Da Vinci based many his ideas on things he observed in nature. His armoured tank for example is based on the strength of a tortoise's shell and his Leocopter is believed to be based on the seeds of a maple tree. Da Vinci’s flying machine is built using the measurements he made of birds and bats in flight. The pilot would power the flying machine by pedalling a crank which would move the wings up and down. The pilot would need to pedal with both hands and feet leaving steering to be done with a device strapped to their head. The pilot would lie in the flying machine a lot like a hang glider does. The wingspan of the flying machine was over 33 feet. The skeleton was to be made in lightweight pine and covered in silk, a very lightweight fabric.