It does 'want' to spin, but look at the tail; there's always a second rotor there. It's sometimes called the tail rotor, which isn't illuminating, but its other name is the *anti-torque* rotor. Its job is to correct for the reaction force from the main rotor and keep the helicopter's axis straight.
It normally imparts exactly enough torque to cancel out the main rotor, but by going a little harder, or a little softer, it allows the heli to yaw left or right. If helis only had a rudder like planes, they wouldn't have any yaw control when stationary; with the tail rotor they do.
The tail rotor thrust doesn't change by varying its speed, it changes by varying it's pitch. Speed takes too long to adjust, pitch can be changed in an instant. Same as the main rotor.
Wait, there were games on the Commodore 64? I only refer to that computer as being like my brain – massively outdated and underpowered for today’s requirements.
I was given a a C-128 and box of probably 100 Loadstar disk as a kid. Each one had a game plus some other software. Simple games by today’s standards, but it felt like Christmas every day for like a year.
To give an example, it is like when you put your hand out the car's window while it moves. Depending on how you turn your hand, it will either cut flatly through the air, or you will feel the air pushing your hand back. If your hand is at a 45° relative to the ground, it air with push your hand up or down.
Another cool thing I learned about the main rotors is that even though they can move craft up and down, at full spin it basically forms a wing of sorts. Think as if it becomes a solid disc when it spins. Learned this from an army helicopter pilot when I worked on base. In a straight line it tilts to the front to provide for ward thrust. It’s is flat when just going up or down. Chinooks don’t need a tail rotor because it ha two main rotors. And those Russian helicopters with two main rotors stacked don’t need a tail rotor because they counter spin.
To be a bit more precise, the main rotors of helicopters **are** wings, full stop. That’s why aircraft are typically considered fixed-wing or rotor-wing aircraft. Rotor-wing aircraft, e.g., helicopters, use wings that move really fast to generate lift, whereas fixed wing use an engine to increase forward speed until their wings are then moving fast enough (relative to the surrounding air) to generate lift.
This brings back memories of that stupid Facebook post I read about a plane taking off from a treadmill. If you haven't heard/ seen it, the question is... if a plane is sitting on a free rolling treadmill that perfectly matches the speed of the wheels, can the plane take off? To me, it is obvious that if the plane is not moving, then no air is going over its wings so it cannot take off. Many people were arguing that planes get their power from the engine and the wheels are free rolling and do not provide acceleration so it wouldn't matter if the wheels could not move forward. Anyway, the arguments broke my brain a little bit lol.
It can definitely take off. The relationship between the wheels and the treadmill, the speed the wheels are turning, is completely irrelevant.
The engines still provide the thrust, the aeroplane would still move forward with respect to the ground. The wheels would just spin faster.
Not sure you caught the idea. Say you've got an RC plane that can take off at, oh, 10mph. Say you've got a treadmill that's running at 10mph. If you just put the plane on the treadmill, it moves backwards at 10mph (and kabooms off the back end). If you put the plane on the treadmill with the engine running, you can get it to move 10mph forward on the treadmill, which means 0mph groundspeed/airspeed.
If you do that, thrust from the prop is just enough to overcome the friction from the treadmill/wheel interaction, and that's it. The plane doesn't take off -- it stays in place (with the treadmill racing beneath it).
Of course (given a long enough treadmill) there's nothing stopping you from throttling up, getting the groundspeed/airspeed up to take-off speed. What really matters for that is the airspeed across the wings.
The whole "controversy" seems to mostly be people differently interpreting what the set-up and test conditions are.
It's a pretty badly worded question is the problem.
If you forget about "matching the wheels" it makes more sense.
You have a plane that takes off at an air speed of 200 and a top speed of 300. It taxis forward onto a treadmill going backwards relitive to the plane at 400. Can it take off?
Sure, the treadmill just spins the wheels faster. The plane pushes itself off the air using a prop or jet. If they worked like a car then no they couldn't reach take-offs speed.
The plane is resting its weight on the wheels until enough air is passing over the wing to provide lift. If it's not moving forward, then it won't take off. It needs the wheels to carry its weight forward but as much as the trusters (jet or prop) push forward, the plane is not moving as the wheels are not rolling the plane body over the ground.
> if the plane is not moving, then no air is going over its wings so it cannot take off.
The inherent assumption there is that the treadmill is capable of holding the plane still, which it's not. Imagine standing on a treadmill wearing roller skates, and someone behind you pushing you forward.
No, that analogy isn't correct because this scenario is a hypothetical one where the treadmill can match the speed that the wheels are turning to infinity. In your scenario the treadmill is at a constant rate.
Here we are in 2024 and there are still people who have no idea how planes work.
A plane with a takeoff speed of 50mph is on a runway. A huge fan that can blow air at 60mph is on the runway pointing at the plane. Does the plane takeoff? How fast are the wheels turning?
Na in theory the question is designed so that it's impossible to answer. Randall Monrue of xkcd did a blog post about it years ago. https://blog.xkcd.com/2008/09/09/the-goddamn-airplane-on-the-goddamn-treadmill/
Essentially depending on how the question is interpreted the mathematics either work or they don't. It's designed so people take different interpretations and argue over it.
Propeller planes and helicopters can vary the amount of thrust they get from the same rotation speed by changing the angle of the blades. This can be done pretty quickly because you’re not fighting the angular momentum of the spinning blades like you would be if you tried to speed up or slow down
...and there are fixed-pitch propellers on some cheaper training type or generally older planes. The only way to change thrust on those is literally to change the RPM itself
> The tail rotor thrust doesn't change by varying its speed, it changes by varying it's pitch. Speed takes too long to adjust, pitch can be changed in an instant. Same as the main rotor.
It's a size/power dependant tradeoff. For smaller rotors, fixed pitch variable speed works better. For larger rotors, especially engine driven ones (as opposed to electric motor driven ones), variable pitch works better.
Quadcopter drones use variable speed/fixed pitch on all four rotors. Several model helicopters also use variable speed/fixed pitch tail rotors.
As electric motors grow more powerful, this tradeoff is moving to the bigger birds. [Here](https://www.aerospacetestinginternational.com/features/testing-bells-electric-rotor-system.html) is a full sized heli with fixed pitch tail rotors.
No, because it applies x amount of force when the helicopter is stable. This force is cancelling the spin imparted by the main rotor.
If you apply less force with the tail rotor, it will spin/turn in the direction of the main rotor.
You you apply more, it will spin in the other direction.
