wrote

Yes, however:-

Hydrostatic drives shuch as this are fairly common in
heavy construction equipment and the like however
there is a problem.

There is too much loss even for ordinary car use and the
fuel consumption is unacceptably poor.

I would guess that this would be an even more serious
issue in aircraft.

Indeed, there would be, and one large problem is called weight. It wo8uld
be extremely heavy.

Also, those loss issues bring up another problem. When you have loss, what
happens to that energy? Energy can not be created or destroyed, and that
energy put into loss shows up as heat. Boatloads of heat that must be
dissipated, and that will take a lot of radiator, and air to go through it.
That will cause wind resistance, which will slow the plane, so much as to
make a biplane seem speedy.
--
Jim in NC