Feeds

X2 supercopter in first tail-drive flight

Sikorsky preps Osprey bitchslap

Build a business case: developing custom apps

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. ®

Secure remote control for conventional and virtual desktops

More from The Register

next story
LOHAN packs bags for SPACEPORT AMERICA!
Spanish launch goes titsup, we're off to the US of A
Gigantic toothless 'DRAGONS' dominated Earth's early skies
Gummy pterosaurs outlived toothy competitors
'Leccy racer whacks petrols in Oz race
ELMOFO rakes in two wins in sanctioned race
Boffins ID freakish spine-smothered prehistoric critter: The CLAW gave it away
Bizarre-looking creature actually related to velvet worms
CRR-CRRRK, beep, beep: Mars space truck backs out of slippery sand trap
Curiosity finds new drilling target after course correction
Astronomers scramble for obs on new comet
Amateur gets fifth confirmed discovery
Boffins build CYBORG-MOTHRA but not for evil: For search & rescue
This tiny bio-bot will chew through your clothes then save your life
Vulture 2 takes a battering in 100km/h test run
Still in one piece, but we're going to need MORE POWER
What does a flashmob of 1,024 robots look like? Just like this
Sorry, Harvard, did you say kilobots or KILLER BOTS?
prev story

Whitepapers

Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Top 10 endpoint backup mistakes
Avoid the ten endpoint backup mistakes to ensure that your critical corporate data is protected and end user productivity is improved.
Top 8 considerations to enable and simplify mobility
In this whitepaper learn how to successfully add mobile capabilities simply and cost effectively.
Rethinking backup and recovery in the modern data center
Combining intelligence, operational analytics, and automation to enable efficient, data-driven IT organizations using the HP ABR approach.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.