I am very new the field of RCs.
So right now I am building up my technical knowledge first.
What is the use of a servo motor and is it used in both heli and planes?

Regards
Vaibhav

Change in direction of movement of planes and helis is usually accomplished by changing the angle of a "control surface" (aileron/elevator/rudder in the case of airplanes and main/tail blades in the case of helis).  This physical movement of control surfaces is achieved by a device that can convert electrical signals to physical movement. That is the function of servos.

First of all clear my doubts:
What is the actual terminology to be used:
1. Servo
2. Servo Motor, or
3. Servo controlled motor

Not sure if we should get into that detail on this question    Looks like the original question was about the servos we all use routinely (regardless of how it was put in the question itself).

There is an electric motor inside the servo that causes the gears inside to turn (which is finally transferred to the arm outside that rotates), that is usually referred to as the "servo motor" (at least that is the street term). 

Not sure what a "servo controlled motor" is, I am assuming a servo is used to control some kind of motor ?

What is can see by going through the wiki below:
http://en.wikipedia.org/wiki/Servomechanism
is that the actual should be either SERVO or SERVO CONTROLLED MOTOR. "Servo motor" inside the servo is only used as a primary means of creating mechanical force
Correct me readers if i am wrong. well final outcome is the controlled/guided position of mechanical system.

Our servos are not just "servo controlled motors" but complete mechanisms. The term "servo" is both legitimate, and adequate.

Agreed Mr. Sushil.
Anwar. penalize the person who use the word "Servo motor" 

I suppose if Anwar did that then one could say "it servos you right" !!

Ganging up on a beginner ?      

>

good threat! AFAIK , there are 'Stepper Motors' inside a 'Servo' , which move in 'Steps' when you give signal. When you put appropriate periphery apparatus like Gear and Arms, the setup becomes a 'Servo'. Just lame knowledge from school times electronics.

As far as i have seen a servo, there is no stepper motor inside, i may be wrong also. there is a simple micro dc brushed motor which one can use as a motor to drive a small prop also.

Thank you Sirs for the information.
I am more interested in building RCs than flying. Although I bet flying will be great fun aswell  ...
Even though servo seems necessary  for helicopters. Is it also important for planes?

Regards
Vaibhav

Servos don't use stepper motors. Theoretically a stepper motor can be used in a servo, but is a waste of drive electronics, motor cost and weight when a simple motor will do the job.

Both servos and stepper motors are used for positioning. Difference is in the feedback. In a stepper you give the step inputs and hope the motor has moved properly. In a servo, there is feedback about the position to the drive electronics. It will drive the motor until the desired position is reached. Steppers are usually used where there is no significant variation in load. So you can make sure there are no lost steps due to varying conditions.

Vaibhav,
You might have seen toy Heli and planes in local market which is available from Rs. 500 to Rs.1500. and they fly very well without servos. Servos are basically meant for changing the direction of moving object which is connected to a control surface with push rods. In toy heli and planes, variable speed is used to change the direction of plane or heli. so use of servos in heli or plane is important but from a certain level. professional plane or heli cannot fly without Servos. Take an example of remote control toy car. it doesn't have a servo but can change direction, that is done using a simple dc brushed motor setup which is connected with a triangular base with teeth at one end. that triangular setup is acting like a control horn connected to a steering setup. as the direction of motor is changed the steering setup turns. the same setup can be used in a toy plane also, but weight will be an issue........so if you really want to FULLY enjoy R/C Flying, servo is ALSO an Important part of R/C setup.