The date is not known, about 1500.
During the 1930's.
In 1907 Paul Cornu was experimenting with a vertical lift rotor blade system and performed the first VTOL (vertical take off and landing) flight, thus inventing the first helicopter. The helicopter was initially an idea by Leonardo Da Vinci. he developed an ornithocopter which set the basis for the structure of the modern Helicopter
A helicopter and a calculator
Igor Sikorski was well on the way with inventing the first practical helicopter then
There were hundreds of problems.
A. Igor Sikorsky
Igor Sikorsky
Igor Sikorsky
Leonardo da Vinci drew a helicopter about 500 years ago
inventing things
cookies :D
He did not, Leonardo da Vinci did.