The multi rotor helicopter is a special product which can fall down because of a small error. So safety is a basic requirement. Multi rotor helicopter like the DJI Phantom, AEE Toruk use the traditional radio control which the precision and reliability of operation is higher. But it takes long time for the operator to take charge of flying the multi rotor helicopter. Smartphone controlling via app has been used by multi rotor helicopter like Ehang Ghost. It is easier for the operator to master the flying, but inferior in operating precision. Do you think the smartphone is suitable to control multi rotor helicopter? If there is no safety problem, will you choose to use the radio controlled multi rotor helicopter or the smartphone controlled multi rotor helicopter?