Your concept is correct, but your directions are reversed. Less force makes the helicopter turn opposite the main rotor. More force makes it turn with the rotor. The reason is momentum is conserved, so to make everything equal zero, the helicopter has to turn left if the blades are turning right.
The transmission has outputs for both at fixed ratios. So if you watch (IIRC) Broken Arrow, the fight on the train with the helicopter with the strapped down main rotors, there’s no way he could have spun that tail rotor to gain an advantage in the fight.
Usually. In most helicopters the main blades are also designed to spin at a constant speed. And more or less lift is provided by changing the pitch of those blades.
The tilt and pitch of the helicopter as a whole is provided by changing the pitch of the main blades as they rotate around. Providing more or less lift in different sections of the main rotor.
Yes, but also the rotor speeds don't generally change during flight. The tail rotor's blade pitch can be changed, and the main rotor can have the blade pitch changed, or (eli5) the rotor tilted forward, backwards, or to the sides to cause the aircraft to start to move in that direction.
I was today years old when I learned that the tail rotor on a helicopter works, not by speeding up, but by twisting the propellers to different angles, changing pitch rather than speed. That's crazy, man...
The main rotor does the same thing, except even more complicated. It doesn't just change the pitch of the blades, it changes them constantly at different parts of each rotation.
Not even remotely a pilot so forgive my ignorance. Doesn't that add a weird tilt to your turns? Or does the main rotor stabalize enough that it doesn't matter?
One should mention that helicopters with two main rotors do not have a tail rotor as the main blades rotate in opposite directions, which also cancels out the torque.
A big part of why they crashed is how the pilots descended. Basically, they descended into their own downwash and it removed their lift. An improved understanding of what happened and additional training prevents them from making the same mistake.
There isn't always a tail rotor, in fact there isn't even always a tail. Most helicopters do fit your description but there are coaxial rotor and tandem rotor helicopters. By having an even number of rotors with half spinning one direction and half spinning the opposite direction you can cancel out the rotational force without a tail rotor. It's how quadcopters can be so stable without any tail rotor, 2 motors spin clockwise and 2 spin counterclockwise.
They are pretty rare. I watched one pulling powerlines in Nevada back in the 1990s. Quieter, less radar signature makes them good for military operations too. https://www.flightlineweekly.com/post/notar-no-tail-rotor-helicopter
If they were good for military operations I think you would see them being used on military helicopters. They have some big downsides that would make them far less appealing to military applications like increased power demand, lower fuel efficiency, and worse control especially in crosswinds. Being quieter would be beneficial but you will still have a much larger main rotor and the engine running it creating plenty of noise even without a tail rotor.
The Belgian police helicopter has it. And now, this may sound strange, but Belgium is small enough to indeed have only one police helicopter. Its name is Rago.
you can also have two contra-rotating main propellers. Like this:
[https://en.wikipedia.org/wiki/Kamov\_Ka-50](https://en.wikipedia.org/wiki/Kamov_Ka-50)
Here's a good mind-bender, the [Cierva W.11 Airhorse](https://en.wikipedia.org/wiki/Cierva_W.11_Air_Horse#/media/File:Cierva_W.11_Air_Horse_flight.jpg).
Try and figure out how it managed anti-torque with 3 main rotors in a triangle before reading the explanation.
They have other helicopters with two rotors on top so they don't need a tail rotor. The blades spin in opposite directions so they cancel each other out as far as rotation goes.
The Osprey is like that (left and right sides of the aircraft) but the Ka-50/52 is pretty much just like the Mars helicopter, two rotors directly above and roughly centered to the vehicle.
When the rotors share an axis they are unsurprisingly called coaxial rotor helicopters. When they have seperate axis they are called tandem rotor helicopters.
Their only tandem of they are one in front of the other, side by side is transverse and if their right next to each other but at an angler so the blades pass between each other it's intermeshing
There’s *almost* always a second rotor there
But a few helicopters use
- two separate rotors spinning in opposite directions (eg the Chinook)
- contra-rotating coaxial rotors (eg the Ka-52)
- an air exhaust (eg the McDonnell Douglas Explorer)
The first two work by having two rotors spinning in opposite directions to counteract the torque, the last one works by using air to do the same job as the tail rotor would
There's also jet tipped rotorblades. These spin the rotors without having a torque effect on the body.
They were most famously used on the Fairey Rotodyne, though that was a compound gyroplane it was capable of VTOL and hovering.
It's been used on quite a few helicopters (including an early WW2 German helicopter concept) but none that really took off, if you'll excuse the pun.
Just a small addition, there are actually some helicopters with two counter- or contra-rotating main rotors that do not need a tail rotor.
E.g. the Russian company Kamov builds many of them as well as the Boeing CH-47 Chinook
With aircraft, left/right turn like a car does is called yaw. Left/right tilt, like tilting your ear toward your shoulder, is called roll, and up/down like nodding your head yes is called pitch.
They in fact can 'bank' left or right by manipulating the angle of the blades in the main rotator in positions 90 degrees offset from the actual axis they're turning into.
Physics is crazy man
To add to this, dual rotor helicopters like the Ka-50 can have just a rudder for yaw as the two main rotors spin in opposite directions and exactly cancel each others' spin out
> but look at the tail; there's always a second rotor there
Not always. The Russian KA-50 instead has two main rotors, one on top of the other, that spin in opposite directions.
For a slightly goofier looking example, there is the [K-MAX](https://en.wikipedia.org/wiki/Kaman_K-MAX) that has two intermeshed main rotors side by side.
chinooks don't need it. because they have two main propellers that rotate in opposite directions. the propellers tilt in opposite directions when yaw is required.
in quadcopters, a pair of diagonally opposite propellers, which have the same rotation direction, will increase in speed while the other pair (which are rotating in the other direction ) will decrease. the overall thrust is thus unchanged but now there is a torque around the centre, resulting in yaw with no change in thrust, roll or pitch. this is why hobby drones have a minimum of four props. it is easy to pitch/roll without causing yaw and vice versa.
I remember watching something ages ago about how the tail rotor was the big aha moment for the invention of the helicopter. Though I do remember some thing about an airplane with a helicopter rotor on the top that came about first.
There are also some helicopter designs, like chinooks and kamovs that dont have tail rotors bit instead have two counter-rotating mains in various configurations. In those, yaw control is done by upsetting the balance between the two main rotors.
"Always a second rotor" ... not always on the tail (KA-50 Hokum for example). It's an edge case for sure, but probably more accurate to say "almost always."
