"Richard" wrote:

"Mxsmanic" wrote in message
...
I know that some gliders have small powerplants that they can use in
an emergency for thrust, but are there any gliders that are simply
powered by the pilot? Is the thrust required to keep a glider in the
air small enough that a human pilot could supply it for any length of
time? They seem very efficient, so it occurred to me that a crank or
pedals or something driving a small propeller might be sufficient to
stay aloft in bad situations. Would it?

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No, man power has only worked in extremely light weight gliders.
http://en.wikipedia.org/wiki/Gossamer_Albatross
http://en.wikipedia.org/wiki/MIT_Daedalus

A trained person could generate just enough power to keep the Gossamer
Albatross in the air, which required 0.3 hp (200 W).
The power of a sustainer motor of a glider equals between: 18-30 hp (14-22
kW), so this is too much for a human pilot to supply.