Electrically Powered Ultralight Aircraft

wrote:
In rec.aviation.piloting cavelamb himself wrote:
wrote:
To carry more weight at the same speed and altitude takes more power, so
you have to account for the energy expended kiting you deadweight
electric takeoff system around the sky as well. Sizing an engine for
cruise has been done, if only backwards. Think JATO. Most JATO's are
actually RATO (rocket assisted takeoff). I expect RATO would beat an
electric system based on energy density and the fact that when it is
done you have reduced your weight by the fuel. I also suspect for a
given amount of thrust the rocket will be lighter than an electric motor
and associated clutches and gearing. In my opinion, at this point in
time it is just as practical for a homebuilt as well as in not.

Well, that's true enough, but the above was about hybrid cars.



No, it's not true enough.

To carry more weight at the same speed and altitude requires more LIFT.

A higher CL - and/or more wing area.

THEN, to overcome the increased drag, THEN you need more power.

But more power by itself won't satisfy the constraints...

So if I add 1 pound to a 2400 pound gross aircraft loaded to 2300 pounds,
it would be impossible to cruise at the same speed and altitude without
the 1 pound unless I added wing area?

How about 50 pounds?


No. You can increase the angle of attack, which increases the lift ( to
a limit) and also increases the drag, which must be overcome with more
power. If your speed drops, so does the lift. If you could increase
your aspect ratio, you could get more lift at the same speed at the same
power I think. So I guess Richard is flying a swing wing texas
parasol.;') For the rest of us, we have to add power to carry more
weight at the same speed and altitude. Since most planes lose weight
while in flight in the real world, you actually have the opposite issue.

Charles