why can't helicopters go super sonic?

Question

just wondering

Answer 1

The rotation of the main rotor implies that a blade goes forward on one side while another goes back on the other.
To provide lift on the way back, the receding blade has to move faster than flight speed, which means it has to move at the same speed on the other side relative to the airframe, compounding the speed with the forward motion. The result is that the forward moving blade would have to move at twice the speed of sound at the very least. The amount of power needed would be staggering...

For the record, the tip of the rotor of very fast helicopter (which are still far from going Mach 1) is actually sometime exceeding the speed of sound, using a lot of power due to compressibility effect, and causing a lot of stress on the tip themselves.

Answer 2

Helicopters are not efficient machines. An airplane stays up due to the airfoil of the wings, and needs power for forward motion only. A helicopter uses it's rotor to both provide forward motion and stay up. Twice as much fuel (or more) is required for this. Anyway, to answer your question. The open blades of the helicopter rotor can only "grab" so much air. Only the air above the rotor. A jet engine has air funneled in to it under pressure to spin the blades on the turbine. If there were some method of compressing the air before a helicopter's rotor directed it down and back, it could indeed fly higher and faster. As it is though, the rotor has only the atmospheric pressure to work with, which is limited. Good question.

Answer 3

As an object such as a plane reaches sonic speeds, a shock wave will develop along the exterior of the plane. Helicopter designs with the rotor would be hard to stabilze and would require plenty of energy as suggested earlier by Vincent G.
This is why fighter jets have a swept wing, to reduce this build-up. It is more feasible to have a jet that can hover like the Harrier to do the job.

Answer 4

I Can Go Super Sonic

Answer 5

unlike an aircraft with fixed wings that cause "lift" when air passes over the top rounded portion of the wing slower than the air passes under the bottom "flat" part. a helicopter gets it's lift from the turning blades. There comes a speed (roughly 200MPH depending on the type of material and shape of the blade) when the Lift created by the blades is insufficient to continue "lifting" the craft.

Answer 6

If you mean super sonic as in breaking the sound barrier, I believe some can now. They're called Mach I.

Answer 7

They try to use roters to go up and forward not just forward.
if you want to see something go supersonic (or almost) see the harrier or the F-35 lighting.

Answer 8

because helicopters aren't made for speed, they are made for manuverability and to have the advantage over planes in tight surroundings.

Answer 9

Because you wouldnt be able to do cool stuff like this:
http://www.youtube.com/watch?v=W-6ThJBc9a4

Answer 10

They are based on lift rather than forward thrust.