First of all: That happens extremely rarely. Then we do not fall "down like a stone" - as is widely assumed. The pilot then initiates the "autorotation" - which means "the rotor continues to rotate on its own". The main rotor is further driven by the air flow coming from below, which means that the helicopter remains maneuverable and can be “sailed” and landed in a targeted manner to an open area. Due to the principle of autorotation, autogyros can take off and fly in the first place. The autorotation also rotates the maple seeds falling from the tree. Disadvantage: You only have one attempt. This is why professional pilots practice this and many other maneuvers at least once a year in order to be prepared for the very unlikely emergency.