Distance sensor on a helicopter toy

So I want to attach a distance sensor on a helicopter toy, so when it measures a certain distance between itself and the ground, it goes up or down, for example if the distance measures less than one meter, then it elevates till the distance is one meter again, also when the distance is more than one meter, it goes down till the distance is one meter ... any ideas how I can do that? what do i need? do i have to also attach arduino with it or can arduino manage it remotely with radio control or something?

any insights would be helpful, thanks.

any ideas how I can do that?

It would be useful to know more about the helicopter. Does it already have an Arduino that is controlling things?

what do i need?

A sensor, at a minimum. Some idea how to read it. Some concept of how to alter the helicopters actions to control it's height.

do i have to also attach arduino with it or can arduino manage it remotely with radio control or something?

It? What is "it"? The sensor? The helicopter? The PC? A tree in your yard?

How about the second it? Perhaps you missed school that day, but it is a pronoun. Each an every pronoun needs a referent, so we have some clue what the pronoun refers to.

PaulS:

It would be useful to know more about the helicopter. Does it already have an Arduino that is controlling things?

No, not already controlled by Arduino whatsoever.

It? What is "it"? The sensor? The helicopter? The PC? A tree in your yard?

I meant do I have to attach Arduino to the helicopter or is there a way to make a connection between the sensor in the helicopter and Arduino remotely (so Arduino receives information from sensor remotely, and responds by sending commands to helicopter remotely)?

Thank you.

Without knowing how the helicopter is controlled, what capacity it has to lift extra weight etc, its impossible to answer your questions.

I meant do I have to attach Arduino to the helicopter or is there a way to make a connection between the sensor in the helicopter and Arduino remotely (so Arduino receives information from sensor remotely, and responds by sending commands to helicopter remotely)?

No. The sensor has to be directly connected to the Arduino. It is the Arduino that causes the sensor to send a pulse train and to read the time taken for that pulse train to be echoed back.

Note that the ultrasonic sensors work best when the pulse train reflects off hard, flat surfaces (like walls), and not so well when the pulse train reflects off soft surfaces like people, grass, etc.