"Fritz" wrote in message
...
A ground turbine runs at almost constant speed, near its design point,
so even at small dimension can still be fuel efficient. Part load fuel
consumption of a gas turbine is a bit too high, particularly for GA
aircraft (considering their flight pprofile).

Hmmm...define "fuel efficient"?

Your comment brings to mind the Toyota Prius hybrid engine. It essentially
has a "continuously variable transmission" that doesn't involve a
complicated, maintenance-hungry belt or chain and pully system.

I wonder if the answer to bringing turbine engines to small airplanes might
not be using a hybrid system. The weight of the batteries (which is
substantial) is offset by the relatively low weight of the rest of the power
train. The engine would only run during climbs, and when the batteries need
to be recharged. Biggest problem I see right off the bat is the problem of
starting and stopping the turbine frequently...my understanding is that
there are "issues" there, but I don't know what they are, or whether they
can be addressed by design.

Using such a system, a turbine could be run "at almost constant speed, near
its design point", while accomodating a variety of power settings.

All that said, someone else mentioned turbine-engined locomotives; that's a
much bigger power demand and yet somehow diesel-electric engines wound up
the standard. I suppose looking at the history of train locomotives might
offer some insight into how feasible hybrid technology might be for
airplanes. It might be that there are some unsolveable problems, or it
might be that we're at a stage in engine development now where things that
used to be problems aren't anymore.

Pete