Why do i need Servos in a RC helicopter?

accelerometer? I never heard of that being in an RC helicopter. Well… it depends on what kind of helicopter you are building. Is it a fixed-pitched helicopter? or not? If not, the servos help tilt the blades so it could create lift and make the helicopter take off. But yea… the Servos help tilt the blades to move the helicopter forward, backward, left and right. It is done by moving something called a swashplate on the helicopter. Fixed pitched helicopters usually require only 2 servos, but pitched helicopter require 3-4. 3 for the main and sometimes 1 for the tail rotor if the helicopter is a belt driven helicopter. As in it runs on 1 motor instead of 2. I think its better for you to buy a RC helicopter first before attempting to build one.
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RC Pilot.

It sounds like you're trying to build some type of coaxial helicopter. Accelerometers and gyros are essentially the same thing and I don't see any reason to use them together. On a coaxial helicopter you'll need two motors to drive each of the blades, and two independent speed controls for those two motors. The gyro works in between these two speed controls to provide yaw stability. Then using the rudder channel on your remote you can provide yaw control by manipulating one motor independent of the other. This assumes you'll be building a coaxial heli like the E-Flite Blade CX series of helis. The servos are used to control your head assembly. 2, 3 and sometimes even 4 servos are used to control the helicopters' pitch and roll and in some cases collective pitch. The servos are mounted to the main frame of the heli and then connect to the swashplate which connects to the head assembly.
If you're going to be building a helicopter and you need to ask why servos are necessary, maybe you should broaden your understanding of how rc helicopters function.
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