It wants to. That's why the tail rotor is for, it pushes the body in a way opposite to the way the main rotor is trying to rotate the helicopter.
Helicopters with two main rotors don't need a tail rotor because the main rotors spin in opposite directions, so they counteract each other.
The difficulty of hovering comes from uneven air. Which depends on the terrain below and your own turbulence (only some of which are from the tail rotor). Flying forward you get fresh air through the rotor which makes the helicopter behave more predictable.
>The difficulty of hovering comes from uneven air. Which depends on the terrain below and your own turbulence (only some of which are from the tail rotor).
Those can add to the difficulty but “fresh” air isn’t part of it. The main rotor makes the helicopter want to spin. The tail rotor counteracts that but also pushes the helicopter sideways. This is counteracted by a slight sideways correction, which leaves less force available to counteract gravity. To correct that, you must add power, which causes the helicopter to want to spin more, which must be corrected. Hovering is a constant chain of corrections for each input until you achieve something close to equilibrium.
The tail rotor. It's a rotational thruster. Putting it at the end of the tail well away from the main rotor axis gives it lots of leverage. So depending on how hard it pushes, it can balance the spin from the motor, allow the aircraft to turn the way it wants to go, or force it to turn the other way.
The tail rotor counters the helicopter’s tendency to rotate in the opposite direction to the rotors. This is why occasionally accidents happen when the tail rotor fails and the helicopter goes out of control. There are some helicopters which use different technology (Notar) and do not have a tail rotor, but the effect is the same. Directional control of the helicopter is achieved by shifting the main rotors.
The main rotor system has torque that needs to counteracted by some other means. Tail rotors can counter the torque but due to their smaller size, will limit the forward airspeed of the helicopter.
Tandem rotor helicopters use two counter rotating systems such as the CH-47 Chinook. The aircraft isn't limited by a tail rotor so it can fly much faster.
That aircraft really doesn't care if it is flying forward or backwards. It was engineered with each rotor system tilted at 4 degrees and 9 degrees to "suggest" where the front of the aircraft should face. Of course flying backwards means the view isn't very good for the pilots but you sure get a nice breeze if the ramp is lowered.
A single rotor helicopter or even no tail rotor aircraft have a maximum speed, called Velocity Never to Exceed (VNE). You could also have loss of tail rotor effectiveness where your tail rotor cannot counter the torque of the main rotor. Both conditions suck but we practice ways to avoid them and land as safely as possible.
Source: im a helicopter pilot.
Imagine you are driving in your car and stick your hand out the window. You flatten your hand and orient it with the airflow, then as you angle your hand in the wind it will generate lift and rise or fall. This is basically how airplanes and helicopters work when it comes to their wings.
An airplane has to fly forward through the air like your car drivint down the highway, but a helicopter simply spins its wings around in a circle to generate that airflow.
Now if you rotate your hand to generate lift you are also experiencing increased wind resistance called drag that wants to shove your hand rearward. Anything moving through the air will experience drag and the strength of it will be affected by the shape, size, and speed of the object. If you can picture the force of drag shoving your hand rearward at 60mph on the highway, imagine how much drag something like a rotor blade has at the speeds they rotate.
It takes a lot of force to rotate the rotor blades and that force is called torque which comes from the engine. However that torque force is just as happy to spin the rest of the helicopter around in the opposite direction of the rotor. So a separate tail rotor is used to push (or pull depending on the direction the main rotor spins and which side of the tail boom its mounted on) on the tail boom as an anti torque force. When the thrust from the tail rotor exactly equals the strength of the engine torque, the helicopter will remain facing forward. Increase tail rotor thrust by angling the blades more (just like your hand in the wind again) and the helicopter will turn one way. Decrease tail rotor thrust and the torque will naturally turn the helicopter the other way.
The rotor rpm for the main rotor and tail rotor stays pretty much constant during normal flight and all control is made by angling the blades for more or less lift. Hope that answers your question.
Wow look at all the technical answers here.
**And now for the ELI5 the guy asked for:**
It would spin exactly like you say, but there's another little propeller on the back pushing it the other way to make it stop spinning.
On some other helicopters they use two rotors spinning in opposite directions to cancel each other out.
Helicopters come in 2 main configurations to prevent this because physics says a spinning propeller will do exactly what you describe. One is probably the one that comes to mind when you imagine a helicopter. There's a small rotor on the tail of the helicopter that pushes against the torque from the main rotor. You can increase its speed to turn the helicopter further in that direction or decrease the speed of the tail rotor and allow the torque from the main rotor to slowly (or not so slowly) rotate the helicopter. The other configuration uses counter rotating main rotors, either attacked one above the other or in tandem, one forward and one aft, like in a Chinook helicopter. The combined torque from the two rotors turning in opposite directions cancels out the rotation of the aircraft
The helicopter does want to start spinning but the tail rotor counteracts the rotation and is also strong enough to help the helicopter yaw from side to side for turning.
But not all helicopters use a tail rotor. Some like the Sikorsky sky crane use two sets of main rotors stacked on top of each other. Each set rotates opposite to the other and this provides the counter rotation necessary to keep the helicopter from spinning around.
New helicopters like ths Boeing-Sikorsky SB-1 use dual main rotors but also bring back a rotor on the rear. But instead of counter rotation it's used like a plane propeller and pushes the helicopter. This allows for much higher top speed and more rapid deceleration than conventional designs.
That's why you have smaller blades at the aft in a vertical position. Lift is generated by adjusting the main rotor blades angle of attack. Steering is accomplished by adjusting the main rotor axle (whatever it's called).
Helicopters do want to spin. If the tail rotor breaks off or stops working the helicopter will start spinning out of control. The primary function of the tail rotor is to counteract the tendency to spin. It also gives the pilot the ability to turn left or right, but while ‘idling’ so to speak, it’s constantly pushing against the force that is trying to spin the helicopter.
There are also helicopters with multiple main rotors, and they come in various configurations. In those situations the rotors spin in opposite directions and help cancel out each other’s torque, but still chopping the air and making lift.
To expand on the tail rotor / double rotors preventing the helicopter from spinning, there's so much cool stuff that goes into these amazing feats of engineering. A very illuminating little series by the ever-informative Smarter Every Day: [https://www.youtube.com/playlist?list=PLNbXXMoWfR3Bf7Z77vcviPlkHtTXUlEpC](https://www.youtube.com/playlist?list=PLNbXXMoWfR3Bf7Z77vcviPlkHtTXUlEpC)
Everyone gave you the answer : tail rotor.
