The 9402 is not the best servo for a helicopter. The futaba 9252 digital servo is probably better and the price is probably not too much different.

Digital servos are more precise and have better holding power. The analog servos have all their torque at the end of the rotation as where digitals have a more distributed amount of torque with location. Metal gears are not ideal for helicopters because they wear faster, but they don't strip as easily. A servo gear in a heli is not likely to strip even though it can happen. Digitals drain more power. If you read the correct specs on the servo on 4.8 volts it should be around the same as the 9252.

That servo can be used for anything, but it is costly.