Earlier, wrote:

The human-powered planes that
have crossed the English channel
required something like 2.5 HP
(about 2000 Watts).

No, I don't think that that's right. I believe that both the Gossamer
Condor and the later channel-crossing Gossamer Albatross took only
about 1/3 horsepower (about 250 watts) to stay in the air.

Bob K.