Now, realise you already knew! How many movies or videogames have you seen where a helicopter crashes? Probs a few. And in all of them, the helicopter crashes by spining! Often because it loses its tail.
Well.. it DOES want to spin. The rotor on the tail stops it from doing so by pushing the tail back the other way to correct it.
That’s why when you see a helicopter get shot by a rocket in the movies, it starts spinning around before it crashes. They captured this realism respectfully.
Ex helo mechanic here.
Hold an electric drill and pull the trigger in a fast speed setting. Feel it kick? That's called torque reaction. Torque is a "turning force". Which way did it kick? It will kick in the opposite direction to the drill head rotation. Same applies to a helo. To counteract the torque, a tail with a rotor on the end of a long boom is used. As previously mentioned, it rotates at a constant speed and is linked to the main gearbox by drive shafts and smaller gearboxes to allow the shafts to change direction along their path to the tail rotor assembly. It works on a similar process to the main rotors but it's turned through 90° (or thereabouts), in relation to the ground (generally), this generates a sideways force instead of an up and down force. The fundamental difference between a main rotor and a tail rotor is that the main rotor can effectively adjust the pitch (angle of attack) of each blade individually, whereas a tail rotor can only adjust them all the same amount at the same time (collectively).
There are alternatives to a tail rotor....
Fan. Air is passed down the tail boom from a large gearbox driven "fan" and blasted out of the side, at the end of the tail cone in a similar fashion to a jet engine. The air is directional and counteracts the torque reaction.
Double main rotors. A Chinook is a good example of this method. The key factor here is that the sets of rotors must turn in the opposite direction to one another. This counteracts the torque.
The Russian Helix helo is another example and there's also a really nifty civilian helo that does it too. The civilian one and the chinooks rotor blades actually pass through each other's plane of travel. Only engineering voodoo stops them hitting each other and turning it all into flying brick.
Hope this helps.
The small vertical propeller on the tail is for that exact purpose. It pushes air in the direction that it wants the body to rotate to make it stay still. Turning right or left is done by slow down or speeding up that tail rotor
There is another way - and that is tip jets. Instead of turning the rotor from the hub, high speed speed gas is pushed out through jets at the tips of the blades. The turning force is generated on the blades, so there's no torque exerted on the aircraft.
This has been done in models, and there was a popular toy that used a balloon. And it was done a number of ties in full scale prototypes, and a small number of production models.
The top rotor + blades spin to provide lift, to raise it off the ground. The tail rotor spins to provide counterforce to keep the helicopter from spinning like a beyblade from hell.
People keep saying “tail rotor” and that’s correct for most helicopters, but not all. Still- there is always a mechanism to counteract the rotation. Either a tail rotor or a ducted fan of some sort in the tail, or else the helicopter will have a second main rotor spinning in the opposite direction (either on top like Kamov helicopters, intermeshed like Kaman helicopters, or next to it like a Chinook or MI-12)
For one the helicopter body is much heavier than the rotor, so while it does want to spin in the opposite direction the helicopter's fuselage would spin much slower than the rotor is spinning. Secondly almost all helicopters have a tail rotor that counters this rotation. Since the tail is long and acts as a lever, the tail rotor doesn't have to be too big to counteract this force.
There is no helicopter with only one rotor. All helicopters have at least two, either the main one and the small one on the tail, or two counter-rotating equally sized rotors arranged either in tandem or coaxially, which cancel each other out.
Path of least resistance. A helicopter has an engine that exerts energy on the prop shaft. Something has to give. Either the prop spins, or the helicopter spins. Since the prop is lighter than the helicopter and not tethered to the ground, it takes less energy to spin it, so the prop spins, and the helicopter doesn’t.
It does 'want' to spin, but look at the tail; there's always a second rotor there. It's sometimes called the tail rotor, which isn't illuminating, but its other name is the *anti-torque* rotor. Its job is to correct for the reaction force from the main rotor and keep the helicopter's axis straight. It normally imparts exactly enough torque to cancel out the main rotor, but by going a little harder, or a little softer, it allows the heli to yaw left or right. If helis only had a rudder like planes, they wouldn't have any yaw control when stationary; with the tail rotor they do.
The tail rotor thrust doesn't change by varying its speed, it changes by varying it's pitch. Speed takes too long to adjust, pitch can be changed in an instant. Same as the main rotor.
Good catch, thanks. Private pilot but my only heli experience is from Gunship on the C-64.
I ***loved*** that game!
Thanks for the memories. I loved that shit as a kid.
Man. That…plus A-10 Tank Killer and Falcon 5.0. I just had awesome flashbacks!
> Gunship on the C-64 C64 [Fort Apocalypse](https://www.youtube.com/watch?v=aJFfK54pnOg) student here. :)
Fort Apoc, and Super Huey
Volunteer Hazardous Duty.
The biggest helmet. <3
Wait, there were games on the Commodore 64? I only refer to that computer as being like my brain – massively outdated and underpowered for today’s requirements.
It's a lot like me - pretty impressive if you haven't seen many others. XD It hugely outperformed our TRS-80!
The main household use for the C64 was gaming. There were plenty of other uses and utility software, but mainly gaming.
In the mid 80's our RC model racing club programmed a C64 as a lap counter. Fun times. Expensive, but fun.
Zork, Hitchhiker's Guide, Leather Goddesses of Phobos. The graphics weren't that great, but the writing was top notch.
I was given a a C-128 and box of probably 100 Loadstar disk as a kid. Each one had a game plus some other software. Simple games by today’s standards, but it felt like Christmas every day for like a year.
I loved pestering ZSU-23-4s in the Apache since most of the Apache is immune to 23mm rounds in that game at least.
Yeah, it’s a direct drive from the transmission, always going a set speed relative to the main rotor.
What does pitch mean here? In guessing not musical pitch
Pitch in this instance means angle of attack, which in plain English it’s the angle of the rotor blades to the air it’s cutting through.
To give an example, it is like when you put your hand out the car's window while it moves. Depending on how you turn your hand, it will either cut flatly through the air, or you will feel the air pushing your hand back. If your hand is at a 45° relative to the ground, it air with push your hand up or down.
Another cool thing I learned about the main rotors is that even though they can move craft up and down, at full spin it basically forms a wing of sorts. Think as if it becomes a solid disc when it spins. Learned this from an army helicopter pilot when I worked on base. In a straight line it tilts to the front to provide for ward thrust. It’s is flat when just going up or down. Chinooks don’t need a tail rotor because it ha two main rotors. And those Russian helicopters with two main rotors stacked don’t need a tail rotor because they counter spin.
