Helicopter and a turntable

[ja1484]

Originally posted by: maxster
Think about it more carefully. All that is required for the helicopter to take off is that the rotors moves at a certain velocity, which we assume it reaches, relative to the air directly around the rotor.

The velocity of the turntable would not come into the equation at all.

Thus, the helicopter would take off.

Problem with this thought being, the rotor doesn't move.

 

[maxster]

Originally posted by: ja1484

Originally posted by: maxster
Think about it more carefully. All that is required for the helicopter to take off is that the rotors moves at a certain velocity, which we assume it reaches, relative to the air directly around the rotor.

The velocity of the turntable would not come into the equation at all.

Thus, the helicopter would take off.

Problem with this thought being, the rotor doesn't move.

I see your point. The two angular velocities would cancel out because they're connected. :beer: For this to be true though, you would have to assume that the speed of the blades are relative to the helicopter and not relative to the stationary air.

Ofcourse the helicopter would be spinning around with mad speed in this situation. Would the friction force be enough then to keep the helicopter stationary on the turntable?

 

[Raduque]

Originally posted by: 91TTZ
The helicopter's tail rotor would be useless since the helicopter is anchored to a turntable that is turning at an equal and opposite speed of the main rotor. The main rotor would have no velocity in relation to the outside air.

That's why it won't take off.

 

[maxster]

Lets think about this problem a little bit more.

Lets assume that the angular velocity of the rotor is fixed from the point of view of an outside observer (stationary observer).

This would mean that the blades now have some set speed relative to the air, also stationary. It would take off no matter what.

Now then, in this situation, what happens to the body of the helicopter?

The turn table would be spinning in the opposite direction, so the body of the helicopter would have the opposite angular velocity.

This is interesting because now you see that at the moment you start spinning the turntable and get it up to the right velocity, the blades would be stationary.

Now, the original problem have both going simultaneously. This means the blades would be stationary.

This basically means that the original assumption is incorrect and for this problem to work in the real world, the blades would always be stationary to the outside observer as long as both the turntable and the blades are spinning in synch with each other.

 

[RapidSnail]

The heli would not take off because the axis of rotation for the blades is located in the body of the heli. If the body of the heli is spinning in the opposite direction at the same speed as the blades (because of the rotating platform), the blades will be motionless relative to he air. Therefore, the heli cannot take off. Right?

 

[Rubycon]

I like bagels.

It would not take off regardless of direction because a dizzy pilot can not fly it.

 

[Zenmervolt]

A Chinook would indeed take off because at least one of the rotors would provide lift.

ZV

 

[maxster]

Originally posted by: Zenmervolt
A Chinook would indeed take off because at least one of the rotors would provide lift.

ZV

LOL

 

[Jeff7]

Originally posted by: Raduque

Originally posted by: 91TTZ
The helicopter's tail rotor would be useless since the helicopter is anchored to a turntable that is turning at an equal and opposite speed of the main rotor. The main rotor would have no velocity in relation to the outside air.

That's why it won't take off.

:laugh:
Nice catch.

Originally posted by: Zenmervolt
A Chinook would indeed take off because at least one of the rotors would provide lift.

ZV

More like, half of it would take off, but then either flip or crash - and, the entire thing would be spinning really fast around either the axis of rotation of one of the rotors, or else about the center of the Chinook's body.

 

[GoatMonkey]

Airwolf would also take off once Dom kicks the turbos on and they move off the turntable.

 

[Rubycon]

This fella didn't even need to be on a turntable to have problems.