Typical helicopters have a built-in velocity restrict, imposed by the bodily limitations of their top-rotor raise programs. This fascinating Airbus venture has discovered a approach to break by way of that velocity restrict, and it is already performed it in flight testing.
The velocity limiter in query right here known as rotating blade stall. You may consider a helicopter’s high rotor blades as wings – wings able to various their pitch to generate kind of raise as they rotate round the principle rotor shaft – an idea demonstrated superbly by a a lot youthful yours actually utilizing a cricket bat within the again yard in our magnificently low-budget Tips on how to Fly a Helicopter video from 2010.
The difficulty is that this: if the highest rotor’s rotating counterclockwise, the blades on the left hand aspect of the helicopter are travelling backwards, and the blades on the correct are travelling forwards. So that they generate an equal quantity of raise all the best way round at zero airspeed, however as quickly as you are transferring relative to the air, the blades on one aspect are transferring into the wind, growing airflow over the blade and producing extra raise, whereas the blades on the opposite aspect are transferring again with the wind, reducing airflow and lowering raise.
The sooner you go, the extra pronounced this asymmetry turns into, till you attain some extent at which you’ll be able to now not steer your manner out of it with the cyclic management, and if you happen to tried to go any sooner, the helicopter would possibly go right into a damaging sequence of harmonic vibrations, or flip over and fall out of the sky, which isn’t ultimate.
Airbus
The “Vne,” or Velocity By no means Exceed, or aerial velocity restrict on typical helicopters takes this retreating blade stall under consideration as one in all its key components. A typical civilian chopper just like the Robinson R44 is proscribed to simply 241 km/h (150 mph), for instance, and even the quickest cannot go a lot additional than 370 km/h (230 mph). The official DAI-approved Guinness World Document for the quickest velocity in a helicopter has stood quick at 400.87 km/h (249.09 mph) because it was set in 1986, in a modified Westland Lynx.
Unofficially, the fairly unconventional Sikorsky X2 is the quickest helicopter in historical past. In 2010, Sikorsky claims this high-speed demonstrator achieved 463 km/h (287.69 mph) in stage flight, and a few 481.5 km/h (299.2 mph) in a shallow dive.
Thoughts you, the X2 will get round retreating blade stall by placing an advancing blade and a retreating one on either side of the plane – it runs a stacked coaxial pair of high rotors, rotating in reverse instructions, in addition to an enormous pusher prop on the again, to go that fast.
Racer – First Flight
Which brings us to the Airbus Racer, which has simply overwhelmed its stage flight cruise velocity goal of 407 km/h (253 mph) in a check flight, topping out at a claimed 420 km/h (261 mph).
This outstanding plane makes use of only a single high rotor – however it’s nonetheless removed from what you’d name typical. The racer would not run a typical tail rotor; as a substitute, a pair of comparatively slim field wings prolong out sideways from the highest of the cabin, then tuck underneath and return to hitch the underside of the cabin. On the ends of those wings sit two massive pusher propellers.
In a hover, these props can stability out the torque from the principle rotor very similar to a standard tail rotor does. However at velocity, the field wing configuration contributes increasingly raise, till the Racer is ready to decelerate its high rotor, and successfully depends primarily on the wing raise for prime velocity cruise flight, whereas tucking its touchdown gear away for diminished drag.
It is a fairly wild wanting machine – test it out:
Racer – Contained in the excessive velocity demonstrator
There are different benefits than simply bulk velocity – the Racer additionally derives vital effectivity advantages from performing like a aircraft. Helicopters burn a ton of gasoline consistently holding themselves up on engine energy, and because of this the Racer saves an estimated 15-30% on gasoline prices by incorporating winged cruise, permitting it to modify one in all its 2,500-plus horsepower engines onto standby.
Airbus says it is also nice for the plane’s noise profile to sluggish that huge rotor down, since that is the place the majority of a helicopter’s floor noise signature comes from.
However velocity is unquestionably a key focus, and the Racer probably has extra up its sleeve, since this check was actually geared toward validating that the plane is able to reaching its cruise velocity fairly than pushing for a report.
Airbus
Just like the Sikorsky X2, although, the Airbus Racer is only a demonstrator at this stage, proving ideas that’ll take some years but to filter by way of to the industrial market. But it surely’s actually promising to notice that it is almost met all its flight envelope aims inside simply seven check flights and round 9 hours within the air.
“This achievement in such a brief area of time can be a testimony to the arduous work of our 40 companions in 13 European nations to carry all of this innovation to flight,” stated Bruno Even, CEO of Airbus Helicopters. “On high of its efficiency, the plane’s aerodynamic conduct and stability are promising. We’re all wanting ahead to the subsequent section of flight testing, particularly the eco-mode which can allow us to close down one engine in ahead flight, thus lowering gasoline consumption, and reducing the CO2 emissions.”
Supply: Airbus