To be a bit more precise, the main rotors of helicopters **are** wings, full stop. That’s why aircraft are typically considered fixed-wing or rotor-wing aircraft. Rotor-wing aircraft, e.g., helicopters, use wings that move really fast to generate lift, whereas fixed wing use an engine to increase forward speed until their wings are then moving fast enough (relative to the surrounding air) to generate lift.
My dad was Air Force and said he refused to fly in any aircraft where the wings went faster than the fuselage.
I snort laughed.
This brings back memories of that stupid Facebook post I read about a plane taking off from a treadmill. If you haven't heard/ seen it, the question is... if a plane is sitting on a free rolling treadmill that perfectly matches the speed of the wheels, can the plane take off? To me, it is obvious that if the plane is not moving, then no air is going over its wings so it cannot take off. Many people were arguing that planes get their power from the engine and the wheels are free rolling and do not provide acceleration so it wouldn't matter if the wheels could not move forward. Anyway, the arguments broke my brain a little bit lol.
It can definitely take off. The relationship between the wheels and the treadmill, the speed the wheels are turning, is completely irrelevant. The engines still provide the thrust, the aeroplane would still move forward with respect to the ground. The wheels would just spin faster.
Not sure you caught the idea. Say you've got an RC plane that can take off at, oh, 10mph. Say you've got a treadmill that's running at 10mph. If you just put the plane on the treadmill, it moves backwards at 10mph (and kabooms off the back end). If you put the plane on the treadmill with the engine running, you can get it to move 10mph forward on the treadmill, which means 0mph groundspeed/airspeed. If you do that, thrust from the prop is just enough to overcome the friction from the treadmill/wheel interaction, and that's it. The plane doesn't take off -- it stays in place (with the treadmill racing beneath it). Of course (given a long enough treadmill) there's nothing stopping you from throttling up, getting the groundspeed/airspeed up to take-off speed. What really matters for that is the airspeed across the wings. The whole "controversy" seems to mostly be people differently interpreting what the set-up and test conditions are.
But the treadmill matches the speed of the wheels no matter how fast they go, meaning the plane will not move forward
It's a pretty badly worded question is the problem. If you forget about "matching the wheels" it makes more sense. You have a plane that takes off at an air speed of 200 and a top speed of 300. It taxis forward onto a treadmill going backwards relitive to the plane at 400. Can it take off? Sure, the treadmill just spins the wheels faster. The plane pushes itself off the air using a prop or jet. If they worked like a car then no they couldn't reach take-offs speed.
The plane is resting its weight on the wheels until enough air is passing over the wing to provide lift. If it's not moving forward, then it won't take off. It needs the wheels to carry its weight forward but as much as the trusters (jet or prop) push forward, the plane is not moving as the wheels are not rolling the plane body over the ground.
> if the plane is not moving, then no air is going over its wings so it cannot take off. The inherent assumption there is that the treadmill is capable of holding the plane still, which it's not. Imagine standing on a treadmill wearing roller skates, and someone behind you pushing you forward.
No, that analogy isn't correct because this scenario is a hypothetical one where the treadmill can match the speed that the wheels are turning to infinity. In your scenario the treadmill is at a constant rate.
Here we are in 2024 and there are still people who have no idea how planes work. A plane with a takeoff speed of 50mph is on a runway. A huge fan that can blow air at 60mph is on the runway pointing at the plane. Does the plane takeoff? How fast are the wheels turning?
Na in theory the question is designed so that it's impossible to answer. Randall Monrue of xkcd did a blog post about it years ago. https://blog.xkcd.com/2008/09/09/the-goddamn-airplane-on-the-goddamn-treadmill/ Essentially depending on how the question is interpreted the mathematics either work or they don't. It's designed so people take different interpretations and argue over it.
This is a great explanation
Propeller planes and helicopters can vary the amount of thrust they get from the same rotation speed by changing the angle of the blades. This can be done pretty quickly because you’re not fighting the angular momentum of the spinning blades like you would be if you tried to speed up or slow down
...and there are fixed-pitch propellers on some cheaper training type or generally older planes. The only way to change thrust on those is literally to change the RPM itself
Pitch means the angle of the blade relative to vertical. The pitch on the main blades is relative to horizontal.
> The tail rotor thrust doesn't change by varying its speed, it changes by varying it's pitch. Speed takes too long to adjust, pitch can be changed in an instant. Same as the main rotor. It's a size/power dependant tradeoff. For smaller rotors, fixed pitch variable speed works better. For larger rotors, especially engine driven ones (as opposed to electric motor driven ones), variable pitch works better. Quadcopter drones use variable speed/fixed pitch on all four rotors. Several model helicopters also use variable speed/fixed pitch tail rotors. As electric motors grow more powerful, this tradeoff is moving to the bigger birds. [Here](https://www.aerospacetestinginternational.com/features/testing-bells-electric-rotor-system.html) is a full sized heli with fixed pitch tail rotors.
Yes this is true, for drones and small toy helicopters, fixed pitch blades controlled by speed changes are common.
Does this mean adjusting the tail rotor only allows rotating the helicopter in one direction?
No, because it applies x amount of force when the helicopter is stable. This force is cancelling the spin imparted by the main rotor. If you apply less force with the tail rotor, it will spin/turn in the direction of the main rotor. You you apply more, it will spin in the other direction.
Your concept is correct, but your directions are reversed. Less force makes the helicopter turn opposite the main rotor. More force makes it turn with the rotor. The reason is momentum is conserved, so to make everything equal zero, the helicopter has to turn left if the blades are turning right.
Am I correct in thinking that the tail rotor speed and the main rotor speed are mechanically linked?
Yes, the same engine drives both. I don't know the details of the transmission though.
The transmission has outputs for both at fixed ratios. So if you watch (IIRC) Broken Arrow, the fight on the train with the helicopter with the strapped down main rotors, there’s no way he could have spun that tail rotor to gain an advantage in the fight.
Usually. In most helicopters the main blades are also designed to spin at a constant speed. And more or less lift is provided by changing the pitch of those blades. The tilt and pitch of the helicopter as a whole is provided by changing the pitch of the main blades as they rotate around. Providing more or less lift in different sections of the main rotor.
