Torque Reaction???
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The blades are being turned (torque) one way and because, as Newton says, for every action there is an equal and opposite reaction the body of the helicopter wants to go the other. The tail rotor creates a force in opposition to this "torque reaction" to stop this happening when required.
And remember to explain that the helicopter will not instantly spin/crash and killl everyone on board just because the tailrotor failed. There are way´s to land it.
Seems like a common misunderstanding among non aviation folks.
Seems like a common misunderstanding among non aviation folks.
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For some reason people don´t seem to ask as often about that since it´s given that if the main rotor comes off it´s going to be fatal or likely very serious if in low hover.
However if I have been asked about the likelyhood that the rotor or blade will come of then I say it´s about as likely as a wing breaking off an airplane. Which I think is probaly not far off.
However if I have been asked about the likelyhood that the rotor or blade will come of then I say it´s about as likely as a wing breaking off an airplane. Which I think is probaly not far off.
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As said above Newtons second law. If they dont understand that what I do with students is get them to stand in front of me with legs together, then I give them a little push they go back but it is plain to see that I do to at the same speed ie equal and opposite.
The same is happening with helo,the engine is pushing rotors around and reaction is for airframe to turn opposite way. We normally fix this using a tail rotor which in essence works the same as main rotor providing lift only we turn on the side to oppose rotation, also giving us yaw control.
The same is happening with helo,the engine is pushing rotors around and reaction is for airframe to turn opposite way. We normally fix this using a tail rotor which in essence works the same as main rotor providing lift only we turn on the side to oppose rotation, also giving us yaw control.
Last edited by crispy69; 12th Nov 2006 at 00:02.
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Try this:
The main rotor is being pushed around by the engines which are mounted on the helicopter's body. It is a very hard push that keeps the main rotor turning because of all the drag the blades create as they produce the lift. The force exerted by the fuselage on the main rotor is about 600 pounds on an S76, as measured at the tail. To exert this force, the fuselage must brace itself against something to keep from turning in the opposite direction. These are the same choices that you would have as you stand on ice and try to push a car.
Simply said, the tail rotor develops the force that the fuselage braces against as it pushes the main rotor around.
The main rotor is being pushed around by the engines which are mounted on the helicopter's body. It is a very hard push that keeps the main rotor turning because of all the drag the blades create as they produce the lift. The force exerted by the fuselage on the main rotor is about 600 pounds on an S76, as measured at the tail. To exert this force, the fuselage must brace itself against something to keep from turning in the opposite direction. These are the same choices that you would have as you stand on ice and try to push a car.
Simply said, the tail rotor develops the force that the fuselage braces against as it pushes the main rotor around.
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Another way to demonstrate it, is to get someone to sit on an office chair (on castors), preferably on a hard floor, whilst holding something fairly heavy.
Ask them to lift their legs off the ground, then throw the object. The chair (and them) will move in the oposite direction to the thrown object.
Explain to them that the chair represents the helicopter, and the thrown object is one of the rotor blades, and as the blade goes one way, the helicopter moves the other way.
Ask them to lift their legs off the ground, then throw the object. The chair (and them) will move in the oposite direction to the thrown object.
Explain to them that the chair represents the helicopter, and the thrown object is one of the rotor blades, and as the blade goes one way, the helicopter moves the other way.
Thread Starter
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Thanks Guys,
some really good stuff here. You know how it is... we know how it is and how and why it works but breaking it down to explain to the "public" isnt that easy.
I find if you cant explain it quickly and simply they loose intrest and you might as well have not bothered.
Great explanation from 419 by the way, everyone can relate to that,
Thanks
MADY
some really good stuff here. You know how it is... we know how it is and how and why it works but breaking it down to explain to the "public" isnt that easy.
I find if you cant explain it quickly and simply they loose intrest and you might as well have not bothered.
Great explanation from 419 by the way, everyone can relate to that,
Thanks
MADY
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Surely Newtons Third Law?
"For every action, there is an equal and opposite reaction."
= Torque reaction.
His Second Law;
"The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object."
= Acceleration depends on the force and its mass.
"For every action, there is an equal and opposite reaction."
= Torque reaction.
His Second Law;
"The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object."
= Acceleration depends on the force and its mass.
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Drilling 2*4
One explanation that most people seem to understand is this:
If you are using a drill on a wooden plank (ie. 2*4), you are applying antitorque with your arm. It's easy to see if the drill hits a hardspot, your hand will be turned around by the increased force of the drill.....increased torque. So you have to hold it harder to avoid the whole drill to spin....increase antitorque with your arm.
Like stated above....action vs. reaction!
If you are using a drill on a wooden plank (ie. 2*4), you are applying antitorque with your arm. It's easy to see if the drill hits a hardspot, your hand will be turned around by the increased force of the drill.....increased torque. So you have to hold it harder to avoid the whole drill to spin....increase antitorque with your arm.
Like stated above....action vs. reaction!
Combine Operations
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On the other hand, and sticking to the electric drill scenario:
If you have something like a polishing pad fitted to the drill (i.e. something fairly large and heavy), and you switch the drill on, the pad turns clockwise. The drill, obeying Newton's Third Law, tends to turn anti-clockwise.
If you select reverse on the drill, and switch it on, the pad obviously turns anti-clockwise. And so does the drill.
If you have something like a polishing pad fitted to the drill (i.e. something fairly large and heavy), and you switch the drill on, the pad turns clockwise. The drill, obeying Newton's Third Law, tends to turn anti-clockwise.
If you select reverse on the drill, and switch it on, the pad obviously turns anti-clockwise. And so does the drill.
and if anyone is wondering what his first law is: "an object will remain at constant velocity (includes being stationary) until acted upon by a force"
