The drag not work with rigidbody.AddTorque

I make a simple helicopter, but i have problem with the rotation , when i press left the helicopter rotate but when i key up it still rotate and not stop never
i use rigidbody.AddTorque and the JS language

sorry for my bad English

Change your angularDrag in the inspector or via code to a higher setting if you are adding torque. The normal drag value is for linear velocity.