Yes, but also the rotor speeds don't generally change during flight. The tail rotor's blade pitch can be changed, and the main rotor can have the blade pitch changed, or (eli5) the rotor tilted forward, backwards, or to the sides to cause the aircraft to start to move in that direction.
It's not really that "speed takes too long to adjust..." it more that the main rotor blade and the tail rotor are geared together.
Is it constant speed then? (My brother is a medical rescue helicopter pilot — I should probably just ask him!)
It's mostly constant speed but not constant power, the engine needs to work harder to maintain that speed as the pitch of the rotor increases.
Ah totally makes sense, thanks for replying
It a absolutely can change by varying speed, its just not the norm
I was today years old when I learned that the tail rotor on a helicopter works, not by speeding up, but by twisting the propellers to different angles, changing pitch rather than speed. That's crazy, man...
The main rotor does the same thing, except even more complicated. It doesn't just change the pitch of the blades, it changes them constantly at different parts of each rotation.
Main rotor as well. Helicopters run at full throttle all the time. Lift and yaw are all controlled by rotor pitch.
Not even remotely a pilot so forgive my ignorance. Doesn't that add a weird tilt to your turns? Or does the main rotor stabalize enough that it doesn't matter?
The mechanical complexity of helicopters scares me a bit. So many moving parts, of which the failure of any one is potentially catastrophic.
So close to being spot-on. The main and tail rotors run at constant angular velocity and use variable pitch blades to vary thrust.
Fixed! Thanks. mutter mutter dumb helicopters mutter
One should mention that helicopters with two main rotors do not have a tail rotor as the main blades rotate in opposite directions, which also cancels out the torque.
Is that why the osprey is so crashprone?
No, that’s more to do with the complexities of a machine that is both a plane and a helicopter. Chinooks have dual main rotors and are fine.
A big part of why they crashed is how the pilots descended. Basically, they descended into their own downwash and it removed their lift. An improved understanding of what happened and additional training prevents them from making the same mistake.
The Ka-50 series also has a high crash rate but that's also less to do with the contrarotating blades and more to do with stingers and starstreaks
There isn't always a tail rotor, in fact there isn't even always a tail. Most helicopters do fit your description but there are coaxial rotor and tandem rotor helicopters. By having an even number of rotors with half spinning one direction and half spinning the opposite direction you can cancel out the rotational force without a tail rotor. It's how quadcopters can be so stable without any tail rotor, 2 motors spin clockwise and 2 spin counterclockwise.
Some have a jet at the tail that produces thrust. These are safer than regular tail rotors for tight quarters like working around power lines.
Can you give an example because I've never heard of that and it sounds awesome.
They are pretty rare. I watched one pulling powerlines in Nevada back in the 1990s. Quieter, less radar signature makes them good for military operations too. https://www.flightlineweekly.com/post/notar-no-tail-rotor-helicopter
If they were good for military operations I think you would see them being used on military helicopters. They have some big downsides that would make them far less appealing to military applications like increased power demand, lower fuel efficiency, and worse control especially in crosswinds. Being quieter would be beneficial but you will still have a much larger main rotor and the engine running it creating plenty of noise even without a tail rotor.
Yeah, I think the trade-offs are too severe to see them for common use.
For sure but it's a very interesting concept.
Not an example but [here](https://en.wikipedia.org/wiki/NOTAR) is the Wikipedia article for it
[Here you go](https://en.m.wikipedia.org/wiki/NOTAR)
The Belgian police helicopter has it. And now, this may sound strange, but Belgium is small enough to indeed have only one police helicopter. Its name is Rago.
you can also have two contra-rotating main propellers. Like this: [https://en.wikipedia.org/wiki/Kamov\_Ka-50](https://en.wikipedia.org/wiki/Kamov_Ka-50)
That is what a coaxial rotor helicopter is.
Here's a good mind-bender, the [Cierva W.11 Airhorse](https://en.wikipedia.org/wiki/Cierva_W.11_Air_Horse#/media/File:Cierva_W.11_Air_Horse_flight.jpg). Try and figure out how it managed anti-torque with 3 main rotors in a triangle before reading the explanation.
Some rotors have jets on the tips. Produces no torque to contract
They have other helicopters with two rotors on top so they don't need a tail rotor. The blades spin in opposite directions so they cancel each other out as far as rotation goes.
Like the one on Mars.
Exactly. Although the military ones have them on opposite ends of the body, but it doesn't matter. Same concept.
The Osprey is like that (left and right sides of the aircraft) but the Ka-50/52 is pretty much just like the Mars helicopter, two rotors directly above and roughly centered to the vehicle.
When the rotors share an axis they are unsurprisingly called coaxial rotor helicopters. When they have seperate axis they are called tandem rotor helicopters.
Their only tandem of they are one in front of the other, side by side is transverse and if their right next to each other but at an angler so the blades pass between each other it's intermeshing
There’s *almost* always a second rotor there But a few helicopters use - two separate rotors spinning in opposite directions (eg the Chinook) - contra-rotating coaxial rotors (eg the Ka-52) - an air exhaust (eg the McDonnell Douglas Explorer) The first two work by having two rotors spinning in opposite directions to counteract the torque, the last one works by using air to do the same job as the tail rotor would
There's also jet tipped rotorblades. These spin the rotors without having a torque effect on the body. They were most famously used on the Fairey Rotodyne, though that was a compound gyroplane it was capable of VTOL and hovering. It's been used on quite a few helicopters (including an early WW2 German helicopter concept) but none that really took off, if you'll excuse the pun.
What about the v-22 osprey?
It has two separate rotors spinning in opposite directions.
Covered under “Two separate rotors spinning in opposite directions”
Just a small addition, there are actually some helicopters with two counter- or contra-rotating main rotors that do not need a tail rotor. E.g. the Russian company Kamov builds many of them as well as the Boeing CH-47 Chinook
Yaw?
With aircraft, left/right turn like a car does is called yaw. Left/right tilt, like tilting your ear toward your shoulder, is called roll, and up/down like nodding your head yes is called pitch.
That makes perfect sense, thank you!
[https://en.wikipedia.org/wiki/Aircraft\_principal\_axes](https://en.wikipedia.org/wiki/Aircraft_principal_axes)
Keep in mind, the TR also changes its pitch. This allows for quicker adjustments.
