting helos like the CH-47 Chinook (aka the Prince Willy taxi).
Jobs cos that's not a halo, they're supersonic rotor tips!
For those who commented about the 'coolness' of jets, be they turbojets or turbofans compared with a turboprop, two main factors.
1. The pusher prop is driven off the main engine, i.e. it doesn't require an additional powerplant for the forward propulsion. This saves weight and hence fuel while allowing greating lift capacity and greater range.
2. Turboprops are more fuel efficient at these sort of speeds than either turbojets or turbofans. Fuel savings again giving rise to increased range and lift capacity.
As for comparisons with the V-22, hmm. It's taken over two decades effort by Boeing and the aircraft still isn't performing correctly. The V-22 is big, horrendously complicated and uses all manner of technology to perform certain tasks, e.g. auto-rotation, that have been solved perfectly well in the previous fifty years. The X-2, on the other hand, uses some very clever engineering *where it is needed* and in all other respects it is as simple as can be.
Now that's good engineering in my book.
An FYI for everyone.
Most helicopters, probably including this one, DO use jet engines. Go look up "turboshaft". It's a kind of jet engine optimized for producing shaft power rather than jet thrust, common on helicopters and even the M-1 tank.
Using jet engines to drive bigger fans actually works out rather well for efficiency and power. See: turbofan
This is better than using the turbojets for raw thrust, and is why a helicopter with relatively puny jet engines can lift itself off the ground while the Harrier and F-35 need monster engines.
If you'd rather have a cool looking vehicle than a working one, by all means use bog standard turbojets.
You may be thinking of the Kaman Husky which had two side by side rotors that overlapped by about a rotor span. Despite looking like the worst idea ever I think it had 0 fatal accidents in service, it may not have had any accidents.
As to the downdraft from above affecting the bottom rotor, it would alter the relative airflow, but this is rectified by having the lower blades at a different angle of attack to generate the same amount of lift.
can a coaxial rotorcraft autorotate? My CX2 can't autorotate, but it's admittedly a toy.
The control linkages for a real aircraft, with variable speed rotors, means each rotor needs separate collective and cyclic control linkages or acutators..is this all driven by electronic actuators? because mechanical linkages on two spinning shafts would be a nightmare. Toy coaxials only do the cyclic on the lower rotor and I haven't seen one that does collective on any rotor.
As far as transmission difficulties, this has a slightly less difficult design (tho the Osprey's power sharing transmission is unique not in implementation but dealing with the horsepower and being lightweight) but it's control implementation may provide some serious challenges. If it's all electronic it's easier but then you have absolutely no control if your electrical power is lost. Six of one, half-dozen of the other.
War is dangerous, and high performance aircraft for war use are even more so. Been that way forever, and isn;t going to change no matter what contractor is supplying hardware.
BTW, excellent article, LP!
@Joe Cooper (why turbojets)
Read (or rather sing) Ash's comment whilst you look up and wave at Msrs. Santini and Hawke, Ms. O'Shannessy (and the joke) as they fly over your head.
And obviously only the TOP of the helicopter is black - the bottom must be as white as Archangel's suit.
Mine's the "Santini Air" jacket.
There was another design where there were two main rotor disks that intersected each other at a 90 degree angle. Each rotor hub was angled outboard, away from the fuselage, at a 45 degree angle.
It's name escapes me.
Mine's the one with the pilot wings drawn in with Crayola because it makes my passengers make funny faces.
Looks like a maintenance nightmare with all those enclosed and open shafts and numerous other vibration hazard points , all in all probably more trouble then it is really worth ! Might be a goer if the main blades are redesigned to take into account a concept that was solved by nature aeons ago though and only just rediscovered by man recently !
One should also not forget the current bulk of RAF aircraft are down and out due to either overtime on the frames , lack of decent spare parts or being flown by many pilots who can't even hit the broadside of a barn at even 100 paces , all thanks to Tony B Liar and his assorted boot licking take a bribe friends being too cheap to fund the real cost of his "Follow the DC Chimp's in your posterior adventures"
I thought the main reason heli's are not in common use in urban environments is more to do with the cost of running and maintaining them. That and the rotors tend to be a safety concern (something the X2 doesn't really address) needing quite a large safety exclusion zone for takeoff and landing. I would think the noise levels would be only a minor issue by comparison.
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