I heard a kind of knocking noise coming from the a/c compressor every time it kicks on almost like a helicopter like noise any one know what the cause may b i know its not normal thinking it maybe the clutch plz help

 

Could be a bad clutch. Post a video with sound.

 

A while ago my ac compressor started making a grinding noise and eventually locked up. it was the bearings and i replaced the whole unit. if you post a video it would help.