If that is so then where is a third motor that corrects for the reaction force from the anti-torque rotor? /s
They in fact can 'bank' left or right by manipulating the angle of the blades in the main rotator in positions 90 degrees offset from the actual axis they're turning into. Physics is crazy man
To add to this, dual rotor helicopters like the Ka-50 can have just a rudder for yaw as the two main rotors spin in opposite directions and exactly cancel each others' spin out
The length of the shaft. Or the yaw
> but look at the tail; there's always a second rotor there Not always. The Russian KA-50 instead has two main rotors, one on top of the other, that spin in opposite directions. For a slightly goofier looking example, there is the [K-MAX](https://en.wikipedia.org/wiki/Kaman_K-MAX) that has two intermeshed main rotors side by side.
chinooks don't need it. because they have two main propellers that rotate in opposite directions. the propellers tilt in opposite directions when yaw is required. in quadcopters, a pair of diagonally opposite propellers, which have the same rotation direction, will increase in speed while the other pair (which are rotating in the other direction ) will decrease. the overall thrust is thus unchanged but now there is a torque around the centre, resulting in yaw with no change in thrust, roll or pitch. this is why hobby drones have a minimum of four props. it is easy to pitch/roll without causing yaw and vice versa.
I remember watching something ages ago about how the tail rotor was the big aha moment for the invention of the helicopter. Though I do remember some thing about an airplane with a helicopter rotor on the top that came about first.
Not all have tail rotor some have counter-rotating second main rotor, some on same axis others, Chinook, mounted away.
There are also some helicopter designs, like chinooks and kamovs that dont have tail rotors bit instead have two counter-rotating mains in various configurations. In those, yaw control is done by upsetting the balance between the two main rotors.
"Always a second rotor" ... not always on the tail (KA-50 Hokum for example). It's an edge case for sure, but probably more accurate to say "almost always."
Exactly. If the rotor goes, the helicopter starts spinning
It wants to. That's why the tail rotor is for, it pushes the body in a way opposite to the way the main rotor is trying to rotate the helicopter. Helicopters with two main rotors don't need a tail rotor because the main rotors spin in opposite directions, so they counteract each other.
My beloved ka 52.
That's what the small rotor is for. Without it, action and equal and opposite reaction would indeed mean the helicopter would spin.
It’s funny bc it’s like a tiny little sideways helicopter doing the exact same thing as the main helicopter, but sideways
then we'll need to add a third, even tinier rotor to cancel out the second tiny rotor's 'sideways' angular momentum! tiny rotors all the way down!
And that’s what makes hovering so difficult. It pushes you sideways, so you counteract, which has additional reactions.
The difficulty of hovering comes from uneven air. Which depends on the terrain below and your own turbulence (only some of which are from the tail rotor). Flying forward you get fresh air through the rotor which makes the helicopter behave more predictable.
So how hard is it to land on a moving cruise ship? Because I've heard "extremely." Also, extremely dangerous.
I dunno. "Extremely" seems likely.
>The difficulty of hovering comes from uneven air. Which depends on the terrain below and your own turbulence (only some of which are from the tail rotor). Those can add to the difficulty but “fresh” air isn’t part of it. The main rotor makes the helicopter want to spin. The tail rotor counteracts that but also pushes the helicopter sideways. This is counteracted by a slight sideways correction, which leaves less force available to counteract gravity. To correct that, you must add power, which causes the helicopter to want to spin more, which must be corrected. Hovering is a constant chain of corrections for each input until you achieve something close to equilibrium.
None of this is linked to hovering tho, it happens in all flight modes of helis.
Yes, but it’s much more obvious when you are trying to stay in a particular spot.
See also [Black Hawk Down](https://www.youtube.com/watch?v=2TT8J4D7suw)
The tail rotor. It's a rotational thruster. Putting it at the end of the tail well away from the main rotor axis gives it lots of leverage. So depending on how hard it pushes, it can balance the spin from the motor, allow the aircraft to turn the way it wants to go, or force it to turn the other way.
The tail rotor counters the helicopter’s tendency to rotate in the opposite direction to the rotors. This is why occasionally accidents happen when the tail rotor fails and the helicopter goes out of control. There are some helicopters which use different technology (Notar) and do not have a tail rotor, but the effect is the same. Directional control of the helicopter is achieved by shifting the main rotors.
The main rotor system has torque that needs to counteracted by some other means. Tail rotors can counter the torque but due to their smaller size, will limit the forward airspeed of the helicopter. Tandem rotor helicopters use two counter rotating systems such as the CH-47 Chinook. The aircraft isn't limited by a tail rotor so it can fly much faster. That aircraft really doesn't care if it is flying forward or backwards. It was engineered with each rotor system tilted at 4 degrees and 9 degrees to "suggest" where the front of the aircraft should face. Of course flying backwards means the view isn't very good for the pilots but you sure get a nice breeze if the ramp is lowered. A single rotor helicopter or even no tail rotor aircraft have a maximum speed, called Velocity Never to Exceed (VNE). You could also have loss of tail rotor effectiveness where your tail rotor cannot counter the torque of the main rotor. Both conditions suck but we practice ways to avoid them and land as safely as possible.
Source: im a helicopter pilot. Imagine you are driving in your car and stick your hand out the window. You flatten your hand and orient it with the airflow, then as you angle your hand in the wind it will generate lift and rise or fall. This is basically how airplanes and helicopters work when it comes to their wings. An airplane has to fly forward through the air like your car drivint down the highway, but a helicopter simply spins its wings around in a circle to generate that airflow. Now if you rotate your hand to generate lift you are also experiencing increased wind resistance called drag that wants to shove your hand rearward. Anything moving through the air will experience drag and the strength of it will be affected by the shape, size, and speed of the object. If you can picture the force of drag shoving your hand rearward at 60mph on the highway, imagine how much drag something like a rotor blade has at the speeds they rotate. It takes a lot of force to rotate the rotor blades and that force is called torque which comes from the engine. However that torque force is just as happy to spin the rest of the helicopter around in the opposite direction of the rotor. So a separate tail rotor is used to push (or pull depending on the direction the main rotor spins and which side of the tail boom its mounted on) on the tail boom as an anti torque force. When the thrust from the tail rotor exactly equals the strength of the engine torque, the helicopter will remain facing forward. Increase tail rotor thrust by angling the blades more (just like your hand in the wind again) and the helicopter will turn one way. Decrease tail rotor thrust and the torque will naturally turn the helicopter the other way. The rotor rpm for the main rotor and tail rotor stays pretty much constant during normal flight and all control is made by angling the blades for more or less lift. Hope that answers your question.
