Actually I think the turbo charged IC engine is pretty good
all the way up to 57,000 feet. Our man Jeff Spitzer, chief engineer
on the Predator, at General Atomics and resident rotor head got
the turbo charged Rotax 914 powered Predator up to 57,000 feet.

Back in WW II a lot of turbo charged airplanes flew up to 45,000 feet.
It was years before a jet fighter could climb to the operating
altitude of a turbo charged piston engine B36. The big improvement in
jets was when they developed intake ducts to act as ram jets
...sort of super charging the turbine engine.

lets not forget  the modern criteria for  "airbus "  type jets - minumum fuel
burn , poor service ceiling & generally underpowered  in practical terms. Our
BAC / AvRo RegionalJet - aka BAC 146  has 4 modified helicopter engines -
from turboshaft to turbofan IIRC.  It can't cruise above 20,000 feet.

Fly Good - Bryan

 
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