I made an "addon" to remove ALL sounds from the Heli. Get it
HERE
It should hopefully be approved soon.
As stated before I see no reason why this can or would ever get you banned. You are not modifying anything or editing anything. You are using built in game mechanics and doing as the game was designed to do.
There are many addons out there that do this exact same thing. There are ones to change the Fishing Splash sound and to change the DK mount sound to the voice of the car KITT from Knight Rider.
If there is an issue the it will surely be removed.