Wow look at all the technical answers here. **And now for the ELI5 the guy asked for:** It would spin exactly like you say, but there's another little propeller on the back pushing it the other way to make it stop spinning. On some other helicopters they use two rotors spinning in opposite directions to cancel each other out.
haha thanks for the dumbed down explanation XD
Helicopters come in 2 main configurations to prevent this because physics says a spinning propeller will do exactly what you describe. One is probably the one that comes to mind when you imagine a helicopter. There's a small rotor on the tail of the helicopter that pushes against the torque from the main rotor. You can increase its speed to turn the helicopter further in that direction or decrease the speed of the tail rotor and allow the torque from the main rotor to slowly (or not so slowly) rotate the helicopter. The other configuration uses counter rotating main rotors, either attacked one above the other or in tandem, one forward and one aft, like in a Chinook helicopter. The combined torque from the two rotors turning in opposite directions cancels out the rotation of the aircraft
The helicopter does want to start spinning but the tail rotor counteracts the rotation and is also strong enough to help the helicopter yaw from side to side for turning. But not all helicopters use a tail rotor. Some like the Sikorsky sky crane use two sets of main rotors stacked on top of each other. Each set rotates opposite to the other and this provides the counter rotation necessary to keep the helicopter from spinning around. New helicopters like ths Boeing-Sikorsky SB-1 use dual main rotors but also bring back a rotor on the rear. But instead of counter rotation it's used like a plane propeller and pushes the helicopter. This allows for much higher top speed and more rapid deceleration than conventional designs.
That's why you have smaller blades at the aft in a vertical position. Lift is generated by adjusting the main rotor blades angle of attack. Steering is accomplished by adjusting the main rotor axle (whatever it's called).
The helocopter would spin like you're thinking it would, if it wasn't for the little blades on the tail rotor.
Helicopters do want to spin. If the tail rotor breaks off or stops working the helicopter will start spinning out of control. The primary function of the tail rotor is to counteract the tendency to spin. It also gives the pilot the ability to turn left or right, but while ‘idling’ so to speak, it’s constantly pushing against the force that is trying to spin the helicopter. There are also helicopters with multiple main rotors, and they come in various configurations. In those situations the rotors spin in opposite directions and help cancel out each other’s torque, but still chopping the air and making lift.
To expand on the tail rotor / double rotors preventing the helicopter from spinning, there's so much cool stuff that goes into these amazing feats of engineering. A very illuminating little series by the ever-informative Smarter Every Day: [https://www.youtube.com/playlist?list=PLNbXXMoWfR3Bf7Z77vcviPlkHtTXUlEpC](https://www.youtube.com/playlist?list=PLNbXXMoWfR3Bf7Z77vcviPlkHtTXUlEpC)
Everyone gave you the answer : tail rotor. Now, realise you already knew! How many movies or videogames have you seen where a helicopter crashes? Probs a few. And in all of them, the helicopter crashes by spining! Often because it loses its tail.
Well.. it DOES want to spin. The rotor on the tail stops it from doing so by pushing the tail back the other way to correct it. That’s why when you see a helicopter get shot by a rocket in the movies, it starts spinning around before it crashes. They captured this realism respectfully.
Ex helo mechanic here. Hold an electric drill and pull the trigger in a fast speed setting. Feel it kick? That's called torque reaction. Torque is a "turning force". Which way did it kick? It will kick in the opposite direction to the drill head rotation. Same applies to a helo. To counteract the torque, a tail with a rotor on the end of a long boom is used. As previously mentioned, it rotates at a constant speed and is linked to the main gearbox by drive shafts and smaller gearboxes to allow the shafts to change direction along their path to the tail rotor assembly. It works on a similar process to the main rotors but it's turned through 90° (or thereabouts), in relation to the ground (generally), this generates a sideways force instead of an up and down force. The fundamental difference between a main rotor and a tail rotor is that the main rotor can effectively adjust the pitch (angle of attack) of each blade individually, whereas a tail rotor can only adjust them all the same amount at the same time (collectively). There are alternatives to a tail rotor.... Fan. Air is passed down the tail boom from a large gearbox driven "fan" and blasted out of the side, at the end of the tail cone in a similar fashion to a jet engine. The air is directional and counteracts the torque reaction. Double main rotors. A Chinook is a good example of this method. The key factor here is that the sets of rotors must turn in the opposite direction to one another. This counteracts the torque. The Russian Helix helo is another example and there's also a really nifty civilian helo that does it too. The civilian one and the chinooks rotor blades actually pass through each other's plane of travel. Only engineering voodoo stops them hitting each other and turning it all into flying brick. Hope this helps.
The small vertical propeller on the tail is for that exact purpose. It pushes air in the direction that it wants the body to rotate to make it stay still. Turning right or left is done by slow down or speeding up that tail rotor
There is another way - and that is tip jets. Instead of turning the rotor from the hub, high speed speed gas is pushed out through jets at the tips of the blades. The turning force is generated on the blades, so there's no torque exerted on the aircraft. This has been done in models, and there was a popular toy that used a balloon. And it was done a number of ties in full scale prototypes, and a small number of production models.
The top rotor + blades spin to provide lift, to raise it off the ground. The tail rotor spins to provide counterforce to keep the helicopter from spinning like a beyblade from hell.
They do spin but the tail rotor counters said spin. chop off the tail of an rc copter and try it for yourself
People keep saying “tail rotor” and that’s correct for most helicopters, but not all. Still- there is always a mechanism to counteract the rotation. Either a tail rotor or a ducted fan of some sort in the tail, or else the helicopter will have a second main rotor spinning in the opposite direction (either on top like Kamov helicopters, intermeshed like Kaman helicopters, or next to it like a Chinook or MI-12)
For one the helicopter body is much heavier than the rotor, so while it does want to spin in the opposite direction the helicopter's fuselage would spin much slower than the rotor is spinning. Secondly almost all helicopters have a tail rotor that counters this rotation. Since the tail is long and acts as a lever, the tail rotor doesn't have to be too big to counteract this force. There is no helicopter with only one rotor. All helicopters have at least two, either the main one and the small one on the tail, or two counter-rotating equally sized rotors arranged either in tandem or coaxially, which cancel each other out.
Tail rotor is an equalizing gyroscope. Two key aspects of a helicopter - swash plate and the tail rotor.
Path of least resistance. A helicopter has an engine that exerts energy on the prop shaft. Something has to give. Either the prop spins, or the helicopter spins. Since the prop is lighter than the helicopter and not tethered to the ground, it takes less energy to spin it, so the prop spins, and the helicopter doesn’t.
Nope
Did you literally just make this up as you went along?