Feeds

X2 supercopter in first tail-drive flight

Sikorsky preps Osprey bitchslap

Choosing a cloud hosting partner with confidence

US-based whirlybird megacorp Sikorsky announced yesterday that its "X2" high speed helicopter prototype has now made test flights using its tail propulsor. The aircraft had already flown, but only using its main rotors.

The Sikorsky X2 demonstrator craft

Third prop's the charm, apparently.

The idea of the X2 is to achieve a helicopter which can cruise twice as fast as ordinary whirlybirds, even exceeding the speed abilities of tiltrotor aircraft like the V-22 Osprey and the BA609. While being fast, X2 choppers would also offer superior hover performance to that of tiltrotors; and perhaps easier maintenance and operation.

The X2 is intended to achieve all this by the use of two main rotor sets spinning in opposite directions. This avoids one of the problems suffered by ordinary helicopters attempting to go fast, the issue of "retreating blade stall" - where the backwards-going blade briefly becomes almost stationary with respect to the air it cleaves owing to the aircraft's forward speed, so losing lift on one side of the rotor disc. An X2 or other stacked-rotor copter has forwardgoing blades on both sides, however.

That's just one of the snags to be solved, though. As the retreating blade slows, so the forward-going blade tips tend to go supersonic as the helicopter accelerates. In general this is hard to deal with, as most choppers spin their rotors at a fixed rpm.

But the X2 has variable speed equipment, allowing it to slow the blades' spin as it speeds up and so keep the blade tips safely subsonic. It also has modern superstiff low-drag rotors and active damping tech, which Sikorsky hope will quell the violent vibration which bedevilled previous efforts along these lines.

As the twin main rotors counteract each other's torque, an X2 needs no side-thruster on its tail for steering. This means that it can put a forward-driving propellor there instead, to provide the extra thrust necessary to reach high speeds. A previous attempt at an X2-like aircraft, the XH-59A demonstrator, used extra strap-on jet engines instead: but these made the XH-59 overly heavy and complex, and a fuel hog besides. Sikorsky believe that their tail prop driven from the X2's single turbine is the way forward - smaller X2 craft of the future could also be single-engined and thus probably cheaper to operate than tiltrotors.

All that said, the moment of truth is still not here for the X2. The just-announced flights with tail drive in use, made on Tuesday by Sikorsky's chief test pilot Kevin Bredenbeck, saw maximum speeds of just 52 knots. In coming months the X2, having been thoroughly shaken out and tested at lower speeds, will start working up towards its design speed of 250 knots (290 mph).

It appears that the trials are going well so far, however. Bredenbeck said that "vibration and noise levels were very low" with the propulsor engaged.

"Certainly we've got much more to do," said Sikorsky R&D veep Mark Miller, "but interest continues to grow... These are exciting times."

Miller needs interest to grow, because so far Sikorsky has no customer for production X2 craft. The firm is developing the idea with its own money for now, though there have been some small US government contracts for design studies on large heavy-lift versions. ®

Choosing a cloud hosting partner with confidence

More from The Register

next story
Renewable energy 'simply WON'T WORK': Top Google engineers
Windmills, solar, tidal - all a 'false hope', say Stanford PhDs
FORGET the CLIMATE: FATTIES are a MUCH BIGGER problem - study
Fat guy? Drink or smoke? You're worse than a TERRORIST
SEX BEAST SEALS may be egging each other on to ATTACK PENGUINS
Boffin: 'I think the behaviour is increasing in frequency'
HUMAN DNA 'will be FOUND ON MOON' – rockin' boffin Brian Cox
Crowdfund plan to stimulate Blighty's space programme
Post-pub nosh neckfiller: The MIGHTY Scotch egg
Off to the boozer? This delicacy might help mitigate the effects
I'M SO SORRY, sobs Rosetta Brit boffin in 'sexist' sexy shirt storm
'He is just being himself' says proud mum of larger-than-life physicist
NASA launches new climate model at SC14
75 days of supercomputing later ...
Britain's HUMAN DNA-strewing Moon mission rakes in £200k
3 days, and Kickstarter moves lander 37% nearer takeoff
prev story

Whitepapers

Why and how to choose the right cloud vendor
The benefits of cloud-based storage in your processes. Eliminate onsite, disk-based backup and archiving in favor of cloud-based data protection.
Getting started with customer-focused identity management
Learn why identity is a fundamental requirement to digital growth, and how without it there is no way to identify and engage customers in a meaningful way.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
Getting ahead of the compliance curve
Learn about new services that make it easy to discover and manage certificates across the enterprise and how to get ahead of the compliance curve.
Intelligent flash storage arrays
Tegile Intelligent Storage Arrays with IntelliFlash helps IT boost storage utilization and effciency while delivering unmatched storage savings and performance.