World's New Fastest Helicopter

[Kingman]

[video=youtube;gK7ktLXhq88]http://www.youtube.com/watch?v=gK7ktLXhq88&feature=player_embedded[/video]

Helicopters have trouble moving at high speeds. That's because their rotor blades start doing odd things. This new design from Sikorsky helps eliminate that problem. It uses two rotors and a pusher prop. That lets it hit speeds over 280 mph.

 

[Chris A.]

Cool post!

 

[HHGT]

I think a show down with Peak's beast is in order.

 

[Empty Pockets]

'Kinda looks like a flying paper shredder, duzzunit.

 

[BlackICE]

I think a show down with Peak's beast is in order.

Nah, Peak's jet would win.

 

[GT38]

The aerodynamic issue that limits helicopter speeds is retreating blade stall, and there are at least three ways to mitigate the problem, 1) unload the main rotor with stub wings, 2, slow the rotor at higher speeds, or 3) use coaxial main rotors so there is always an advancing blade on one of the rotors.

Technically the Sikorsky X2 is a compound helicopter because of the pusher prop. The prop gives additional forward thrust that you could not obtain through the main rotors alone.

In the mid-sixties Lockheed built the XH-51N which achieved 302.6 mph. It had a P&W J60 jet engine for forward thrust in addition to the P&W PT6 driving the rotor, making it a compound helicopter too. The retreating blade stall was countered with the stub wings; at high speed the main rotor was almost completely unloaded and was used mainly for control at those speeds.

http://wapedia.mobi/en/Lockheed_XH-51

[video=youtube;P94g7TszBFg]http://www.youtube.com/watch?v=P94g7TszBFg[/video]

The current FAI speed record for helicopters was set in 1986 in a British Westland Lynx at 249.1 mph (400.87 kph), which is noteworthy because it is a conventional main & tail rotor configuration - no jet or pusher prop for auxiliary thrust, and no stub wings to counter retreating blade stall.

http://records.fai.org/rotorcraft/absolute.asp

Here's the Lynx doing some aerobatics.
[video=youtube;ba-dln366-E]http://www.youtube.com/watch?v=ba-dln366-E[/video]

 

[CH53Driver]

Cool stuff for sure!

 

[GT38]

Cool stuff for sure!

...and you should know!!

 

[HHGT]

And don't forget the V22 Osprey

 

[Kingman]

GT38 Said - "The aerodynamic issue that limits helicopter speeds ..............."

Holy Moly! Where da hell do you guys come from!? I have a techie background, but.....I don't have a tech manual that explains what you just said.:confused

Well done!!

 

[BlackICE]

GT38 Said - "The aerodynamic issue that limits helicopter speeds ..............."

Holy Moly! Where da hell do you guys come from!? I have a techie background, but.....I don't have a tech manual that explains what you just said.:confused

Well done!!

It makes sense when explained. The blades moving away from the direction of travel have less lift and those moving toward, more lift. Another problem can happen where the blades moving torwards the front will approach the sound barrier and fail to operate, but I suppose the lack of lift problem will occur 1st.

 

[GT38]

And don't forget the V22 Osprey

Technically the Osprey is a convertiplane, and it's side-by-side rotors have their own aerodynamic idiosyncrasies.

GT38 Said - "The aerodynamic issue that limits helicopter speeds ..............."

Holy Moly! Where da hell do you guys come from!? I have a techie background, but.....I don't have a tech manual that explains what you just said.:confused

Well done!!

Decades of flying helicopters!

It makes sense when explained. The blades moving away from the direction of travel have less lift and those moving toward, more lift. Another problem can happen where the blades moving torwards the front will approach the sound barrier and fail to operate, but I suppose the lack of lift problem will occur 1st.

Very astute; approaching Mach 1 at the tip of the advancing blade is the other half of the problem. But you're correct that the loss of lift on the retreating blade will occur first in most cases. There is actually a region of reverse flow near the root of the retreating blade that creeps outwards towards the tip as forward speed increases. The really bizarre thing is that because of gyroscopic precession, the force (or in this case the lack of force) is applied 90 degrees later - meaning that the helicopter doesn't roll when you encounter retreating blade stall as you would expect, but it pitches up.

Igor Sikorsky didn't consider gyroscopic precession in his first design, and when he test flew it, the cyclic control stick (the one between your legs) was 90 degrees out of sync. In other words, when he pushed the stick forward the helicopter went left. To his great credit, he recognized what was happening and adjusted his control movements accordingly. I'm amazed that he was able to to that and get the helicopter down on the ground in one piece.

 

[GT38]

And then there's this - the Mi-12. I saw it in 2002 at the Russian Federation Air Force Museum in Monino, near Moscow. It's like a Boeing 737 with rotor blades!

[video=youtube;kKsWTdjnXiw]http://www.youtube.com/watch?v=kKsWTdjnXiw[/video]

 

[Neilda]

Those test pilots are pretty brave fellows!