What kind of wings would a person need to fly? I heard from a teacher in school that in order to fly, he would need a wingspan much wider than the wood shop where he was standing. Thinking back on it, I assume the number of times you can beat your wings should have something to do with it, since it looks like hummingbirds have shorter wings than eagles.

(source: animalia-life.com) 

(source: minnesotawaters.org) 
What even goes into the computation to answer the requisite wingspan for flight, let alone how do you do it?
This may be like How to compute the speed necessary for an airplane to fly?  but I think it's significantly different since flapping would be involved.
Also like Is it possible to fly like a bird using semi-motorized wings? but I believe also different because I want to know what wing size whereas that has a general flight/aerodynamics equation.

Finally: would people with no legs have an advantage in flying? (I assume this would be true if they weigh half as much and legs contribute no flapping power. Of course it could be different if you found a way to use leg strength.)
 A: 
what kind of wings would a person need to fly?

long and thin.

Human powered flapping-wing aircraft (ornithopter)
It seems this couldn't take off under human power alone but, once airborne, could produce enough thrust to overcome drag for up to 145 meters in 20 seconds of flight.

to achieve flight on the limited power of the human engine, the aircraft must be designed to fly quite slowly. At these slow speeds, the wing must be incredibly large to produce the required lift, and the structure must be incredibly light. To help support the light structure, external wire bracing is typically used, and although these wires add drag, the weight savings in the structure is significant. This wire-braced structure favours a hanging fuselage design, which is typical for human-powered aircraft. In the case of a human-powered ornithopter, the bracing wires are additionally used to pull the wing down during the thrusting portion of the stroke.



would people with no legs have an advantage in flying?

So far, most human-powered flights seem to rely mostly on leg muscles.
