# What makes these type of helicopters fly?

These are called coaxial helicopters, but it seems very weird that how can these helicopters fly? I had a toy helicopter like this and something that I noticed was when it's blades were rotating, they rotate in the opposite direction. They both rotates with the same angular velocity so far. My question is, when the upper blade produces the thrust force then, the lower blade beneath also produces the thrust force in the same direction. Then what's the use of this second blade beneath If the first blade is doing the same work?

Rather This should intruppt the amount of air that the first blade want to throw downwards and push the helicopter downwards as well because of the obstacle i.e the second rotating blade, if it want to move upwards then then anything should not intruppt the air, if this happens then the forces will get cancelled and the helicopter will remain stationary but this doesn't happen at all, rather it's even more stable while it levitates. How is this possible? And why do we need that second blade while the normal single blade would also do that work very easily as the huge original single blade helicopters does?

Why are these toy helicopters made like these? Why the coaxial helicopters are uncommon in the real life, is there any reason that the large helicopters can't be made like this? I've gone through some articles on the internet and noted some conclusions according to them regarding this but that didn't helped me a lot to understand.