Expert: Mark Janus - 5/10/2008

Question
If you had a scaled down pair of helicopter blades (made out of something light, such as plastic), how many RPM would it need to lift itself along with 150 lbs? (about 150 lbs for the human, itself (lets just assume the copter was 200 lbs, so 350 lbs total), and if it had a 10 foot wing span? (So, how many RPM would 10 feet of helicopter blade-span need to lift 350 lbs).  (I know you would need to know how efficient the blades were at pushing against air, I just want to know the RPM it would need if it had an average efficiency.

Answer
Just roughing out some numbers...  a 10 ft blade with 1/2 chord would need to rotate at least ~500rpm to produce ~400 lbs ....

A human being can only produce about 1/10 Hp...  so if you think about yourself lifting your weight plus the weight of a vehicle (even only a 200lb vehicle) a lot of work has to be done (to climb for sure)...(hovering is a bit different but you still have to overcome the torque of the rotor)

mj