This has baffled me for years. I know the little fan on the back keeps the body of the chopper from whirling instead of the blade–but does it also cause lateral movement? Just how fast can a helicopter travel laterally/forward (including the kind with two rotors on the top)?
They lean over and fall forward, real fast. Then they rev up the engines to keep from falling down, while they fall forward.
A remarkably unlikely vehicle, all in all.
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Simple, but basically correct explanation:
The rotors mostly push air down to keep the helicopter up, but they also push some air backwards to go forward.
There are limits to how fast a helicopter can go. It can’t “outfly” its rotor, for example: while spinning, one half of the rotor disc is advancing and the other half is retreating. If the helicopter is flying forward as fast as the blades are retreating then the retreating blades aren’t generating any lift. (It’s actually more complicated since the speed of any point on the blade increases as you move outward.) Another limitation is that you (usually) don’t want the tips of the blades to go supersonic. If you’re flying forward at half the speed of sound and the advancing blades are rotating at half the speed of sound then you’re going to get supersonic effects.
There are helicopter/fixed wing hybrids that operate like a helicopter at low speeds but at high speeds the rotors are locked and act like fixed wings. Forward thrust is provided by a jet engine and there are provisions for the transitional speeds.
And why isn’t this a General Question?
“Vandelay!! Say Vandelay!!”
Beats me, Pluto. I once put a question about roasting pans in the BBQ Pit forum.
I’d also like to know how those copters with two overhead blades work.
Twin rotor helicopters work the same way as any other helicoper. They are just more complicated. What do you want to know about them?
Must I say something about helicopters to shamelessly hijack this thread?
What the heck, it’s in a randomly selected forum anyway.
Now to the point,…starfish, I see you’re a denizen of Houston. Please be advised that the Houston SDMB crew is trying to organize a meeting with the visiting Byzantine this Friday (logistics not worked out as yet), Raleigh poster extraordinaire Satan will be visiting here on Dec. 19, and Mike King will be here sometime in January. And we haven’t met you yet.
There’s a few Houston threads floating around; check in if you’d like.
The principle behind helicopter flight is simple: Helicopters beat the air into submission.